UBC Theses and Dissertations

UBC Theses Logo

UBC Theses and Dissertations

The thermal preservation of apple slices in flexible retort pouches Christenson, Clarence Gordon 1978

Your browser doesn't seem to have a PDF viewer, please download the PDF to view this item.

Item Metadata

Download

Media
831-UBC_1978_A6_7 C49.pdf [ 6.3MB ]
Metadata
JSON: 831-1.0094321.json
JSON-LD: 831-1.0094321-ld.json
RDF/XML (Pretty): 831-1.0094321-rdf.xml
RDF/JSON: 831-1.0094321-rdf.json
Turtle: 831-1.0094321-turtle.txt
N-Triples: 831-1.0094321-rdf-ntriples.txt
Original Record: 831-1.0094321-source.json
Full Text
831-1.0094321-fulltext.txt
Citation
831-1.0094321.ris

Full Text

THE THERMAL PRESERVATION OF APPLE SLICES IN FLEXIBLE RETORT POUCHES by CLARENCE GORDON CHRISTENSON B.Sc, University of B r i t i s h Columbia, 1967 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENT FOR THE DEGREE OF MASTER OF SCIENCE i n THE FACULTY OF GRADUATE STUDIES DEPARTMENT OF FOOD SCIENCE UNIVERSITY OF BRITISH COLUMBIA We accept t h i s thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA January, 197 8 (cT) Clarence Gordon Christenson, 1978 In p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t of the requirements f o r an advanced degree at the U n i v e r s i t y o f B r i t i s h Columbia, I agree t h a t the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and study. I f u r t h e r agree t h a t p e r m i s s i o n f o r ex-t e n s i v e copying of t h i s t h e s i s f o r s c h o l a r l y purposes may be granted by the Head of my Department or by h i s r e p r e s e n t a t i v e s . I t i s understood t h a t copying or p u b l i c a t i o n of t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l not be allowed without my w r i t t e n p e r m i s s i o n . C. Gordon C h r i s t e n s o n Department of Food Science The U n i v e r s i t y of B r i t i s h Columbia Vancouver, Canada Date 21 , /97Y ABSTRACT Newtown P i p p i n and Winesap apples were taken from t e r m i n a l storage, and prepared as s l i c e s to be processed i n r e -t o r t a b l e pouches to determine an optimum process u s i n g the r e l -a t i v e l y new pouch technology. P r e p r o c e s s i n g treatments i n -cluded c a l c i u m c h l o r i d e as a t e x t u r e m o d i f i e r , sodium b i s u l f i t e as a m i c r o b i a l i n h i b i t o r and c o l o u r s t a b i l i s e r , and sodium a c i d pyrophosphate as a c o l o u r s t a b i l i z e r . These reagents were added to the s l i c e s by vacuum i n f u s i o n , hot b l a n c h i n g or c o l d d i p p i n g to determine t h e i r e f f e c t s on the f i n a l product. The s l i c e s were packed i n 300 gram pouches t h a t were evacuated, then f l u s h e d w i t h e i t h e r n i t r o g e n or carbon d i o x i d e before s e a l i n g . The samples were s t o r e d a t 22 and 35°C and were ex-amined by p h y s i c a l , chemical and sensory methods, a t i n t e r v a l s of two weeks, s i x weeks and f i v e months a f t e r p r o c e s s i n g to de-termine the changes o c c u r r i n g w i t h i n the samples. During s t o r -age, q u a l i t y changes d i d occur, which a f f e c t e d the acceptance of the s a m P l e s / p a r t i c u l a r l y a t the hig h e r temperatures. Texture was v a s t l y improved w i t h the a d d i t i o n o f c a l -cium ions to o l d apples. Colour remained s i g n i f i c a n t l y l i g h t e r i n samples with h i g h e r SC>2 l e v e l s . The a d d i t i o n o f pyrophosphate was a l s o shown to i n c r e a s e the l i g h t n e s s of the samples. The l e v e l s of r e d u c i n g sugars and pH were shown to i n c r e a s e w i t h the l e n g t h and temperature of sto r a g e . P r e p a r a t o r y methods were a l s o shown to have a gr e a t i n f l u e n c e on the q u a l i t y o f the f i n a l product. Hot b l a n c h i n g of apple s l i c e s l e a d to a lower q u a l i t y product than e i t h e r vacuum i n f u s i o n or c o l d d i p p i n g . Vacuum i n f u s i o n was by f a r the most e f f i c i e n t p r e p a r a t o r y method but r e s u l t e d i n a prod-uct with a t r a n s l u c e n t appearance and a b l a n d f l a v o u r . C o l d d i p p i n g produced the b e s t f i n a l product. The use of carbon d i -oxide atmospheres w i t h i n the pouch produces a lower pH and a s o f t e r t e x t u r e i n the samples. N i t r o g e n was found to be the b e t t e r of the two gases f o r q u a l i t y maintenance. In g e n e r a l , i t was determined t h a t apples from term-i n a l storage were more d i f f i c u l t to process i n t o a product of good q u a l i t y than were apples s t o r e d f o r on l y a s h o r t time a f -t e r h a r v e s t . - i v -TABLE OF CONTENTS Page L I S T OF TABLES v i i i L I S T OF FIGURES x i i ACKNOWLEDGMENTS x i i i INTRODUCTION 1 REVIEW OF THE LITERATURE 3 P r o c e s s Time 3 P r e p a r a t o r y M e t h o d s " 4 C h e m i c a l A d j u n c t s 6 V a r i e t i e s 9 EXPERIMENTAL METHODS 11 EXPERIMENTAL DESIGN 11 PROCESSING 12 P r o c e s s Time D e t e r m i n a t i o n 12 T h e r m a l D i f f u s i v i t y S t u d i e s 12 H e a t P e n e t r a t i o n 20 ..SAMPLE PREPARATION AND PROCESSING 27 STORAGE TESTS 32 PRODUCT PHYSICAL PROPERTIES 33 M a g n e s s - T a y l o r P r e s s u r e T e s t - F r e s h A p p l e T e x t u r e 33 S i n g l e B l a d e S h e a r - A p p l e S l i c e T e x t u r e 35 V i s c o u s B e h a v i o r - P u r e e 36 C o l o u r - A p p l e S l i c e s 39 - v -J Page PRODUCT CHEMICAL ANALYSES 39 C a l c i u m A n a l y s i s 39 SO2 D e t e r m i n a t i o n 41 S u g a r A n a l y s e s 42 A s c o r b i c A c i d A n a l y s i s 44 pH D e t e r m i n a t i o n 46 SENSORY ANALYSIS 4 6 S T A T I S T I C A L ANALYSES 4 7 RESULTS 49 PROCESSING 49 P r o c e s s D e t e r m i n a t i o n 49 T h e r m a l D i f f u s i v i t y 49 H e a t P e n e t r a t i o n 51 Sample P r e p a r a t i o n s a n d T h e i r E f f e c t s 51 SAMPLE DIFFERENCES 5 6 T e x t u r e 5 6 I n s t r o n S i n g l e B l a d e S h e a r 56 V i s c o m e t r y 5 8 C o l o u r 61 C h e m i c a l D i f f e r e n c e s 64 SENSORY ANALYSIS 81 DISCUSSION 87 - v i -Page PROCESSING 87 Process Time Determination 8 7 Sample P r e p a r a t i o n and T h e i r E f f e c t s 89 SAMPLE DIFFERENCES 95 Texture 95 Colour 102 Chemical Analyses 112 Calcium A n a l y s i s 113 S0 2 A n a l y s i s 115 T o t a l Sugar A n a l y s i s 118 Reducing Sugar A n a l y s i s 120 A s c o r b i c A c i d 122 pH Changes 128 SENSORY ANALYSIS 129 CONCLUSIONS 133 LITERATURE CITED 137 - v i i -L I S T OF TABLES T a b l e Page 1 R e s u l t s o f T h e r m a l D i f f u s i v i t y M e a s u r e m e n t s o f Raw A p p l e S l i c e s 50 2 R e s u l t s o f t h e H e a t P e n e t r a t i o n S t u d i e s o f A p p l e S l i c e s i n R e t o r t P o u c h e s 52 3 L e v e l s o f A d d i t i v e s U s e d f o r t h e P r e p a r a t o r y T r e a t m e n t s o f A p p l e S l i c e s i n R e t o r t P o u c h e s 54 4 R e s u l t s o f S t e p w i s e M u l t i p l e R e g r e s s i o n o f I n s t r o n S h e a r F o r c e on E x p e r i m e n t a l F a c t o r s U s i n g S i n g l e F a c t o r s O n l y 57 5 R e s u l t s o f S t e p w i s e M u l t i p l e R e g r e s s i o n o f I n s t r o n S h e a r F o r c e on E x p e r i m e n t a l F a c t o r s U s i n g Two-Way I n t e r a c t i o n F a c t o r s 57 6 R e s u l t s o f S t e p w i s e M u l t i p l e R e g r e s s i o n o f n o n E x p e r i m e n t a l F a c t o r s U s i n g S i n g l e F a c t o r s O n l y 59 7 R e s u l t s o f S t e p w i s e M u l t i p l e R e g r e s s i o n o f m on E x p e r i m e n t a l F a c t o r s U s i n g S i n g l e F a c t o r s O n l y 59 8 R e s u l t s o f S t e p w i s e M u l t i p l e R e g r e s s i o n o f a v on E x p e r i m e n t a l F a c t o r s U s i n g S i n g l e F a c t o r s O n l y 60 9 R e s u l t s o f S t e p w i s e M u l t i p l e R e g r e s s i o n o f n40 o n E x p e r i m e n t a l F a c t o r s U s i n g S i n g l e F a c t o r s O n l y 6 0 10 R e s u l t s o f S t e p w i s e M u l t i p l e R e g r e s s i o n o f n on E x p e r i m e n t a l F a c t o r s U s i n g Two-Way I n t e r a c t i o n F a c t o r s 62 11 R e s u l t s o f S t e p w i s e M u l t i p l e R e g r e s s i o n o f m on E x p e r i m e n t a l F a c t o r s U s i n g Two-Way I n t e r a c t i o n F a c t o r s 6 2 - v i i i -T a b l e Page 12 R e s u l t s o f S t e p w i s e M u l t i p l e R e g r e s s i o n o f Oy on E x p e r i m e n t a l F a c t o r s U s i n g Two-Way I n t e r a c t i o n F a c t o r s 63 13 R e s u l t s o f S t e p w i s e M u l t i p l e R e g r e s s i o n o f ruo o n E x p e r i m e n t a l F a c t o r s U s i n g Two-Way I n t e r a c t i o n F a c t o r s 6 3 14 R e s u l t s o f S t e p w i s e M u l t i p l e R e g r e s s i o n o f H u n t e r "L" V a l u e s on E x p e r i m e n t a l F a c t o r s U s i n g S i n g l e F a c t o r s O n l y 65 15 R e s u l t s o f S t e p w i s e M u l t i p l e R e g r e s s i o n o f H u n t e r " a " V a l u e s on E x p e r i m e n t a l F a c t o r s U s i n g S i n g l e F a c t o r s O n l y 65 16 R e s u l t s o f S t e p w i s e M u l t i p l e R e g r e s s i o n o f H u n t e r "b" V a l u e s on E x p e r i m e n t a l F a c t o r s U s i n g S i n g l e F a c t o r s O n l y 66 17 R e s u l t s o f S t e p w i s e M u l t i p l e R e g r e s s i o n o f H u n t e r "L" V a l u e s on E x p e r i m e n t a l F a c t o r s U s i n g Two-Way I n t e r a c t i o n F a c t o r s 66 18 R e s u l t s o f S t e p w i s e M u l t i p l e R e g r e s s i o n o f H u n t e r " a " V a l u e s on E x p e r i m e n t a l F a c t o r s U s i n g Two-Way I n t e r a c t i o n F a c t o r s 67 19 R e s u l t s o f S t e p w i s e M u l t i p l e R e g r e s s i o n o f H u n t e r "b" V a l u e s on E x p e r i m e n t a l F a c t o r s U s i n g Two-Way I n t e r a c t i o n F a c t o r s 6 7 20 R e s u l t s o f A n a l y s i s o f V a r i a n c e f o r t h e E f f e c t o f P y r o p h o s p h a t e on t h e L e v e l o f SO2 i n P r o c e s s e d A p p l e S l i c e s 70 21 R e s u l t s o f A n a l y s i s o f V a r i a n c e f o r the. E f f e c t o f A p p l e V a r i e t y on t h e L e v e l o f S O 2 i n P r o c e s s e d A p p l e S l i c e s 70 22 R e s u l t s o f A n a l y s i s o f V a r i a n c e f o r t h e Co m b i n e d E f f e c t s o f S t o r a g e Time a nd T e m p e r a t u r e on t h e T o t a l S u g a r C o n t e n t o f P r o c e s s e d A p p l e S l i c e s 72 - i x -T a b l e Page 23 R e s u l t s o f A n a l y s i s o f V a r i a n c e f o r t h e E f -f e c t o f S t o r a g e Time on t h e R e d u c i n g S u g a r C o n t e n t o f P r o c e s s e d A p p l e S l i c e s 72 24 R e s u l t s o f A n a l y s i s o f V a r i a n c e f o r t h e E f -f e c t s o f S t o r a g e T e m p e r a t u r e on t h e Re-d u c i n g S u g a r C o n t e n t o f P r o c e s s e d A p p l e S l i c e s 75 25 R e s u l t s o f A n a l y s i s o f V a r i a n c e f o r t h e E f -f e c t s o f S 0 9 on t h e R e d u c i n g S u g a r C o n -t e n t o f P r o c e s s e d A p p l e S l i c e s 75 26 R e s u l t s o f A n a l y s i s o f V a r i a n c e f o r t h e E f -f e c t s o f P r e p a r a t o r y T r e a t m e n t s on t h e R e d u c i n g S u g a r C o n t e n t o f P r o c e s s e d A p p l e S l i c e s 76 27 R e s u l t s o f A n a l y s i s o f V a r i a n c e f o r t h e E f -f e c t s o f P r e p a r a t o r y T r e a t m e n t s on t h e A s c o r b i c A c i d C o n t e n t o f P r o c e s s e d A p p l e S l i c e s 76 28 R e s u l t s o f A n a l y s i s o f V a r i a n c e f o r t h e E f -f e c t s o f S t o r a g e Time on t h e L e v e l s o f V i t a m i n C i n P r o c e s s e d A p p l e S l i c e s 77 29 R e s u l t s o f A n a l y s i s o f V a r i a n c e f o r t h e E f -f e c t s o f A d d e d C a l c i u m on t h e A s c o r b i c A c i d C o n t e n t o f P r o c e s s e d A p p l e S l i c e s 77 30 R e s u l t s o f A n a l y s i s o f V a r i a n c e f o r t h e E f -f e c t s o f A p p l e V a r i e t y on t h e A s c o r b i c A c i d C o n t e n t o f P r o c e s s e d A p p l e S l i c e s 79 31 R e s u l t s o f A n a l y s i s o f V a r i a n c e f o r t h e E f -f e c t s o f S t o r a g e Time o n t h e pH o f P r o -c e s s e d A p p l e S l i c e s 79 32 R e s u l t s o f A n a l y s i s o f V a r i a n c e f o r t h e E f -f e c t s o f S t o r a g e T e m p e r a t u r e on t h e pH o f P r o c e s s e d A p p l e S l i c e s 80 33 R e s u l t s o f A n a l y s i s o f V a r i a n c e f o r t h e E f -f e c t s o f P r e p a r a t o r y M e t h o d a n d L e v e l o f S O 2 on t h e pH o f P r o c e s s e d A p p l e S l i c e s 80 - x -R e s u l t s of A n a l y s i s of V a r i a n c e f o r the E f -f e c t s of Calcium on the pH of Processed Apple S l i c e s R e s u l t s of A n a l y s i s of Variance f o r the E f -f e c t of Pyrophosphate on the pH Value of Processed Apple S l i c e s R e s u l t s of A n a l y s i s of V a r i a n c e f o r the E f -f e c t s of Apple V a r i e t y on the pH of Processed Apple S l i c e s R e s u l t s of A n a l y s i s of Variance f o r the E f -f e c t o f B a c k f l u s h Gas on the pH o f Pro-cessed Apple S l i c e s R e s u l t s of A n a l y s i s of V a r i a n c e f o r the E f -f e c t of Time on the Four Q u a l i t y Para-meters i n the Sensory E v a l u a t i o n of Processed Apple S l i c e s R e s u l t s of A n a l y s i s of Variance f o r the E f -f e c t s of Storage Temperature on the Four Q u a l i t y Parameters i n the Sensory E v a l u -a t i o n of Processed Apple S l i c e s R e s u l t s of A n a l y s i s of V a r i a n c e f o r the E f -f e c t of Calcium on the Four Q u a l i t y Para-meters i n the Sensory E v a l u a t i o n of Pro-cessed Apple S l i c e s R e s u l t s of A n a l y s i s of V a r i a n c e f o r the E f -f e c t s of Calcium on the Shear R e s i s t a n c e of Processed Apple S l i c e s R e s u l t s of A n a l y s i s of Variance f o r the E f -f e c t s of the P r e p a r a t o r y Treatment on the Shear R e s i s t a n c e Readings of Pro-cessed Apple S l i c e s - x i -9 LIST OF FIGURES Fi g u r e Page 1 Mean L e v e l s of SO2 I n c o r p o r a t e d i n t o Apple T i s s u e s by the D i f f e r e n t P r e p a r a t o r y Methods 55 2 Mean L e v e l s o f Calcium Incorporated i n t o the Apple T i s s u e s by the D i f f e r e n t P r e p a r a t o r y Methods 55 3 The E f f e c t s of Storage Temperature on the L e v e l s of S O 2 Found i n Apple S l i c e s " 69 4 The Changes i n Reducing Sugar Content w i t h Time i n Apple S l i c e s Stored at 22°C and 37°C. 73 - x i i -ACKNOWLEDGMENTS The author wishes to express h i s g r a t i t u d e f o r the a s s i s t a n c e given by Dr. M. A. Tung, Dr. W. D. Powrie, Dr. J . Vanderstoep, Food Science Department and P r o f e s s o r E. L. Watson, A g r i c u l t u r a l E n g i n e e r i n g Department. The w r i t e r a l s o extends h i s a p p r e c i a t i o n f o r the t e c h n i c a l a s s i s t a n c e and encouragement of Mrs. M. R. Garland and Miss L. Robinson o f the Food Science Department. The author would a l s o l i k e to express.his. a p p r e c i -a t i o n t o Sun Rype L t d . of .Kelowna f o r t h e i r h e l p i n s e c u r i n g apples f o r t h i s p r o j e c t . T h i s r e s e a r c h was f i n a n c e d by the B r i t i s h Columbia M i n i s t r y o f A g r i c u l t u r e - x i i i -- 1 -INTRODUCTION Since the end of the second world war, the develop-ment of the p e t r o - c h e m i c a l i n d u s t r y has l e d to an i n c r e a s e i n the types of m a t e r i a l s a v a i l a b l e f o r the packaging of food. During t h i s time, a number of f l e x i b l e wraps became popular i n the food i n d u s t r y , but i t has o n l y been w i t h i n the l a s t f i f t e e n years t h a t f l e x i b l e polymers, capable of w i t h s t a n d i n g the temperatures r e q u i r e d t o s t a b i l i z e low a c i d foods, have been developed (Mermelstein, 1976.) . „With t h i s has come the r i s e of a v a r i e t y of laminated f l e x i b l e r e t o r t pouches which have found widespread acceptance i n some p a r t s of the world, n o t a b l y Japan. In o t h e r a r e a s , however, the appearance of the pouch has been p a r t i c u l a r l y slow. T h i s was e s p e c i a l l y t r u e on the North American c o n t i n e n t where the progress of pouch t e c h -nology has been impeded by the r e f u s a l o f the Food and Drug A d m i n i s t r a t i o n t o g i v e approval f o r i t s use i n the food i n d u s -t r y of the United S t a t e s . Recently, however, with the develop-ment, by C o n t i n e n t a l Can Company of a new heat bonded t r i l a m -i n a t e which does not r e q u i r e .the .use of the o f f e n d i n g p o l y u r e -thane adhesives, the. l a s t o b s t a c l e s to acceptance .of the pouch have been.removed, opening a l a r g e market to t h i s concept. - 2 -Since the p h y s i c a l aspects of the pouch are somewhat d i f f e r e n t to those of c o n v e n t i o n a l g l a s s and t i n p l a t e c o n t a i n -e r s , there a r i s e s the need to e s t a b l i s h food f o r m u l a t i o n s , to conduct heat p e n e t r a t i o n s t u d i e s , and to assess consumer r e -a c t i o n s t o such foods b e f o r e a f u l l s c a l e e n t r y i n t o the f i e l d of pouched food can be attempted. I t i s t h e r e f o r e the purpose of t h i s r e s e a r c h to i n v e s t i g a t e the aspects o f p r o c e s s i n g some f r u i t products i n t h i s manner, to monitor changes which o c c u r r e d over a p r e s e l e c t e d storage p e r i o d and to determine the accept-a b i l i t y o f the samples by a s m a l l group of p a n e l i s t s . D i f f e r -ent v a r i e t i e s of apples were chosen f o r t h i s p r o j e c t s i n c e ap-p l e s are the most important f r u i t crop r a i s e d i n Canada, of which more than ten percent of the t o t a l domestic consumption i s i n the form of canned f r u i t p r o d u c t s . (Canada Year Book, 1975). Si n c e the h i s t o r y and l e n g t h o f storage o f apples can i n f l u e n c e t h e i r subsequent t e x t u r e , and s i n c e processes i n -v o l v i n g pouches are l e s s s t r i n g e n t , apples from t e r m i n a l s t o r -age were used to determine i f s l i c e s of s u i t a b l e q u a l i t y c o u l d be produced. - 3 -REVIEVT O F T H E L I T E R A T U R E The problems a r i s i n g from the p r o c e s s i n g o f apple s l i c e s i n f l e x i b l e r e t o r t pouches f o r t h i s p r o j e c t were d i -v i d e d i n t o four c a t e g o r i e s as f o l l o w s : i ; E s t a b l i s h i n g a safe process time 2. A s s e s s i n g a number of p r e p a r a t o r y treatments 3^ A s s e s s i n g the value and need f o r a number of chemical adjuncts used i n p r o c e s s i n g 4. E v a l u a t i o n of d i f f e r e n t apple v a r i e t i e s taken from t e r m i n a l storage f o r t h i s process Process Time The shape of the r e t o r t pouch presentsa.aithinner p r o f i l e f o r heat p r o c e s s i n g when compared to o t h e r c o n v e n t i o n a l c o n t a i n e r s and t h e r e f o r e , a s h o r t e r heat treatment would be r e -q u i r e d t o achieve m i c r o b i a l s t a b i l i t y . (Thorpe.and A t h e r t o n , 19 72). For t h i s reason, the degree of q u a l i t y d e t e r i o r a t i o n which u s u a l l y accompanies thermal p r o c e s s i n g i n o t h e r c o n t a i n e r s should be l e s s when the pouch i s employed. The e s t a b l i s h m e n t of a process time f o r any product can be c a r r i e d out by e i t h e r d i r e c t measurement or by mathemati-c a l c a l c u l a t i o n . Heat p e n e t r a t i o n methods f o r pouched foods as d e s c r i b e d by Tung e t a l . , (1976) and Tung and Garland (1976) are an example of a d i r e c t measurement and c a l c u l a t i o n of a r e l i a b l e p rocess time. The mathematical method i n v o l v e s the use of the apparatus and method d e s c r i b e d by Dickerson (1965) along w i t h the equation f o r a t h e o r e t i c a l b r i c k shape (Olson and Jackson, 1942) t o p r o v i d e an f - v a l u e which i s subsequently used i n B a l l 1 s t r a i g h t - l i n e semilog h e a t i n g curve equation (Stumbo, 1973) to e s t a b l i s h a process time. The mathematical approach p r o v i d e s a r e l a t i v e l y r e -l i a b l e process time p r o v i d e d t h a t the process m a t e r i a l heats by conduction and i t i s q u i c k l y c a r r i e d out u s i n g r e l a t i v e l y simple apparatus. Heat p e n e t r a t i o n s t u d i e s a l s o p r o v i d e r e -l i a b l e process times but require, care t h a t the slowest heat-i n g p o i n t i n the c o n t a i n e r i s monitored throughout the process f o r a number of runs to reduce the e f f e c t s o f n a t u r a l v a r i a -t i o n . T h i s method a l s o r e q u i r e s much complicated c a l c u l a t i o n which i s time consuming unless there i s access to a computer. Pre p a r a t o r y Methods In the canning i n d u s t r y , a g r e a t number o f p r e p a r a -t o r y treatments have been used f o r the p r e s e r v a t i o n o f f r u i t s and v e g e t a b l e s . G e n e r a l l y , these procedures are c a r r i e d out to accomplish s p e c i f i c purposes such as a i r removal, t i s s u e shrinkage, enzyme i n a c t i v a t i o n , t e x t u r e enhancement and the a d d i t i o n of chemical adjuncts (Bee, 1958; C o l l i n s and jtf i l e y , , 1967; Hoover and M i l l e r , 1975). For the p r o c e s s i n g of apple s l i c e s , i t i s d e s i r a b l e to r e t a i n a f a i r l y f i r m t e x t u r e while - 5 -removing gases, e s p e c i a l l y oxygen and i n a c t i v a t i n g enzymes. Oxygen removal i s necessary to prevent browning and o x i d a t i v e f l a v o u r changes (Hope, 1961). A submerged vacuum i n f u s i o n method d e s c r i b e d by Hoover and M i l l e r (1975) was r e p o r t e d to be s u c c e s s f u l i n the e l i m i n a t i o n of gas and the p r o v i s i o n of a f i n e t e x t u r e w h i l e p e r m i t t i n g the a d d i t i o n of chemical p r e s e r v a t i v e s t o the t i s -sues. C o l l i n s and Wiley (1967) found t h a t t h i s method was the most s a t i s f a c t o r y t o achieve an even d i s t r i b u t i o n of c a l -cium s a l t s throughout apple t i s s u e . The disadvantage of t h i s method was found to be t h a t enzyme a c t i v i t y was not c u r t a i l e d , u n l e s s l i v e steam was used to break the vacuum i n which case the s l i c e s c o u l d not be submerged i n a l i q u i d medium, thus e l i m i n a t i n g the p o s s i b i l i t y of chemical a d d i t i o n . S u l f u r d i -o x i d e , however, i s known to be an i n h i b i t o r o f c e r t a i n enzyme-c a t a l y z e d r e a c t i o n s , n o t a b l y enzymic browning (Lindsay, 19 76) and t h e r e f o r e , i f t h i s chemical i s p r e s e n t i n the t i s s u e s , the importance of enzyme a c t i v i t y i s g r e a t l y reduced. T i s s u e shrinkage i s not as important i n t h i s procedure s i n c e the ad-d i t i o n of f l u i d t o the s l i c e s i n c r e a s e s the d e n s i t y thereby making i t e a s i e r t o a t t a i n a proper f i l l weight* (Gutterson, 1972). Hot b l a n c h i n g , a s . d e s c r i b e d by Lee (1958), p r o v i d e s t i s s u e shrinkage, a i r removal, enzyme i n a c t i v a t i o n , and l i m i -t e d chemical a d d i t i o n . The major disadvantage o f t h i s method i s the l o s s of firmness which occurs w i t h h e a t i n g (Gutterson, - 6 -1972). The a d d i t i o n of f i r m i n g agents, such as c a l c i u m s a l t s , i s known to c o u n t e r a c t s o f t e n i n g due to p r o c e s s i n g (Wiley and Lee, 19 70). A second and more s e r i o u s disadvantage to t h i s process i s the l o s s of s o l u b l e s , p a r t i c u l a r l y n u t r i e n t s , from heat blanched t i s s u e s (Holmquist e t a l . , 1954). A t h i r d method of p r e p a r a t o r y treatment used i n f r u i t and vegetable p r o c e s s i n g i s c o l d d i p p i n g . T h i s method i s used more i n the f r o z e n and r e f r i g e r a t e d storage of these products and i s employed mainly to apply a s u r f a c e c o a t i n g o f chemical p r e s e r v a t i v e s . Enzyme i n h i b i t i o n , a i r removal, and t i s s u e shrinkage are not accomplished by t h i s method and t h e r e f o r e , problems can a r i s e from both o x i d a t i v e and enzymic browning and d i f f i c u l t y c o u l d be encountered when t r y i n g t o achieve an optimum f i l l weight i n a c o n t a i n e r . The browning problems can be g r e a t l y reduced with the a p p l i c a t i o n of s u l f u r d i o x i d e (Lindsay, 1976). The main advantage to t h i s method i s the r e -t e n t i o n of the f r e s h t e x t u r e . Chemical Adjuncts In the p r o c e s s i n g of apple s l i c e s , v a r i o u s chemical a d d i t i v e s can be used to enhance and maintain t h e i r t e x t u r e , f l a v o u r and c o l o u r . I t i s d e s i r a b l e , however, from both an economic and a e s t h e t i c p e r s p e c t i v e , to use as few chemical ad-d i t i v e s as p o s s i b l e i n the p r o c e s s i n g of a l l food m a t e r i a l s . - 7 -T e x t u r e i n a p p l e s l i c e s c a n be a p a r t i c u l a r l y d i f -f i c u l t p r o b l e m s i n c e i t i s r e l a t e d t o a p p l e v a r i e t y , m a t u r -i t y , t y p e a n d l e n g t h o f s t o r a g e , a n d the. p r o c e s s i n g t e c h n i q u e s t o w h i c h t h e y a r e s u b j e c t e d ( W i l e y a n d Thompson, 1960; W i l e y a n d S t e m b r i d g e , 1 9 6 2 ) . C a l c i u m s a l t s a r e p r o v e n f i r m i n g a g e n t s b u t c a n n o t a l w a y s be r e l i e d on t o g i v e a p r o d u c t o f u n i f o r m f i r m n e s s b e c a u s e o f t h e a f o r e m e n t i o n e d v a r i a b l e s . C o l l i n s a n d W i l e y (196 7) r e p o r t e d t h a t t h e d i s t r i b u t i o n o f c a l c i u m s a l t s t h r o u g h o u t t h e f r u i t t i s s u e s h a d a m a r k e d e f f e c t on t h e f i n a l t e x t u r e . The a d d i t i o n o f s u c r o s e a n d t h e r a i s i n g o f t h e pH o f t h e a d d i t i o n medium t o a r a n g e o f 5.5 - 6.5, a l s o was shown t o ha v e a b e n e f i c i a l e f f e c t on t h e f i r m i n g a c t i o n o f a d d e d c a l c i u m i n a p p l e s l i c e s ( W i l e y a n d L e e , 1970; P o n t i n g e t a l . , 1 9 7 1 ) . T h i s f i r m n e s s was s u b s e q u e n t l y m a i n t a i n e d when t h e pH was l o w -e r e d w i t h t h e a d d i t i o n o f c i t r i c a c i d , a w e l l known c h e l a t o r o f c a l c i u m i o n s . C o l o u r i n a p p l e s l i c e s i s e n h a n c e d a n d m a i n t a i n e d w i t h t h e u s e o f v a r i o u s c h e m i c a l a d d i t i v e s . S u l f u r d i o x i d e i s commonly u s e d a nd i s h i g h l y e f f e c t i v e i n m a i n t a i n i n g l i g h t -n e s s i n a p p l e s l i c e s a n d h a s b e e n s u c c e s s f u l f o r t h i s p u r p o s e i n u n p r o c e s s e d r e f r i g e r a t e d a p p l e s l i c e s f o r up t o s e v e r a l w eeks ( P o n t i n g e t a l . , 1 9 7 1 ) . . A s c o r b i c a c i d i s a l s o e f f e c -t i v e i n m a i n t a i n i n g l i g h t n e s s i n a p p l e s l i c e s ( P o n t i n g e t a l . , 1972) b u t i t s c o s t i s much h i g h e r t h a n t h e a c c e p t a b l e s u l f i t e s w h i c h makes i t s u s e l e s s a t t r a c t i v e t o p r o c e s s o r s . P o n t i n g - 8 -e t a l . , (1972) were a l s o able to show t h a t c a l c i u m i o n s were s y n e r g i s t i c with both s u l f u r d i o x i d e and a s c o r b i c a c i d i n m a i n t a i n i n g l i g h t n e s s . I t has a l s o been r e p o r t e d by Timberlake (1957) t h a t m e t a l l i c ions such as copper are r e s p o n s i b l e f o r c a t a l y z i n g the o x i d a t i o n of p h e n o l i c compounds producing a dark c o l o u r i n the j u i c e s of apples and pears. Ortho and polyphosphate ions are known to be c h e l a t o r s of v a r i o u s m e t a l l i c ions i n -c l u d i n g i r o n and c o p p e r , ( E l l i n g e r , 1972) and t h e r e f o r e , c o u l d be u s e f u l i n l e n g t h e n i n g the s h e l f l i f e o f canned apple prod-ucts . Sucrose can be added to processed apple products as a f l a v o u r enhancer although t h i s i s not always done i n i n -dustry, (Hope, 1961). Added sugar a l s o p r o v i d e s a degree of body to the j u i c e s which are r e l e a s e d from apple .tissues when-heated and as s t a t e d e a r l i e r , are thought to enhance the ac-t i o n of c a l c i u m i n f i r m i n g apple t i s s u e s . A number of o r g