UBC Theses and Dissertations

UBC Theses Logo

UBC Theses and Dissertations

Effect of aging, thawing and frozen storage on the tenderness of chicken broiler muscle Ruddick, Jane Elizabeth 1974

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

Item Metadata

Download

Media
831-UBC_1974_A6_7 R83.pdf [ 4.68MB ]
Metadata
JSON: 831-1.0099900.json
JSON-LD: 831-1.0099900-ld.json
RDF/XML (Pretty): 831-1.0099900-rdf.xml
RDF/JSON: 831-1.0099900-rdf.json
Turtle: 831-1.0099900-turtle.txt
N-Triples: 831-1.0099900-rdf-ntriples.txt
Original Record: 831-1.0099900-source.json
Full Text
831-1.0099900-fulltext.txt
Citation
831-1.0099900.ris

Full Text

THE EFFECT OF AGING, THAWING AND FROZEN STORAGE ON THE TENDERNESS OF CHICKEN BROILER MUSCLE by • JANE ELIZABETH RUDDICK B.Sc. Hons. U n i v e r s i t y of London, 1972 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n the Department of Food Science We accept t h i s t h e s i s as conforming to the r e q u i r e d standard THE UNIVERSITY OF BRITISH COLUMBIA May, 1974 In p r e s e n t i n g t h i s t h e s i s in p a r t i a l f u l f i l m e n t o f the r e q u i r e m e n t s 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 Co lumb ia , I a g ree tha 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 s tudy . 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 e x t e n s i v e c o p y i n g o f 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 g r a n t e d by the Head o f my Department o r by h i s r e p r e s e n t a t i v e s . It i s u n d e r s t o o d that c o p y i n g o r p u b l i c a t i o n o f 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 a l l o w e d w i thou t my w r i t t e n p e r m i s s i o n . Department o f *Fo<^c? ^>o£^Cn The U n i v e r s i t y o f B r i t i s h Co lumbia Vancouver 8, Canada Date 2>ovv~ i i ABSTRACT The e f f e c t s of v a r i o u s aging, thawing and storage methods on the tenderness of f r o z e n b r o i l e r P e c t o r a l i s  major muscle were s t u d i e d . I n i t i a l experiments were c a r r i e d out to e s t a b l i s h standard methods of f r e e z i n g , cooking and tenderness e v a l u a t i o n to be used i n subsequent experiments. The e f f e c t s of v a r y i n g the aging, thawing and storage techniques were then i n v e s t i g a t e d u s i n g the e s t a b l i s h e d methods. Whole c a r c a s s e s were f r o z e n i n a l i q u i d n i t r o g e n b l a s t f r e e z e r a f t e r c o o l i n g i n i c e water f o r p e r i o d s of 1 to 10 hours a f t e r s l a u g h t e r , s t o r e d f o r 1 week a t -31°C and thawed f o r v a r y i n g lengths of time. The P. major muscles were removed and cooked i n b o i l i n g water between metal p l a t e s . Tenderness e v a l u a t i o n s were c a r r i e d out u s i n g the Allo-Kramer shear p r e s s . The l e n g t h o f thawing time was shown to g r e a t l y i n f l u e n c e the degree of toughness of the cooked muscles. When a thawing p e r i o d o f 4 hours i n water a t 25°C was used, a decrease i n toughness took p l a c e i n c a r c a s s e s f r o z e n between 1 and 2 hours post-mortem. T h i s was f o l l o w e d by an i n c r e a s e to maximum toughness i n b i r d s f r o z e n between 4 and 8 hours post-mortem. Maximum tenderness o c c u r r e d i n b i r d s f r o z e n 10 hours a f t e r death. Thawing b i r d s i n a i r a t 4°C f o r 24 and 4 8 hours decreased the l e v e l o f toughness a t t a i n e d a f t e r f r e e z i n g 4 t o 8 hours post-mortem. I t d i d not s i g n i f i c a n t l y a l t e r the degree of tenderness reached a f t e r 10 hours. S i m i l a r l y , the decrease i n toughness i n b i r d s f r o z e n between 1 and 2 hours post-mortem, remained s i g n i f i c a n t . Longer storage (3 months) a t -23°C f o l l o w e d by r a p i d thawing e l i m i n a t e d both the d e c l i n e i n toughness of ca r c a s s e s f r o z e n between 1 and 2 hours post-mortem and the maximum