a n i c a c i d s , n o t a b l y c i t r i c , m a l i c , and fumaric, may a l s o be added to apple s l i c e s t o i n c r e a s e t h e i r t a r t n e s s (Gutterson, 1972) . Ifi many v a r i e t i e s of ap-...J.. p i e s , however, t h i s i s unncecessary s i n c e the n a t u r a l l e v e l s of a c i d s , p a r t i c u l a r l y m a l i c a c i d , are s u f f i c i e n t t o p r o v i d e the r e q u i r e d a c i d i t y (Eheart andMason, 1967). C i t r i c a c i d and to a l e s s e r extent o t h e r o r g a n i c a c i d s are c h e l a t o r s of - 9 -ca l c i u m ions (Gardner, 196 8) and t h e r e f o r e , might have a d e t r i m e n t a l e f f e c t on the t e x t u r e o f apple t i s s u e . V a r i e t i e s In the B r i t i s h Columbia area there are s e v e r a l v a r i e t i e s o f apples produced which are s u i t a b l e f o r pro-c e s s i n g i n c l u d i n g : Golden D e l i c i o u s , Red D e l i c i o u s , New-town P i p p i n s , Winesaps, Spartans, Rome Beauties and Mc-i n t o s h . Some of these v a r i e t i e s can pro v i d e p r o c e s s i n g problems when taken from prolonged storage ( K i t s o n , 1 9 7 6 ) . Mcintosh and Spartan v a r i e t i e s tend t o have a high l e v e l o f c h l o r o p h y l l i n the t i s s u e which when processed, g i v e a grey green c a s t t o the product. Both have r e l a t i v e l y s h o r t s t o r -age l i v e s and are u s u a l l y not a v a i l a b l e a f t e r December of the year of h a r v e s t . Red D e l i c i o u s have very low l e v e l s o f a c i d and do not have very good f l a v o u r when processed. Rome Beauties and Winesaps have a f a i r l y l o n g storage l i f e but have a tendancy to t u r n pink when processed. T h i s i s p o s s i b l y due to the presence o f leucoanthocyanins p r e s e n t i n the t i s -sues. Golden D e l i c i o u s are e x c e l l e n t p r o c e s s i n g apples and have a f a i r l y long storage l i f e o f approximately s i x months a f t e r h a r v e s t . They a l s o have been known t o have a green c a s t when processed. Newtown P i p p i n apples have a very long storage l i f e of about ten months. They have e x c e l l e n t t e x -t u r e and because of t h e i r f a i r l y h igh a c i d content, p r o v i d e - 10 -a good processed product. T h i s v a r i e t y , however, i s a l s o very popular on the f r e s h market. Storage c o n d i t i o n s and h a r v e s t m a t u r i t y a l s o have a profound e f f e c t on the f i n a l q u a l i t y of apple p r oducts. Wiley and Thompson (196 0) found t h a t processed apple s l i c e q u a l i t y was about the same i f apples used from common s t o r -age had o n l y been s t o r e d f o r h a l f the time of apples from c o l d s t o r a g e . They a l s o concluded t h a t apple m a t u r i t y a t h a r v e s t i n f l u e n c e d the l e n g t h of storage f o r which apples c o u l d be h e l d b e f o r e they were past a p r o c e s s i n g q u a l i t y . Long storage times produced processed apple s l i c e s l a c k i n g both firmness and a b r i g h t c o l o u r . Apples h a r v e s t e d a t a post optimum m a t u r i t y produced the b e s t canned apple s l i c e s e s p e c i a l l y i f processed immediately a f t e r h a r v e s t . From t h i s study, they a l s o found t h a t no s i n g l e chemical or phys-i c a l measurement on raw apples was s u i t a b l e f o r p r e d i c t i n g the o v e r a l l q u a l i t y of processed s l i c e s but t h a t shear press measurements on raw s l i c e s showed promise as an i n d i c a t o r of processed s l i c e t e x t u r e . EXPERIMENTAL METHODS EXPERIMENTAL DESIGN For t h i s p r o j e c t i t was decided t h a t a l a r g e pack o f apple s l i c e s would be su b j e c t e d t o a number of d i f f e r e n t t r e a t -ments and undergo a storage t r i a l i n an attempt t o determine an approximate s h e l f l i f e and the e f f e c t o f the v a r i o u s treatment f a c t o r s on i t . The f a c t o r s examined i n c l u d e d two v a r i e t i e s o f apples, the a d d i t i o n o f SO2 which was v a r i e d both by method of a d d i t i o n and l e v e l s , the a d d i t i o n o f c a l c i u m ions which was v a r i e d both by method of a d d i t i o n and l e v e l s , the a d d i t i o n o f pyrophosphate ions which was v a r i e d by methods of a d d i t i o n and l e v e l s , the replacement of a i r i n the pouch by two d i f f e r e n t gases, and three d i f f e r e n t methods of p r e h e a t i n g treatments be-for e thermal p r o c e s s i n g . The experiment was s e t up so t h a t a t o t a l of 2 9 d i f -f e r e n t experimental sample groups were produced. The sample groups were each d i v i d e d i n h a l f and s t o r e d a t d i f f e r e n t tem-pe r a t u r e s (22 and 37° C) to note the e f f e c t s on s h e l f l i f e . W i t h i n the d i f f e r e n t experiments there were s e v e r a l comparisons which c o u l d be made on each o f the f a c t o r s w h ile m a i n t a i n i n g the other c o n d i t i o n s constant. - 12 -A simple a n a l y s i s of v a r i a n c e employing a Duncan's M u l t i p l e Range t e s t f o r d i f f e r e n c e s between ranked samples at a 5% p r o b a b i l i t y l e v e l was used. Simple and stepwise m u l t i p l e r e g r e s s i o n procedures were a l s o employed t o determine the r e -l a t i o n s h i p s among the d i f f e r e n t v a r i a b l e s and measurements made on the samples. These analyses were submitted t o the U n i v e r s i t y ' s I.B.M. computer f o r c a l c u l a t i o n . PROCESSING Process Time Determination For the purposes of t h i s r e s e a r c h , a thermal process time was determined. T h i s goal was accomplished by u s i n g two procedures. Thermal D i f f u s i v i t y S t u d i e s The f i r s t method used t o e s t a b l i s h a thermal process time i n v o l v e d the measurement of the thermal d i f f u s i v i t y o f apple t i s s u e i n an attempt to a r r i v e a t a r a t e o f heat pene-t r a t i o n which c o u l d then be used to determine a process time depending on shape and dimensions of the c o n t a i n e r . Because the pouch was somewhat d i f f e r e n t i n geometric shape than the co n v e n t i o n a l t i n p l a t e can and the process technology f o r the pouch was l i m i t e d , i t was f e l t t h a t the measurement of thermal - 13 -d i f f u s i v i t y of apple tissue might be b e n e f i c i a l i n determining a process time for apple s l i c e s i n a pouch and perhaps a rapid method for ca l c u l a t i n g a process time for any size of pouch. The measurement of thermal d i f f u s i v i t y of apple t i s -sue involved the use of an apparatus designed s p e c i f i c a l l y for this purpose (Dickerson, 1965). The apparatus consisted of a stainle s s s t e e l c y l i n d r i c a l container and two plexiglas end caps. One of the caps was d r i l l e d , threaded and f i t t e d with two 1.6 mm diameter thermocouple probes, one positioned at the outer edge of the cap while the other passed through the cen-t r a l axis. This permitted the outer thermocouple to come i n contact with the wall of the cylinder at a position midway a-long the length of the cylinder when the end cap with thermo-couples was inserted i n the end, while the central thermocouple was positioned i n the geometric centre of the container. The cylinder had an inner diameter of 35 mm and a void length of 2 3 cm. In order to use raw apple tissue i n thi s apparatus i t was necessary to prepare discs of apple which were pe r f e c t l y round and of a s u f f i c i e n t diameter to f i t snugly into the c y l -inder. Each disc had an even thickness so that adjacent s l i c e s i n the cylinder would f i t snugly together leaving no spaces for the c o l l e c t i o n of juices. The discs were c a r e f u l l y threaded on to the probes so that the central thermocouple penetrated the - 14 -exact c e n t e r of a d i s c while the o t h e r probe was p a r t i a l l y em-bedded i n the edge of the d i s c . Care was taken to gauge the t h i c k n e s s of each d i s c so t h a t the l a s t d i s c t o be threaded on ( c e n t r a l p o s i t i o n i n the c y l i n d e r ) was o n l y p e n e t r a t e d t o one-h a l f i t s t h i c k n e s s . T h i s ensured a more r e l i a b l e r e a d i n g than would have been achieved i f the ends of the probes had been p o s i t i o n e d a t the j u n c t i o n between two s l i c e s . When the probes had been thus embedded i n the d i s c s , the e n t i r e assembly was i n s e r t e d c a r e f u l l y i n t o the c y l i n d e r . A d d i t i o n a l d i s c s were then i n s e r t e d i n the other end u n t i l the c y l i n d e r was f i l l e d and the remaining end cap was i n s e r t e d so t h a t the apple d i s c s were compressed snugly t o g e t h e r . Both end caps were s e a l e d with waterproof tape and c i r c u l a r hose clamps were a p p l i e d to prevent a blowout of the cap when the t i s s u e expanded w i t h i n -c r e a s i n g temperature. The f u l l c y l i n d e r was then immersed to the l e v e l o f the top clamp on the probe end of the c y l i n d e r i n an i n s u l a t e d 4.5 1 water bath a t room temperature. S u f f i c i e n t time was a l -lowed f o r the temperature to e q u i l i b r a t e between the c y l i n d e r and the water bath before the experiment was s t a r t e d . The water bath was equipped with a submerged h e a t i n g c o i l , a pro-p e l l e r - t y p e s t i r r e r to ensure uniform d i s t r i b u t i o n o f heat, and a l a r g e t e m p e r a t u r e - s e n s i t i v e probe. Both the h e a t i n g element and the t e m p e r a t u r e - s e n s i t i v e probe were connected to - 15 -a temperature programmer ( V a l l e y Forge Instrument Co.) which p r o v i d e d a constant r i s e i n temperature w i t h time i n the water bath and was governed by feedback from the t e m p e r a t u r e - s e n s i t i v e probe. The o u t e r ends of the thermocouple probes were f i t t e d w i t h connector plugs f o r the attachment of copper/constantan leads t o a p o t e n t i o m e t r i c data l o g g e r ( D i g i t e c Model 1268, U n i t e d Systems Corp.) which c o u l d monitor the changes i n temper-ature of the two thermocouple probes by r e c o r d i n g the m i l l i v o l t s i g n a l at one minute i n t e r v a l s . As the temperature of the water bath r o s e , so d i d the temperature r e c o r d e d by the o u t e r probe. Due t o the i n -s u l a t i n g nature of the apple t i s s u e there was a h e a t i n g l a g a t the p o s i t i o n of the c e n t r a l probe. When the c e n t r a l temp-e r a t u r e began to i n c r e a s e , the temperature recorded by the outer probe was a l r e a d y much h i g h e r . I n i t i a l l y the r a t e of temperature change per u n i t time of the c e n t r a l probe was not as f a s t as t h a t of the outer probe but e v e n t u a l l y the d i f f e r -ence between the two r a t e s decreased u n t i l the temperature d i f f e r e n c e between the two probes became e s s e n t i a l l y c o nstant. T h i s i s d e s c r i b e d as the l i n e a r h e a t i n g r a t e s of both probes. The thermal d i f f u s i v i t y o f the apple t i s s u e c o u l d then be c a l c u l a t e d u s i n g the equation: - 16 -Equation I cc = A(R 2) 4 ( T r - T 0) (Dickerson, 1965) whe r e : cc = thermal d i f f u s i v i t y (in^/min) A = d^ = the l i n e a r r a t e of h e a t i n g (°F/min) dt R = the i n n e r r a d i u s of the c y l i n d e r (in) T r = temperature r e g i s t e r e d by the o u t e r thermocouple (o F) T 0 = temperature r e g i s t e r e d by the i n n e r thermocouple (°F) Since the h e a t i n g r a t e s a t the two p o s i t i o n s were not q u i t e equal nor was the temperature d i f f e r e n c e e x a c t l y constant but seemed to f l u c t u a t e back and f o r t h , a method to o b t a i n a mean h e a t i n g r a t e was d e v i s e d . A Wang 600 desk top c a l c u l a t o r with a l i n e a r r e g r e s s i o n a n a l y s i s program was used to o b t a i n the s t r a i g h t l i n e parameters f o r the l i n e a r p o r t i o n s of the two h e a t i n g curves. The time-temperature data f o r these p o r t i o n s were submitted to the program to r e c e i v e : - 17 -Equation I I T = a + b t where: T = temperature (°F) t = time (min) In t h i s e quation the slope or b value i s equal to the h e a t i n g r a t e and because the h e a t i n g r a t e s f o r the curves were never q u i t e e q u a l , i t was decided t o take t h e i r mean as a common h e a t i n g r a t e f o r both thermocouple probes. Once having e s t a b l i s h e d a separate o r d i n a t e i n t e r c e p t f o r each h e a t i n g curve along w i t h a time from the a b s c i s s a common to both l i n e a r p o r t i o n s , the two corres p o n d i n g temperatures, T r and T Q , were e s t a b l i s h e d . When a l l o f the parameters and the temperature v a l u e s f o r each probe a t a given time had been e s t a b l i s h e d , the ap-p r o p r i a t e v a l u e s were s u b s t i t u t e d i n t o the thermal d i f f u s i v i t y equation (Equation I) and the thermal d i f f u s i v i t y o f apple t i s -sue was c a l c u l a t e d . T h i s o p e r a t i o n was c a r r i e d out 21 times and the thermal d i f f u s i v i t y v alues were t o t a l l e d and a mean and standard d e v i a t i o n were c a l c u l a t e d . In order t o reduce the p o s s i b i l i t y of an e r r o r r e s u l t i n g i n a process too s h o r t t o achieve p a s t e u r i z a t i o n , a value o f three times the standard d e v i a t i o n was s u b t r a c t e d from the mean value o f the thermal d i f f u s i v i t y g i v i n g a value known as the m o d i f i e d thermal d i f f u s i v i t y (<**) . - 18 -Once the value of a* had been determined, i t could be used i n the equation, derived from the works of B a l l (1928)', Olson and Jackson (1942), and Stumbo (1973) for rectangular food containers to determine the f^ or time (min) required for the l i n e a r portion of a semilog heating curve to traverse one log cycle. Equation III f h = .933  a* [(^ 2) + (H2} + ( c J 2 ) ] (Olson and Jackson, 1942) where: f h = time required for the l i n e a r portion of a semilog heating curve to traverse 1 log cycle (min) a* = corrected thermal d i f f u s i v i t y (in 2/min) a = h the width of the pouch (in) b = % the length of the pouch (in) c = h the thickness of the pouch (in) Using the f^ derived for a pouch of apple tissue and Stumbo's Method (Stumbo, 1973), a process time was,calculated as follows: - 19 -Equation IV B = f h ( l o g JcbJh- 1 0^) where: B = process time (min) j c j i = l a g f a c t o r i n a h e a t i n g curve f o r the centre of a c o n t a i n e r . 1^ = d i f f e r e n c e between the r e t o r t temperature and the product temperature a t the s t a r t o f h e a t i n g (°F) *c = d i f f e r e n c e between the r e t o r t temperature and the temperature i n the centre of the product at the end of h e a t i n g (°F) For the purpose of t h i s r e s e a r c h and s i n c e the pouch most c l o s e l y resembles a b r i c k shape, a ^ch v a l u e °f 2.064 was chosen- (Olson and Jackson, 1942) .• The i n i t i a l c e n t r e tempera-t u r e of the product, the centre temperature a t steam o f f , and the r e t o r t temperature were s e t a t 80, 180 and 220°F r e s p e c t i v e l y . The process time or time from when t h e r e t o r t reaches i t s o p e r a t i n g temperature u n t i l steam o f f (min) i s c a l -c u l a t e d u s i n g the e q u a t i o n : Equation V - 20 -w h e r e : 1 = t h e t i m e t a k e n f o r t h e r e t o r t t o r e a c h i t s o p e r a t i n g t e m p e r a t u r e a f t e r t h e s t e a m i s t u r n e d o n . H e a t P e n e t r a t i o n The s e c o n d m e thod u s e d t o d e t e r m i n e a p r o c e s s i n g t i m e f o r t h e a p p l e s l i c e s was a h e a t p e n e t r a t i o n m e t h o d (Tung, 1974) w h i c h was u s e d t o v e r i f y t h e r e s u l t s o f t h e t h e r m a l d i f -f u s i v i t y s t u d y . B e c a u s e a p p l e s a r e n a t u r a l l y a c i d i c (pH l e s s t h a n 4.0) t h e h e a t i n g r e q u i r e m e n t s d i d n o t n e e d t o be as s t r i n -g e n t as f o r n o n - a c i d p r o d u c t s t o a c h i e v e m i c r o b i a l s t a b i l i t y i n a s e a l e d c o n t a i n e r (Stumbo, 1 9 7 3 ) . I t was t h e r e f o r e d e -c i d e d t h a t t h e a c h i e v e m e n t o f a t e m p e r a t u r e o f 180°F (82.2°C) a t t h e p o i n t o f g r e a t e s t t e m p e r a t u r e l a g w o u l d be s u f f i c i e n t ( B a l l , 1 9 3 8 ) . B e c a u s e o f t h e i n s u l a t i n g n a t u r e o f a p p l e t i s -s u e a n d t h e g e o m e t r i c s h a p e o f t h e p o u c h , t h e p o i n t o f g r e a t e s t t e m p e r a t u r e l a g was c o n s i d e r e d t o be t h e g e o m e t r i c c e n t r e o f an a p p l e s l i c e l o c a t e d p r e c i s e l y a t t h e g e o m e t r i c c e n t r e o f a p o u c h . To e s t a b l i s h t h e p r o c e s s c o n d i t i o n s , r e t o r t a b l e p o u c h e s were e q u i p p e d w i t h m e t a l p a c k i n g g l a n d s ( 0 . F. E c k -l a n d L t d . ) n e a r t h e b o t t o m c e n t r e o f t h e c o n t a i n e r . T h i s f a c i l i t a t e d t h e e n t r y o f c o p p e r / c o n s t a n t a n t h e r m o c o u p l e s t o - 21 -monitor the temperature i n the package. The 15.2 x 2 3.4 cm f l e x i b l e packages were constructed of 0.5 mil Mylar/0.35 mil aluminium f o i l / 3 . 0 mil C-79 p o l y o l e f i n (Continental Can Co.). The thermocouple junction was inserted into the centre of a f a i r l y large apple s l i c e which was secured i n a h e l i c a l wire c o i l of 2.5 cm diameter and 6-7 cm i n length. The r i g i d c o i l maintained the package thickness at 2.5 cm (1 in) and pre-vented the s l i c e from being dislodged from the thermocouple during subsequent movement of the pouch. Data from packages i n which the thermocouple had moved from the central position were l a t e r discarded. The thermocouple wire after passing through the packing gland to the exterior of the package was maintained at a length of at least 10 m. This allowed for passage through the r e t o r t l i d and attachment to a potentio-metric data logger (Digitec, United Systems Corp.) consisting of a d i g i t a l voltmeter coupled to a 20 point scanner and pr i n t e r . The sp e c i a l pouches were then f i l l e d with 270 g of prepared s l i c e s , 30 g sucrose, and immediately sealed using a Multivac vacuum/gas sealer. Headspace i n the package was mini-mized before sealing by manually f l a t t e n i n g the pouch above the product near the sealing area. The sealing was accomplished following evacuation and a nitrogen backflush. - 22 -T h e r m a l p r o c e s s i n g was c a r r i e d o u t i n a 60 cm d i a -m e t e r v e r t i c a l l a b o r a t o r y r e t o r t u s i n g a 220°F (108°C) c o o k w i t h 8 p s i g a i r o v e r p r e s s u r e . The p o u c h e s w e r e a r r a n g e d h o r i -z o n t a l l y on t h e o p e n w o r k s h e l v e s o f t h e r e t o r t r a c k a n d s p a c e d s o as t o a l l o w c i r c u l a t i o n o f t h e h e a t i n g medium. A w i r e s c r e e n was c l i p p e d o v e r e a c h s h e l f t o p r e v e n t p o u c h f l o t a t i o n . Dummy p o u c h e s f i l l e d w i t h w a t e r w e r e u s e d t o m a i n t a i n a f u l l r e t o r t l o a d o f 30 p a c k a g e s a t a l l t i m e s . T h e r m o c o u p l e s w e r e a t t a c h e d t o t h e r a c k s n e a r t h e t e s t p o u c h e s t o m o n i t o r t h e r e t o r t temp-e r a t u r e s t h r o u g h o u t e a c h p r o c e s s r u n . W a t e r i n t h e r e t o r t was p r e h e a t e d t o 160°F (71°C), t h e l o a d e d r a c k was i m m e r s e d , t h e r e t o r t c l o s e d a n d b r o u g h t up t o t h e p r o c e s s i n g t e m p e r a t u r e o f 220°F (108°C) i n s e v e n m i n u t e s . R e t o r t a n d p r o d u c t c e n t r e t e m p e r a t u r e s w e re m o n i t o r e d a t one m i n u t e i n t e r v a l s a n d t h e d a t a w e r e r e c o r d e d b y t h e d a t a l o g g e r f o r a 15 m i n u t e h e a t i n g t i m e f o l l o w e d b y a 15 m i n u t e c o o l i n g p e r i o d d u r i n g w h i c h a l l t h e r m o c o u p l e s r e g i s t e r e d a^ maximum o f a t l e a s t 1 3 0 ? F (82.2°C). The p r o c e s s d e t e r m i n a t i o n was t h e n c a r r i e d o u t u s i n g a s e r i e s o f c o m p u t e r o r i e n t e d p r o c e d u r e s d e s c r i b e d b y Tung and G a r l a n d (19 76) w h i c h u t i l i z e d t h e h e a t p e n e t r a t i o n d a t a f r o m t h e d a t a l o g g e r t o p r o v i d e e s t i m a t e s o f a p r o c e s s t i m e r e q u i r e d t o a c h i e v e a s p e c i f i e d l e t h a l i t y a t a s i n g l e p o i n t w i t h i n t h e p r o d u c t . D a t a f r o m two s e p a r a t e r e t o r t r u n s w e r e u t i l i z e d i n o r d e r t o p a r t i a l l y a c c o u n t f o r t h e e f f e c t s o f r u n _ t o r u n v a r i a -t i o n o f t h e t h e r m a l p a r a m e t e r s . - 23 -The heat penetration data were entered on punch cards and an I.B.M. 370/168 computer was used for i t s analysis. The analysis occurred i n four basic steps. The f i r s t step converted the m i l l i v o l t readings from the data logger to temperatures i n °F. The come up time was also supplied at t h i s stage so that i n addition to supplying the process l e t h a l i t y , which i s i r r e l -evant for acid foods requiring only pasteurization, i t supplied time-temperature data pairs on separate cards which were re-quired for the next step. The second step made use of a 10 inch Calcomp p l o t t e r to display the data i n the form of the log of the temperature difference between the r e t o r t and the product for the heating curve or the log of the temperature difference between the prod-uct and the cooling water for the cooling curve as a function of time. The r e t o r t and cooling water temperatures were the means derived from the re p l i c a t e r e t o r t thermocouple data and were supplied to t h i s program along with the time-temperature data pairs which had been separated into t h e i r respective heating and cooling curves. The heating curves (log g versus time, where g rep-resented the difference between the temperatures of the re t o r t and the product at a sp e c i f i e d time) generally contained three regions: an i n i t i a l curved portion representing the lag period for the centre temperature, a l i n e a r portion v e r i f y i n g the the o r e t i c a l semilog decrease of the temperature difference - 24 -between r e t o r t and product centre temperatures, and a f i n a l region showing deviations of the data from the l i n e a r model due to widening precision l i m i t s of measurement as the prod-uct temperature approached the re t o r t temperature. Cooling curves (log m versus time:' where m represents the difference between the temperatures of the product and the cooling water at a s p e c i f i c time) demonstrated an i n i t i a l cooling lag upon the commencement of cooling procedures, followed by a l i n e a r portion which represented a steady-state cooling. This graphical examination of the data was useful for i d e n t i f y i n g the beginnings and ends of the l i n e a r regions of heating and cooling curves as was required for the next step of the computer program. Data points that deviated from the expected trend could at t h i s time be checked for possible keypunching errors. The t h i r d program of the series made use of the data taken from the l i n e a r portions of the curves, and applied least-squares l i n e a r regression to compute heating and cooling curve parameters. Data selection for t h i s program was f a c i l i -tated by the conversion of the time-temperature data to i n d i v i d -ual cards i n step one. The heating rate ( f h ) was calculated as the negative reci p r o c a l slope of the straight l i n e portion of the heating curve. The ps e u d o - i n i t i a l heating temperature (Tpi n) was - 25 -d e r i v e d by e x t r a p o l a t i n g the s t r a i g h t l i n e p o r t i o n of the semi-l o g h e a t i n g curve t o -40% of the r e t o r t l a g p e r i o d (Stumbo, 1973). With the i n i t i a l temperature of the product ( T ^ ) , Tp^^ was used to c a l c u l a t e the h e a t i n g l a g f a c t o r J c h . Equation VI _ T r ~ T p i h 3 ch -T r " T i h The p s e u d o - i n i t i a l c o o l i n g temperature (Tp-_c) was c a l c u l a t e d by e x t r a p o l a t i o n o f the l i n e a r p o r t i o n of the c o o l i n g curve to the "steam-off" time i n the p r o c e s s . The c o o l i n g l a g f a c t o r ( 3 C C ) was then computed as: Equation VII _ Tw " T p i c Jcc = Tw ~ T i c where: T w = the c o o l i n g water temperature (°F) T i c = the product temperature a t the "steam-off" time (°F) The c o o l i n g r a t e ( f c ) , the time r e q u i r e d f o r the s t r a i g h t l i n e p o r t i o n of the semilog c o o l i n g curve to t r a v e r s e one l o g c y c l e on the c o o l i n g r e c o r d was c a l c u l a t e d to use i n e x t r a p o l a t i n g the c o o l i n g curve to "steam-off" f o r e v a l u a t i o n o f T p i c -- 26 -T h i s step p r o v i d e d a t a b u l a t i o n of the p e r t i n e n t thermal parameters f o r a l l experimental data i n a s e r i e s i n -c l u d i n g means and standard d e v i a t i o n s . The f o u r t h step o f the c a l c u l a t i o n of the process time was c a r r i e d out with a program on a Wang 600 advanced programmable desktop c a l c u l a t o r . Thermal parameter means and standard d e v i a t i o n s from the p r e v i o u s step were used f o r t h i s purpose. Since the product i n t h i s r e s e a r c h was c o n s i d e r e d to be an a c i d food (pH < 4.5) the approach taken was to assure t h a t c o n t a i n e r s with a h e a t i n g r a t e three standard d e v i a t i o n s above the mean (fh*) a t t a i n e d a s p e c i f i e d i n t e r n a l temperature. The s p e c i f i e d temperature i n t h i s case was 180°F, a temperature adequate f o r the d e s t r u c t i o n o f non-spore-bearing organisms (Stumbo, 1973). The equation used to c a l c u l a t e the p r o c e s s i n g time was: Equation V I I I B = f h * ( l o g J c h I h - l o g g c) where: B = process time (min) Ih = r e t o r t temperature minus the i n i t i a l temp-e r a t u r e o f the product (°F) - 27 -9C = r e t o r t temperature minus the product centre temperature at "steam-off" (°F) f^* = the mean f^ + 3 S.D. f^ ^ch = t n e mean 3 ch Since T c i n t h i s research had a fixed value of 180°F the f c derived also had a fixed target value. The operators process time ( P t ) , the time i n t e r v a l from when the re t o r t f i r s t reaches i t s operating temperature u n t i l "steam-off" i s derived from the equation: Equation IX P t = B - 0.4 1 where: 1 = the come up time (min) The figure thus derived from t h i s procedure was then used as the process time for the apple s l i c e s i n the test pack. SAMPLE PREPARATION AND PROCESSING Apples of the fancy grade were used for t h i s project. Three v a r i e t i e s were examined as possible subjects for processing of which two were chosen. These were Newton Pippins and Winesaps with Golden Delicious being d i s q u a l i f i e d because of colour, tex-ture and flavour problems as determined i n the preliminary tests. - 28 -The apples f o r the main experiment were r e f r i g e r a t e d (4°C) u n t i l p r o c e s s i n g a t which time they were p e e l e d and cored by a mechanical p e e l e r . S l i c i n g was accomplished with a rad-i a l e i g h t s e c t i o n k i t c h e n s l i c e r which produced s l i c e s of r e l -a t i v e l y uniform s i z e . The apple s l i c e s were then immersed i n a 1% NaCl s o l u t i o n to prevent browning on the cut s u r f a c e . From t h i s p o i n t the treatment o f the s l i c e s d i v e r g e d a c c o r d i n g to the pretreatments to be examined. Apple t i s s u e has a h i g h l y porous nature and conse-q u e n t l y c o n t a i n s a g r e a t d e a l o f gas trapped i n i n t e r s t i t i a l spaces. Oxygen present i n a i r i s known to have a s i g n i f i c a n t e f f e c t on the r a t e and degree of browning which can occur i n processed apple s l i c e s ( O l l i v e r , 1971). For t h i s reason i t was deemed important to remove as much of the gas as p o s s i b l e t o determine whether t h i s would s i g n i f i c a n t l y r e t a r d or pre-vent darkening d u r i n g l a t e r s torage. Gas removal was accomplished by submerging the s l i c e s i n a l i q u i d w i t h i n a vacuumizing c o n t a i n e r , and then drawing a vacuum o f - 10 p s i g . Under these c o n d i t i o n s a l a r g e amount of gas was removed i f the s l i c e s were allowed a 10 min " b o i l i n g -o f f " p e r i o d . Reentry o f a i r i n t o the t i s s u e was prevented on b r e a k i n g of the vacuum by the surrounding l i q u i d which was drawn i n t o the t i s s u e . With t h i s method the l i q u i d c o u l d be used as a v e h i c l e t o achieve the e n t r y o f some of the p r e s e r v -a t i v e s such as c a l c i u m i o n s , pyrophosphate ions or S0 2 i n t o - 29 -the t i s s u e . These were added i n the form of calcium chloride, sodium acid pyrophosphate and sodium b i s u l f i t e solutions re-spectively. This was the basis for one of the pretreatment methods. A second method of pretreatment was less concerned with the removal of a i r but concentrated more on the applica-tion of preservatives to the outer surface of the s l i c e s . The advantage of this method was that i t was easy, economical and the apples would not suffer textural changes due to physical changes such as gas removal or heating. With t h i s method the apple s l i c e s were dipped i n containers of room temperature preservative solutions. A 2 min dip was used i n the applica-tion of SC>2 and pyrophosphate; a 5 min application was re-quired for Ca++ ions. B a s i c a l l y three types of solutions were used with t h i s method - calcium chloride solutions, sodium b i -s u l f i t e solutions and sodium b i s u l f i t e with sodium acid pyro-phosphate solutions. The t h i r d pretreatment method involved a hot blanch of 1 min at 180°F to remove gases and inactivate enzymes. The solution used for the blanch was also used as a vehicle for the addition of preservatives. Two types of solution were used i n thi s case, sodium b i s u l f i t e or the combination of sod-ium b i s u l f i t e and sodium acid pyrophosphate. If C a + + ions were to be added to the tissue during t h i s method, they were added i n the form of a cold dip before the hot blanch. In a l l cases, treatment with C a + + ions preceeded SO? treatments. - 30 -The preservatives were added to the s l i c e s at various levels depending on the method of pretreatment. Calcium ions were added as a firming agent at levels of 0.25% of the solu-tion weight for the vacuum solution and 0.5% of the solution weight for the cold dip. Sodium acid pyrophosphate was added at levels of 1.0% of the solution weight i n the cold dip solu-tion and 0.33% of the solution weight i n the vacuum solution. This chemical, added for the maintenance of whiteness i n apple s l i c e s , was always included i n the same solutions as the S O 2 . Sulfur dioxide was added at levels of 560 parts per m i l l i o n (ppm) of solution i n the vacuum solution, 1160 ppm and 1080 ppm of solution for the hot blanches of Newtowns and Winesaps respectively. Three l e v e l s of S O 2 were used i n the cold dips to obtain a comparison of the effectiveness of t h i s method of addition. These leve l s included a low, 1730 ppm of solution, a medium of 2160 ppm of solution and a high of 2810 ppm of solution. The addition of S 0 2 was made to preserve the l i g h t -ness of the apple s l i c e s . In general the leve l s used i n the evacuation process were always much lower because of the i n -creased e f f i c i e n c y of t h i s method of addition. Once the apple s l i c e s had undergone the pretreat-ments they were weighed into 270 g l o t s and placed i n numbered f l e x i b l e r e t o r t pouches with 30 g of sucrose which gave a f i n a l pouch weight of 300 g. The pouches were then manually - 31 -flattened to reduce the headspace and sealed i n a Multivac vac-uum/gas sealer. Sealing was accomplished with the removal of most of the remaining a i r i n the pouch and replacement with an i n e r t packing gas such as N 2 or CO2. Following t h i s , sealing was carried out. The pouches were then placed on the rack of a 60 cm diameter v e r t i c a l laboratory r e t o r t with no more than 35 pouches per run. The r e t o r t was f i l l e d with water and pre-heated to 160°F (70°C) before the rack was lowered i n and the r e t o r t closed. Once the re t o r t was sealed the process was started with an operating temperature of 220°F (108°C) and a i r overpressure of 8 psig to maintain pouch i n t e g r i t y and thick-ness. The come up time for the r e t o r t was 7 min. The process time (P-j-) derived from the thermal d i f f u s i v i t y studies was 19.8 min aft e r which time the steam was shut o f f and cold water cooling and pressure release was begun. The cooling procedure .was maintained u n t i l the r e t o r t reached a temperature of 100°F (38°C) at which time the pressure had diminished to atmospheric and the r e t o r t was opened. The pouches were then removed, dried and sorted into d i f f e r e n t groups according to storage temperature treatment (22° or 35° C). Calcium chloride was added to the apples because c a l -cium ions bind with pectic substances notably p e c t i n i c acids of a low methoxyl count to give a firm texture (Hodge and Osman, 1976). This reagent must be used with caution, however, as too much can impart a woody texture and b i t t e r flavour to f r u i t tissues. - 32 -Sodium b i s u l f i t e was added to the apple tissue be-cause i t acts as an antioxidant and helps to maintain the white colour expected i n apple s l i c e s . The use of too much of thi s reagent creates flavour problems and therefore appropriate levels should be determined. Sodium acid pyrophosphate (S.A.P.) can also be used to maintain the l i g h t colour in. some food- products. Its action i s derived from i t s a b i l i t y to chelate metal ions which are capable of catalyzing various degradation reactions re-sponsible for browing (Furia, 1968). It was found from pre-vious experience that apple s l i c e s preserved with SO2 and stored at a warm temperature (35°C) eventually underwent a darkening. I t was thought that the addition of S.A.P. might retard t h i s thereby increasing the shelf l i f e of the product. This reagent also caused flavour problems i f used i n excess. STORAGE TESTS The 29 sample groups were divided i n half with one half being stored at a controlled temperature of 35°C while the other half was stored at room temperature (22°C). Tests were carried out on one of the samples one week afte r processing to determine the i n i t i a l c h a r a c t e r i s t i c s of the products. A second t e s t i n g of the samples was carried out six weeks afte r processing which included a l l samples from the 22°C storage - 33 -and one of the twenty-nine samples from the 35°C_storage. F o l l o w i n g a p e r i o d of f i v e months, a t h i r d t e s t i n g was c a r r i e d out and i n c l u d e d a l l the samples i n the 35°C storage p l u s the remaining pouches o f the-same sample from the 22°C s t o r a g e . PRODUCT PHYSICAL PROPERTIES Magness-Taylor Pressure T e s t - Fresh Apple Texture In some f r u i t s , i n c l u d i n g a pples, m a t u r i t y can be used as an i n d i c a t i o n o f probable t e x t u r e . T h i s , however, can vary with d i f f e r e n c e s " i n v a r i e t y ' and "in storage c o n d i t i o n s . At the be-g i n n i n g o f the p r o j e c t three d i f f e r e n t v a r i e t i e s o f apples from d i f f e r e n t areas and d i f f e r e n t storage f a c i l i t i e s were a v a i l a b l e f o r study. Due to the numbers of f a c t o r s b e i n g t e s t e d , i t was f e l t t h a t the p r o c e s s i n g of three v a r i e t i e s would l e a d t o an extremely l a r g e pack which would be too cumbersome t o handle. For t h i s reason attempts were made to decrease the number of v a r i e t i e s used. One of the t e s t s used to separate them was the Magness-Taylor Pressure T e s t . T h i s t e s t i s o r d i n a r i l y c a r r i e d out i n the f i e l d w i t h a s m a l l p o r t a b l e apparatus but f o r our purposes, the apparatus was m o d i f i e d to y i e l d accurate r e s u l t s on e x i s t i n g l a b o r a t o r y equipment. T h i s equipment con-s i s t e d o f a puncture probe of Magness T a y l o r dimensions, 7.9 mm t i p diameter, connected t o the l o a d c e l l o f an I n s t r o n - 34 -i -j Model 1122 U n i v e r s a l T e s t i n g Machine (Bourne, 1965). The l o a d c e l l which sensed the f o r c e r e q u i r e d t o puncture the s u r f a c e of the apple was connected to a s t r i p c h a r t r e c o r d e r which produced a g r a p h i c account of the a p p l i e d f o r c e throughout the d u r a t i o n of the puncture t e s t . The I n s t r o n i s i d e a l l y s u i t e d t o t h i s type of t e s t because both the speed and depth of p e n e t r a t i o n are c o n t r o l l e d e l e c t r o n i c a l l y and t h e r e f o r e are not s u b j e c t t o the v a r i a t i o n s p r e s e n t when performing t h i s t e s t manually. The g r a p h i c r e c o r d a l s o g i v e s some i n s i g h t i n t o the behaviour of the apple t i s s u e d u r i n g puncture. I t has been found t h a t the speed of p e n e t r a t i o n of the Magness-Taylor has l i t t l e i n f l u e n c e on the f o r c e r e q u i r e d f o r p e n e t r a t i o n ^(Bourne, 1965). Thus, a speed of 5 cm/min was a r b i t r a r i l y chosen. The puncture depth was s e t at 0.79 cm i n a l l cases. An equal number of apples was chosen randomly from each of the three v a r i e t i e s i n c o l d storage and were given s u f -f i c i e n t time to reach room temperature b e f o r e proceeding. A maximum of four punctures were made at r i g h t angles to each other around the "equator" of the apple. In order t o e l i m i n a t e the h igh y i e l d pressure r e q u i r e d to puncture the tough apple s k i n a shallow c i r c u l a r s e c t i o n 1 cm diameter was pared (with a sharp k n i f e ) a t each puncture p o i n t on the apple (Bourne, 1965) . I t was necessary to have a f l a t s u r f a c e f o r p u n c t u r i n g - 35 -(Schomer & O l s o n , 1962) and i t was r e q u i r e d t h a t t h e p l a n e ' o f o p p o s i n g f l a t s u r f a c e s on t h e a p p l e be i n p a r a l l e l p l a n e s . T h i s p e r m i t t e d t h e p r e s e n t a t i o n o f a f l a t s u r f a c e p e r p e n d i c u l a r t o t h e p r o b e when t h e a p p l e was r e s t i n g on t h e o p p o s i n g f l a t s u r f a c e a n d g a v e t h e mos t c o n s i s t e n t r e s u l t s . D u r i n g t h e p u n c -t u r e t e s t , t h e a p p l e was s u p p o r t e d on a f i r m b e d o f p l a s t i c i n e t o p r e v e n t m e c h a n i c a l damage t o t h e u n d e r s i d e i n a l l c a s e s . The f o r c e - d e f o r m a t i o n c u r v e s p r o d u c e d ' i n t h i s e x p e r i -ment c o n s i s t e d o f an e s s e n t i a l l y l i n e a r r i s e , a t t h e s e l e c t e d c h a r t s p e e d , t o a b r e a k o r y i e l d p o i n t , r e p r e s e n t i n g p e n e t r a -t i o n , t h e n a f l a t t e r " s a w - t o o t h e d " c u r v e r e p r e s e n t i n g a s e r i e s o f s m a l l e r y i e l d s a s t h e t i p p e n e t r a t e d f u r t h e r i n t o t h e t i s -s u e . The m a j o r y i e l d p r e s s u r e was u s e d i n a l l c a s e s a s an i n -d i c a t i o n o f t e x t u r e ( M o h s e n i n e t al.-.y 1962). S i n g l e B l a d e S h e a r - A p p l e S l i c e T e x t u r e T e x t u r e o f t h e f r e s h a n d s t o r e d a p p l e s l i c e s was m e a s u r e d w i t h an I n s t r o n M o d e l 1122 U n i v e r s a l T e s t i n g M a c h i n e c o u p l e d t o a s i n g l e b l a d e s h e a r c e l l f r o m an A l i o K r a m e r . S h e a r P r e s s . The c e l l c o n s i s t e d o f t h r e e m a i n p a r t s . The m e t a l s h e a r b l a d e (12 x 7 x 0.3 cm) was f a s t e n e d t o t h e l o a d c e l l o f t h e I n s t r o n b y an a d a p t o r . The c e l l b o d y c o n s i s t e d o f a b a s e p l a t e w i t h a s l i t (0.35 x 7.5 cm) and two s i d e p l a t e s w i t h g u i d e s l o t s f o r b l a d e a l i g n m e n t . The s u p p o r t f r a m e f u n c t i o n e d t o f a s t e n t h e c e l l b o d y t o t h e b a s e o f t h e I n s t r o n w h i l e p e r m i t t i n g a d j u s t m e n t s - 36 -so t h a t the p o s i t i o n of the c e l l body was i n alignment with the blade thus m i n i m i z i n g f r i c t i o n between the moving p a r t s which c o u l d give erroneous r e s u l t s . The t e s t s were c a r r i e d out by p l a c i n g f i v e randomly chosen s l i c e s adjacent to one another across the s l i t of the base p l a t e with the i n n e r or core edge up. The blade was low-ered a t a speed of 5.0 cm/min and the shear f o r c e sensed by the l o a d c e l l was recorded on a s t r i p c h a r t r e c o r d e r . The peak or h i g h e s t r e a d i n g was taken as the measure of t e x t u r e i n a l l cases. Care was taken to i n s u r e t h a t the s l i c e s i n each t e s t were e s s e n t i a l l y the same dimensions. T e s t s were c a r r i e d out i n d u p l i c a t e . V i s c o u s Behaviour - Puree The f u n c t i o n o f added c a l c i u m i o n s i n f r u i t t i s s u e s i s t o combine wi t h p e c t i c substances l o c a t e d i n i n t e r c e l l u l a r spaces. T h i s renders the p e c t i n s water i n s o l u b l e and c r e a t e s a bonding between adjacent c e l l w a l l s and consequently ..a f i r m e r t e x t u r e . I t was thought t h a t i f i n c r e a s e d i n t e r c e l l u l a r bond-i n g o c c u r r e d , i t should be more d i f f i c u l t t o achieve mechanical d i s r u p t i o n and maintain the d i s r u p t e d c o n d i t i o n a f t e r b l e n d i n g the c a l c i u m - t r e a t e d t i s s u e s . Such t i s s u e s should y i e l d a h i g h e r p r o p o r t i o n of "clumped" c e l l s than non-treated t i s s u e s . One method of o b s e r v i n g such a d i f f e r e n c e would be to examine - 37 -the flow behaviour of t i s s u e purees. To do t h i s , a Haake Roto-v i s k o c o a x i a l c y l i n d e r viscometer w i t h an MVII s p i n d l e (gap width 2.55 mm) was employed. Purees o f a l l experimental samples were made u s i n g 250 g of apple s l i c e s w i t h 100 ml d i s t i l l e d water i n a Waring blendor f o r 2 min. The puree was allowed t o stand f o r a t l e a s t one hour a f t e r b l e n d i n g i n a c l o s e d c o n t a i n e r a t room tempera-t u r e to permit the escape o f a i r i n c o r p o r a t e d d u r i n g b l e n d i n g . J u s t p r i o r t o measurement on the Rotovisko, each sample was s t i r r e d with a spoon t o i n s u r e a uniform sample and an a p p r o p r i -ate amount was poured i n t o the sample .cup. T h i s c o n t a i n e r .was then e x t e r n a l l y coated with g l y c e r i n e to f a c i l i t a t e heat t r a n s -f e r and i n s e r t e d i n t o the c o n t r o l l e d , t e m p e r a t u r e water j a c k e t over the s p i r i d l e . The sample was then allowed.a b r i e f p e r i o d to e q u i l i b r a t e w i t h the water j a c k e t temperature of 20°C. During each t e s t the s p i n d l e r o t a t i o n was v a r i e d i n a stepwise f a s h i o n through a s e r i e s of speeds from maximum to minimum. The t r a n s m i s s i o n was then disengaged and the shear r e -l a x a t i o n was recorded u n t i l a constant v a l u e , r e f l e c t i n g the y i e l d s t r e s s (ay), was obt a i n e d . F o l l o w i n g t h i s the transmis-s i o n was again engaged and the s p i n d l e r o t a t i o n was v a r i e d from minimum t o maximum speeds t o complete the measurement. Shear r a t e s o f 529 to 3.27 sec--"- were employed, as c a l c u l a t e d u s i n g Newtonian flow i n the gap. The torque caused by the v i s c o u s - 38 -d r a g o f t h e f l u i d was s e n s e d by an e l e c t r o n i c t o r s i o n d y n a -mometer and was r e c o r d e d on a R i k a d e n k i m u l t i - p e n s t r i p c h a r t r e c o r d e r . F l o w b e h a v i o u r c u r v e s w e r e c o n s t r u c t e d f o r e a c h o f t h e t e s t s u s i n g t h e d a t a d e r i v e d f r o m t h e s t r i p c h a r t r e c o r d -i n g . The f l o w p a r a m e t e r s m and n w e r e e v a l u a t e d b y a c o m p u t e r p r o g r a m w h i c h e m p l o y e d two f o r m s o f t h e p o w e r l a w f l o w m o d e l . E q u a t i o n X a - m^n and E q u a t i o n X I a = m f n + a y w h e r e : 2 a = s h e a r s t r e s s (dyne cm" ) ay = y i e l d s t r e s s (dyne c m - 2 ) f = s h e a r r a t e ( s e c - x ) m = c o n s i s t e n c y c o e f f i c i e n t (dyne s e c 1 1 c m - 2 ) n = f l o w b e h a v i o u r i n d e x (no u n i t s ) D a t a c a r d s c o n t a i n i n g t h r e e d a t a v a l u e s (dynamometer s e t t i n g , g e a r s e t t i n g a nd s c a l e r e a d i n g ) w e r e made f o r e a c h s h e a r r a t e o f e a c h t e s t . T h e s e c a r d s w e re t h e n c o m b i n e d w i t h a p r o g r a m and s u b m i t t e d t o t h e I.B.M. 370/16 8 c o m p u t e r w h i c h e v a l u a t e d s h e a r s t r e s s and s h e a r r a t e d a t a f o r e a c h p o i n t and - 39 -then the rheogram parameters were computed u s i n g the method o f l e a s t squares and a n o n l i n e a r curve f i t t i n g technique. The pro-gram a l s o c a l c u l a t e d s t a t i s t i c a l parameters t o estimate the ac-curacy o f the flow model f i t t o the data. Colour - Apple S l i c e s Maintenance of a l i g h t c o l o u r i n the apple t i s s u e was one o f the main concerns o f t h i s p r o j e c t and t h e r e f o r e c o l o u r was monitored throughout the storage p e r i o d t o determine the e f -f e c t s o f the d i f f e r e n t treatments on browning p r e v e n t i o n . Colour measurements were made wit h a Hunterlab Colour D i f f e r e n c e Meter. The machine was s t a n d a r d i z e d u s i n g the white ceramic standard. S u f f i c i e n t sample (drained s l i c e s ) was p l a c e d i n the sample con-t a i n e r t o completely cover the bottom. The samples were p l a c e d over the a p e r t u r e , covered and read f o r t h e i r L, a and b v a l u e s . Each sample was r o t a t e d 180° a f t e r r e a d i n g and r e r e a d to gi v e d u p l i c a t e s of a l l measurements. A l l readings were made on a r e p r e s e n t a t i v e sample of two pooled pouches. PRODUCT CHEMICAL ANALYSES Calcium A n a l y s i s The a n a l y s i s f o r c a l c i u m ions i n the samples of apple t i s s u e p r o v i d e d a second e v a l u a t i o n of the e f f i c i e n c y of the pr e p a r a t o r y methods and a l s o p r o v i d e d i n f o r m a t i o n on the l e v e l s - 40 -of c a l c i u m l a t e r to be r e l a t e d t o the t e x t u r e r e s u l t s . These analyses were c a r r i e d out w i t h a P e r k i n Elmer Model 306 atomic a b s o r p t i o n spectrophotometer. P r i o r t o the a n a l y s i s , samples o f the 29 experimental groups were reduced t o a l i q u i d form so t h a t the elements pre-sent were i n an i o n i c s t a t e and c o u l d be e a s i l y a s p i r a t e d i n the spectrophotometer. T h i s was done u s i n g a r a p i d d i g e s t i o n method t h a t c o u l d be used t o a c c u r a t e l y determine the l e v e l s of copper, z i n c , t i n , i r o n and c a l c i u m i n f o o d s t u f f s (Simpson and Blay, 1966). The samples were prepared by t a k i n g 5 g of puree (250 g s l i c e s : 100 ml H2O) and p l a c i n g i t i n a 250 ml f l a s k w i t h 25 ml 6M HCl. The mixture was then b o i l e d f o r a p e r i o d of 5 - 10 min to i n s u r e complete s o l u b i l i z a t i o n o f the sample and r e l e a s e of the c a l c i u m i n the form of i o n s . The r e s u l t i n g s o l u t i o n was then c o o l e d and t r a n s f e r r e d to a 50 ml v o l u m e t r i c f l a s k and brought up to volume w i t h d i s t i l l e d water. Lanthanum c h l o r i d e s o l u t i o n of a c o n c e n t r a t i o n of 10,000 ppm was added t o the samples i n a r a t i o of 1:1 thereby l e a v i n g a L a + + + l e v e l of 5,000 ppm. T h i s t i e d up the phosphate ions and r e l e a s e d Ca which would normally be i n the form of c a l c i u m phosphate. The s o l u t i o n s were then a s p i r a t e d i n t h i s form. The a n a l y s i s was c a r r i e d out i n the c o n c e n t r a t i o n mode and readings were taken i n ppm or y.g/g. The samples were read i n d u p l i c a t e . - 41 -The concentration of Ca +' + i n the o r i g i n a l samples were calculated by: Equation XII Reading x 100 x 350 = UgCa + + /g of apple s l i c e 5 250 SO? Determination In order to compare the e f f i c i e n c y of the pretreat-ment methods of chemical addition and the e f f e c t of S O 2 addi-tion on browning i t was decided to measure the residual SO2 i n the sample packs over the ,storage period. The rapid but simple t i t r a t i o n method of Ross and Treadway (196 0) was employed. This method involved the homogenization of a representative sample of drained tissue i n a Waring blendor for 2 min with a c i t r i c acid-disodium phosphate buffer to maintain the pH at 4.4 thus preventing losses of SO2 through oxidation. Follow-ing f i l t r a t i o n of the homogenate a small amount of f i l t r a t e was combined with starch indicator and t i t r a t e d with a stand-ardized iodine solution. A reagent blank, prepared from the same f i l t r a t e with added hydrochloric acid and formaldehyde solution to t i e up free S O 2 was also t i t r a t e d to determine the reducing power of the apple tissue i t s e l f . Timing was c r i t i c a l i n t h i s procedure with 5 min aft e r homogenization being optimum for t i t r a t i o n . - 42 -W i t h t h e v a l u e s o b t a i n e d f r o m t h e t i t r a t i o n s , c a l c u -l a t i o n s w e r e made t o d e t e r m i n e t h e c o n c e n t r a t i o n o f S O 2 i n ppm f o r e a c h s a m p l e : E q u a t i o n X I I I S 0 2 = ( I s - I b ) x N I 2 x E - w - x 1 x 1 0 6 S.W. x 0.1 w h e r e : I s = V o l . o f i o d i n e a d d e d t o t h e s a m p l e (ml) •*-b = v°l« o f i o d i n e a d d e d t o t h e b l a n k (ml) N I 2 = N o r m a l t y o f t h e i o d i n e E.W. = E q u i v a l e n t w e i g h t S.W.„= Sample w e i g h t S u g a r A n a l y s e s The s u g a r a n a l y s e s w e r e c a r r i e d o u t u s i n g t h e method o f T i n g (1956) w h i c h i s b a s e d on t h e r e d u c t i o n o f a l k a l i n e f e r -r i c y a n i d e . f o l l o w e d - b y c o n v e r s i o n t o a b l u e - g r e e n a r s e n o m o l y b d a t e c o m p l e x . The a b s o r b a n c e o f t h i s c o m p l e x a t a w a v e l e n g t h o f 515 nm i s t h e n r e a d w i t h a s p e c t r o p h o t o m e t e r . F i v e grams o f p u r e e w e r e t a k e n f o r e a c h s a m p l e a n d e x -t r a c t e d i n 250 m l o f b o i l i n g 80% e t h y l a l c o h o l . The s a m p l e s w e r e t h e n h e a t e d f o r 30 m i n i n an 8 5 0 c w a t e r b a t h t h e n vacuum f i l t e r e d t h r o u g h Whatman J 2 f i l t e r p a p e r i n a B u c h n e r f u n n e l . The f i l -t r a t e was t h e n c o o l e d t o room t e m p e r a t u r e a n d made up t o 1,000 m l w i t h d i s t i l l e d w a t e r . - 43 -To d e t e r m i n e t h e t o t a l s u g a r c o n t e n t a 50 m l a l i q u o t o f t h e d i l u t e e x t r a c t was p l a c e d i n a 200 m l b e a k e r w i t h 10 m l o f 6M H C l . The b e a k e r was s w i r l e d a n d a l l o w e d t o s t a n d a t room t e m p e r a t u r e f o r 18 h o u r s . F o l l o w i n g i n v e r s i o n , t h e m i x t u r e was p a r t i a l l y n e u t r a l i z e d w i t h 5 m l o f 10 M NaOH and t h e pH was a d -j u s t e d t o b e t w e e n 5 and 7 w i t h 1M NaOH. The s o l u t i o n was t h e n t r a n s f e r r e d t o a 200 o r 250 m l v o l u m e t r i c f l a s k a n d made up t o v o l u m e . A t t h i s p o i n t t h e p r o c e d u r e f o r t h e t o t a l a n d r e -d u c i n g s u g a r s became i d e n t i c a l . One m l s a m p l e s o f t h e o r i g i n a l d i l u t e d f i l t r a t e s a n d one m l s a m p l e s o f t h e d i l u t e d i n v e r t e d s o l u t i o n s w e r e t a k e n f o r t h e r e d u c i n g s u g a r s a n d t o t a l s u g a r a n a l y s e s r e s p e c t i v e l y . E a c h was t h e n t r a n s f e r r e d b y p i p e t t e t o a 100 m l v o l u m e t r i c f l a s k a n d 5 m l o f f e r r i c y a n i d e r e a g e n t was a d d e d . The f l a s k was s w i r l e d a n d t h e n h e a t e d i n a b o i l i n g w a t e r b a t h f o r 10 m i n . A f t e r h e a t i n g t h e f l a s k was q u i c k l y c o o l e d i n a s t r e a m o f r u n n i n g w a t e r . The c o n t e n t s w e r e t h e n p a r t i a l l y n e u t r a l i z e d w i t h 10 m l o f 1M H2SO4 and w e r e s h a k e n u n t i l g as e v o l u t i o n c e a s e d . F o u r m l o f a r s e n o m o l y b d a t e r e a -g e n t was a d d e d a nd t h e s o l u t i o n was t h o r o u g h l y m i x e d a n d made up t o v o l u m e . The f l a s k was a l l o w e d t o s t a n d a t l e a s t 15 m i n b e f o r e a r e a d i n g was t a k e n . - 44 -Absorbance of the ferricyanide-arsenomolybdate complex was measured at 515 nm and a s l i t width of 0.016 mm with a Beck-man DB spectrophotometer. A reagent blank with d i s t i l l e d water was used to standardize the spectrophotometer and glucose and fructose solutions^ were, used to construct a standard;, curve..... The reducing sugar content of each alcoholic extract was determined i n duplicate. Ascorbic Acid Analysis The processing of apple s l i c e s i n r e t o r t pouches should require a shorter heating process to achieve pasteurization be-cause of the thin geometric shape of the container. Under these conditions there should be less destruction of heat l a b i l e n u t r i -ents present i n the s l i c e s . One of these nutrients most commonly considered i s ascorbic acid or vitamin C. I t was f e l t that the monitoring of the vitamin C content of the preserved apple s l i c e s would provide some ind i c a t i o n of the behaviour of other heat-l a b i l e components. The method chosen to analyze for vitamin C was taken from the Association of Vitamin Chemists O f f i c a l Methods. This method consists of the oxidation of an a c i d i c extract of the ap-ple tissue containing vitamin C with 2,6$dichlorophenolindophenol d y e m o n i t o r e d by v i s u a l t i t r a t i o n . - 45 -To p r e p a r e t h e s a m p l e , a known w e i g h t o f a p p l e s l i c e s (200 g) was c o m b i n e d w i t h an e q u a l w e i g h t o f 6% m e t a p h o s p h o r i c a c i d . F r o m t h i s s l u r r y , 30 g w e r e t r a n s f e r r e d t o a 100 m l v o l u -m e t r i c f l a s k . T w e n t y m l o f a c e t o n e w e r e a d d e d t o s t a b l i z e SO2 p r e s e n t w h i c h w o u l d be o x i d i z e d b y t h e dye a n d g i v e h i g h e r v a l u e s . The s o l u t i o n was made up t o v o l u m e w i t h 3% m e t a p h o s p h o r i c a c i d s o l u t i o n . The s o l u t i o n s w e r e t h e n s h a k e n v i g o r o u s l y t o e n s u r e t o t a l e x t r a c t i o n o f t h e a s c o r b i c a c i d . P a r t o f t h e s o l u t i o n was t h e n t r a n s f e r r e d t o c e n t r i f u g e t u b e s a n d s p u n f o r 10 m i n . Upon c o m p l e t i o n , two 10 m l a l i q u o t s o f c l e a r l i q u i d w e r e p i p e t t e d o f f i n t o s m a l l E r l e n m e y e r f l a s k s t o be t i t r a t e d w i t h a s t a n d a r d i z e d 2 , ; 6 - d i c h l o r o p h e n o l i n d o p h e n o l d y e a n d c o n s t a n t s t i r r i n g . The e n d -p o i n t was c o n s i d e r e d t o be t h e f i r s t f a i n t p i n k c o l o u r w h i c h a p -p e a r e d a n d p e r s i s t e d f o r 15 s e c . C a l c u l a t i o n s w e r e made u s i n g t h e f o r m u l a : E q u a t i o n X I V V x T x 100 = mg a s c o r b i c a c i d p e r 100 g s a m p l e W w h e r e : V = v o l u m e o f dye u s e d (ml) T = t h e a s c o r b i c a c i d e q u i v a l e n t (mg/ml o f dye) W = w e i g h t o f t h e s a m p l e i n t h e a l i q u o t t i t r a t e d (g) t o d e t e r m i n e t h e amount o f a s c o r b i c a c i d p r e s e n t i n 100 g o f s a m p l e . - 46 -pH Determination The pH of the apple s l i c e s was monitored throughout the storage p e r i o d as an i n d i c a t o r of any chemical change which might have o c c u r r e d . Measurements were made u s i n g a F i s h e r Model 420 d i g i t a l pH meter. Measurements were made on the pureed sam-p l e s (250 g s l i c e s . 