toughness l e v e l a t t a i n e d by c a r c a s s e s f r o z e n 4 to 8 hours a f t e r death. An attempt was made to e x p l a i n the decrease i n toughness i n c a r c a s s e s f r o z e n between 1 and 2 hours p o s t -mortem i n terms o f the aging temperature and medium used p r i o r t o f r e e z i n g . No d i f f e r e n c e i n the p a t t e r n was observed, however, when oth e r p r e - f r e e z i n g aging techniques were used. Increases i n the sarcomere l e n g t h s o f muscle f r o z e n a t 2 hours post-mortem were observed, c o r r e s p o n d i n g to the i n c r e a s e i n tenderness o c c u r r i n g i n c a r c a s s e s f r o z e n at t h i s time. I s o m e t r i c t e n s i o n measurements, however, d i d not c o r r e l a t e w e l l w i t h these o b s e r v a t i o n s . Taste panel members were unable to d i s c e r n d i f f e r e n c e s i n the tenderness o f muscle f r o z e n between 1 and 3 hours post-mortem a l t h o u g h e x c e l l e n t c o r r e l a t i o n s were obtained between Allo-Kramer shear p r e s s v a l u e s and s a r c o -mere l e n g t h measurements. The r e s u l t s o f these experiments t h e r e f o r e show t h a t the u l t i m a t e tenderness of b r o i l e r muscle can be g r e a t l y i n f l u e n c e d by the i n t e r a c t i o n of p r e - f r e e z i n g aging time, l e n g t h o f storage and thawing techniques used p r i o r to cooking. V TABLE OF CONTENTS Page ABSTRACT i i LIST OF TABLES ix LIST OF FIGURES x i LIST OF PLATES x i i i ACKNOWLEDGEMENTS xiv CHAPTER I : SURVEY OF THE LITERATURE 1 Muscle Tenderness 1 Rigor and i t s R e s o l u t i o n 2 Thaw Rigor 4 P r o c e s s i n g and i t s E f f e c t on Muscle Tenderness 5 Aging 6 a) Time of Aging 6 b) Temperature of Aging 8 F r e e z i n g Rate 9 Thawing Rate 10 Temperature o f Frozen Storage 11 Length of Frozen Storage 11 Methods of Measuring Muscle Tenderness 12 O b j e c t i v e and' S u b j e c t i v e Methods 12 Measurement o f Sarcomere Lengths 13 I s o m e t r i c T ension Measurement 14 CHAPTER I I : THE TENDERNESS OF CHICKEN BROILER MUSCLE FROZEN AT VARIOUS POSTMORTEM AGING TIMES - METHODS OF FREEZING, COOKING AND TENDERNESS EVALUATION. INTRODUCTION MATERIALS AND METHODS Experiment 1. - A Comparison of S u b j e c t i v e and O b j e c t i v e Methods of Tenderness E v a l u a t i o n Muscle Source Method of F r e e z i n g and Muscle P r e p a r a t i o n S u b j e c t i v e Method o f Tenderness E v a l u a t i o n O b j e c t i v e Method of Tenderness E v a l u a t i o n Experiment 2. - L i q u i d N i t r o g e n B l a s t F r e e z i n g RESULTS AND DISCUSSION Experiment 1. Experiment 2. CHAPTER I I I : THE TENDERNESS OF CHICKEN BROILER MUSCLE FROZEN AT VARIOUS POSTMORTEM AGING TIMES - THE EFFECT OF VARYING AGING, THAWING AND FROZEN STORAGE TECHNIQUES. INTRODUCTION MATERIALS AND METHODS Experiment 3.- - The E f f e c t of Rapid Thaw on the Tenderness of Chicken B r o i l e r Muscle Frozen a t V a r i o u s Postmortem Aging Times. Experiment 4. - The E f f e c t of a 24 Hour Thaw on the Tenderness of Chicken B r o i l e r Muscle Frozen a t V a r i o u s Postmortem Aging Times. v i i Page Experiment 5. - The E f f e c t of a 48 Hour Thaw on the Tenderness of Chicken B r o i l e r Muscle Frozen a t V a r i o u s Postmortem Aging Times 39 Experiment 6. - The E f f e c t o f V a r y i n g the P r e - F r e e z i n g Aging Medium and Temperature on the Tenderness of Chicken B r o i l e r Muscle Frozen a t V a r i o u s Postmortem Aging Times. 39 Experiment 7. - The E f f e c t o f Length of Storage on the Tenderness of Chicken B r o i l e r Muscle Frozen a t V a r i o u s Postmortem Aging Times. 39 RESULTS AND DISCUSSION 41 Experiments 3, 4 and 5 41 Experiment 6 55 Experiment 7 61 CHAPTER IV: THE TENDERNESS OF CHICKEN BROILER MUSCLE FROZEN AT VARIOUS POSTMORTEM AGING TIMES - OTHER METHODS OF EVALUATING MEAT TENDERNESS- 6 5 INTRODUCTION 6 5 MATERIALS AND METHODS 68 Experiment 8. - The E f f e c t o f F r e e z i n g a t V a r i o u s Postmortem Aging Times on the Tension Development i n Muscle S t r i p s . 