100 ml d i s t i l l e d water) o n l y . SENSORY ANALYSIS Sensory analyses were c a r r i e d out on a number of sam-p l e s to determine i f d i f f e r e n c e s r e s u l t i n g from d i f f e r e n t v a r i -e t i e s , l e v e l s of a d d i t i v e s and p r e p a r a t o r y treatments c o u l d be d e t e c t e d s u b j e c t i v e l y . As s t a t e d e a r l i e r the three p r e s e r v a -t i v e s used were c a l c i u m c h l o r i d e , sodium b i s u l f i t e and sodium a c i d pyrophosphate: the v a r i e t i e s i n c l u d e d Newtown P i p p i n s and Winesaps and the b a c k f l u s h gases used f o r packaging were n i t r o -gen and carbon d i o x i d e . A l l of the samples were s u b j e c t e d to one of the three p r e p a r a t o r y treatments which were a l s o sus-pected to have c r e a t e d d i f f e r e n c e s i n the samples. A c c o r d i n g l y a s u b j e c t i v e comparison, which i n c l u d e d r e p r e s e n t a t i v e samples of each of these v a r i a b l e s , was c a r r i e d out by 10 p a n e l i s t s who were asked to rank them on a continuous hedonic s c a l e and to r e -cord t h e i r reasons. A l l p a n e l i s t s had p r e v i o u s experience w i t h sensory a n a l y s i s and were f a m i l i a r w i t h the procedure. The - 47 -sensory evaluations were carried out at both the 1.5 and 5 month storage t r i a l s with a series of 7 samples for each time. A t o t a l of 8 samples of the 29 available were panelled. Due to a severe browning problem and a short supply, one of the samples used i n the f i r s t panel had to be replaced i n the second panel. The samples from the f i r s t panel time were taken exclusively from the 22°C storage while a l l samples excepting one for the second panel time were taken from the 35°C storage. The sample taken from both storage temperatures for the second panel was suspected to be the best of our 29 samples. The paneling was conducted i n 5 booths i n two s i t t i n g s per time. The panelists were presented with a l l samples i n p l a i n white containers i n random order on a tray. The evaluations were carried out under white fluorescent l i g h t so that colour d i f f e r -ences could be detected. The panelists were aske!d to evaluate the samples according to four quality attributes which included appeal (colour and appearance), texture of s l i c e s , flavour and ov e r a l l a c c e p t a b i l i t y . D i s t i l l e d water and p l a i n soda crackers were supplied to cleanse the palate between samples. STATISTICAL ANALYSES A l l data from the apple project were analyzed using the University I.B.M. computer f a c i l i t i e s . The sensory analysis data were subjected to an analysis of variance procedure em-ploying a Duncan's Test for s i g n i f i c a n t differences between - 48 -ranked means at a 5% p r o b a b i l i t y l e v e l . The remaining data c o l l e c t e d from the apple p r o j e c t were punched on a s e r i e s of cards. These cards were then used i n a s e r i e s of mini analyses using an a n a l y s i s of variance design again w i t h the Duncan's M u l t i p l e Range Test at a 5% p r o b a b i l i t y l e v e l . The data cards were a l s o combined w i t h programs f o r simple and stepwise m u l t i p l e r e g r e s s i o n analyses using both s i n g l e , and s i n g l e w i t h two-way i n t e r a c t i o n f a c t o r s t o deter-mine the r e l a t i o n of the experimental f a c t o r s w i t h the r e s u l t s of the t e s t s c a r r i e d out. In t h i s way some i n s i g h t could be gained as to the probable important f a c t o r s which were able to i n f l u e n c e the q u a l i t y of the samples. - 49 -RESULTS PROCESSING P r o c e s s D e t e r m i n a t i o n T h e r m a l D i f f u s i v i t y D u r i n g t h e t h e r m a l d i f f u s i v i t y s t u d i e s p r o b l e m s o f m a i n t a i n i n g a c o n s t a n t h e a t i n g r a t e b e t w e e n t h e two t h e r m o -c o u p l e s w e re e n c o u n t e r e d a n d t h e r e f o r e a method h a d t o be d e -v i s e d t o d e t e r m i n e a mean h e a t i n g r a t e f o r t h e l i n e a r p o r t i o n s o f t h e h e a t i n g c u r v e s . T h e s e means w e r e t h e n u s e d t o d e r i v e t h e t h e r m a l d i f f u s i v i t i e s f o r t h e d i f f e r e n t r u n s ( T a b l e 1 ) . I n o r d e r t o c a l c u l a t e t h e p r o c e s s t i m e s , i t was assumed t h a t t h e p o u c h a p p r o x i m a t e d a b r i c k s h a p e and t h e r e f o r e a v a l u e o f 2.06 4 c o u l d be u s e d f o r t h e c a l c u l a t i o n ( O l s o n a n d J a c k s o n , 1 9 4 2 ) . A l s o , t o p r o v i d e a s a f e t y f a c t o r t h a t t h e c h a n c e o f d e t e r m i n i n g a s m a l l e r mean t h a n t h e one c a l c u l a t e d was l e s s t h a n 1%, a v a l u e o f t h r e e s t a n d a r d d e v i a t i o n s a b o u t t h e mean was s u b t r a c t e d t o g i v e a m o d i f i e d mean t h e r m a l d i f f u s i v i t y . .-The m o d i f i e d mean t h e r m a l d i f f u s i v i t y o f t h e a p p l e t i s s u e f o u n d i n t h i s r e s e a r c h was 0.01032 i n 2 / m i n . From t h i s an f h v a l u e o f 26.29 m i n and a p r o c e s s t i m e ( P ^ j o f ±9.8 m i n w e r e - e s t a b l i s h e d . . - 50- -Table 1 Res u l t s o f the Thermal D i f f u s i v i t y Measurements of Raw Apple Samples Thermal Run # D i f f u s i v i t y (in z/min) 1 0.01462 2 0.01285 3 0.01273 4 0.01230 5 0.01409 6 0.01434 7 0.01461 8 0.01493 9 0.01385 10 0.01267 11 0.01220 12 0.01256 13 0.01382 14 0.01274 15 0.01292 16 0.01257 17 0.01248 18 0.01424 19 0.01121 20 0.01313 21 0.01318 Mean Thermal D i f f u s i v i t y X =-0.01324 Standard D e v i a t i o n _ S.D. =0.00097 M o d i f i e d Thermal D i f f u s i v i t y X-3S.D. = 0.01032 - 51 -Heat P e n e t r a t i o n The second method used t o determine a process time was c a r r i e d out as a v e r i f i c a t i o n o f the f i r s t method and these r e s u l t s were used i n the f i n a l p r o c e s s . T h i s method i n v o l v e d a measurement of heat p e n e t r a t i o n u s i n g pouches f i t -t e d w i t h thermocouples as d e s c r i b e d e a r l i e r . The r e s u l t s of a l l the heat p e n e t r a t i o n s t u d i e s were submitted t o the UBC computer with a s e r i e s o f programs which c a l c u l a t e d the f ^ and J c h f o r each (Table 2 ) . Again, i n order t o reduce the p r o b a b i l i t y o f r e -q u i r i n g a h i g h e r f n than the c a l c u l a t e d mean to 0.5%, three times the value of the standard d e v i a t i o n about the mean was added t o the f n t o g i v e a m o d i f i e d h e a t i n g r a t e , f h * , which was 23.91 minutes. The process time (Pt) c a l c u l a t e d from these r e s u l t s was 15.6 minutes. Sample P r e p a r a t i o n s and T h e i r E f f e c t s In t h i s p r o j e c t , three b a s i c methods o f p r e p a r a t i o n were compared to assess t h e i r e f f i c i e n c y i n regards t o the l e v e l s of p r e s e r v a t i v e s used, t h e i r convenience and t h e i r e f f e c t s on the q u a l i t y a t t r i b u t e s of the f i n a l product. I t was d i s c o v e r e d i n numerous p r e l i m i n a r y t e s t s t h a t the amounts o f the p r e s e r v a t i v e s added t o the vacuum i n f u s i o n s o l u t i o n s c o u l d be reduced i n comparison w i t h the hot blanch and c o l d d i p methods. A l s o , i t was found t h a t - 52 -Table 2 Res u l t s of the Heat P e n e t r a t i o n S t u d i e s o f Apple S l i c e s i n Re t o r t Pouches Testpack # f h (min) Jch 1 15. 38 2.106 2 23.03 1.076 3 19.93 1.295 4 16. 83 1.444 5 14.21 2.322 6 16. 73 1.609 7 15. 86 1.780 8 15.17 1. 832 9 15.31 1.433 10 12.29 2.170 11 9.63 3.483 12 14. 30 2. 820 13 17. 39 1.266 14 16.06 1. 319 15 18.10 1.146 16 14.82 1. 374 17 15.44 1.228 18 15.54 1.498 19 19.14 0.966 20 14.84 1.785 21 15.60 1.305 22 14.80 1.598 Mean f"h X =' 15. 93 1.675 Standard D e v i a t i o n - S.D. = 2. 66 0.60 3 M o d i f i e d f h " X + 3S.D. = 23. 91 = f * h -- 53 -the hot blanch method seemed to r e q u i r e a lower l e v e l o f the a d d i t i v e s than the c o l d d i p s o l u t i o n s . The l e v e l s of chemi-c a l s added t o the s o l u t i o n s o f each method are presented i n Table 3 as c o n c e n t r a t i o n s o f t h e i r f u n c t i o n a l groups. The r e s u l t s o f these treatments i n regards t o the i n c o r p o r a t i o n o f the p r e s e r v a t i v e s i n t o the f r u i t t i s s u e can be observed i n the min i - a n a l y s e s of v a r i a n c e r e s u l t s com-p a r i n g the r e s u l t s o f the SO2 and C a + + analyses i n the sam-p l e s undergoing the d i f f e r e n t p r e p a r a t o r y treatments. F i g -ures 1 and 2 demonstrate the d i f f e r e n c e s between some of the mean l e v e l s of SO2 i n samples taken from the d i f f e r e n t p r e -p a r a t o r y treatments. Since no a n a l y s i s was c a r r i e d out on the phosphate content o f the samples the l e v e l s i n c o r p o r a t e d i n t o the t i s -sues by the d i f f e r e n t methods cannot be presented. The d i f f e r e n t p r e p a r a t o r y methods and the r e s u l t i n g l e v e l s o f p r e s e r v a t i v e s i n c o r p o r a t e d by them can be shown to have i n f l u e n c e d some of the other measurements c a r r i e d out. These, however, w i l l be presented and d i s c u s s e d i n the f o l -lowing s e c t i o n s . - 54 -Table 3 L e v e l s o f A d d i t i v e s Used f o r the Pr e p a r a t o r y Treatments of Apple S l i c e s i n Re t o r t Pouches V a r i e t y Treatment C a + + S O 2 S.A.P, (ppm) (ppm) (ppm) Newtown V a c In-f u s i o n 2,500 560 3,330 Hot Blanch — 1,160 10,000 Cold Dip (Low) 5,000 2,150 10,000 (Med) — 1,720 10,000 (High) -- 2,790 Winesap Vac. In-f u s i o n 2,500 560 Hot Blanch — 1,070 Cold Dip (Med) 5,000 2,150 10,000 - 55 -P.! C N o F i g . 1 150 100 Hot S0 2 Blanch I n f u s i o n Mean L e v e l s of S0 2 Incorporated i n t o the Apple T i s s u e s by the D i f f e r e n t P r e p a r a t o r y Methods tn \ Cn 3-o u s •H o r-H u NO Calcium C o l d C a + + Dip Hot S 0 2 Blanch C o l d C a + + Dip C o l d S0 2 Blanch Calcium Vacuum I n f u s i o n F i g . 2 Mean L e v e l s o f Calcium Incorporated i n t o the Apple T i s s u e s by the D i f f e r e n t P r e p a r a t o r y Methods - 56 -SAMPLE DIFFERENCES The v a r i a b i l i t y noted between the d i f f e r e n t samples of t h i s experiment can be s p l i t i n t o three c a t e g o r i e s ( i . e . t e x t u r e , c o l o u r and chemical d i f f e r e n c e s ) and so w i l l be presented as such. Texture I n s t r o n S i n g l e Blade Shear D i f f e r e n c e s i n t e x t u r e between the v a r i o u s samples were determined with the a i d of the I n s t r o n - Kramer s i n g l e blade shear combination and the Haake Rotovisko viscometer. The I n s t r o n shear f o r c e measurements were shown by the step-wise m u l t i p l e r e g r e s s i o n u s i n g both s i n g l e and two-way i n t e r a c t i o n f a c t o r s and the simple r e g r e s s i o n a n a l y s i s to vary s i g n i f i c a n t l y with the l e v e l s o f c a l -cium added and the temperature at which the samples were s t o r e d (Table 4). When both s i n g l e and two-way i n t e r a c t i o n f a c t o r s were i n c l u d e d i n the m u l t i p l e r e g r e s s i o n a n a l y s i s , i t was found t h a t s i g n i f i c a n t s i n g l e f a c t o r s of the pre v i o u s analyses were i n v o l v e d i n two-way i n t e r a c t i o n s which gave a b e t t e r e x p l a n a t i o n of the v a r i a n c e i n the I n s t r o n r e s u l t s (Table 5 ) . t The e f f e c t s of the c a l c i u m content o f the s l i c e s and the p r e p a r a t o r y treatments on the shear r e s i s t a n c e o f the samples i s f u r t h e r demonstrated by the r e s u l t s o f the analyses o f v a r i a n c e (Tables 41, 42) . - 57 -T a b l e 4 R e s u l t s o f S t e p w i s e M u l t i p l e R e g r e s s i o n o f I n s t r o n S h e a r F o r c e on E x p e r i m e n t a l F a c t o r s U s i n g S i n g l e F a c t o r s O n l y V a r i a b l e P o l y n o m i a l Name C o e f f i c i e n t F - R a t i o C o n s t a n t 2.780 C a l c i u m 0.008401 126.1 ** T e m p e r a t u r e - 0.706 98.03 ** S t a n d a r d E r r o r o f Y = 0.586, R 2 = 0.657 ** ** p s> 0.01 T a b l e 5 R e s u l t s o f S t e p w i s e M u l t i p l e R e g r e s s i o n o f I n s t r o n S h e a r F o r c e on E x p e r i m e n t a l F a c t o r s U s i n g Two-way I n t e r a c t i o n F a c t o r s V a r i a b l e P o l y n o m i a l Name C o e f f i c i e n t F - R a t i o C o n s t a n t 1.022 T o t a l S u g a r x C a l c i u m 0.002444 53.82 ** R e d u c i n g S u g a r x C a l c i u m - 0.00277 18.81 ** R e d u c i n g S u g a r x T e m p e r a t u r e - 0.001556 10.67 ** C a l c i u m x Time 0.001872 5.090 * S t a n d a r d E r r o r o f Y = 0.4988, R 2 = 0.7559 ** * P < 0.05 ** P <• 0.01 - 58 -V i s c o m e t r y The r e s u l t s f r o m t h e Haake R o t o v i s k o m e a s u r e m e n t s were u s e d t o c a l c u l a t e f o u r p a r a m e t e r s d e s c r i b i n g t h e f l o w b e h a v i o u r o f t h e p u r e e d a p p l e s l i c e s . T h e s e p a r a m e t e r s i n -c l u d e t h e f l o w b e h a v i o u r i n d e x ( n ) , t h e c o n s i s t a n c y c o e f f i -c i e n t (m) , t h e y i e l d s t r e s s (ay) , a n d a n a p p a r e n t v i s c o s i t y c o -e f f i c i e n t c a l c u l a t e d u s i n g t h e d e r i v e d n v a l u e o f e a c h s a m p l e as w e l l a s an i n t e r m e d i a t e s h e a r r a t e v a l u e w h i c h f o r t h e M V II s p i n d l e was t a k e n t o be 4 0 s e c ^. T h i s p a r a m e t e r was t h u s l a b e l l e d n \ 0 T h e s e f a c t o r s c o m b i n e d c a n p r o v i d e i n -s i g h t i n t o t h e p o s s i b l e i n f l u e n c e t h a t t h e d i f f e r e n t f a c t o r s c a n h a v e on t h e f l o w b e h a v i o u r o f t h e p u r e e . The s i n g l e f a c t o r s w h i c h w ere s i g n i f i c a n t i n e x -p l a i n i n g t h e v a r i a b i l i t y i n some o r a l l o f t h e f l o w p a r a m e t e r s w e re t h e t o t a l a s c o r b i c a c i d c o n t e n t , t h e l e n g t h o f s t o r a g e , t h e t o t a l s u g a r c o n t e n t o f t h e s a m p l e , t h e b a c k f l u s h gas and t h e v a r i e t y o f a p p l e ( T a b l e s . 6 , 7, 8, 9 ) . - 59 -Table 6 Results of Stepwise Multiple Regression of n on Experimental Factors Using Single Factors Only Variable Polynomial Name Co e f f i c i e n t F-Ratio Constant 0.3872 Gas - 0.0246 12.45 ** Total Sugar - 0.004681 4.019 * Ascorbic Acid 0.005 17.38 ** Time 0.00791 26.00 ** Standard Error of Y ~= 0.0284, R 2 = 0.3903 ** * P £ 0.05 ** P < 0.01 Table 7 Results of Stepwise Multiple Regression of m on Experimental Factors Using Single Factors Only Variable Polynomial Name Coef f i c i e n t F-Ratio Constant 61.99 Variety - 19.47 7.255 ** Gas 18.10 6.746 * Total Sugar 7.466 10.19 ** Ascorbic Acid - 6.821 19.63 ** Time - 9.920 40.76 ** Standard Error Y = 28.36, R 2 = 0.4805 ** * P 0.05 ** P < 0.01 - 60 -T a b l e 8 R e s u l t s o f Stepwise M u l t i p l e R e g r e s s i o n o f ay on E x p e r i m e n t a l F a c t o r s U s i n g S i n g l e F a c t o r s Only V a r i a b l e P o l y n o m i a l Name C o e f f i c i e n t F - R a t i o C o n s t a n t 40.12 A s c o r b i c A c i d - 4.041 15.49 ** S t a n d a r d E r r o r o f Y = 2 2 . 5 5 , R 2 = 0.116 ** ** p < 0.01 T a b l e 9 R e s u l t s o f Stepwise M u l t i p l e R e g r e s s i o n o f rwo on E x p e r i m e n t a l F a c t o r s U s i n g S i n g l e F a c t o r s Only V a r i a b l e P o l y n o m i a l Name C o e f f i c i e n t F - R a t i o C o n s t a n t 5.099 V a r i e t y - 1.240 7.417 ** Gas 0.9532 4.719 * T o t a l Sugar 0.6074 17.02 ** A s c o r b i c A c i d - 0.4332 19.98 ** Time - 0.6083 38.66 ** S t a n d a r d E r r o r o f Y = 1.786, R 2 = 0.4961 ** * P < 0.05 ** P I 0.01 - 61 -When two-way i n t e r a c t i o n f a c t o r s as w e l l as s i n g l e f a c t o r s were c o n s i d e r e d as independent v a r i a b l e s a b e t t e r e x p l a n a t i o n f o r the v a r i a n c e o f the four dependent v a r i a b l e s was achieved. In the case o f the y i e l d s t r e s s r e s u l t s the e x p l a n a t i o n was v a s t l y improved by c o n s i d e r i n g two-way i n -t e r a c t i o n f a c t o r s as i s shown i n a comparison o f the R 2 values 0.1160 t o 0.3080. For t h i s case, i t can again be seen t h a t the s i n g l e f a c t o r s which c o r r e l a t e d with the dependent v a r i a b l e s , are i n v o l v e d i n the i n t e r a c t i o n s , g i v i n g a b e t t e r e x p l a n a t i o n of r e s i d u a l v a r i a n c e than before (Tables 10, 11, 1-2," arid 13). Some of the new f a c t o r s which combine i n the i n t e r a c t i o n terms are c a l c i u m content, r e d u c i n g sugar content and s t o r -age temperature. Colour Colour d i f f e r e n c e between the samples and the changes o c c u r r i n g i n each sample throughout the t e s t p e r i o d were monitored with the a i d of a Hunterlab Colour D i f f e r e n c e Meter. The three Hunter parameters o f c o l o u r (L, a and b values) were recorded and subsequently used as dependent v a r i a b l e s i n the r e g r e s s i o n analyses t o determine which of the experimental f a c t o r s v a r i e d s i g n i f i c a n t l y w i t h the c o l o u r - 62 -T a b l e 10 R e s u l t s o f S t e p w i s e M u l t i p l e R e g r e s s i o n o f n on E x p e r i m e n t a l F a c t o r s U s i n g Two-Way I n t e r a c t i o n F a c t o r s V a r i a b l e P o l y n o m i a l Name C o e f f i c i e n t F - R a t i o C o n s t a n t 0.3904 T o t a l S u g a r - 0.004920 4.653 * Gas x C a l c i u m - 0.0001705 25.38 ** A s c o r b i c x Tempe r a -t u r e 0.0001609 17.36 ** C a l c i u m x Time 0.00006223 22.64 ** S t a n d a r d E r r o r o f Y = 0.0277, R^ = 0.4175 ** * P < 0.05 ** P 0.01 T a b l e 11 R e s u l t s o f S t e p w i s e M u l t i p l e R e g r e s s i o n o f m on E x p e r i m e n t a l F a c t o r s U s i n g Two-Way I n t e r a c t i o n F a c t o r s V a r i a b l e P o l y n o m i a l Name C o e f f i c i e n t F - R a t i o C o n s t a n t 44.96 T o t a l S u g a r 6. 766 7.912 ** V a r i e t y x C a l c i u m - 0.1002 4.820 * V a r i e t y x Time - 2.681 4.911 * Gas x C a l c i u m 0.1720 15.69 ** A s c o r b i c x Tempera-t u r e - 0.1932 19.57 ** C a l c i u m x Time - 0.0348 4.093 * S t a n d a r d E r r o r o f Y = 2 8 . 3 0 , R z = 0.4876 ** * P • * 0.05 ** P <-. 0.01 - 63 -Table 12 Results of Stepwise Multiple Regression of ay on E x p e r i m e n t a l F a c t o r s U s i n g Two-Way I n t e r a c t i o n F a c t o r s V a r i a b l e P o l y n o m i a l Name C o e f f i c i e n t F - R a t i o C o n s t a n t 199.1 pH - 71.91 8.557 ** V a r i e t y x T o t a l S u g a r 1.591 12.31 ** Gas x C a l c i u m 0.0796 8,093 ** T o t a l S u g a r x R e d u c i n g S u g a r 0.3862 17.66 ** A s c o r b i c x Temper a -t u r e 0.0922 6. 380 * C a l c i u m x Time 0.0297 7.938 ** S t a n d a r d E r r o r o f Y = 20. 3 9 , R2 = 0.3080 ** * P < 0.05 ** P 0.01 T a b l e 13 R e s u l t s o f S t e p w i s e M u l t i p l e R e g r e s s i o n o f n w on E x p e r i m e n t a l F a c t o r s U s i n g Two-Way I n t e r a c t i o n F a c t o r s V a r i a b l e P o l y n o m i a l Name C o e f f i c i e n t F - R a t i o C o n s t a n t 7.481 V a r i e t y x C a l c i u m - 0.0121 26.83 ** Gas x C a l c i u m 0.009786 19.49 ** T o t a l S u g a r x R e d u c i n g S u g a r 0.0510 17.98 ** R e d u c i n g S u g a r x Time - 0.0938 36.98 ** A s c o r b i c x T e m p e r a t u r e - 0.0123 22.91 ** S t a n d a r d E r r o r o f Y = 1.674, R 2 = 0.5573 ** ** P < 0.01 - 64 -changes. The s i n g l e f a c t o r s whose v a r i a n c e c o i n c i d e d s i g n i f -i c a n t l y w i t h the v a r i a n c e i n the three dependent v a r i a b l e s of c o l o u r were not the same f o r each (Tables 14, 15, and 16). When two-way i n t e r a c t i o n f a c t o r s as w e l l as s i n g l e f a c t o r s were c o n s i d e r e d i n the m u l t i p l e r e g r e s s i o n analyses i t was found t h a t the s i n g l e f a c t o r s of the p r e v i o u s analyses combined i n i n t e r a c t i o n f a c t o r s t o give a b e t t e r e x p l a n a t i o n of the v a r i a n c e i n the c o l o u r parameters (Tables 17, 18, and 19) . Chemical D i f f e r e n c e s In order to p a r t i a l l y understand the changes oc-c u r r i n g i n the samples over the storage p e r i o d and the" d i f -ferences between samples which had been t r e a t e d d i f f e r e n t l y , a number of chemical analyses were c a r r i e d out. These i n -cluded analyses f o r t o t a l c a l c i u m , SO2 content, t o t a l and r e d u c i n g sugar c o n t e n t s , a s c o r b i c a c i d content and pH. The r e s u l t s of the analyses f o r t o t a l c a l c i u m d i d not show any d i f f e r e n c e s over the storage time but d i d i n -d i c a t e d i f f e r e n c e s between samples t r e a t e d d i f f e r e n t l y ( F i g . 2) . The c a l c i u m l e v e l s were a l s o shown to vary w i t h the b a c k f l u s h gas used i n packing. The use of carbon d i -oxide f o r t h i s purpose seemed to i n c r e a s e the l e v e l of - 65 -T a b l e 14 R e s u l t s o f S t e p w i s e M u l t i p l e R e g r e s s i o n o f H u n t e r " L " V a l u e s on E x p e r i m e n t a l F a c t o r s U s i n g S i n g l e F a c t o r s . O n l y V a r i a b l e P o l y n o m i a l Name C o e f f i c i e n t F - R a t i o C o n s t a n t 55.64 Gas - 2.874 12.08 ** T o t a l S u g a r 1. 075 13.79 ** R e d u c i n g S u g a r 1.308 4.569 * Time - 2.038 11.53 ** T e m p e r a t u r e - 0.6463 15.24 ** S t a n d a r d E r r o r o f Y = 3.365, R 2 = 0. 7590 i * * * P -.<• 0.05 ** P < 0.01 T a b l e 15 R e s u l t s o f S t e p w i s e M u l t i p l e R e g r e s s i o n o f H u n t e r " a " V a l u e s on E x p e r i m e n t a l F a c t o r s U s i n g S i n g l e F a c t o r s O n l y V a r i a b l e P o l y n o m i a l Name C o e f f i c i e n t F - R a t i o C o n s t a n t - 1.994 V a r i e t y - 1.438 16.83 ** S 0 2 - 0.0163 33.80 ** A s c o r b i c A c i d - 0.3794 . 16.37 ** Time 1.128 171.8 ** S t a n d a r d E r r o r o f Y = 1.352, R z = 0.8001 ** ** P x 0.01 - 66 -Table 16 R e s u l t s o f Stepwise M u l t i p l e Regression o f Hunter "b Values on Experimental F a c t o r s Using S i n g l e F a c t o r s Only V a r i a b l e Polynomial Name C o e f f i c i e n t F -Ratio Constant 15.54 Pyrophosphate 0.9151 11.43 ** so 2 0.006625 10.15 ** T o t a l Sugars 0.4497 16.30 ** Standard E r r o r o f Y = 1.393, R 2 = 0. 2765 ** ** P I 0.01 Table 17 R e s u l t s of Stepwise M u l t i p l e Regression of Hunter "L".Values' , on Experimental F a c t o r s Using,Two-Way I n t e r a c t i o n F a c t o r s V a r i a b l e Polynomial Name C o e f f i c i e n t F -Ratio Constant 54.00 Pyrophosphate x V a r i e t y 0.8846 6.952 ** Gas x S0 2 - 0.0182 9.112 ** Gas x Calcium - 0.0101 11.68 ** Gas x Time 0.5872 7.198 ** T o t a l Sugar x Reducing Sugar 0.1067 32.67 ** S0 2 x Time 0.0128 45.23 ** A s c o r b i c Acid, x pH - 0.1297 5.872 * Time x Temperature - 0.1565 142.6 ** Standard E r r o r o f Y = 2.719, R 2 = 0.8467 ** * P £ 0.05 ** P < 0.01 - 67 -T a b l e 18 R e s u l t s o f S t e p w i s e M u l t i p l e R e g r e s s i o n o f H u n t e r " a " V a l u e s on E x p e r i m e n t a l F a c t o r s U s i n g Two-Way I n t e r a c t i o n F a c t o r s V a r i a b l e P o l y n o m i a l Name C o e f f i c i e n t F - R a t i o C o n s t a n t - 0.2862 V a r i e t y x S O 2 - 0.0134 72.36 ••••** Gas x A s c o r b i c A c i d 0.3620 7.538 ** Gas x pH - 0.6784 11.83 ** A s c o r b i c A c i d x pH - 0.2519 24.01 ** Time x T e m p e r a t u r e 0.0272 242.2 ** S t a n d a r d E r r o r o f Y = 1.231, R 2 = 0. 8358 ** ** P £ 0.01 T a b l e 19 R e s u l t s o f S t e p w i s e M u l t i p l e R e g r e s s i o n o f H u n t e r "b" V a l u e s on E x p e r i m e n t a l F a c t o r s U s i n g Two-Way I n t e r a c t i o n F a c t o r s V a r i a b l e P o l y n o m i a l Name C o e f f i c i e n t F - R a t i o C o n s t a n t 21.29 P y r o p h o s p h a t e x S O 2 0.004187 6.466 * Gas x S O 2 - 0.007170 10.62 ** S O 2 x R e d u c i n g S u g a r 0.2483 22.32 ** S O 2 x A s c o r b i c A c i d - 0.1002 22.28 ** T o t a l S u g a r x A s c o r b i c 0.1002 55.65 ** A s c o r b i c x T e m p e r a t u r e - 0.0282 53.34 ** S t a n d a r d E r r o r o f Y = 1.202, R^ = 0.4750 ** * P < 0.05 ** P < 0.01 - 68 -c a l c i u m i n the samples. A n a l y s i s of v a r i a n c e r e s u l t s from a comparison o f s i x o f the samples showed t h a t those samples packed with carbon d i o x i d e had s i g n i f a n c t l y (P £ 0.01) h i g h e r l e v e l s of c a l c i u m (133.5 ug/g) than those packed w i t h n i t r o -gen (112.3 ug/g). The other f a c t o r s such as v a r i e t y , SC^, pyrophosphate and temperature d i d not have any s i g n i f i c a n t (P y 0.05) i n f l u e n c e on the l e v e l s o f t o t a l c a l c i u m p r e s e n t i n the samples. The l e v e l s of SC>2 found i n the samples were a l s o found to vary s i g n i f i c a n t l y w i t h the p r e p a r a t o r y methods ( F i g . 1 ) . The temperature o f storage had the e f f e c t o f de-c r e a s i n g the SC>2 l e v e l i n the samples w i t h i n c r e a s i n g tem-^ pera t u r e ( F i g . 3). The presence o f pyrophosphate ions i n the apple t i s s u e was a l s o shown to have the e f f e c t of i n -c r e a s i n g the amount of SC>2 d e t e c t e d i n comparable samples (Table 20.) . The v a r i e t y o f apple used i n the t e s t was a l s o found to have an e f f e c t on the amount of S0 2 found i n the samples (Table 21). The presence of c a l c i u m and the type of b a c k f l u s h gas used i n the sample c o u l d not be shown by the Duncan's t e s t t o have any s i g n i f i c a n t e f f e c t (P > 0.05) on the l e v e l o f SOn i n c o r p o r a t e d i n t o the t i s s u e s . - 69 -e a. CL) -P o u C N O 250 200 150 i 100-50 o-22° C \ 37° C F i g . 3 1.5 5.0 Time (months) The E f f e c t s o f S t o r a g e T e m p e r a t u r e on t h e L e v e l s o f SO? F o u n d i n A p p l e S l i c e s - 70 -Table 20 Res u l t s of A n a l y s i s of Variance f o r the E f f e c t o f Pyrophosphate on the L e v e l o f S O 2 i n Processed Apple S l i c e s T e s t Sample Mean S O 2 L e v e l s (ppm) # S i z e No Pyrophosphate Pyrophosphate 1 6 149.2 a* 163.6 b 2 4 131.0 a 146.6 b 3 4 119.3 a 147.6 b * Mean values i n a row f o l l o w e d by the same l e t t e r do not d i f f e r s i g n i f i c a n t l y (P ->:• 0.05) by Duncan's t e s t . Table 21 Res u l t s of A n a l y s i s of Variance -cfor the E f f e c t o f Apple V a r i e t y on the L e v e l o f S O 2 i n Processed Apple S l i c e s T e s t Sample Mean SO2 L e v e l s (ppm) # S i z e Newtown Winesap 1 4 144.3 b* 107.4 a 2 4 161.3 b 116.4 a * Mean value s i n a row f o l l o w e d by the same l e t t e r do not d i f f e r s i g n i f i c a n t l y (P.>:-0.05) by Duncan's t e s t . - 71 -The l e v e l s of t o t a l sugars i n the samples was shown by the valu e s i n the c o r r e l a t i o n matrix from the com-puter p r i n t o u t t o decrease with i n c r e a s i n g time and tempera-ture of s t o r a g e . Although the e f f e c t s o f these two f a c t o r s on the t o t a l sugar content c o u l d not be shown i n d i v i d u a l l y , t h e i r combined e f f e c t s can be demonstrated by the r e s u l t s i n Table 22. The e f f e c t s of the i n d i v i d u a l f a c t o r s cannot be separated by v i r t u e o f the nature of the t e s t i n g procedures. The remaining f a c t o r s which i n c l u d e the presence of S0 2, c a l c i u m i o n s , pyrophosphate i o n s , apple v a r i e t y and b a c k f l u s h gas d i d not show s i g n i f i c a n t i n f l u e n c e s (P > 0.05) on the t o t a l sugar content of the s l i c e s . The l e v e l s of r e d u c i n g sugars were a l s o analyzed and i t was found t h a t i n c r e a s e s i n storage time and tempera-t u r e s have the e f f e c t of i n c r e a s i n g the red u c i n g sugar l e v e l s (Tables 2 3 and 24). The combined e f f e c t s of time and temperature can be seen i n F i g u r e 4. Table 22 Results of Analysis of Variance ifor the Combined Eff e c t s . o f Storage Time and Temperature on the Total Sugar Content of Processed Apple S l i c e s Mean Total Sugar Content (mg/100 mg) Test Sample 22°C for 1.5 35°C for 5 # Size Months Months 1 8 13.55 b* 12.75 a 2 4 14.24 b 13.20 a 3 6 13.90 b 12.80 a 4 3 14.52 b 12.67 a 5 9 14.00 b 12.9 3 a * Mean values i n a row followed by the same l e t t e r do not d i f f e r s i g n i f i c a n t l y (P > 0.05) by Duncan's t e s t . Table 23 Results of Analysis of Variance for the E f f e c t of Storage Time on the Reducing Sugar Content of Processed Apple S l i c e s Mean Reducing Sugar Content (mg/100 mg)  Test Sample 1.5 5 # Size Months Months 1 2 8.85 a * 10.80 b * Mean values i n a row followed by the same l e t t e r do not d i f f e r s i g n i f i c a n t l y (P :> 0.05) by Duncan's te s t . 1 2 . 3 4 5 Storage Time (months) F i g . 4 The Changes i n the Reducing Sugar Content with Time i n Samples Stored a t 22° C and 35° C - 74 -The i n f l u e n c e on the remaining f a c t o r s i n c l u d i n g the presence of c a l c i u m and pyrophosphate i o n s , the presence o f SC>2, the v a r i e t y of apple and the type of b a c k f l u s h gas was not shown to be s i g n i f i c a n t (P > 0.05) by Duncan's t e s t . The c o e f f i c i e n t f o r the SC^-reducing sugar r e l a t i o n s h i p from the c o r r e l a t i o n m atrix i n d i c a t e s t h a t added SC>2 may have some e f f e c t on the l e v e l s of r e d u c i n g sugars produced over the storage p e r i o d . With a c l o s e r look a t the r e s u l t s , how-ever, i t was found t h a t i t was not the S0 2 l e v e l (Table 25) but the method of i n c o r p o r a t i o n of the S0 2 i n t o the t i s s u e s which had an i n f l u e n c e on the subsequent l e v e l s of r e d u c i n g sugars i n the apple s l i c e s (Table 26). These r e s u l t s i n d i -cate t h a t the l e v e l o f r e d u c i n g sugars was lower i n samples s u b j e c t e d t o the hot blanch treatment. The a s c o r b i c a c i d l e v e l s were a l s o determined i n each t e s t pack and i t was found t h a t these l e v e l s were i n -f l u e n c e d by the p r e p a r a t o r y methods (Table 27). The l e n g t h of storage time was a l s o found to i n f l u e n c e the v i t a m i n C l e v e l s of the apple s l i c e s (Table 28). The presence of c a l -cium was a l s o shown to have an i n f l u e n c e on the a s c o r b i c a c i d content (Table 29). The d i f f e r e n t l e v e l s of c a l c i u m i n c o r p o r a t e d i n t o the apple t i s s u e v i a the d i f f e r e n t prep-a r a t o r y methods, however, c o u l d not be shown to have any s i g -n i f i c a n t e f f e c t (P > 0.05) on the a s c o r b i c a c i d content of the s l i c e s . - 75 -Table 24 Results of /Analysis of Variance ;for the Effects of Storage Temperature on the Reducing Sugar Content of Processed Apple S l i c e s Mean Reducing Sugar Content (mg/100 mg)  Test Sample # Size 22°C 35°C 1 2 8.43 a * 11.22 b * Mean values i n a row followed by the same l e t t e r do not d i f f e r s i g n i f i c a n t l y (P > 0.05) by Duncan's te s t . Table 25 Results of Analysis of Variance for the Eff e c t s of S 0 9 on the Reducing Sugar Content of Processed Apple S l i c e s Mean Reducing Sugar Content (mg/100 mg)  Test Sample 1720 ppm 2150 ppm 2795 ppm # Size S0 2 S0 2 S0 2 1 3 10.42 a* 10.15 a 10.50 a Mean values i n a row followed by the same l e t t e r do not d i f f e r s i g n i f i c a n t l y (P > 0.05) by Duncan's te s t . - 76 -Table 26 Res u l t s o f A n a l y s i s o f Variance f o r the E f f e c t s o f P r e p a r a t o r y Treatments on the Reducing Sugar Content of Processed Apple S l i c e s Mean Reducing Sugar Content (mg/100 mg)  Test Sample Hot Vacuum Cold # S i z e Blanch I n f u s i o n Dip 1 9 9.42 a* 9.87 b 9.98 b * Mean values i n a row f o l l o w e d by the same l e t t e r do not d i f f e r s i g n i f i c a n t l y (P-> 0.05) by Duncan's t e s t . Table 2 7 Resul t s o f A n a l y s i s of V a r i a n c e " f o r the E f f e c t s of Pr e p a r a t o r y Treatments on the A s c o r b i c A c i d Content of Processed Apple S l i c e s Mean A s c o r b i c A c i d Content (mg/100 mg) " Test Sample Hot Vacuum Cold # S i z e Blanch I n f u s i o n Dip 1 9 1.56 a* 4.78 b 5.03 c 2 8 1.49 a 4. 30 b 4. 80 c 3 3 1.47 a 5.28 b 5. 80 b 4 3 1.71 a 5.72 b 5.50 b * Mean values i n a row f o l l o w e d by the same l e t t e r do not d i f f e r s i g n i f i c a n t l y (P ;> 0.05) by Duncan's t e s t . - 11 -Table 2 8 Resu l t s o f A n a l y s i s o f Variance f o r the E f f e c t s of Storage Time on the L e v e l s of Vit a m i n C i n Processed Apple S l i c e s Mean A s c o r b i c A c i d Content (mg/10 0 mg)  Test Sample # S i z e 1.5 months 5.0 months 1 2 5.19 a * 6.52 b * Mean Values i n a row f o l l o w e d by the same l e t t e r do not d i f f e r s i g n i f i c a n t l y (T? > 0.05) by Duncan's t e s t . Table 29 Res u l t s o f A n a l y s i s o f Variance ifor the E f f e c t s o f Added . Calcium on" the" A s c o r b i c A c i d C o n t e n t , o f Processed Apple S l i c e s Mean A s c o r b i c A c i d Content (mg/100 mg)  Test Sample # S i z e No Calcium Calcium 1 8 3.63 a * 4.84 b 2 4 3.08 a 4.13 b * Mean values i n a row f o l l o w e d by the same l e t t e r do not d i f f e r s i g n i f i c a n t l y (P V-0.05) by Duncan's t e s t . - 78 -The v a r i e t y of apple used f o r p r o c e s s i n g was a l s o shown to have i n f l u e n c e d the l e v e l of a s c o r b i c a c i d i n the samples (Table 30). The remaining f a c t o r s such as temperature, S0 2 con-t e n t , pyrophosphate content and b a c k f l u s h gas c o u l d not be demonstrated c o n c l u s i v e l y to have an e f f e c t on the l e v e l of a s c o r b i c a c i d i n the apple s l i c e s . The pH of the samples was a l s o monitored throughout the t e s t p e r i o d . I t was thought t h a t changes i n the pH would be an i n d i c a t i o n of chemical changes o c c u r r i n g i n the samples. For t h i s reason, i t was f e l t t h a t f a c t o r s which i n f l u e n c e d the pH of the samples c o u l d be r e l a t e d to the chemical changes o c c u r r i n g and these were determined w i t h analyses of v a r i a n c e . Time was demonstrated to have a s i g n i f i c a n t i n f l u e n c e on the pH of the samples (Table 31)'. Storage temperature was a l s o shown to have i n f l u e n c e d the pH of the samples s i g n i f i c a n t l y (Table 32). The S0 2 i n c o r p o r a t e d i n t o the apple t i s s u e by the d i f f e r e n t p r e p a r a t o r y methods was demonstrated to have i n f l u e n c e d the pH of the samples d i r e c t l y w i t h the amount of S0 2 i n c o r p o r a t e d (Table 33). The l e v e l of c a l c i u m i n c o r p o r -ated i n t o the apple s l i c e s a l s o had a s i g n i f i c a n t i n f l u e n c e on t h e i r pH with g r e a t e r l e v e l s o f c a l c i u m y i e l d i n g lower pH values (Table 34). - 79 -T a b l e 30 R e s u l t s o f A n a l y s i s o f V a r i a n c e f o r t r i e E f f e c t s o f A p p l e V a r i e t y on t h e A s c o r b i c A c i d C o n t e n t o f P r o c e s s e d A p p l e S l i c e s Mean A s c o r b i c A c i d C o n t e n t (mg/100 mg)  T e s t # Sample S i z e Newtown W i n e s a p 1 2 4 4 4.80 b * 2.41 a 5.65 b 2.43 a * Mean v a l u e s i n a row d i f f e r s i g n i f i c a n t l y f o l l o w e d b y t h e same l e t t e r do n o t (P :>i 0.05) by Duncan's t e s t . T a b l e 31 R e s u l t s o f A n a l y s i s o f V a r i a n c e f o r t h e E f f e c t s o f S t o r a g e Time on t h e pH o f P r o c e s s e d A p p l e S l i c e s T e s t # Sample S i z e Mean pH V a l u e s 1.5 months 5.0 months 1 2 3.29 a * 3.39 b Mean v a l u e s i n a row f o l l o w e d b y t h e same l e t t e r do n o t d i f f e r s i g n i f i c a n t l y (P > 0.05) by Duncan's t e s t . \ - 80 -T a b l e 32 R e s u l t s o f A n a l y s i s o f V a r i a n c e f o r t h e E f f e c t s o f S t o r a g e T e m p e r a t u r e on t h e pH o f P r o c e s s e d A p p l e S l i c e s Mean pH V a l u e s T e s t Sample # S i z e 22° C 35° C 1 2 3.30 a * 3.37 b * Mean v a l u e s i n a row f o l l o w e d b y t h e same l e t t e r do n o t d i f f e r s i g n i f i c a n t l y (P > 0.05) b y Duncan's t e s t . T a b l e 33 R e s u l t s o f A n a l y s i s o f V a r i a n c e ^ o r t h e E f f e c t s o f P r e p a r a t o r y M e t h o d a n d L e v e l o f SC»2 on t h e pH o f P r o c e s s e d A p p l e S l i c e s Mean S O 2 L e v e l s (ppm) and C o r r e s p o n d i n g Mean pH V a l u e s T e s t Sample H o t Vacuum C o l d f o r S i z e B l a n c h I n f u s i o n D i p S 0 2 8 42.38 a* 57.88 b 144.3 c pH 8 3.36 a 3.36 a 3.31 b * Mean v a l u e s i n a row f o l l o w e d b y t h e same l e t t e r do n o t d i f f e r s i g n i f i c a n t l y (P > 0.05) by Duncan's t e s t . - 81 -The presence of pyrophosphate ions i n the apple t i s s u e was a l s o found to be r e l a t e d to a lower pH re a d i n g i n the sam-p l e s (Table 35). The v a r i e t y of apple used a l s o p l a y e d an important r o l e i n the de t e r m i n a t i o n o f the pH of the samples (Table 36). The ch o i c e o f the b a c k f l u s h gas a l s o had an e f -f e c t on the f i n a l pH of the processed apple s l i c e s (Table 37). SENSORY ANALYSIS The r e s u l t s o f the sensory e v a l u a t i o n o f the d i f -f e r e n t apple s l i c e samples i n d i c a t e t h a t the product was gen-e r a l l y a cceptable although some c o n f u s i o n d i d e x i s t as to what c o n s t i t u t e s an acceptable apple s l i c e . The f a c t o r s which were found t o i n f l u e n c e the ac-ceptance of the product were l e n g t h o f storage (Table 38), storage temperature (Table 39), and the presence of c a l c i u m ions (Table 40). Other f a c t o r s such as pyrophosphate i o n s , S0 2 l e v e l s , v a r i e t y and type of b a c k f l u s h gas d i d not p r o r duce d i s c e r n i b l e d i f f e r e n c e s (P > 0.05) i n the sensory e v a l u a t i o n s . - 82 -Table 34 Res u l t s o f A n a l y s i s of Variance f o r the E f f e c t s o f Calcium on the pH of Processed Apple S l i c e s Corresponding Mean pH Values Test Sample No . C o l d Dip Vac. I n f u s i o n f o r S i z e Calcium: Calcium Calcium Calcium 6 2 8.0 a* 74.4 b 2 30.5 c pH 6 3.34 a 3.33 b 3.25 c * Mean values i n a row f o l l o w e d by the same l e t t e r do not d i f f e r s i g n i f i c a n t l y (P >0.05) by Duncan's t e s t . Table 35 Res u l t s o f A n a l y s i s o f Variance f o r the E f f e c t o f Pyrophosphate on the pH Value o f Processed Apple S l i c e s Mean pH Values T e s t Sample No With # S i z e Pyrophosphate Pyrophosphate 1 6 3.33 b* 3.28 a 2 4 3.42 b 3.36 a * Mean values i n a row f o l l o w e d by the same l e t t e r do not d i f f e r s i g n i f i c a n t l y (P 05) by Duncan's t e s t . - 83 -Table 36 Resul t s o f A n a l y s i s of Variance -'for the E f f e c t s o f Apple V a r i e t y on the pH of Processed Apple S l i c e s Mean pH Values Te s t Sample # S i z e Newtons Winesaps 1 4 3.37 a* 3.45 b 2 4 3.33 a 3.44 b * Mean values i n a row f o l l o w e d by the same l e t t e r do not d i f f e r s i g n i f i c a n t l y (P > 0.05) by Duncan's t e s t . Table 37 Res u l t s o f A n a l y s i s o f Variance .-for the E f f e c t of B a c k f l u s h Gas on the pH of Processed Apple S l i c e s T e s t # Sample S i z e Mean pH Values N i t r o g e n Carbon Dioxide 3.33 b* 3.26 a * Mean values i n a row fo l l o w e d by the same l e t t e r do not d i f f e r s i g n i f i c a n t l y (P > 0.05) by Duncan's t e s t . - 84 -Table 38 R e s u l t s o f A n a l y s i s o f Variance f o r the E f f e c t s o f Time on the Tour Q u a l i t y Parameters i n the Sensory E v a l u a t i o n o f Processed Apple S l i c e s Q u a l i t y Parameter Sample Siz e Mean L e v e l 1.5 months o f Acceptance (%) 5.0 months Appeal 6 61.10 b* 50.29 a Texture 6 58.42 b 51.21 a Flav o u r 6 63.45 b 55.95 a A c c e p t a b i l i t y 6 59.02 b 49.36 a * Mean values i n a row f o l l o w e d by the same l e t t e r do not d i f f e r s i g n i f i c a n t l y (P >. 0.05) by Duncan's t e s t . Table 39 R e s u l t s of A n a l y s i s of Va r i a n c e -for the E f f e c t s o f Storage Temperature on the Four Q u a l i t y Parameters i n the Sensory E v a l u a t i o n o f Processed Apple S l i c e s Test Parameter Sample S i z e Mean L e v e l 22° c of Acceptance (%) 35° C Appeal 2 72.56 b* 47.90 a Texture 2 65.11 b 37.56 a F l a v o u r 2 72.17 b 56.58 a A c c e p t a b i l i t y 2 68.60 b 42.55 a * Mean valu e s i n a row fo l l o w e d by the same l e t t e r <j0 not d i f f e r s i g n i f i c a n t l y (P > 0.05) by Duncan's t e s t . - 85 -T a b l e 40 f R e s u l t s o f A n a l y s i s o f V a r i a n c e ' f o r . t h e E f f e c t o f C a l c i u m on t h e F o u r Q u a l i t y P a r a m e t e r s i n t h e S e n s o r y E v a l u a t i o n o f P r o c e s s e d A p p l e S l i c e s T e s t P a r a m e t e r Sample S i z e Mean L e v e l o f No C a l c i u m A c c e p t a n c e (%) C a l c i u m A p p e a l 10 41.18 a* 66.28 b T e x t u r e 10 25.38 a 59.28 b F l a v o u r 10 54.54 a 65.02 b A c c e p t a b i l i t y 10 32.96 a 62.00 b * Mean v a l u e s i n a row f o l l o w e d b y t h e same l e t t e r do n o t d i f f e r s i g n i f i c a n t l y (P' > 0.05) by Duncan's t e s t . T a b l e 41 R e s u l t s o f A n a l y s i s o f V a r i a n c e f o r .the E f f e c t s o f C a l c i u m on t h e S h e a r R e s i s t a n c e o f P r o c e s s e d A o o l e S l i c e s Mean S h e a r R e s i s t a n c e (kg) T e s t Sample # S i z e No C a l c i u m W i t h C a l c i u m 1 8 0.77 a* 1.85 b 2 6 0.71 a 2.04 b 3 4 0.88 a 1.94 b 4 6 0.76 a 1.95 b 5 9 0.78 a 1.85 b * Mean v a l u e s i n a row f o l l o w e d b y t h e same l e t t e r do n o t d i f f e r s i g n i f i c a n t l y (P > 0.05) by Duncan's t e s t . - 86 -T a b l e 42 R e s u l t s o f A n a l y s i s o f V a r i a n c e f o r t h e . E f f e c t s o f t h e P r e p a r a t o r y T r e a t m e n t on t h e S h e a r R e s i s t a n c e R e a d i n g s o f P r o c e s s e d A p p l e S l i c e s Mean S h e a r R e s i s t a n c e (kg) T e s t Sample H o t C o l d Vacuum # S i z e B l a n c h D i p I n f u s i o n 1 9 0.77 a* 1.55 b 1.85 c 2 3 0.89 a 1.57 b 2.21 c 3 3 1.48 a 2.52 b 3.26 c * Mean v a l u e s i n a row f o l l o w e d b y t h e same l e t t e r do n o t d i f f e r s i g n i f i c a n t l y (P > 0.05) b y Duncan's t e s t . - 87 -DISCUSSION PROCESSING Process Time Determination I t was found when comparing the p r o c e s s i n g times de-r i v e d by the thermal d i f f u s i v i t y and heat p e n e t r a t i o n methods d e s c r i b e d e a r l i e r t h a t there was a c o n s i d e r a b l e d i s c r e p a n c y between them. T h i s d i s c r e p a n c y amounted to 4.2 minutes which i s a d i f f e r e n c e of approximately 20% o f the time used f o r our p r o c e s s . Since the s l i c e was processed f o r the f u l l 19.8 minutes, there i s no doubt t h a t the process was s u f f i c i e n t to achieve m i c r o b i a l s t a b i l i t y . In f a c t , i t i s suspected t h a t t h i s process was more than adequate and t h a t the product c o u l d have been s l i g h t l y over processed. The reason f o r the d i s c r e p a n c i e s i n process time r e s u l t from the f a c t t h a t i n the thermal d i f f u s i v i t y method the apple t i s s u e i n a pouch i s c o n s i d e r e d to be a s o l i d b r i c k i n s t e a d of d i s c r e t e s l i c e s surrounded by a l i q u i d phase. T h i s would r e s u l t i n a product which heats by conduction r a t h e r than by both conduction and c o n v e c t i o n as i s the case f o r apple s l i c e s . I t i s known t h a t a food product u s u a l l y heats more q u i c k l y by combined c o n v e c t i o n and conduction than by conduction alone . (Schultz and Olson, 1938). , - 88 -I t a l s o should be noted t h a t t h i s product probably does not conform s t r i c t l y t o a conv e c t i o n - c o n d u c t i o n model e i t h e r s i n c e the d r a i n e d dry s l i c e s were p l a c e d i n the pouch wit h g r a n u l a t e d sugar and s e a l e d . I t i s then d u r i n g the he a t i n g process t h a t l i q u i d i s withdrawn from the s l i c e s by osmosis and c e l l w a l l d i s r u p t i o n due t o the h e a t i n g p r o c e s s . T h i s c o u l d r e p r e s e n t a product t h a t i n i t i a l l y heats by con-d u c t i o n and g r a d u a l l y i n c l u d e s c o n v e c t i o n h e a t i n g as the s y r -up f r a c t i o n i n c r e a s e s . I f t h i s i s the case, the time l a g be-tween when the sugar i s added to the s l i c e s and when the ac-t u a l heat p r o c e s s i n g commences w i l l have an e f f e c t on the p r o c e s s i n g time as osmosis w i l l occur and some l i q u i d w i l l be withdrawn depending on the time e l a p s e d . Hot b l a n c h i n g o f samples c o u l d a l s o a f f e c t t h i s as some c e l l w a l l s would be d i s r u p t e d and would l i k e l y r e l e a s e a d d i t i o n a l l i q u i d . The s i g n i f i c a n c e o f these f a c t o r s was not determined i n t h i s r e s e a r c h , but c o u l d p o s s i b l y be of i n t e r e s t i n some f u t u r e study. I t was noted, however, t h a t there were d i f f e r e n c e s i n the types o f h e a t i n g curves f o r heat p e n e t r a t i o n s t u d i e s i n which the t e s t pouches were allowed t o stand f o r a few hours before p r o c e s s i n g and those i n which the samples were processed immediately. The curves o f the former e x h i b i t e d l i n e a r i t y , whereas those o f the l a t t e r had a more c u r v i -l i n e a r nature. - 89 -The value d e r i v e d from the heat p e n e t r a t i o n method was a d j u s t e d by the a d d i t i o n of three times the s t a n -dard d e v i a t i o n to i n s u r e t h a t the p r o b a b i l i t y of r e q u i r i n g a h i g h e r f h value was l e s s than 0.005. S i m i l a r l y , the thermal d i f f u s i v i t y was c o r r e c t e d by s u b t r a c t i n g three times i t s s t a n -dard d e v i a t i o n . By c a r r y i n g out these procedures, the pro-cess time d e r i v e d was somewhat longer than i f no c o r r e c t i o n s had been made, thus p r o v i d i n g a s a f e t y f a c t o r to reduce the chances of underprocessing. Sample P r e p a r a t i o n and T h e i r E f f e c t s Observation of the samples undergoing the d i f f e r -ent p r e p a r a t o r y treatments, b e f o r e the f i n a l heat p r o c e s s , turned up some d i f f e r e n c e s which i n f l u e n c e d t h e i r t e x t u r e , f l a v o u r and appearance i n subsequent t e s t s . I t was noted t h a t the apple s l i c e s t h a t underwent the ten minute vacuum i n f u s i o n treatment a c q u i r e d a t r a n s -l u c e n t appearance and a bland, watery f l a v o u r . The f l a v o u r changes were p a r t i a l l y masked i n the f i n a l product by the a d d i t i o n .of sucrose to the pouches. For t h i s reason, these samples were not downgraded by the p a n e l i s t s and, i n the a n a l -y s i s of v a r i a n c e of the r e s u l t s , no s i g n i f i c a n t d i f f e r e n c e was found. There were, however, s e v e r a l i n d i v i d u a l comments which c l e a r l y i n d i c a t e d t h a t a number o f the p a n e l i s t s d i d d e t e c t the f l a v o u r change. The t r a n s l u c e n c e of the samples - 90 -was also carried over into the finished product and resulted i n a s l i g h t l y lower score on appeal than i d e n t i c a l samples undergoing d i f f e r e n t preparatory treatments. Again, the i n -divi d u a l comments of some of the panelists s p e c i f i c a l l y men-tioned a frozen-thawed look or at least that the colouration was not uniform. The texture of the samples undergoing the hot blanch treatment was quite soft and t h i s was found to i n f l u -ence the results i n the subsequent texture t e s t s . The hot blanch medium contained the sodium b i s u l f i t e as an SC>2 source for the product and also the sodium acid pyrophosphate as the pyrophosphate ion source for those samples i n which i t was included. The hot blanch was also always car r i e d out afte r a cold dip i n a calcium chloride solution i f calcium ions were to be introduced to the sample. This may have resulted i n the leaching of calcium ions which had not been bonded to pectin molecules. Also, SO2 i s known to have a softening ef-fect on apple texture but the addition of calcium ions to the same tissue i n a basic medium does p a r t i a l l y or even com-pl e t e l y reverse t h i s effect; (Eonting et a l . , 1971). The vitamin C l e v e l i n the hot blanched samples was also found to be s i g n i f i c a n t l y lower than i n those samples undergoing the other preparatory treatments^(Table 27). This resulted from heating the s l i c e s i n the presence of an ample supply of oxygen which, resulted i n oxidation of L- ascorbic acid (Tannenbaum, 1976). - 91 -The apple s l i c e s t h a t underwent the c o l d d i p r e -t a i n e d t h e i r n a t u r a l appearance and much of t h e i r f r e s h tex-ture but i t was found t h a t t h i s a l s o c r e a t e d a problem i n t h a t the s l i c e s tended to be q u i t e bulky and r e s u l t e d i n g r e a t e r pouch t h i c k n e s s than was produced by s l i c e s under-going the other treatments. T h i s had the p o t e n t i a l of r e -q u i r i n g an i n c r e a s e d thermal process time to i n s u r e t h a t m i c r o b i a l s t a b i l i t y was achieved. The gases trapped i n the t i s s u e s a l s o contained oxygen which when i n c l u d e d i n the pouch would i n c r e a s e the degree of nonenzymic browning. The a n a l y s i s f o r c a l c i u m and SO2 l e v e l s i n the ap-p l e samples a f t e r heat p r o c e s s i n g i n d i c a t e t h a t the optimum cho i c e of p r e p a r a t o r y treatment i s important i n the i n c o r -p o r a t i o n of these p r e s e r v a t i v e s i n t o the t i s s u e s . For ex-ample, the vacuum i n f u s i o n treatment was found to be very e f f i c i e n t i n t r a n s p o r t i n g c a l c i u m i o n s i n t o the apple s l i c e s ( F i g . 2 ) but o n l y s l i g h t l y more e f f i c i e n t than the hot blanch method f o r the i n c o r p o r a t i o n of SO2 ( F i g . 1). Comparison of the l e v e l s of c a l c i u m i o n s added to the vacuum i n f u s i o n s o l u -t i o n and the c o l d d i p s o l u t i o n and the l e v e l s found i n the r e s p e c t i v e samples, i n d i c a t e s t h a t f o r the i n c o r p o r a t i o n of c a l c i u m ions the vacuum i n f u s i o n method i s approximately s i x times more e f f i c i e n t than the c o l d d i p treatment. - 92 -Comparison of the SO2 l e v e l s added to the vacuum infusion solutions and the cold dip solutions with the l e v e l s found i n the respective samples indicate that for SO2 incor-poration the vacuum infusion method i s only two times more e f f i c i e n t than the cold dip method. I t i s not known i f the e f f i c i e n c y of these methods in incorporating these additives i s influenced by concentration i . e . as the concentration of additive increases the e f f i c i e n c y increases. This occurrence seems un l i k e l y , but further study would be required for v e r i f i c a t i o n . There i s also the p o s s i b i l i t y that some of the SO2 i n the solution i n the form of dissolved gas may have been removed during the evacuation thus e f f e c t i v e l y lowering the o r i g i n a l concentration of SO2 available for infusion into the tissues when the vacuum was broken. A l e v e l of 1 0 0 ppm of SO2 residing i n the apple tissue was the target l e v e l since higher le v e l s gave r i s e to the c h a r a c t e r i s t i c unpleasant SO2 flavour which was d i s -cernible by c e r t a i n people. As i t was some of the panelists commented on the chemical taste of the cold dip sample i n the sensory analysis. The hot blanch method consistently incorporated lower lev e l s of the additives than the other methods. This again could have been corrected by increasing the levels of additives i n t h e i r respective solutions and further work i s - 93 -r e q u i r e d t o e s t a b l i s h t h e l e v e l s r e q u i r e d . The m a i n a d v a n - ^ t a g e s o f t h e h o t b l a n c h m e thod a r e t h e r e m o v a l o f g a s e s a n d enzyme i n h i b i t i o n . D e c r e a s e s i n f i r m n e s s ( T a b l e 42) and v i t a m i n C c o n t e n t ( T a b l e 27) and t h e l o w e r e f f i c i e n c y o f t h i s p r o c e s s make i t l e s s d e s i r a b l e t h a n t h e o t h e r m e t h o d s . The vacuum i n f u s i o n m e t hod h a s t h e a d v a n t a g e s o f r e m o v a l o f g a s f r o m t h e t i s s u e s b y r e p l a c e m e n t w i t h l i q u i d a n d g r e a t e f f i c i e n c y as f a r a s i n c o r p o r a t i o n o f c h e m i c a l s i s c o n c e r n e d . D i s a d v a n t a g e s o f t h i s p r o c e d u r e a r e t h a t i t c a u s e s a t r a n s l u c e n t a p p e a r a n c e a n d a l o s s o f f l a v o u r , a nd w o u l d t e n d t o be a b a t c h p r o c e s s on a c o m m e r c i a l l i n e a l -t h o u g h H o o v e r and M i l l e r (1975) h a v e r e p o r t e d t h e d e v e l o p m e n t o f a c o n t i n u o u s vacuum i m p r e g n a t i o n p r o c e s s . T h i s p r o c e s s a l s o h a s no i n h i b i t o r y e f f e c t on enzyme a c t i v i t y u n l e s s s t e a m i s u s e d t o b r e a k t h e vacuum. I t was a l s o r e p o r t e d i n t h e same p a p e r t h a t t h e f l a v o u r c h a n g e s t h a t accompany t h i s m e t hod c a n be e c o n o m i c a l l y masked by t h e a d d i t i o n o f 0.1% m a l i c a c i d a l o n g w i t h s u c r o s e t o t h e i n f u s i o n s o l u t i o n ( H o o v e r and M i l l e r , 1 9 7 5 ) . W i l e y and L e e (1970) f o u n d t h a t vacuum i n -f u s i o n w i t h a s u g a r s o l u t i o n i n c r e a s e d t h e f i r m n e s s o f a p p l e s l i c e s w h i c h was p a r t i a l l y d e c r e a s e d w i t h t h e f i n a l p r o c e s s i n g . The c o l d d i p m e t h o d i s n o t as e c o n o m i c a l i n t e r m s o f amounts o f a d d i t i v e s r e q u i r e d , b u t i s somewhat e a s i e r a n d p r o v i d e s g o o d r e s u l t s a s f a r a s i n c o r p o r a t i o n o f t h e c h e m i c a l s i s c o n c e r n e d . T h i s m e t h o d d o e s , h o w e v e r , h a v e s e v e r a l d i s a d -v a n t a g e s . The f i r s t o f t h e s e i s t h a t e n z y m a t i c a c t i v i t y i s - 94 -not necessarily c u r t a i l e d by t h i s method although SO2 i s known to i n h i b i t enzymatic browning (Lindsay, 1976; Creuss, 1948), thus i f an SO2 dip i s used,'this problem i s eliminated. The second problem encountered with t h i s system i s that the gas trapped i n the i n t e r c e l l u l a r spaces i s not removed. Since the oxygen content of t h i s gas can vary from 3 to 15% depend-ing on the r e s p i r a t i o n rate of the apple (Lazar and Hudson, 1976) , i t increases the oxygen content of the container aft e r sealing and i s conducive to nonenzymic browning. It also re-tains the bulky shape of the apple s l i c e s and makes i t more d i f -f i c u l t to achieve an economic f i l l weight and s t i l l seal the . pouch. This also produces a thicker pouch which then requires a s l i g h t l y longer heat process to insure microbial s t a b i l i t y . Of the three methods, i t i s d i f f i c u l t to say that one i s superior to another since i n a commerical plant much would depend on the space available and the economics of the s i t u a t i o n . However, i t i s safe to say that i n view of the loss of texture, sugars and nutrients (Lee, 1958), the hot blanching process i s the l e a s t desirable of the three methods as far as the processing of apples i s concerned. Steam blanching i s less detrimental to f r u i t tissues but i t s t i l l causes some losses i n quality (Guerrant, 1948) and can create flavour changes (Lee, 1958). - 95 -SAMPLE DIFFERENCES  Texture Probably the most u s e f u l and r e l i a b l e method o f measuring the t e x t u r e of the apple s l i c e s used i n t h i s r e -search was the Instron-Kramer s i n g l e blade shear t e s t method. I t has been r e p o r t e d t h a t the measurement of shear f o r c e i s the b e s t estimate of sensory e v a l u a t i o n and t h e r e f o r e the most l i k e l y t o i n d i c a t e the degree of a c c e p t a b i l i t y o f a sample (Bowman et a l . , 1972). Measurement of the v i s c o m e t r i c p r o p e r t i e s of a puree of the samples, showed l i t t l e r e l a t i o n s h i p to the r e -s u l t s o f t e x t u r e measurement on whole s l i c e s w i t h the I n s t r o n . O r i g i n a l l y i t was thought t h a t the c e l l s o f the apple t i s s u e s would be separated i n t o d i s c r e t e u n i t s on maceration and t h a t the presence of c a l c i u m ions i n t h i s puree would cause r e a s s o -c i a t i o n of the c e l l s . T h i s would be accomplished by the form-a t i o n of the c a l c i u m b r i d g e s between the f r e e c a r b o x y l groups of p e c t i c substances i n the w a l l s of the i n d i v i d u a l c e l l s . I t was hoped t h a t the degree of agglomeration c o u l d be meas-ured v i s c o m e t r i c a l l y and t h a t d i f f e r e n c e s i n l e v e l s o f c a l -cium would be r e f l e c t e d by i n c r e a s e d v i s c o s i t y . When the v i s -cometric measurements were s u b j e c t e d to the m u l t i p l e r e g r e s -s i o n a n a l y s e s , c a l c i u m was shown to have a s i g n i f i c a n t r e l a -t i o n s h i p o n l y when i n c l u d e d i n two-way i n t e r a c t i o n s but