69 Experiment 9. - The Tenderness of Chicken B r o i l e r Muscle Frozen a t V a r i o u s Postmortem Aging Times - Sarcomere Length Measurements as a P r e d i c t i o n of Cooked Meat Tenderness. 69 RESULTS AND DISCUSSION 7 3 Experiment 8 73 Experiment 9 78 v i i i Page SUMMARY AND CONCLUSIONS 86 LITERATURE CITED 8 8 LIST OF TABLES Analyses of v a r i a n c e f o r s u b j e c t i v e and o b j e c t i v e tenderness e v a l u a t i o n s . Duncan's New M u l t i p l e Range T e s t on s i g n i f i c a n t treatment means from tenderness e v a l u a t i o n s - Experiment I. C o r r e l a t i o n m a t r i x f o r s u b j e c t i v e and o b j e c t i v e methods of tenderness e v a l u a t i o n , a t each time of f r e e z i n g , postmortem. Means, standard d e v i a t i o n s and c o e f f i c i e n t s of v a r i a t i o n of shear v a l u e s from P. major muscle thawed f o r 4 hours -Experiment 3. Means, standard d e v i a t i o n s and c o e f f i c i e n t s of v a r i a t i o n of shear v a l u e s from P. major muscle thawed f o r 2 4 hours -Experiment 4. Means, standard d e v i a t i o n s and c o e f f i c i e n t s of v a r i a t i o n of shear v a l u e s from P. major muscle thawed f o r 48 hours -Experiment 5. Analyses of v a r i a n c e o f shear v a l u e s from P. major muscle thawed f o r 4, 24 and 48 hours. Duncan's New M u l t i p l e Range T e s t on s i g n i f i c a n t treatment means from Experiments 3, 4 and 5. Combined a n a l y s i s of v a r i a n c e of shear v a l u e s from P. major muscle thawed f o r 4, 24 and 4 8 hours. Duncan's New M u l t i p l e Range T e s t on s i g n i f i c a n t treatment i n t e r a c t i o n means from Experiments 3, 4 and 5. A n a l y s i s o f v a r i a n c e of shear v a l u e s from P. major muscle aged i n i c e s l u s h and i n a i r a t room temperature. Means, standard d e v i a t i o n s and Duncan's New M u l t i p l e Range T e s t on combined means of shear v a l u e s from Experiment 6. A n a l y s i s of v a r i a n c e of shear v a l u e s from P. major muscle s u b j e c t e d to long term f r o z e n s t o r a g e . Means, standard d e v i a t i o n s and c o e f f i c i e n t s of v a r i a t i o n of sheag v a l u e s from P. major muscle s t o r e d a t -23 C f o r 3 months. Analyses of v a r i a n c e f o r shear v a l u e s and t e n s i o n measurements recorded i n Experiment 8. Standard d e v i a t i o n s and Duncan's New M u l t i p l e Range T e s t on the s i g n i f i c a n t treatment means from Experiment 8. Analyses o f v a r i a n c e f o r panel s c o r e s , shear v a l u e s and sarcomere l e n g t h s recorded i n Experiment.9. Duncan's New M u l t i p l e Range T e s t on the s i g n i f i c a n t treatment means from Experiment C o r r e l a t i o n m a t r i x f o r the th r e e parameters s t u d i e d i n Experiment 9. LIST OF FIGURES S u b j e c t i v e assessment o f toughness o f b r o i l e r muscle f r o z e n a f t e r v a r i o u s postmortem a g i n g p e r i o d s . O b j e c t i v e assessment o f toughness o f b r o i l e r muscle f r o z e n a f t e r v a r i o u s postmortem a g i n g p e r i o d s . Temperature h i s t o r y of P . m a j o r muscle i n a l i q u i d n i t r o g e n b l a s t f r e e z e r . The e f f e c t o f a 4 hour thaw on the t e n d e r n e s s o f c h i c k e n b r o i l e r muscle f r o z e n a t v a r i o u s postmortem a g i n g t i m e s . The e f f e c t o f a 24 hour thaw on the t e n d e r n e s s o f c h i c k e n b r o i l e r muscle f r o z e n a t v a r i o u s postmortem a g i n g t i m e s . The e f f e c t o f a 48 hour thaw on the t e n d e r n e s s o f c h i c k e n b r o i l e r muscle f r o z e n a t v a r i o u s postmortem a g i n g t i m e s . The e f f e c t s o f a 4, 24 and 48 hour thaw on the t