bore no s i g n i f i c a n t r e l a t i o n s h i p when c o n s i d e r e d as a s i n g l e f a c t o r . - 96 -The s i n g l e f a c t o r s shown t o r e l a t e m o s t s i g n i f i c a n t -l y t o t h e s h e a r f o r c e m e a s u r e m e n t s were t h e c a l c i u m l e v e l o f t h e s a m p l e a n d t h e t e m p e r a t u r e a t w h i c h t h e s t o r a g e was m a i n -t a i n e d ( T a b l e 4 ) . These f a c t o r s are shown i n T a b l e 5 t o g i v e a b e t t e r e x p l a n a t i o n o f t h e v a r i a n c e i n t h e s h e a r f o r c e i n a s e r i e s o f two-way i n t e r a c t i o n s w i t h o t h e r f a c t o r s i n v o l v e d . The e f f e c t o f c a l c i u m i o n s on p r o c e s s e d f r u i t t e x -t u r e h a v e b e e n known f o r many y e a r s ( L o c c n t i and K e r t e s z , 1 9 4 1 ) . The u s e o f c a l c i u m i o n s t o f i r m a p p l e s l i c e s w h i c h a r e t o u n -d e r g o i n t e n s i v e h e a t p r o c e s s i n g h a s b e e n l i m i t e d t o c e r t a i n v a r i e t i e s w h i c h i n c l u d e t h e v a r i e t i e s u s e d i n t h i s r e s e a r c h (Reeve and L e i n b a c h , 195 3 ) . The r e s u l t s o f t h e m u l t i p l e r e -g r e s s i o n a n a l y s i s i n d i c a t e t h a t a n i n c r e a s e d l e v e l o f c a l c i u m i o n s r e s u l t s i n an i n c r e a s e i n t h e f o r c e r e q u i r e d t o s h e a r t h e s l i c e s . T h i s i s a l s o s u p p o r t e d b y t h e r e s u l t s o f t h e m i n i a n a l y s e s o f v a r i a n c e ( T a b l e 4 1 ) . I n t h e m u l t i p l e r e g r e s s i o n a n a l y s i s u s i n g two-way i n t e r a c t i o n f a c t o r s , c a l c i u m i s shown t o i n t e r a c t w i t h t h e t o t a l s u g a r c o n t e n t , t h e r e d u c i n g s u g a r c o n t e n t and t h e l e n g t h o f s t o r a g e t o i n f l u e n c e t h e t e x t u r e o f t h e s a m p l e . V J i l e y and Lee (1970) d e m o n s t r a t e d t h a t t h e p r e s e n c e o f s u c r o s e i n t h e t i s s u e s a i d s i n f i r m i n g a p p l e s l i c e s . I t i s known t h a t t h e p e c t i n i c a c i d s o f p l a n t t i s s u e s a r e c a p a b l e o f f o r m i n g g e l s w i t h s u g a r a n d a c i d , o r i f t h e y a r e o f a l o w m e t h o x y l c o n t e n t , w i t h c e r t a i n m e t a l l i c i o n s , s u c h a s c a l c i u m (Hodge and Osman, 1 9 7 6 ) . - 97 -Increases i n r e d u c i n g sugar l e v e l s i n d i c a t e the hy-d r o l y s i s of sucrose to i t s component r e d u c i n g sugars glucose and f r u c t o s e . T h i s event occurs over prolonged storage times and e l e v a t e d storage temperatures. T h i s i s a l s o accompanied by a breakdown of p e c t i c substances (Adams and Blundstone, 1971) r e s u l t i n g i n s e p a r a t i o n of the t i s s u e c e l l s . Turgor w i t h i n the c e l l s i s l o s t d u r i n g the i n i t i a l h e a t i n g process due to a d e n a t u r a t i o n of the c e l l membrane r e s u l t i n g i n a l o s s of the s e l e c t i v e p e r m e a b i l i t y . T h i s e f f e c t i s r e v e r s e d w i t h the formation o f the c a l c i u m and sugar b r i d g e s between the p e c t i c substances of the c e l l w a l l , most of which have become water s o l u b l e w i t h the i n i t i a l h e a t i n g . The r e s u l t s of 7these p h y s i c a l and chemical changes i s t h a t p e c t i c m a t e r i a l s , when h y d r o l y s e d , are l o s t t o the surrounding medium wit h h y d r o l y z e d sugars and firmness i s reduced. The f a c t o r s which were shown to correspond s i g n i f -i c a n t l y w i t h the v i s c o m e t r i c r e s u l t s by the m u l t i p l e r e g r e s -s i o n analyses were the a s c o r b i c a c i d content, the b a c k f l u s h gas, the t o t a l sugars content and the l e n g t h o f storage • (Tables 6, 7, 8, and 9 ) . The v a r i e t y of apple was shown t o be a s i g n i f i c a n t f a c t o r i n r e l a t i o n t o the d e t e r m i n a t i o n of the c o n s i s t e n c y c o e f f i c i e n t s . On c l o s e r examination (Table 1 0 , 1 1 , 1 2, and 13) u s i n g two-way i n t e r a c t i o n f a c t o r s , c a l -cium i n two-way i n t e r a c t i o n s w i t h the b a c k f l u s h gas and time emerge as f a c t o r s with h i g h l y s i g n i f i c a n t r e l a t i o n s h i p s t o the v i s c o m e t r i c r e s u l t s . An i n t e r a c t i o n between the a s c o r b i c - 98 -a c i d content and the storage temperature was a l s o shown to have a h i g h l y s i g n i f i c a n t r e l a t i o n s h i p to the v i s c o m e t r i c r e -s u l t s . Other f a c t o r s which p a r t i a l l y e x p l a i n e d the v a r i a n c e i n some of the v i s c o m e t r i c r e s u l t s were the t o t a l sugar con-t e n t , the v a r i e t y - c a l c i u m content i n t e r a c t i o n and a t o t a l sugar - reducing sugar i n t e r a c t i o n . The c a l c i u m content - b a c k f l u s h gas i n t e r a c t i o n e f -f e c t can be e x p l a i n e d i n t h a t i n those samples packed with carbon d i o x i d e , a c e r t a i n amount of the CO2 was d i s s o l v e d i n the syrup. The carbonate i o n s thus formed would i n t e r a c t with f r e e c a l c i u m ions forming i n s o l u b l e c a l c i u m carbonate p a r t i -c l e s which would i n c r e a s e . t h e v i s c o s i t y of purees formed from such samples. Ni t r o g e n being l e s s s o l u b l e and more i n e r t would have l i t t l e or no i n f l u e n c e on the t i s s u e s ( J o s l y n , 1964). An i n t e r e s t i n g s p e c u l a t i o n a r i s i n g from t h i s i s t h a t , given time, the l e v e l of gaseous CO2 remaining i n the pouch should d i m i n i s h and t h e r e f o r e the p r o t e c t i o n p r o v i d e d by the n a t u r a l t h i c k n e s s o f a b a c k f l u s h e d pouch would be l o s t r e s u l t i n g i n a g r e a t e r chance o f mechanical damage due t o h a n d l i n g . The c a l c i u m content - storage time i n t e r a c t i o n e f f e c t i n d i c a t e s t h a t as time i n c r e a s e s those samples wi t h g r e a t e r c a l c i u m l e v e l s have g r e a t e r decreases i n v i s c o s i t y than those of lower c a l c i u m content. The mechanism of t h i s i n t e r a c t i o n i s not c l e a r and t h e r e f o r e cannot be e x p l a i n e d w i t h any c e r -t a i n t y . I t i s known t h a t i n those samples wi t h h i g h e r l e v e l s of c a l c i u m there are more c a l c i u m b r i d g e s formed between the - 99 -p o l y s a c c h a r i d e s of the c e l l w a l l s . I t i s a l s o known t h a t d u r i n g maceration the bonds are broken and the c e l l s are sep-ar a t e d . I t i s p o s s i b l e t h a t w i t h time the a c t u a l w a l l of the c e l l i s weakened. T h i s weakening may be of l a r g e enough mag-nitude t h a t the f o r c e r e q u i r e d to rupture the w a l l i s l e s s than the f o r c e r e q u i r e d to break the h i g h e r number o f c a l c i u m b r i d g e s . In t h i s case, then the rupture o f the c e l l s would l e a d to a lower v i s c o s i t y of the puree which was noted i n a l l cases over the storage p e r i o d . Reagglomeration of c e l l s would be decreased as the number of ruptured c e l l s i n c r e a s e d a l s o r e s u l t i n g i n a lower v i s c o s i t y . F u r t h e r s t u d i e s u s i n g micro-scopy are needed t o v e r i f y t h i s p r o p o s i t i o n . The i n t e r a c t i o n between the a s c o r b i c a c i d content -and the temperature i s a l s o d i f f i c u l t t o e x p l a i n . The reason f o r t h i s i s t h a t the experimental r e s u l t s from the a s c o r b i c a c i d a n a l y s i s i n d i c a t e s t h a t the a s c o r b i c a c i d content of the samples i n c r e a s e d w i t h i n c r e a s e d storage time and temperature. Since i t has been w e l l documented t h a t v i t a m i n C i s heat l a b i l e (Blundstone e t a l . , 1971) i t seems u n l i k e l y t h a t these r e s u l t s are c o r r e c t and i t i s b e l i e v e d t h a t the i n c r e a s e d l e v e l s are a c t u a l l y a r e s u l t of a b u i l d up of other i n t e r f e r i n g substances (Tannenbaum, 1976) which gave p o s i t i v e r e s u l t s i n the t i t r a t i o n f o r a s c o r b i c a c i d . - 100 -I t i s known t h a t the p o l y s a c c h a r i d e m a t e r i a l s o f c e l l w a l l s are broken down by prolonged storage at h i g h e r temperature. I t i s p o s s i b l e t h a t the i n t e r f e r i n g substances are e i t h e r a r e s u l t of t h i s breakdown or i n some way i n t e r a c t with temperature t o b r i n g about h y d r o l y s i s o f these m a t e r i a l s thus r e d u c i n g the p o s s i b i l i t i e s o f reagglomeration f o l l o w i n g complete maceration. The t o t a l sugar content of the apple s l i c e s was a l s o found t o i n f l u e n c e the flow behaviour index and the con-s i s t e n c y c o e f f i c i e n t of the apple puree. I n c r e a s i n g t o t a l sugar content was shown to c o i n c i d e with i n c r e a s e d v i s c o s i t y o f the puree. Because the sugar content i s s m a l l when com-pared w i t h the water added to make the puree, i t i s d o u b t f u l t h a t the v i s c o s i t y r e s u l t e d from any changes i n the sy r u p i n e s s of the l i q u i d phase. A more l i k e l y r e s u l t i s t h a t sugar be-haved as a g e l l i n g agent which a t the low pH p e r m i t t e d the formation o f a s u g a r - p e c t i n i c a c i d g e l between adjacent c e l l s and thereby i n c r e a s e d the p a r t i c l e s i z e of the s o l i d s content which r e s u l t e d i n an i n c r e a s e i n v i s c o s i t y (Hodge and Osm'an, 1976) . An i n t e r a c t i o n between the t o t a l sugars content and the r e d u c i n g sugars content was shown to have a r e l a t i o n t o the i n t e r m e d i a t e shear r a t e apparent v i s c o s i t y and the y i e l d s t r e s s . T h i s i n t e r a c t i o n was p o s i t i v e i n r e l a t i o n t o t h a t o f the v i s c o m e t r i c parameters which i n d i c a t e s t h a t i n c r e a s i n g - 101 -r e d u c i n g sugar l e v e l s corresponded to i n c r e a s e d v i s c o s i t y . The e x p l a n a t i o n of t h i s i n t e r a c t i o n i s s i m i l a r t o t h a t of the t o t a l sugar content i n t h a t an i n c r e a s e i n the t o t a l number of sugar molecules r e s u l t s i n a g r e a t e r number of bonds b e i n g formed between the p e c t i n i c a c i d s and the sugars. T h i s would i n d i c a t e t h a t i f molecules o f sucrose were h y d r o l y z e d as was the case i n t h i s r e s e a r c h , the number of sugar molecules pro-duced would double. T h i s would pr o v i d e a d d i t i o n a l molecules capable of forming a g e l w i t h the p e c t i c substances. Thus an i n c r e a s e of the t o t a l sugar content c o u l d l e a d t o a two-f o l d i n c r e a s e i n the t o t a l number of sugar molecules depending on the e x t e n t of h y d r o l y s i s . In an o v e r a l l comparison of the two methods of meas-u r i n g t e x t u r e , i t can be seen by o b s e r v i n g the R 2 v a l u e s f o r the analyses t h a t the most accurate e x p l a n a t i o n of the v a r i a n c e given by the independent v a r i a b l e s i n the m u l t i p l e r e g r e s s i o n analyses i s d e r i v e d when c o n s i d e r i n g both s i n g l e and two-way i n t e r a c t i o n f a c t o r s a g a i n s t the I n s t r o n r e s u l t s . I t i s i n t e r -e s t i n g t o note t h a t the c a l c i u m l e v e l s of the samples had no s i g n i f i c a n t i n f l u e n c e on the v i s c o m e t r i c measurements when only s i n g l e f a c t o r s were c o n s i d e r e d . I t o n l y appeared as a s i g n i f i c a n t c o n t r i b u t o r i n two-way i n t e r a c t i o n f a c t o r s with some of the s i n g l e f a c t o r s which had been found to be s i g n i f i -cant c o n t r i b u t o r s i n the s i n g l e f a c t o r a n a l y s i s . T h i s leads to the c o n c l u s i o n t h a t t h i s method i s not the b e s t method f o r determining d i f f e r e n c e s i n samples due to d i f f e r e n c e s i n - 102 -calcium levels and that t h i s method also provides a poorer estimate of subjective analyses of apple s l i c e texture than does the measurement of shear force with the Instron and Kramer Shear c e l l . Colour The results of the multiple regression analyses on the data from the three colour parameters of the Hunterlab Colour Difference meter indicate, t hat the factors whose v a r i -ance coincides s i g n i f i c a n t l y with the variance of each colour parameter are not the same. For t h i s reason, the parameters must be separated and discussed independently. The f i r s t parameter of Hunter L value i s a measure of the lightness to darkness r a t i o of the samples. The fac-tors shown to influence t h i s parameter are presented i n Tables 14 and 17. The single factors which best explain the variance i n the Hunter L value are the backflush gas, the t o t a l sugars content, the reducing sugar content, the storage time and storage temperature. A s l i g h t l y better explanation i s achieved when both single and two-way interaction factors are considered. In t h i s comparison a number of int e r a c t i o n factors emerge as s i g n i f i c a n t and give an R 2 value of 0.847 of which 0.803 i s de-rived from the f i r s t four of the following factors. The i n t e r -actions found to provide a s i g n i f i c a n t explanation for the v a r i -ance i n the Hunter L value are interactions between storage time - 103 -and storage temperature, the t o t a l and reducing sugar contents, the SC>2 l e v e l and storage time, the backflush gas and calcium content, the backflush gas and the SO2 content, the pyrophos-phate content and the variety, and f i n a l l y the ascorbic acid content and the pH. The time and temperature interaction bears an inverse rela t i o n s h i p to the Hunter L value. This i s an expected re-s u l t since i t has been well established that colours i n canned f r u i t deteriorate with both increasing storage time and stor-age temperature (Daoud and Luh, 1971). This r e s u l t s from the slow b u i l d up of non-enzymic browning products in the tissues. Because the pH of the samples was less than 4.0, t h i s browning cannot be c l a s s i f i e d as of the M a i l l a r d type but i s suspected of being related to the various organic acids and high levels of sugars present (Adams and Blundstone, 1971). Under aerobic conditions, the ascorbic acid levels of samples undergoing t h i s method of browning usually reaches zero before the onset of browning but under conditions approaching anaerobic, as much as 80% of the o r i g i n a l ascorbic acid may remain at the onset of browning (Tressler and Joslyn, 1954). It has been found that t h i s type of browning may have close c o r r e l a t i o n to lower pH's and high t i t r a t a b l e a c i d i t y (Huggart et a l . , 1957). - 104 -Since one of the a c t i o n s of SO2 i n a product i s t o serve as an a n t i o x i d a n t , i t i n h i b i t s the formation of brown pigments r e s u l t i n g from nonenzymic browning p r o c e s s e s . With time, however, the l e v e l s of SO2 decrease due to r e a c t i o n s with the outer atmosphere caused by p e r m e a b i l i t y through p i n -h o l e s or s e a l s t h a t are impervious to l i q u i d s but a l l o w the passage of oxygen. Thus the SO2 content may be d e p l e t e d by the p r o d u c t i o n of s u l f a t e l e a v i n g the product f r e e t o brown (Joslyn and Braverman, 1954). Some of the samples i n t h i s r e s e a r c h were suspected to have undergone such a process as t h e i r SO2 l e v e l s were lower than expected and t h e i r c o l o u r s , as measured by the Hunter c o l o u r meter, were somewhat darker. I t i s i n t e r e s t i n g to note t h a t there seems to be a c e r t a i n amount of t h i s browning which can occur even b e f o r e the t o t a l S 0 2 content i s d e p l e t e d . The SO2 l e v e l s i n a l l samples were found to decrease s i g n i f i c a n t l y w i t h time; ( F i g . 3 ) . The b a c k f l u s h gas was a l s o found to have a s i g n i f i -cant c o r r e l a t i o n with the v a r i a n c e i n the Hunter L v a l u e . T h i s v a r i a b l e was found to be i n v o l v e d i n s e v e r a l i n t e r a c t i o n s . The gas - c a l c i u m content i n t e r a c t i o n was found to have a n e g a t i v e c o r r e l a t i o n w i t h the Hunter L v a l u e . I t i s suspected t h a t C 0 2 "combined wi t h c a l c i u m , v i a the formation of c a r b o n i c a c i d , t o produce i n s o l u b l e c a l c i u m carbonate. T h i s .' i s supported by the l o s s of the c a l c i u m f i r m i n g a c t i o n of s l i c e s packed with CO- as - 105 -mentioned e a r l i e r . I t was r e p o r t e d by Ponting e t a l . , (1972) t h a t c a l c i u m ions d e r i v e d from c a l c i u m c h l o r i d e have a syner-g i s t i c e f f e c t w i t h both SO2 and a s c o r b i c a c i d f o r the mainten-ance of l i g h t n e s s i n apple t i s s u e s . The l o s s of C a + + as i n -s o l u b l e CaCC>3 t h e r e f o r e may have l e d t o darkening. I t was a l s o r e p o r t e d t h a t as the SO2 l e v e l s became g r e a t e r i n apple t i s s u e s the s y n e r g i s t i c e f f e c t o f C a + + became l e s s . Gardner (1968) r e p o r t e d t h a t some a c i d u l a n t s when added to foods a c t as s y n e r g i s t s to a n t i o x i d a n t s i n the p r e -v e n t i o n o f nonenzymic browning. T h i s may e x p l a i n the i n t e r -a c t i o n noted between the b a c k f l u s h gas and the S 0 2 content o f the samples. I t may a l s o help t o e x p l a i n the s i g n i f i c a n t i n -t e r a c t i o n between the b a c k f l u s h gas and the storage time i n t h a t those, samples packed w i t h CO2 maintained a l i g h t e r c o l o u r over a longer p e r i o d of time. T h i s would l e a d t o the c o n c l u -s i o n t h a t carbon d i o x i d e has b e t t e r p r o p e r t i e s i n the mainten-ance o f c o l o u r than does n i t r o g e n . The i n t e r a c t i o n between the pyrophosphate content and the apple v a r i e t y i s probably b e s t e x p l a i n e d by v a r i e t a l d i f f e r e n c e s i n the a p p l e s . Due to growing c o n d i t i o n s as w e l l as v a r i e t y , apples may c o n t a i n v a r y i n g l e v e l s o f m e t a l l i c ions which would i n f l u e n c e the a c t i o n o f pyrophosphate whose main a c t i o n i s t o sequester m e t a l l i c i o n s capable o f i n i t i a t i n g browning r e a c t i o n s . ( F u r i a , 1968). - 106 -The s i n g l e f a c t o r s most c l o s e l y c o r r e l a t e d w i t h the Hunter a value or r a t i o of redness t o greenness i n the apple s l i c e s were shown by the m u l t i p l e r e g r e s s i o n a n a l y s i s t o be the v a r i e t y , the SO2 content, the a s c o r b i c a c i d content and the storage time (Table 15). A s l i g h t l y b e t t e r c o r r e l a t i o n was achieved when two-way i n t e r a c t i o n f a c t o r s as w e l l as s i n g l e f a c t o r s were compared. The f a c t o r s whose v a r i a n c e showed s i g -n i f i c a n t c o r r e l a t i o n with the v a r i a n c e of the Hunter a v a l u e s i n t h i s a n a l y s i s were i n t e r a c t i o n s between the v a r i e t y and the SC>2 content, the pH and the a s c o r b i c a c i d content, the storage time and temperature, the b a c k f l u s h gas and the pH, the back-f l u s h gas and the a s c o r b i c a c i d content. Of these, the f i r s t t hree are the most important as they comprise 0.818 o f the 0.836 P.2 value of the a n a l y s i s . The c o r r e l a t i o n o f the time -temperature i n t e r a c t i o n w i t h the Hunter a value was h i g h l y s i g -n i f i c a n t j u s t as i t had been p r e v i o u s l y w i t h the Hunter L value and t h e r e f o r e the e x p l a n a t i o n remains the same. The c o r r e l a t i o n i n t h i s case i s p o s i t i v e which corresponds t o i n c r e a s i n g redness or browning of the samples wi t h i n c r e a s e d time and temperature. The v a r i e t y - SO2 content i n t e r a c t i o n probably r e s u l t s from the f a c t t h a t one v a r i e t y , the Newtown P i p p i n s , was s u b j e c t to very r a p i d enzymic browning d u r i n g the p e e l i n g and c o r i n g op-e r a t i o n s . Although t h i s was done q u i c k l y and the prepared s l i c e s were immersed i n b r i n e , a c e r t a i n amount of melanin was produced before p r o c e s s i n g t h i s v a r i e t y . The d i f f e r e n t l e v e l s - 107 -of SC>2 were i n p a r t determined by the p r e p a r a t o r y treatments ( F i g . 1) and t h e r e f o r e , i t i s f e l t t h a t these treatments, es-p e c i a l l y the hot b l a n c h method, may have had a s i g n i f i c a n t i n -f l u e n c e on the degree of browning and the Hunter a v a l u e . An-a l y s i s of v a r i a n c e r e s u l t s demonstrated t h a t the SO2 l e v e l s i n the samples which d i f f e r e d very s i g n i f i c a n t l y were a l s o c o r r e -l a t e d t o the Hunter a v a l u e s f o r the same samples (Table 41). I t would appear from the r e s u l t s t h a t the hot b l a n c h may have d e l e t e r i o u s e f f e c t s on the l i g h t n e s s of apple s l i c e s over and above the e f f e c t s of reduced l e v e l s of SO2 i n c o r p o r a t e d . I t i s p o s s i b l e t h a t the l e v e l s of SO2 i n c o r p o r a t e d by the vacuum i n f u s i o n method r e p r e s e n t a bare minimum below which the brown-i n g r a t e i s able to proceed a t an i n c r e a s e d r a t e . A more prob-able e x p l a n a t i o n i s t h a t the heat of the b l a n c h combined wi t h the presence of an abundant oxygen supply, g i v e s r i s e to non-enzymic browning products to such a degree t h a t the low l e v e l s o f SO2 are unable to r e v e r s e i t ; thus, h i g h e r Hunter a v a l u e s are produced. F u r t h e r work u s i n g d i f f e r e n t l e v e l s o f SO2 i n hot b l a n c h i n g s o l u t i o n s would be r e q u i r e d to v e r i f y t h i s . The c o r r e l a t i o n between the i n t e r a c t i o n of the a s c o r -b i c a c i d content and the pH w i t h the Hunter a v a l u e s i s shown to be negative which i n d i c a t e s t h a t as the a s c o r b i c a c i d l e v e l i n c r e a s e s there would be a decrease i n the Hunter a value and a decrease i n browning. I t can a l s o be seen t h a t w i t h i n c r e a s -i n g a s c o r b i c a c i d l e v e l s , the pH of the sample would become lower and i t i s suspected t h a t t h i s i s the key to the i n t e r a c t i o n - 108 -which occurs between the two factors and subsequently i n f l u -ences the Hunter a value. The value of ascorbic acid as an antioxidant i s well documented (Bauernfeind and Pinkert, 1970) and i t i s often used i n the canning industry as a method of combatting nonenzymic browning. In t h i s research as mentioned e a r l i e r , there was some doubt as to the veracity of the r e s u l t s of the ascorbic acid analysis which indicated that there had been an increase i n the l e v e l of t i t r a t a b l e vitamin C over the f i v e month storage period. It i s f e l t , however, that t h i s ef-fect had l i t t l e influence on the interaction factor above since the increase i n ascorbic acid as measured was of roughly the same magnitude for a l l samples and the values were r e l a t i v e as far as browning between the d i f f e r e n t samples was concerned. The remaining in t e r a c t i o n factors contributed only about 0.018 of the 0.836 c o e f f i c i e n t of determination and there-fore, are not considered to be factors of any major influence; consequently, they w i l l not be discussed. The t h i r d parameter of the colour measurement of the Hunterlab colour difference meter measures the r a t i o n of yellow-ness to blueness i n the sample and i s designated as the b value. Although the colour of the samples were d e f i n i t e l y more yellow than white, i t was found that the variance of the d i f -ferent independent variables i n the multiple regression anal-yses provided a-relatively- poor-explanation of the variance i n \ - 109 -the Hunter b values. The highest R 2 value achieved.was only 0.475. In the stepwise multiple regression using single fac-tors only (Table 16) the independent variables which were shown to have a variance with s i g n i f i c a n t c orrelation to the Hunter b value were the presence of pyrophosphate ions, the SC>2 content and the t o t a l sugar content. When single and two-way int e r a c t i o n factors were both considered as independent variables i n the stepwise multiple regression, the factors which were shown to be correlated s i g n i f i c a n t l y to the Hun-ter b values were interactions between the pyrophosphate and SC>2 content, the backflush gas and SO2 content, the SO2 and reducing sugars content, the SO2 and ascorbic acid contents, the t o t a l sugar and ascorbic acid contents and the ascorbic acid contents and storage temperature (Table 19). The three interaction factors which make up the greater part of the R 2 value are interactions between the t o t a l sugars and ascorbic acid contents, the pyrophosphate and SO2 contents and the SO2 and reducing sugar contents. The relationship of these three in t e r a c t i o n factors to the Hunter b value was a posit i v e one ind i c a t i n g that an increase i n the inter a c t i o n term corres-ponded to an increase i n the Hunter b reading. The in t e r a c t i o n between the t o t a l sugar and ascorbic acid contents i n r e l a t i o n to colour i s d i f f i c u l t to explain but Tannenbaum (1976) indicates than the degradation of ascor-b i c acid can follow any of the many complex pathways depending - 110 -on the c o n d i t i o n s p r e s e n t . Some of these are i n f l u e n c e d by sugar content i n t h a t h i g h e r sugar c o n c e n t r a t i o n s have a t e n -dency to " s a l t - o u t " any 0 2 d i s s o l v e d i n the medium. Although the 0 2 content i n these samples i s low, i t i s not completely excluded from the pouch and t h e r e f o r e 0 2 c o u l d i n f l u e n c e the degrad a t i o n o f v i t a m i n C. Some sugars, p a r t i c u l a r l y f r u c t o s e , are capable o f forming complexes w i t h m e t a l l i c i o n s such as C u 2 + and Fe3+ which are capable o f a c t i n g as c a t a l y s t s i n the breakdown of a s c o r b i c a c i d ( P o l l a r d and Timberlake, 1971). T h e r e f o r e , the sugar c o n c e n t r a t i o n a l s o p l a y s another r o l e i n the p r o t e c t i o n o f a s c o r b i c a c i d . The breakdown of the sugars themselves a l s o leads t o the b u i l d up of break-down products and a decrease i n the t o t a l c o n c e n t r a t i o n o f sugars. The breakdown products o f both sugars and a s c o r b i c a c i d are i n v o l v e d i n the p r o d u c t i o n o f non-enzymic browning pigments i n canned f r u i t products (Reynolds, 1965).. Be-cause o f the number of d i f f e r e n t pathways and the s i m i l a r i t y of i n t e r m e d i a t e products the exact pathway and mechanisms of the breakdown of these components i s d i f f i c u l t t o p i n p o i n t and r e q u i r e s work which goes beyond the scope o f t h i s r e s e a r c h . I t i s known t h a t the breakdown o f a s c o r b i c a c i d i s dependent on the temperature o f the media (Tannenbaum, 1976) and t h a t i t s breakdown r e s u l t s i n the p r o d u c t i o n o f reductones which can i n f l u e n c e assays f o r v i t a m i n C. I t has a l s o been shown t h a t SO2 a c t s as an i n h i b i t o r and p o s s i b l y a b l e a c h i n g - I l l -agent i n nonenzymic browning thus b l o c k i n g the browning r e -a c t i o n and b l e a c h i n g any melandidin pigments produced (Gehman and Osman, 1954; Lindsay, 1976). I t i s a l s o known t h a t w i t h i n c r e a s e d storage time and temperature, r e d u c i n g sugars are produced from non-reducing sugars (sucrose) by h y d r o l y s i s (Tables 23 and 24). The r e d u c i n g sugars then undergo f u r t h e r changes which are i n f l u e n c e d by h e a t i n g and a c i d c o n d i t i o n s to produce compounds capable of condensing i n t o brown p i g -ments (Hodge and Osman, 1976). The presence of SO2 i n h i b i t s t h i s a c t i v i t y by forming an a d d i t i o n compound between the c a r b o x y l group of the r e d u c i n g sugar moiety or one of i t s i n t e r m e d i a t e products and the b i s u l f i t e i o n from the s o l u t i o n (Gehman and Osman, 1954). T h i s b l o c k s the condensation step and s e v e r e l y r e s t r i c t s the r a t e of browning. With prolonged storage time and e l e v a t e d storage temperatures, however, browning does e v e n t u a l l y proceed c a u s i n g a darkening of the samples. The a c t i o n of added pyrophosphate ions i n a sample i s to sequester m e t a l l i c i ons such as Fe^+ and C u 2 + which can c a t a l y z e a number of breakdown r e a c t i o n s which i n t u r n i n i -t i a t e browning r e a c t i o n ( F u r i a , 1968). The exact i n t e r a c t i o n mechanism of t h i s i o n w i t h the SO2 i s unknown but i t i s as-sumed t h a t the c h e l a t i n g a c t i v i t y o f the pyrophosphate may i n some way slow the formation o f i n t e r m e d i a t e products which use up the supply of a v a i l a b l e S 0 2 , thereby p r o l o n g i n g i t s a c t i v i t y . - 112 -In g e n e r a l , the c o l o u r parameters which p r o v i d e the b e s t i n d i c a t i o n o f the a c t i o n o f the independent v a r i a b l e s i n c o l o u r changes i n the apple s l i c e s of t h i s r e s e a r c h are the Hunter L and a v a l u e s w i t h R 2 values i n the m u l t i p l e r e g r e s s i o n analyses of approximately 0.80 as compared to the Hunter b readings which had R 2 values o f l e s s than 0.50 which i n d i c a t e t h a t e i t h e r t h i s parameter i s l e s s v a l u a b l e i n p r e d i c t i n g the f a c t o r s r e s p o n s i b l e f o r c o l o u r changes i n apple s l i c e s or t h a t the f a c t o r s r e s p o n s i b l e f o r the changes i n the yellowness to blueness r a t i o are q u i t e d i f f e r e n t than those proposed f o r the other parameters. Since browning i s of primary con-cern and i s more a c c u r a t e l y measured by the Hunter L and a values i t i s l i k e l y t h a t Hunter b v a l u e s c o u l d be i g n o r e d . C he mlca1 Analyses For t h i s r e s e a r c h , there were a number o f chemical analyses which were c o n s i d e r e d as p o s s i b l e methods o f moni-t o r i n g the changes which o c c u r r e d i n the products over the storage p e r i o d at the d i f f e r e n t temperatures. Because the a v a i l a b l e time to c a r r y out these t e s t s was l i m i t e d , o n l y s i x were chosen to be c a r r i e d out. Two of these were done spec-i f i c a l l y t o show i f any d i f f e r e n c e s c o u l d be found between the l e v e l s of a d d i t i v e s which were i n c o r p o r a t e d by the d i f f e r -ent p r e p a r a t o r y treatments. These were the analyses f o r the c a l c i u m and SC>2 contents. The remaining t e s t s , which i n c l u d e - 113 -analyses f o r t o t a l sugars, r e d u c i n g sugars and a s c o r b i c a c i d as w e l l as pH measurements, were c a r r i e d out to e l u c i d a t e changes i n the q u a l i t y a t t r i b u t e s o f the samples wi t h time. However, when the time came to assess the r e s u l t s o f these v a r i o u s t e s t s , i t was found t h a t the r e s u l t s from both c a t e -g o r i e s c o u l d be a p p l i e d i n t e r c h a n g e a b l y , so t h a t C a + + and SO2 analyses c o u l d be used t o i n d i c a t e q u a l i t y changes while a s c o r b i c a c i d and sugar analyses were i n d i c a t i v e o f the e f -f e c t i v e n e s s and d e s i r a b i l i t y o f the p r e p a r a t o r y methods. Calcium A n a l y s i s Because i t was o r i g i n a l l y planned t h a t the measure-ment of c a l c i u m l e v e l s would o n l y serve to i n d i c a t e the e f -f e c t i v e n e s s of the p r e p a r a t o r y treatments, and a l i m i t e d ac-cess to an atomic absorption-spectrophotometer, d u p l i c a t e measurements of the c a l c i u m l e v e l s were not made f o r both t e s t i n g times. S i n g l e samples,.taken a t each time from the s l i c e s undergoing the shear f o r c e t e s t , were used to ob-t a i n c a l c i u m l e v e l s and the r e s u l t s were combined as d u p l i -cates f o r a s s e s s i n g the e f f e c t i v e n e s s o f the p r e p a r a t o r y methods. As a r e s u l t o f t h i s , i t was im p o s s i b l e t o d e t e r -mine i f d i f f e r e n c e s i n storage time and temperature r e a l l y had any e f f e c t on-the t e x t u r e of apple s l i c e s as a d i r e c t r e s u l t o f changes i n the c a l c i u m content. - 114 -I t was thought t h a t pyrophosphate, i n i t s r o l e as a s e q u e s t e r i n g agent, would t i e up some of the c a l c i u m i o n s i n the apple t i s s u e and might t h e r e f o r e have a s i g n i f i c a n t i n f l u e n c e on the r e s u l t s o f the c a l c i u m a n a l y s e s . T h i s , how-ever, c o u l d not be shown i n e i t h e r the mi n i analyses o f v a r i -ance or the m u l t i p l e r e g r e s s i o n analyses where the l e v e l of pyrophosphate had no s i g n i f i c a n t c o r r e l a t i o n w i t h any of the t e x t u r e measurements. The v a r i e t y o f apple seemed t o have no i n f l u e n c e on the l e v e l of c a l c i u m which was i n c o r p o r a t e d i n t o the t i s s u e s although v a r i e t y was i n v o l v e d i n the m u l t i p l e r e g r e s s i o n i n -dependent i n t e r a c t i o n f a c t o r s which e x p l a i n e d some of the v a r i a n c e i n the v i s c o m e t r i c r e s u l t s . The b a c k f l u s h gas was found to have a s i g n i f i c a n t i n f l u e n c e on the l e v e l of c a l c i u m found i n the samples. From the r e s u l t s i t appears t h a t carbon d i o x i d e i n some way i n -creases the r e t e n t i o n o f c a l c i u m i n the t i s s u e s . The explan-a t i o n o f t h i s e f f e c t r e v o l v e s around the s o l u b i l i t y o f the CO2 and i t s a b i l i t y i n t h i s form to combine w i t h C a + + to form i n -s o l u b l e c a l c i u m carbonate. T h i s m a t e r i a l was probably d e p o s i -t e d w i t h i n the t i s s u e s whereas some of the C a + + i n the n i t r o g e n packed samples would be f r e e t o d i f f u s e out of the t i s s u e s and i n t o the syrup media which was d i s c a r d e d b e f o r e the c a l c i u m a n a l y s i s . - 115 -SC>2 A n a l y s i s The SC>2 content of the samples was found to be i n -f l u e n c e d by a number of the f a c t o r s i n v o l v e d i n t h i s r e s e a r c h . The p r e p a r a t o r y methods were found to have a l a r g e i n f l u e n c e on the l e v e l of SO2 found i n the samples ( F i g . 1). The temperature of storage was a l s o found to i n -f l u e n c e the l e v e l s of SO2 found i n the samples. I t i s known t h a t under ambient c o n d i t i o n s , the l e v e l of SO2 i n a canned product w i l l decrease with the l e n g t h o f storage and t h a t t h i s decrease i s a c c e l e r a t e d as the storage temperature i s i n c r e a s e d ( J o s l y n and Braverman, 1954). In t h i s r e s e a r c h , o n l y one of the samples prepared c o u l d be t e s t e d f o r separate time and temperature e f f e c t s because of i t s storage procedure. A n a l y s i s of these r e s u l t s d i d not show c o n c l u s i v e l y a storage time e f f e c t on the SO2 content of the samples. The measure-ment of SO2 l e v e l s f o r the 1.5 month storage time of samples s t o r e d a t the lower temperature gave lower r e s u l t s than expected ( F i g . 3). The reason f o r t h i s i s suspected to have been the s l i g h t p e r m e a b i l i t y of the pouch which allowed slow e n t r y of 0 2 i n t o the product. T h i s d i f f u s i o n was slow enough t h a t a t the 1.5 month p e r i o d the v i s u a l e f f e c t s were not d i s -c e r n a b l e but some of the r e s u l t s of other chemical analyses l e n d support to t h i s s u s p i c i o n . These i n c l u d e a lower a s c o r -b i c a c i d content and Hunter L r e a d i n g coupled w i t h a s l i g h t l y h i g h e r Hunter a value when compared w i t h o t h e r s i m i l a r samples. The r e s u l t s of t h i s was to g i v e a lower mean SO? l e v e l i n the - 116 -samples from the room temperature sample which when combined w i t h the SO2 readings from the warm temperature storage gave an o v e r a l l mean lower than the o v e r a l l mean a f t e r 5.0 months storage. T h i s i n e f f e c t appeared as a s i g n i f i c a n t i n c r e a s e i n SO2 with time which was erroneous. The e f f e c t of the storage temperature on the SO2 content was more obvious as can be seen i n F i g . 3. In t h i s case there seems to have been a profound decrease i n the SO2 content o f samples s t o r e d a t the h i g h e r temperature between the day of p r o c e s s i n g and the 1.5 month storage t e s t time. F o l l o w i n g t h i s , the SO2 content seemed to l e v e l o f f i n d i c a t i n g t h a t most of the r e a c t i o n s which were "consuming" the SO2 were l i m i t e d and had been d e p l e t e d and t h a t o n l y r e a c t i o n s w i t h very slow r e a c t i o n r a t i o s were s t i l l o c c u r r i n g between the 1.5 and 5.0 month storage p e r i o d . The pouches s t o r e d a t the lower temperature on the other hand had a much slower l o s s of SO2 i n d i c a t i n g the pos-s i b i l i t y t h a t the energy o f a c t i v a t i o n o f the r e a c t i o n ( s ) which had caused the sudden decrease i n the SO2 content o f samples s t o r e d at the h i g h e r temperature had not been reached a t the lower temperature. F u r t h e r work must be done wi t h t e s t s at c l o s e r time i n t e r v a l s and g r e a t e r sample numbers i n order to v e r i f y the r e s u l t s and to e s t a b l i s h whether there i s an energy t h r e s h o l d f o r these r e a c t i o n s and l i m i t i n g f a c t o r s t h a t prevent c o n t i n u a t i o n u n t i l a l l the SO2 i s l o s t . I t i s suspected t h a t a t h i g h e r temperatures the r a t e o f sugar de-- 117 -g r a d a t i o n i s i n c r e a s e d r e s u l t i n g i n sugar breakdown products t h a t combine with the S0 2 (Gehman and Osman, 1954). The r e s u l t s of the analyses of v a r i a n c e a l s o i n d i -c ate t h a t the presence of pyrophosphate i n a sample i n c r e a s e d the l e v e l s of S0 2 remaining a t the t e s t i n g time (Table 20). The a c t i o n of pyrophosphate i o n s i s one of s e q u e s t e r i n g metal-l i c i o n s . I t i s suspected t h a t some of these m e t a l l i c i o n s may p l a y a r o l e as c a t a l y s t s i n the breakdown of c e r t a i n com-ponents of the sample such as o r g a n i c a c i d s t o r e a c t i v e c a r b o n y l compounds which i n t u r n would d e p l e t e the S0 2 content of the sample ( P o l l a r d and Timberlake, 1971). .Removal of these ions from t h i s a c t i v i t y would t h e r e f o r e h e l p to conserve the S0 2 content of the sample. An i n t e r a c t i o n f a c t o r between the pyrophosphate content and the S0 2 content was shown by the stepwise m u l t i p l e r e g r e s s i o n a n a l y s i s u s i n g both s i n g l e and two-way i n t e r a c t i o n f a c t o r s t o vary w i t h s i g n i f i c a n t c o r r e l a -t i o n t o the v a r i a n c e of the Hunter b readings of the samples (Table 19). The analyses of v a r i a n c e on the samples a l s o i n d i -c a t e s t h a t the v a r i e t y of apple used f o r each sample had a s i g n i f i c a n t i n f l u e n c e on the amount_of S0 9 remaining i n the sample a t the time of t e s t i n g . From the r e s u l t s o f Table 21 i t can be seen t h a t the Winesap v a r i e t y seemed to have lower l e v e l s of S0 2 than the Newtown P i p p i n v a r i e t y . The reason f o r t h i s cannot be e x p l a i n e d except f o r the p o s s i b i l i t y of - 118 -some v a r i e t a l d i f f e r e n c e s which a f f e c t e i t h e r the i n c o r p o r a t i o n of SO2 i n t o the t i s s u e or the d e p l e t i o n r a t e o f S 0 2 i n c o r p o r -ated. The v a r i a n c e o f an i n t e r a c t i o n term between the v a r i e t y and the S 0 2 content was found t o have a s i g n i f i c a n t c o r r e l a -t i o n to the v a r i a n c e of the Hunter a v a l u e s . The remaining f a c t o r s , such as the c a l c i u m l e v e l and the b a c k f l u s h , c o u l d not be shown t o have had any s i g n i f i c a n t e f f e c t on the l e v e l s o f S 0 2 found i n the samples at the two t e s t times. T o t a l Sugar A n a l y s i s From the analyses of v a r i a n c e t o determine the e f -f e c t s o f a l l the other f a c t o r s on the t o t a l sugars content of the samples i t was found t h a t o n l y time and temperature of storage had a s i g i f i c a n t i n f l u e n c e (Table 23). The other v a r i a b l e s i n c l u d i n g p r e p a r a t o r y methods, c a l c i u m content, SO2 content, pyrophosphate content, b a c k f l u s h gas and v a r i e t y had no e f f e c t on the t o t a l sugar content. Because o f the design o f t h i s experiment i t was again d i f f i c u l t t o separate the e f -f e c t s o f time and temperature and t h e r e f o r e the r e s u l t s must be presented i n a combined form. I t i s im p o s s i b l e to t e l l which of the two f a c t o r s had the g r e a t e r e f f e c t on the t o t a l sugar content, but i t i s suspected t h a t the h i g h e r storage temperatures had the g r e a t e s t e f f e c t . As support f o r t h i s assumption, i t i s known t h a t sugars undergo very few r e a c t i o n s - 119 -i n watery media at approximately pH 4.0 and t h a t the pH must be r a i s e d to n e u t r a l i t y or a s l i g h t l y b a s i c p o i n t i n o r d e r f o r the c y c l i c h e miacetal s t r u c t u r e of r e d u c i n g sugars to con-v e r t t o the a c y c l i c c a r b o n y l form which are then f r e e t o begin a number o f decomposition r e a c t i o n s . However, w i t h the a p p l i -c a t i o n of heat and pH l e s s than 4.0 a slow e n o l i z a t i o n of sugar molecules can occur which i s f o l l o w e d by a r a p i d a c i d c a t a l y z e d d e h y d ration to produce f u r f u r a l s and browning pigments thus r e -ducing the t o t a l sugar content (Hodge and Osman, 1976). I t was thought t h a t the p r e p a r a t o r y methods might have i n f l u e n c e d the t o t a l sugar content of the samples but t h i s c o u l d not be supported s t a t i s t i c a l l y . The probable r e a -son f o r t h i s i s t h a t a f t e r p r o c e s s i n g w i t h the added sucrose there was a gradual d i f f u s i o n of sugars back i n t o the t i s s u e s . Since the sugar content i n the outer media was many times g r e a t e r than the sugar content of the t i s s u e s any d i f f e r e n c e s caused by the p r e p a r a t o r y methods would soon be d i s g u i s e d as s t a b i l i z a t i o n o c c u r r e d . Support f o r t h i s s u p p o s i t i o n can be taken from the measurement of the t o t a l sugar content of one of the samples the day f o l l o w i n g p r o c e s s i n g . In t h i s case a t o t a l sugar content of 12.4% was found i n comparison to 14.9% i n the same sample a f t e r 1.5 months i n s t o r a g e . - 120 -Reducing Sugar A n a l y s i s The analyses of v a r i a n c e to show the i n f l u e n c e of the f a c t o r s on the r e d u c i n g sugar content of the samples i n -d i c a t e s t h a t o n l y three v a r i a b l e s were r e l a t e d s i g n i f i c a n t l y w i t h the r e d u c i n g sugar content. These f a c t o r s i n c l u d e s t o r -age time, storage temperature and the p r e p a r a t o r y treatment (Tables 23, 24, 26). The sucrose content of f r e s h apple t i s s u e i s always l e s s than the r e d u c i n g sugar l e v e l s , and f r u c t o s e i s found i n g r e a t e r q u a n t i t i e s than glucose (Eheart and Mason, 1967). Upon the a d d i t i o n o f sucrose to the apple s l i c e s , the t o t a l sugar content r i s e s and the r a t i o of r e d u c i n g to t o t a l sugars i n the processed samples changes i n a d i r e c t i o n i n d i c a t i n g an i n c r e a s e i n non-reducing sugar l e v e l s . T h i s t r e n d , however, i s r e v e r s e d and the r e d u c i n g sugar content g r a d u a l l y i n c r e a s e s as a r e s u l t of the h y d r o l y s i s of the non-reducing d i s a c c h a r i d e s u c r o s e . T h i s h y d r o l y s i s r e a c t i o n i s known t o be i n f l u e n c e d by many f a c t o r s such as the a c i d i t y of the media, the type of l i n k a g e between the monosaccharide u n i t s , the r i n g form of the sugar u n i t s , the extent of i n t e r m o l e c u l a r hydrogen bonding and the presence of g l y c o s y l h y d r o l a s e s (Hodge and Osman, 19 76). In the analyses o f v a r i a n c e used t o determine the i n -f l u e n c e o f storage time and temperature on the l e v e l s of re-^ ducing sugars i n the samples, the e f f e c t of h y d r o l y t i c enzymes can be d i s c o u n t e d because of the heat d e n a t u r a t i o n which occurs d u r i n g p r o c e s s i n g . However, when c o n s i d e r i n g the i n f l u e n c e of - 121 -the p r e p a r a t o r y methods on the re d u c i n g sugars (Table 26), one l o g i c a l e x p l a n a t i o n which can be presented i s based on the a c t i v i t y of these same h y d r o l y t i c enzymes which are de-natured by the hot blanch method but continue t o f u n c t i o n i n the vacuum i n f u s e d and c o l d dipped samples i n s p i t e o f the pre -sence of~ S 0 2 . . I t i s p o s s i b l e t h a t the d i s t r i b u t i o n of the SO,, throughout the t i s s u e s i s not uniform t h e r e f o r e a l l o w i n g some h y d r o l y s i s to occur 1. > I t i s a l s o p o s s i b l e t h a t S 0 2 does not i n -h i b i t these enzymes as e f f e c t i v e l y as i t does some of the oth e r s i n v o l v e d i n browning r e a c t i o n s . In o r d e r t o assess the e f f e c t s of the p r e p a r a t o r y treatments i t was necessary t o use samples to which the SO2 had been added by the-three d i f f e r e n t methods. In order to -prove t h a t i t was the d i f f e r e n c e i n methods and not the d i f -f erence i n SO2 l e v e l s which were i n f l u e n c i n g the red u c i n g sugar l e v e l s , samples u s i n g d i f f e r e n t l e v e l s o f SO2 i n c o r -porated by the c o l d d i p method were a l s o compared (Table 25). From t h i s i t can be seen t h a t the SO2 l e v e l i t s e l f has no e f f e c t on the red u c i n g sugar l e v e l and t h e r e f o r e the d i f -f e rences must r e s u l t from d i f f e r e n c e s i n treatment. Hodge and Osman (1976) a l s o r e p o r t e d t h a t the - D - f r u c t o - f u r a n o s y l l i n k a g e i n sucrose, which was the pre -dominant d i s a c c h a r i d e i n t h i s case, makes i t l a b i l e even under m i l d l y a c i d i c c o n d i t i o n s at low temperatures and at extremely low water co n t e n t s . The i n c r e a s e i n storage temperature would t h e r e f o r e serve t o hydrolyze the d i f f e r e n t bonds ( F i g . 4). -, - 122 -From t h i s i t w o u l d seem t h a t t h e h y d r o l y s i s o f s u c r o s e i n t o i t s c omponent r e d u c i n g s u g a r s i s a c c o m p l i s h e d e a s i l y u n d e r a w i d e r a n g e o f c o n d i t i o n s . I t i s known t h a t r e d u c i n g s u g a r s a r e r e s p o n s i b l e f o r , o r t a k e p a r t i n , a g r e a t number o f t h e r e a c t i o n s w h i c h a r e d e t r i m e n t a l t o t h e q u a l i t y o f f o o d a n d t h e r e f o r e t h e h y d r o l y s i s o f s u c r o s e and t h e l i b e r a t i o n o f t h e s e s u g a r s i s a l i m i t i n g f a c t o r i n t h e l i f e o f a p r o d u c t . A s c o r b i c A c i d A l t h o u g h a p p l e s c o n t a i n some a s c o r b i c a c i d , t h e y a r e n o t c o n s i d e r e d t o be an i m p o r t a n t s o u r c e o f v i t a m i n C i n man's d i e t . T h e i r r e l a t i v e l y l o w c o n t e n t , when c o m p a r e d t o o t h e r f r u i t s s u c h a s c i t r u s , c a n v a r y w i t h a number o f f a c t o r s i n c l u d i n g g r o w i n g a n d s t o r a g e c o n d i t i o n s , m a t u r i t y , v a r i e t y a n d w h e t h e r t h e s k i n i s consumed a s p a r t o f t h e a p p l e . C a n n e d a p p l e s c o n t a i n e v e n l e s s v i t a m i n C b e c a u s e h e a t p r o -c e s s i n g , e s p e c i a l l y i n t h e p r e s e n c e o f o x y g e n , h a s been shown t o b r i n g a b o u t i t s d e c o m p o s i t i o n , - (Tannenbaum, 1 9 7 6 ) . F r e s h u n p e e l e d a p p l e s c a n c o n t a i n f r o m 6.0 t o 15.0 mg o f a s c o r b i c a c i d p e r 100 grams o f a p p l e t i s s u e w h e r e a s p r e p a r e d and h e a t p r o c e s s e d a p p l e p r o d u c t s h a v e o n l y a p p r o x i m a t e l y 2.0 t o 6.0 mg/100 g , ( W i l e y a n d Thompson, 1960) . The p u r p o s e o f t h e a s c o r b i c a c i d a n a l y s i s i n t h i s r e s e a r c h was t o d e t e r m i n e i f t h e l e s s r i g o r o u s t h e r m a l t r e a t -ment r e q u i r e d t o p r e s e r v e p r o d u c t s i n f l e x i b l e p o u c h e s c o u l d be b e n e f i c i a l i n t h e p r e s e r v a t i o n o f a s c o r b i c a c i d a n d t h u s - 123 -perhaps o t h e r n u t r i e n t s . There are a number of a n a l y t i c a l procedures f o r de-t e c t i n g a s c o r b i c a c i d but none i s e n t i r e l y s a t i s f a c t o r y be-cause of a l a c k o f s p e c i f i c i t y and the presence o f a l a r g e number of i n t e r f e r i n g substances i n most food products (Taft-nenbaum, 1976). The procedure chosen f o r t h i s r e s e a r c h as d e s c r i b e d e a r l i e r was a method based on the o x i d a t i o n - r e -d u c t i o n p r o p e r t i e s of a s c o r b i c a c i d alone and does not take i n t o account the presence of dehydroascorbic a c i d which can a l s o be pr e s e n t and may be converted to a s c o r b i c a c i d . A number of o x i d i z i n g agents can be used i n t h i s method but the 2, 6 - d i c h l o r o p h e n o l i n d o p h e n o l has been found to be the most s u c c e s s f u l although i t too i s s u b j e c t to i n t e r f e r e n c e from a number of sources. Some products which have under-gone e x t e n s i v e heat treatments and/or prolonged storage are s u b j e c t t o the b u i l d up of a number o f substances c o l l e c t i v e -l y known as "reductones" which w i l l i n t e r f e r e w i t h an a n a l y s i s f o r a s c o r b i c a c i d (Assoc.-of V i t . Chem., 1966). The f a c t o r s which were found by the a n a l y s i s o f va r i a n c e t o have an i n f l u e n c e on the a s c o r b i c a c i d content of the samples i n t h i s r e s e a r c h were storage - time, p r e p a r a t o r y treatments, v a r i e t y and the presence of added c a l c i u m . The storage temperature was a n t i c i p a t e d to have an i n f l u e n c e on the a s c o r b i c a c i d content but c o u l d not be shown to have any s i g n i f i c a n t e f f e c t . - 124 -A c c o r d i n g to the a n a l y s i s of v a r i a n c e f o r the e f -f e c t s of storage time on the a s c o r b i c a c i d content of the samples, there was an i n c r e a s e i n v i t a m i n C w i t h i n c r e a s i n g storage time (Table 28). T h i s may have been an erroneous r e s u l t caused by the b u i l d up o f the reductone m a t e r i a l s mentioned e a r l i e r . I t a l s o c o u l d have r e s u l t e d from the r e -d u c t i o n of dehydroascorbic a c i d to a s c o r b i c a c i d although i t must be assumed t h a t the a s c o r b i c a c i d was s t a b l e and t h a t o x i d a t i o n d i d not cause the c o n v e r s i o n of a s c o r b i c to de-h y d r o a s c o r b i c . I t would appear t h a t the v i t a m i n C i n these samples •was s t a b l e because of the l a c k of i n f l u e n c e by temperature; however, s i n c e v i t a m i n C i s noted f o r being s e n s i t i v e to i n c r e a s e s i n temperature t h i s seems u n l i k e l y . P o s s i b l y , the a s c o r b i c a c i d decomposition was accompanied by a b u i l d up of reductones so t h a t the two r e a c t i o n s were i n balance and no d i f f e r e n c e i n the a s c o r b i c a c i d l e v e l s was d e t e c t e d by the a n a l y s i s . I f a g r e a t e r number of samples from the 37°C s t o r -age had been t e s t e d at the 1.5 month storage time i t i s pos-s i b l e t h a t a d i f f e r e n c e between samples from the two storage temperatures c o u l d have been found. From what i n f o r m a t i o n we have, however, i t i s i m p o s s i b l e to a c c u r a t e l y assess the e f -f e c t s o f e i t h e r storage time or temperature on the a s c o r b i c a c i d content of the s l i c e s . - 125 -The e f f e c t of the p r e p a r a t o r y treatments on the as-c o r b i c a c i d content of the samples as determined by the analyses of v a r i a n c e turned out as expected ;(Table 27). Samples under-going the hot blanch treatment were shown to have the lowest a s c o r b i c a c i d content. I t i s i n t e r e s t i n g t o note t h a t although the a s c o r b i c a c i d readings f o r the 5 month storage p e r i o d were somewhat h i g h e r than the 1.5 month r e a d i n g they were s t i l l v ery much lower than those 5 month.' readings f o r the vacuum i n f u s i o n and c o l d d i p methods. T h i s suggests t h a t the i n i t i a l l e v e l of a s c o r b i c a c i d a t the time of p r o c e s s i n g may have had some e f f e c t on the l e v e l of "reductones" produced. The hot blanch samples were expected t o have a lower a s c o r b i c a c i d l e v e l because of the o x i d a t i o n which would occur when v i t a m i n C i s heated i n the presence of oxygen ( P o l l a r d and Timber-l a k e , 1971). I t was a l s o shown i n two of the analyses t h a t more a s c o r b i c a c i d was found i n samples which had undergone the c o l d d i p treatment r a t h e r than the vacuum i n f u s i o n treatment. T h i s can a l s o be e x p l a i n e d i n t h a t a s c o r b i c a c i d i s s o l u b l e and some may have d i f f u s e d from the t i s s u e d u r i n g e v a c u a t i o n o f the i n f u s i o n chamber. When the vacuum was broken, much of the a s c o r b i c a c i d which was withdrawn from the t i s s u e s r e -mained i n the i n f u s i o n media and was l o s t . The e f f e c t of c a l -cium on the l e v e l of a s c o r b i c a c i d i n the t i s s u e s can a l s o be r e l a t e d to the s o l u b i l i t y of v i t a m i n C i n water. Table 29 - 126 -i n d i c a t e s t h a t t h e p r e s e n c e o f a d d e d c a l c i u m i o n s i n t h e s a m p l e s h e l p e d t o m a i n t a i n t h e l e v e l s o f a s c o r b i c a c i d . O t h e r a n a l y s e s c o m p a r i n g t h e e f f e c t s o f d i f f e r e n t l e v e l s o f a d d e d c a l c i u m i n -d i c a t e d t h a t t h e r e was no s i g n i f i c a n t d i f f e r e n c e (P > 0.05) i n r e t a i n e d a s c o r b i c a c i d l e v e l s . T h e r e f o r e , i t w o u l d seem t h a t t h e p r e s e n c e o f c a l c i u m i o n s a n d n o t t h e i r l e v e l i n -f l u e n c e d t h e s t a b i l i t y o f t h e v i t a m i n C. I t i s t h o u g h t t h a t t h i s i n f l u e n c e may h a v e b e e n r e l a t e d t o t h e m a i n t e n a n c e o f . t h e c e l l w a l l s t r u c t u r e s w h i c h l e d t o b e t t e r r e t e n t i o n o f t h e l i q u i d f r a c t i o n o f t h e t i s s u e s and c o n s e q u e n t l y t h e d i s s o l v e d a s c o r b i c a c i d . S a m p l e s w h i c h h a d no a d d e d c a l c i u m h a d v e r y p o o r t e x t u r e m e a s u r e m e n t s and t h e i r a p p e a r a n c e was s i m i l a r t o t h a t o f a p p l e s a u c e . T h i s w o u l d l e a d t o a g r e a t e r l o s s o f l i q u i d a n d s o l u b l e s o l i d s f r o m t h e t i s s u e s . The v a r i e t y o f a p p l e u s e d f o r p r o c e s s i n g was a l s o shown t o i n f l u e n c e t h e l e v e l o f a s c o r b i c a c i d a s d e t e r m i n e d b y t h e a n a l y s i s ( T a b l e 3 0 ) . P r o c e s s e d Newtown P i p p i n s a m p l e s w e re shown t o h a v e h i g h e r l e v e l s o f a s c o r b i c a c i d t h a n p r o -c e s s e d W i n e s a p s . T h i s r e s u l t was d i r e c t l y r e l a t e d t o t h e q u a n -t i t y o f a s c o r b i c a c i d p r e s e n t i n t h e o r i g i n a l p e e l e d f r e s h t i s s u e s . A n a l y s e s o f t h e p e e l e d f r e s h t i s s u e s o f Newtown P i p p i n a n d W i n e s a p a p p l e s c a r r i e d o u t e a r l i e r h a d i n d i c a t e d t h a t a s c o r b i c a c i d l e v e l s o f 7.84 and 3.13 mg/100 g r e s p e c t i v e -l y w e r e p r e s e n t . - 127 -The r e s u l t s of the a s c o r b i c a c i d a n a l y s i s i n d i c a t e t h a t the hot b l a n c h i n g of apple s l i c e s under normal atmospheric c o n d i t i o n s i s d e f i n i t e l y d e t r