e n d e r n e s s o f c h i c k e n b r o i l e r muscle f r o z e n a t v a r i o u s postmortem a g i n g t i m e s . The e f f e c t o f a g i n g i n i c e s l u s h on the t e n d e r n e s s of c h i c k e n b r o i l e r muscle f r o z e n a t v a r i o u s postmortem a g i n g t i m e s . The e f f e c t o f a g i n g i n a i r a t 2 3 ° C on the t e n d e r n e s s o f c h i c k e n b r o i l e r muscle f r o z e n a t v a r i o u s postmortem a g i n g t i m e s . The e f f e c t o f f r e e z i n g a t v a r i o u s postmortem a g i n g t imes on the t e n d e r n e s s of c h i c k e n b r o i l e r muscle s t o r e d . f o r . 3 .months . The e f f e c t of f r e e z i n g a t v a r i o u s postmortem, a g i n g t imes on t e n s i o n development i n muscle s t r i p s . The e f f e c t of f r e e z i n g a t v a r i o u s postmortem a g i n g t imes on t e n d e r n e s s i n b r o i l e r P . major m u s c l e . X l l Page 13 S u b j e c t i v e assessment of toughness of b r o i l e r muscle f r o z e n a f t e r v a r i o u s postmortem aging p e r i o d s . 81 14 O b j e c t i v e assessment o f toughness of b r o i l e r muscle f r o z e n a f t e r v a r i o u s postmortem aging p e r i o d s . 82 15 The measurement of sarcomere le n g t h s i n b r o i l e r muscle f r o z e n a f t e r v a r i o u s postmortem aging p e r i o d s . 83 LIST OF PLATES Apparatus used f o r l i q u i d n i t r o g e n b l a s t f r e e z i n g . D i f f r a c t i o n p a t t e r n o b t a i n e d from muscle f i b r e . x i v ACKNOWLEDGEMENTS The author wishes t o express her s i n c e r e a p p r e c i a t i o n to her. a d v i s o r , Dr. J.F. R i c h a r d s , A s s o c i a t e P r o f e s s o r , Department of Food Science f o r h i s guidance and encouragement d u r i n g the course of t h i s study. She i s a l s o t h a n k f u l t o the members of her graduate committee: Drs. W.D. Powrie, M.A. Tung and J . Vanderstoep of the Department of Food Science and P r o f e s s o r E. Watson of the Department of A g r i c u l t u r a l E n g i n e e r i n g f o r t h e i r h e l p , encouragement and i n t e r e s t i n the r e s e a r c h and f o r the review of t h i s t h e s i s . She i s a l s o g r a t e f u l to Miss Lynne Robinson f o r t a s t e - p a n e l and computer a s s i s t a n c e and to her l o n g - s u f f e r i n g t a s t e panel members. F i n a n c i a l support from the B.C.D.A. A g r i c u l t u r a l S c iences Research and Development Fund i s g r a t e f u l l y acknowledged. CHAPTER I. SURVEY OF LITERATURE Muscle Tenderness Optimum tenderness, t o g e t h e r w i t h optimum f l a v o u r , i s fundamentally important i n the acceptance of a l l types o f meat. Tenderness i s an extremely v a r i a b l e c h a r a c t e r i s t i c . I t v a r i e s from muscle to muscle w i t h i n an animal and among animals of the same or d i f f e r e n t s p e c i e s . These v a r i a t i o n s can be g r e a t l y i n f l u e n c e d by both ante- and post-mortem events. Reviews df such f a c t o r s i n f l u e n c i n g tenderness are gi v e n by B r i s k e y (1963) and Marion (1967). Koonz e t a l . (1954), deFremery and Pool (1960), and Locker (1960) r e c o g n i z e d t h a t the p e r i o d o f time between s l a u g h t e r and r i g o r onset, when s h o r t e n i n g and l o s s o f e x t e n s i b i l i t y of the muscle o c c u r s , i n f l u e n c e d the u l t i m a t e tenderness of the f i n a l p roduct. The p o s t - r i g o r r e s o l u t i o n of these parameters was a l s o found to be important ( G o l l , 1968). I t has been r e c o g n i z e d t h a t modern p r o c e s s i n g and u t i l i z a t i o n p r a c t i c e s may i n f l u e n c e the tenderness of the f i n a l product p a r t i c u l a r l y p r o c e s s i n g techniques t h a t take p l a c e d u r i n g the p e r i o d o f time between s l a u g h t e r and the r e s o l u t i o n of r i g o r