i m e n t a l to the v i t a m i n C l e v e l w h i le the o t h e r methods had a r e l a t i v e l y s m a l l e f f e c t on i t . By o b s e r v i n g the a s c o r b i c a c i d l e v e l s of one sample t e s t e d immediately a f t e r p r o c e s s i n g and then again a t 1.5 months (Table 45) i t can be seen t h a t approximately 25% o f the l e v e l found i n peeled apples was l o s t d u r i n g the process a f t e r which the r a t e of a s c o r b i c a c i d decomposition was reduced. Adams and Blundstone (1971) have i n d i c a t e d t h a t the r e t e n t i o n of v i t a m i n C i n a c i d products with low oxygen par-, t i a l p r e s s u r e s and an absence of copper ions i s q u i t e h i g h . I f some - oxygen i s r e t a i n e d i n the product, g r e a t e r p r o t e c t i o n i s g iven to the ascorbate i n p l a i n t i n p l a t e c o n t a i n e r s as op-posed to lacquered and g l a s s c o n t a i n e r s because t i n ions are more s u s c e p t i b l e to o x i d a t i o n a t low pH than are ascorbate i o n s . T h e i r f e e l i n g was t h a t more v i t a m i n s are l o s t from canned f r u i t products because of t h e i r s o l u b i l i t y . V itamin C i s h i g h l y s o l u b l e and consequently i s l o s t from the t i s s u e s along with the moisture i f the syrup from these products i s d i s c a r d e d . In t h i s r e s e a r c h , the a s c o r b i c a c i d a n a l y s i s was o n l y c a r r i e d out on d r a i n e d samples, thus i t i s l i k e l y t h a t a. l a r g e p o r t i o n of the 25% r e d u c t i o n i n ascorbate content was c o n t a i n e d i n the syrup. T h i s would i n d i c a t e t h a t heat pro-c e s s i n g a t low oxygen p a r t i a l p r e s s u r e s i s not as d e t r i m e n t a l - 128 -to the ascorbate content of a c i d products, such as apple s l i c e s , as i s the p e e l i n g o p e r a t i o n and the anaerobic degrad-a t i o n t h a t occurs r e g a r d l e s s of other c o n d i t i o n s . P r o c e s s i n g u s i n g the f l e x i b l e r e t o r t pouch may t h e r e f o r e have l i t t l e i f any a d d i t i o n a l advantage over c o n v e n t i o n a l c o n t a i n e r s f o r the r e t e n t i o n of v i t a m i n C i n processed apple s l i c e s . pH Changes Changes i n the pH of the apple s l i c e s were found to be i n f l u e n c e d by a number of f a c t o r s . Storage time and temp-e r a t u r e were shown to reduce the a c i d i t y of the products (Tables 31 and 32). T h i s can be e x p l a i n e d by the many chemi-c a l r e a c t i o n s such as the d e s t r u c t i o n of a s c o r b i c a c i d t h a t occur d u r i n g s t o r a g e . Increased storage temperatures supply the energy to i n i t i a t e and c a r r y out these r e a c t i o n s at a f a s t e r r a t e and t h e r e f o r e i n f l u e n c e the pH. The a d d i t i o n of b i s u l f i t e , c a l c i u m ions and pyrophos-phate ions to the samples a l l served to decrease the pH with i n c r e a s i n g l e v e l s of p r e s e r v a t i v e s (Tables 33, 34, and 35);. These decreases were smal l i n the case of c a l c i u m ions but were a l l h i g h l y s i g n i f i c a n t . The samples packed wi t h carbon d i o x i d e were a l s o found to have a lower pH than comparable samples packed wi t h n i t r o g e n (Table 37). T h i s r e s u l t s from the h i g h s o l u b i l i t y o f carbon dioxide- which produces c a r b o n i c a c i d with water, thus s l i g h t l y lowering the pH. - 129 -o The v a r i e t y o f apple used f o r p r o c e s s i n g was a l s o found t o i n f l u e n c e the pH. (Table 36);. Processed Newtown P i p -pi n s had lower pH readings than processed Winesaps. T h i s came as no s u r p r i s e as f r e s h samples of the Newtown P i p p i n s and Winesap v a r i e t i e s were found t o have pH readings o f 3.40 and 3.52 r e s p e c t i v e l y . T h i s aspect o f apple p h y s i o l o g y i s again r e l a t e d t o s e v e r a l f a c t o r s such as growing and storage c o n d i -t i o n s , m a t u r i t y and v a r i e t y . SENSORY ANALYSTS The r e s u l t s o f the t a s t e panel s c o r i n g i n d i c a t e t h a t the important f a c t o r s i n f l u e n c i n g the acceptance o f the samples were the time and temperature of storage and the l e v e l o f c a l -cium ions i n c o r p o r a t e d i n t o the t i s s u e s . I t was found t h a t as the storage time and temperatures were i n c r e a s e d , the accep-tance o f the samples decreased (Table 38 and 39) . ..Calcium l e v e l s are presumed to be l i n k e d with t e x t u r e s i n c e the samples wit h the h i g h e s t scores were samples wi t h h i g h e r c a l c i u m l e v e l s and consequently b e t t e r t e x t u r e r e a d i n g s . There was, however, some c o n f u s i o n among the p a n e l i s t s as t o what c o n s t i t u t e d a d e s i r a b l e apple s l i c e . For i n s t a n c e , most p a n e l i s t s p r e f e r r e d the f i r m e r s l i c e s but some a c t u a l l y p r e f e r r e d the s o f t e r samples which they compared t o apple sauce. There was a l s o d i v e r s i t y i n the c o l o u r p r e f e r e n c e s among the p a n e l i s t s . Some o b j e c t e d to the yellowness of the s l i c e s and - 130 -s t a t e d they p r e f e r r e d white. Others made no mention of y e l -lowness but c r i t i c i z e d the n on-uniformity o f c o l o u r when white s l i c e s were pr e s e n t . Perhaps the most c o n f u s i n g r e s u l t s were ob t a i n e d from the f l a v o u r s c o r e s . S e v e r a l p a n e l i s t s were able to d e t e c t an SO2 t a s t e e s p e c i a l l y a t the 1.5 month t e s t i n g p e r i o d . A l s o , some p a n e l i s t s complained of the blandness or l a c k o f apple f l a v o u r i n the vacuum i n f u s e d samples. G e n e r a l l y , however, the f l a v o u r scores f o r a s i n g l e sample had such wide d i v e r s i t y t h a t l i t t l e can be d e r i v e d from them. I t was noted t h a t on the whole, the Newtown P i p p i n samples r e c e i v e d more fa v o u r a b l e comments than the Winesap samples although no s i g n i f i c a n t d i f f e r e n c e s were de t e c t e d between the sensory scores f o r the v a r i e t i e s by a n a l y s i s of v a r i a n c e . In the o v e r a l l acceptance category as i n the t e x t u r e category, the Duncan's M u l t i p l e Range t e s t d i v i d e d the samples i n t o two groups a c c o r d i n g to the p a n e l i s t s s c o r e s . In both cases, the sample which had no added c a l c i u m made up the group having the lowest scores while the remaining samples were i n -cluded i n the group r e c e i v i n g the h i g h e s t s c o r e s . T h i s i n d i -c ates t h a t t e x t u r e had the g r e a t e s t i n f l u e n c e i n determining the o v e r a l l acceptance o f the samples although from p a n e l i s t s comments i t was f e l t t h a t f l a v o u r was a l s o a major f a c t o r . I t was a l s o i n t e r e s t i n g to note t h a t i n the f l a v o u r and appeal c a t -e g o r i e s , the sample w i t h no added c a l c i u m was always i n c l u d e d i n the group r e c e i v i n g the lowest scores f o r sensory e v a l u a t i o n . - 131 -The c o l d dipped sample was shown by the Duncan's Mul-t i p l e Range t e s t t o be the o n l y sample which was c o n s i s t e n t l y i n c l u d e d i n the groups r e c e i v i n g the h i g h e s t scores i n a l l f o u r c a t e g o r i e s and was never "shared" with groupings r e c e i v i n g lower scores as were the other samples. T h i s sample was thought t o be the optimum when f i r s t processed and was proven to be the b e s t a l l round sample d u r i n g the t e s t i n g . The remaining v a r i a b l e s such as b a c k f l u s h gas, v a r i e t y , b i s u l f i t e l e v e l or the i n c l u s i o n of pyrophosphate c o u l d not be shown by s t a t i s t i c a l a n a l y s i s to have any s i g n i f i c a n t i n f l u e n c e (P > 0.05) on the s c o r i n g of the p a n e l i s t s . The o v e r a l l a c c e p t a b i l i t y category i s c o n s i d e r e d to be an i n d i c a t i o n of whether a product would be accepted or r e -j e c t e d by a p r o s p e c t i v e consumer. Observation of the mean ac-ceptance values f o r a l l samples presented a t the 5 month t e s t -i n g , showed t h a t the c o l d dipped sample had the h i g h e s t score of 69%, which i s an i n d i c a t i o n t h a t the sample c o u l d be accep-t a b l e . Before any d e f i n i t e judgements c o u l d be made, however, more e x t e n s i v e consumer acceptance t e s t s would have to be employed. I t was a l s o found t h a t the method of storage f o r the samples i s c r i t i c a l to t h e i r q u a l i t y . For t h i s r e s e a r c h we had no r i g i d paperboard c o n t a i n e r s to p r o t e c t each i n d i v i d u a l pouch from mechanical damage. As a r e s u l t , i n s p i t e o f the f a c t t h a t the samples were c a r e f u l l y stacked i n l a r g e c o r r u g a t e d paperboard boxes, there was some damage due to the weight of - 132 -the s t a c k . Perhaps i f a more s u i t a b l e method of storage had been employed, some of the t e x t u r e scores would have been im-proved. T h i s i n f o r m a t i o n should be taken i n t o c o n s i d e r a t i o n i n f u t u r e p r o j e c t s i n v o l v i n g f l e x i b l e pouches. - 133 -CONCLUSIONS Due to the d i s c r e p a n c y between the r e s u l t s o f the thermal d i f f u s i v i t y and heat p e n e t r a t i o n methods f o r d e t e r -mination of a process time f o r apple s l i c e s i n f l e x i b l e r e -t o r t pouches, there a r i s e s a q u e s t i o n p e r t a i n i n g t o the r e -l i a b i l i t y o f a t l e a s t one of the methods. Since the heat p e n e t r a t i o n study i s a measurement of the c o n d i t i o n s w i t h i n the s p e c i f i c product under a c t u a l r e t o r t i n g procedures, and s i n c e the measurements were d e r i v e d from a number of " r e t o r t runs", there i s a tendency to be more c o n f i d e n t i n those r e -s u l t s . I t was a l s o found t h a t the heat p e n e t r a t i o n study was l e s s time consuming and the r e t u r n of data was g r e a t e r . For these reasons, i t c o u l d be c o n s i d e r e d the more p r e f e r a b l e method of d e r i v i n g a process time. I t must be conceded, how-ever, t h a t t h i s method r e q u i r e s the use of data a c q u i s i t i o n and computing f a c i l i t i e s which may not always be a v a i l a b l e and t h e r e f o r e , may not be a p p l i c a b l e to a l l s i t u a t i o n s . I t was found t h a t apples taken from long term con-t r o l l e d atmosphere storage are not as good f o r p r o c e s s i n g as those taken from storage s h o r t l y a f t e r h a r v e s t i n s p i t e of the f a c t t h a t a much s h o r t e r heat process i s r e q u i r e d f o r s t a b i l i z a t i o n i n r e t o r t pouches. Texture seems to s u f f e r the g r e a t e s t d e c l i n e i n these apples but i t was shown t h a t c a l c i u m i o n s can be added to improve the f i r m n e s s . Samples without added c a l c i u m had very poor t e x t u r e r a t i n g s and by - 134 -the end of the 5 month storage p e r i o d under e l e v a t e d tempera-t u r e they were reduced to a s a u c e - l i k e c o n s i s t e n c y . Contrary to a p r e v i o u s r e p o r t , (Archer, 1962) s u f f i c i e n t c a l c i u m was added to t h i s product i n the form of c a l c i u m c h l o r i d e i n q u a n t i t i e s low enough to have no n o t i c e a b l e e f f e c t on f l a v o u r . The l i g h t n e s s of the apple s l i c e s was a l s o found t o be maintained by the a d d i t i o n of low l e v e l s of s u l f u r d i o x i d e i n the form of sodium b i s u l f i t e . I t was noted t h a t even at the low l e v e l s added i n t h i s r e s e a r c h , i t was s t i l l d e t e c t e d by some of the p a n e l i s t s . I t i s not known i f the l e v e l s of SC>2 i n c o r p o r a t e d i n the samples was s u f f i c i e n t to m aintain l i g h t n e s s f o r an extended s h e l f l i f e a t room temperature but t h e r e were d e f i n i t e i n d i c a t i o n s o f darkening a f t e r 5 months storage at e l e v a t e d temperatures. The a d d i t i o n of pyrophosphate ions i n the form of sodium a c i d pyrophosphate was a l s o shown to have a s i g n i f i c a n t i n f l u e n c e i n m a i n t a i n i n g l i g h t n e s s i n the samples although i t d i d not seem- to r e t a r d the onset of darkening w i t h i n c r e a s e d storage time. Both v a r i e t i e s of apples chosen f o r t h i s r e s e a r c h were good p r o c e s s o r s and both w i t h s t o o d the prolonged storage q u i t e w e l l . The Newtown P i p p i n s i n t h e i r f r e s h s t a t e seemed t o surpass the Winesaps i n most of the measured q u a l i t y para-meters and t h i s was maintained a f t e r p r o c e s s i n g and throughout the storage p e r i o d . The b i g g e s t problem i n the use of Newtown - 135 -P i p p i n s f o r p r o c e s s i n g i n the B r i t i s h Columbia area a t the p r e s e n t time i s t h e i r p o p u l a r i t y as a f r e s h e a t i n g apple and t h e i r r e l a t i v e l y s h o r t supply to the p r o c e s s i n g market. Wine-saps are a f a m i l i a r p r o c e s s i n g apple which were o n l y s l i g h t l y l e s s d e s i r a b l e i n t h i s process and p r o v i d e a very good prod-u c t as was shown by t h i s r e s e a r c h . N i t r o g e n was shown t o be a h i g h l y e f f e c t i v e b a c k f l u s h gas f o r m a i n t a i n i n g a s t a b l e atmosphere i n the pouch. Carbon d i o x i d e which was a l s o t e s t e d was shown t o have been s o l u b l e i n the l i q u i d media. T h i s reduced i t s e f f e c t i v e n e s s as a cushion a g a i n s t mechanical damage and t i e d up c a l c i u m i o n s i n the form of c a l c i u m carbonate, both of which had an adverse e f f e c t on the t e x t u r e o f the s l i c e s . I t c o u l d not be shown by t h i s r e s e a r c h t h a t n i t r o g e n had any p o s i t i v e e f f e c t s on the s l i c e s o u t s i d e of p r o v i d i n g an i n e r t atmosphere and a reduc-t i o n of the oxygen p a r t i a l p r e s s u r e w i t h i n the pouch. Hot b l a n c h i n g of the apple s l i c e s i s not a d e s i r a b l e p r e p a r a t o r y method as i t was shown to have d e t r i m e n t a l e f f e c t s on the t e x t u r e , c o l o u r and a s c o r b i c a c i d l e v e l s of the samples. Vacuum i n f u s i o n of apple s l i c e s p r o v i d e s good t e x t u r e but was shown to- have s e r i o u s e f f e c t s on c o l o u r and f l a v o u r . Samples t r e a t e d w i t h t h i s method had a t r a n s l u c e n t appearance and bland f l a v o u r due to the l o s s of f l a v o u r v o l a t i l e s d u r i n g the evacu-a t i o n and the i n f u s i o n of water with b r e a k i n g o f the vacuum. The c o l d d i p method, although a l l o w i n g the r e t e n t i o n o f g r e a t e r oxygen l e v e l s w i t h i n the pouch, p r o v i d e d the b e s t product. - 136 -V i s c o s i t y measurements of macerated t i s s u e supply some i n s i g h t i n t o the p o s s i b l e chemical behaviour o f the sam-p l e s ; however, t h i s i s not a good method of determining the i n f l u e n c e of c a l c i u m on t e x t u r e as i s shown by the analyses o f the d i f f e r e n t parameters of v i s c o m e t r i c behaviour. By f a r the most accurate method of t e x t u r e e v a l u a t i o n o f apple s l i c e s i n r e l a t i o n to sensory a n a l y s i s i s the measurement of the f o r c e s r e q u i r e d to shear the s l i c e s . I t i s a l s o e v i d e n t t h a t g r e a t care must be taken when u s i n g pouches, to a v o i d the use of p i n h o l e d c o n t a i n e r s . Care should be taken i n heat s e a l i n g to i n s u r e s a f e t y and the s t o r e d s u p p l i e s should he p r o v i d e d w i t h some form o f p r o t e c -t i o n t o prevent mechanical damage to both the pouch and i t s cont e n t s . - 137 -LITERATURE CITED Adams, J . B., and B l u n d s t o n e , H. A. W., 1971 i n The B i o c h e m -i s t r y o f F r u i t s a n d T h e i r P r o d u c t s . V o l . I I , Hulme, A. C. (ed.) A c a d e m i c P r e s s . L o n d o n : 508-520. A r c h e r , R. W., 1962 F i r m i n g P r o c e s s e d A p p l e s w i t h C a l c i u m C a n n e r / P a c k e r 1 3 1 ( 9 ) : 28-29. A s s o c i a t i o n o f V i t a m i n C h e m i s t s O f f i c i a l M e t h o d s , 1966. Chap-t e r 14, A s c o r b i c A c i d ( V i t a m i n C ) . I n t e r s c i e n c e P u b l i s h -e r s . New Y o r k : 287-344. B a l l , C. 0., 1928 M a t h e m a t i c a l S o l u t i o n o f P r o b l e m s o n T h e r m a l P r o c e s s i n g o f C a n n e d F o o d . U n i v e r s i t y o f C a l i f o r n i a ( B e r k -l e y ) P u b l . P u b l i c H e a l t h 1 ( 2 ) : 1 5 . B a l l , C. 0., 19 38 A d v a n c e m e n t i n S t e r i l i z a t i o n M e t h o d s f o r Can n e d F o o d s . F o o d R e s e a r c h 3: 13-5 5 . B a u e r n f e i n d , J . C , a n d P i n k e r t , D. M., 1970 F o o d P r o c e s s i n g w i t h A dded A s c o r b i c A c i d . A d v a n c e s i n F o o d R e s e a r c h 1 3 : 220-304. B l u n d s t o n e , H. A. W., and R h o d e s , M. J . C , 1971 i n The B i o -c h e m i s t r y o f F r u i t s a n d T h e i r P r o d u c t s . V o l . I I , Hulme, A. C. (ed) A c a d e m i c P r e s s . L o n d o n : 5 6 2 - 5 6 5 . B o u r n e , M. C , 1965 S t u d i e s o n P u n c h T e s t i n g o f A p p l e s . F o o d T e c h n o l o g y 1 9 : 41 3 - 4 1 5 . Bowman, F., K y l e n , A. M., and Adam, S. F., 1972 R e l a t i o n s h i p s B e t w e e n C e r t a i n P h y s i c a l - C h e m i c a l M e a s u r e m e n t s a nd S e n -s o r v A p p r a i s a l o f A p p l e T e x t u r e . J o u r n a l o f T e x t u r e S t u d i e s 3: 4 7 8 - 4 9 1 . C a n a d a Y e a r Book, 19 75 M i n i s t r y o f I n d u s t r y , T r a d e a nd Commerce, S t a t i s t i c s C a n a d a . O t t a w a : 4 5 2 - 4 5 3 , 478. C o l l i n s , J . L., and W i l e y , R. C., 1967 P e n e t r a t i o n a n d D i s t r i -b u t i o n o f C a l c i u m I o n s i n T h e r m a l - P r o c e s s e d A p p l e S l i c e s . J o u r n a l o f F o o d S c i e n c e 32: 18 5 - 1 8 3 . C r e u s s , W. V., 1958 i n C o m m e r c i a l F r u i t a n d V e g e t a b l e P r o d u c t s . 4 t h E d . M c G r a w - H i l l . New Y o r k : 603. - 138 -Daoud, H. N., a n d L u h , B. S., 1971 E f f e c t o f P a r t i a l R e p l a c e -ment o f S u c r o s e b y C o r n S y r u p o n Q u a l i t y a n d S t a b i l i t y o f C a n n e d A p p l e S a u c e . J o u r n a l o f F o o d S c i e n c e 36: 4 1 9-422. D i c k e r s o n , R. W. J r . , 1965 An A p p a r a t u s f o r t h e M e a s u r e m e n t o f T h e r m a l D i f f u s i v i t v o f F o o d s . F o o d T e c h n o l o g y 19: 880-386. E h e a r t , J . F., a n d Mason, 3. S., 1967 S u g a r a n d A c i d i n t h e E d i b l e P o r t i o n o f F r u i t s . J o u r n a l o f A m e r i c a n D i e t e t i c s A s s o c i a t i o n 5 0 ( 2 ) : 1 3 0 - 1 3 2 . E l l i n g e r , R. H., 1972 P h o s p h a t e s a s F o o d I n g r e d i e n t s . E l l i n g e r , R. H. (ed.) C h e m i c a l R u b b e r Company P r e s s . C l e v e l a n d , O h i o : 1,31. F u r i a , T. E., 1968 i n C. R. C. Handbook o f F o o d A d d i t i v e s . F u r i a , T. E. (ed.) C h e m i c a l R u b b e r Company P r e s s . C l e v e -l a n d , O h i o : 2 9 0 - 3 1 2 . G a r d n e r , W. H., 1968 i n C. R. C. Handbook o f Fo o d A d d i t i v e s . F u r i a , T. E. (ed.) C h e m i c a l R u b b e r Company P r e s s . C l e v e -l a n d , O h i o : 247-289. Gehman, H., a n d Osman, E. M., 1954 S u g a r - S u l f i t e R e a c t i o n a n d R e l a t i o n s h i p t o F o o d P r o b l e m s . A d v a n c e s i n F o o d R e s e a r c h 5: 53-96. G u e r r a n t , N. B., F a r d i g , 0. B., V a v i c h , M. G. and E l l e n b e r g e r , H. E., 1943 The N u t r i t i v e V a l u e o f Ca n n e d F o o d s ; I n f l u -e n c e o f T e m p e r a t u r e a n d Time o f S t o r a g e o n V i t a m i n C o n -t e n t s . I n d u s t r i a l a n d E n g i n e e r i n g C h e m i s t r v 40: 2258-2263. G u t t e r s o n , M., 1972 F o o d C a n n i n g T e c h n i q u e s . F o o d P r o c e s s i n g R e v i e w No. 26, N o y e s D a t a C o r p o r a t i o n : 1 66-167. Hodge, J . E., and Osman, E. M., 1976 i n P r i n c i p l e s o f F o o d S c i e n c e - P a r t I - F o o d C h e m i s t r y . Fennema, 0. R. (ed.) M a r c e l D e k k e r I n c . . New Y o r k : 42-130. H o l m q u i s t , J . W., C l i f c o r n , L. E., H e b e r l e i n , D. G., S c h m i d t , C. F. a n d R i t c h e l l , E. C , 1954 St e a m B l a n c h i n g o f P e a s . F o o d T e c h n o l o g y 8: 43 7 - 4 4 5 . - 139 -H o o v e r , M. W. and M i l l e r , N. C., 1975 F a c t o r s I n f l u e n c i n g Im-p r e g n a t i o n o f A p p l e S l i c e s a n d D e v e l o p m e n t o f a C o n t i n -uous P r o c e s s . J o u r n a l o f F o o d S c i e n c e 40: 698-700. Hope, G. W., 1961 The Use o f A n t i o x i d a n t s i n C a n n i n g A p p l e H a l v e s . F o o d T e c h n o l o g y 1 5 : 5 4 8 - 5 5 0 . H u g g a r t , R. L., W e n z e l , F. W. and M o o r e , E. L., 1957 R e l a t i o n o f A c i d i t y t o V a r i a t i o n i n B r o w n i n g o f C a n n e d G r a p e f r u i t S e c t i o n s D u r i n g S t o r a g e . F o o d T e c h n o l o g y 1 1 : 638. J o s l y n , M. A., 1964 i n F o o d P r o c e s s i n g O p e r a t i o n s , V o l . I I I . J o s l y n , M. A. a n d H e i d , J . L. ( e d s . ) A V I Pub. Co.. W e s t p o r t , C o n n . : 335-368. J o s l y n , M. A. a n d B r a v e r m a n , J . B. S., 1954 S u l f u r D i o x i d e T r e a t m e n t o f F r u i t a n d V e g e t a b l e P r o d u c t s . A d v a n c e s i n F o o d R e s e a r c h 5: 102-104. K i t s o n , J . , 1976 P e r s o n a l C o m m u n i c a t i o n . L a z a r , M. E. a n d H u d s o n , J . S., 1976 C o n c e n t r a t e d A p p l e S l i c e s P a c k a g e d i n F l e x i b l e P o u c h e s . F o o d P r o d u c t D e v e l o p m e n t 10 ( 1 ) : 87-89. L e e , F. A., 1953 The B l a n c h i n g P r o c e s s . A d v a n c e s i n F o o d Re-s e a r c h 8: 6 3-10 4. L i n d s a y , R. C , 19 76 i n P r i n c i p l e s o f F o o d S c i e n c e - P a r t I -F o o d C h e m i s t r y . Fennema, 0. R. (ed.) M a r c e l D e k k e r I n c . . Nev/ Y o r k : 490. L o c o n t i , J . D..and K e r t e s z , Z . . I . , . 1 9 4 1 I d e n t i f i c a t i o n o f C a l -c i u m P e c t a t e a s t h e T i s s u e F i r m i n g Compound Formed b y T r e a t m e n t o f Tomatoes w i t h C a l c i u m C h l o r i d e . F o o d R e s e a r c h 6: 4 9 9 - 5 0 3 . M e r m e l s t e i n , N. H., 1976 The R e t o r t P o u c h i n t h e U. S. F o o d T e c h n o l o g y 30 ( 2 ) : 28. M o h s e n i n , N., G o e h l i c h , H . a n d T u k e y , L . D . , 1962 M e c h a n i c a l B e h a v i o r o f A p p l e F r u i t s a s R e l a t e d t o B r u i s i n g . P r o -c e e d i n g s o f t h e A m e r i c a n S o c i e t y f o r H o r t i c u l t u r a l S c i e n c e 8 1: 67-77. - 140 -O l l i v e r , M., 1971 i n The Bioc h e m i s t r y of F r u i t s and T h e i r Prod-u c t s . V o l . I I , Hulme, A. C. (ed.) Academic P r e s s . London: 498. Olson, F. C. W. and Jackson, J . M., 1942 Heating Curves - Theory and P r a c t i c a l A p p l i c a t i o n . I n d u s t r i a l and E n g i n e e r i n g Chem-i s t r y 34: 337.' P o l l a r d , A. and Timberlake, C. F., 1971 i n The Bi o c h e m i s t r y of F r u i t s and T h e i r Products. V o l . I I , Hulme, A. C. (ed.) Academic Press. London: 598-611. Po n t i n g , J . D., Jackson, R. and Watters, G., 1971 R e f r i g e r a t e d Apple S l i c e s : E f f e c t s of pH, S u l f i t e s and Calcium von Tex-t u r e . J o u r n a l o f Food Science 36: 349-350. Ponting, J . D., Jackson, R. and Watters, G., 1972 R e f r i g e r a t e d Apple S l i c e s : P r e s e r v a t i v e E f f e c t s of A s c o r b i c A c i d , C a l -cium and S u l f i t e s . J o u r n a l o f Food Science 37: 434-436. Reeve, R. M. and Leinbach, L. R., 1953 H i s t o l o g i c a l I n v e s t i g a -t i o n s of Texture i n Apples I. Composition and In f l u e n c e of Heat on S t r u c t u r e . Food Research 18: 592-603. Reynolds, T. M., 1965 Chemistry o f Nonenzymic Browning I I . Ad-vances i n Food Research 14: 167-283. Ross, L. R. and Treadway, R. H., 1960 A Rapid Method f o r the De-t e r m i n a t i o n o f S u l f u r Dioxide i n S u l f i t e d Prepeeled Pota-t o e s . American Potato J o u r n a l 37: 102-107. S c h u l t z e , 0. T. and Olson, F. C. W., 1938 Thermal P r o c e s s i n g of Canned Foods i n T i n Cont a i n e r s I. V a r i a t i o n o f Heating Rate with Can S i z e f o r Products Heating by Convection. Food Research 3: 647-651. Schomer, H. A. and Olson, K. L., 1962 A Mechanical Thumb f o r De-te r m i n i n g Firmness o f Apples, Proceedings o f the American S o c i e t y f o r H o r t i c u l t u r a l Science 81: 61-66. Simpson, G. , R. and Blay, R. A., 1966 Rapid Method f o r the De-t e r m i n a t i o n o f the Metals Copper, Z i n c , T i n , Iron and C a l -cium i n F o o d s t u f f s by Atomic A b s o r p t i o n Spectrophotometry. Food Trade Review 36 (8): 35-37. Stumbo, C. R., 1973 i n Thermobacteriology i n Food P r o c e s s i n g . Second E d i t i o n . Stumbo, C. R. (ed.) Academic P r e s s . New York. - 141 -Tannenbaum, S. R., 1976 i n P r i n c i p l e s of Food Science - P a r t I -Food Chemistry. Fennema, 0. R. (ed.) Marcel Dekker Inc.. New York: 360-366. Thorpe, R. H. and A t h e r t o n , D., 1962 S t e r i l i z e d Foods i n F l e x i b l e Packages. The F r u i t and Vegetable P r e s e r v a t i o n A s s o c i a t i o n T e c h n i c a l B u l l e t i n 21. C h i p p i n g Camden, England. Timberlake, C. F., 1957 M e t a l l i c Components of F r u i t J u i c e s I I . The Nature of Some-:C6pperrComplexes i n Apple J u i c e . Jour-n a l of the Science of Food and A g r i c u l t u r e 8: 159. T i n g , S. V., 1956 Rapid C o l o r i m e t r i c Method f o r Simultaneous De-t e r m i n a t i o n of T o t a l , Reducing Sugars and F r u c t o s e i n C i t r u s J u i c e s . J o u r n a l of A g r i c u l t u r a l and Food Chemistry 4: 26 3-266. T r e s s l e r , D. K. and J o s l y n , M. A., 1954 i n The Chemistry and Tech-nology of F r u i t and Vegetable J u i c e P r o d u c t i o n . T r e s s l e r , D. K. and J o s l y n , M. A. (eds.) AVI Pub. Co. Westport, Conn.: 234,338. Tung, M. A., 1974 P e r s o n a l Communication. Tung, M. A. and Garland, T. D., 1976 Computer C a l c u l a t i o n of Ther-mal Processes. Presented at the 1976 Annual Meeting of the American S o c i e t y of A g r i c u l t u r a l Engineers - P a c i f i c North-west S e c t i o n . Tung, M. A., Garland, M. R. and Maurer, A. R., 1976 Vegetables i n F l e x i b l e Pouches. Presented at the 1976 Annual Meeting of the American S o c i e t y of A g r i c u l t u r a l Engineers - P a c i f i c Northwest S e c t i o n . Wiley, R. C. and Lee, Y. S., 1970 M o d i f y i n g Texture o f Processed Apple S l i c e s . Food Technology 24: _ 1168-1170. Wiley, R. C. and Stembridge, G. E., 1962 F a c t o r s I n f l u e n c i n g Ap-p l e Texture. Proceedings of the American S o c i e t y f o r Hort-i c u l t u r a l Science 77: 60-72. Wiley, R. C. and Thompson, A. H., 1960 I n f l u e n c e of V a r i e t y , Storage and M a t u r i t y on the Q u a l i t y of Canned Apple S l i c e s . Proceedings of the American S o c i e t y f o r H o r t i c u l t u r a l Science 75: 61-84. 

Cite

Citation Scheme:

        

Citations by CSL (citeproc-js)

Usage Statistics

Share

Embed

Customize your widget with the following options, then copy and paste the code below into the HTML of your page to embed this item in your website.
                        
                            <div id="ubcOpenCollectionsWidgetDisplay">
                            <script id="ubcOpenCollectionsWidget"
                            src="{[{embed.src}]}"
                            data-item="{[{embed.item}]}"
                            data-collection="{[{embed.collection}]}"
                            data-metadata="{[{embed.showMetadata}]}"
                            data-width="{[{embed.width}]}"
                            async >
                            </script>
                            </div>
                        
                    
IIIF logo Our image viewer uses the IIIF 2.0 standard. To load this item in other compatible viewers, use this url:
https://iiif.library.ubc.ca/presentation/dsp.831.1-0094321/manifest

Comment

Related Items