m o r t i s (Pool e t a^L. , 1959; Klose e t a l . , 1971). Rigor and i t s Resolution When an animal i s slaughtered, blood c i r c u l a t i o n ceases thereby terminating the .transport of oxygen to the muscle. With the onset of anaerobic conditions i n post-mortem muscle, numerous chemical changes occur such as a decrease i n ATP concentration, a reduction i n pH and the formation of numerous bonds between the a c t i n and the myosin filaments, (Bendall, 1969; deFremery, 1966; Lawrie, 1966) . Such changes lead to a l t e r a t i o n s i n the muscle microstructure and a decrease i n the e x t e n s i b i l i t y of the muscle during the f i r s t few hours a f t e r death. Rigor mortis i s the inextensible or r i g i d state of post-mortem muscle. Several investigations have shown that muscles shorten during the onset of rigor and, as a consequence, become tougher, (Bate-Smith et a l . , 1949; Marsh, 1954; Pool, 1963). Newbold and Harris (1972) have extensively reviewed the aspects of pre<-rigor shortening. The extent of shortening i s dependent on the storage temperature and the extent of muscle r e s t r a i n t , i f any. Smith et a l . (1969) showed that shortening of avian muscle stored at 0°C was s i g n i f i c a n t l y greater than that which occurred when the muscle was stored at 12-18°C. The amount of shortening was greatest i n muscle stored at 20°C. Jungk and Marion (1970) demonstrated that 'cold s h o r t e n i n g ' (shortening induced by a l l o w i n g g l y c o l y s i s t o proceed r a p i d l y around 0°C) does not occur i n turkey b r e a s t muscle. However, i n 1971, Marion r e p o r t e d ' c o l d s h o r t e n i n g i n turkey t h i g h muscle. Marsh and Thompson (1958), Locker and Hagyard (1963), and Marsh, arid L e e t (1966) r e p o r t e d t h a t the e x t e n t o f ' c o l d s h o r t e n i n g ' decreased as the p e r i o d between s l a u g h t e r and exposure to c o l d i n c r e a s e d . Muscle s h o r t e n i n g has been r e l a t e d t o a decrease i n sarcomere l e n g t h (Stromer and G o l l , 1968; Buck e t a l . 1970). K l o s e e t a l . C1970) s t u d i e d the e f f e c t o f p r e - r i g o r c o n t r a c t i o n on the tenderness o f post-mortem c h i c k e n muscle E l e c t r i c a l s t i m u l a t i o n , b e a t i n g , freeze-thawing and h e a t i n g a l l reduced muscle l e n g t h , i n most cases, t o between 4 0 and 50% o f the o r i g i n a l r e s t l e n g t h . Subsequent shear v a l u e s f o r the c o n t r a c t e d cooked muscle were found t o be around h a l f those f o r the uncontracted c o n t r o l s . The authors suggested t h a t such an extreme c o n t r a c t i o n caused changes i n the sarcomere l e n g t h which r e s u l t e d i n the m y o f i b r i l s being more s u s c e p t i b l e t o s h e a r i n g s t r e s s . As storage time p r o g r e s s e s , a t above f r e e z i n g temperatures the r i g i d i n ^ r i g o r muscle r e v e r t s to a p l i a b l e p o s t - r i g o r m a t e r i a l . T h i s process of p o s t - r i g o r tenderiza^-t i o n i n muscle i n v o l v e s a ' r e s o l u t i o n ' of r i g o r m o r t i s . Evidence r e l a t i n g t o r i g o r r e s o l u t i o n has been reviewed by G o l l (1968) . The r e s u l t s o f Koonz e t al_. (1954) , deFremery and P o o l C 1 9 6 0 ), deFremery (1966), and deFremery and S t r e e t e r (1969), i n d i c a t e t h a t c h i c k e n muscle h e l d a t 2°C reaches maximum toughness 3 to 4 hours post-mortem f o l l o w e d by minimum toughness a f t e r 12-24 hours. I t has a l s o been r e p o r t e d by Gothaard e t a l . (19 66), Stromer and G o l l (1967, and Takahashi e t a_l. (1967) t h a t sarcomeres which have undergone e x t e n s i v e post-mortem s h o r t e n i n g w i l l , a f t e r s e v e r a l days, lengthen a g a i n . P o s s i b l e e x p l a n a t i o n s f o r the observed r e s o l u t i o n of r i g o r were gi v e n by G o l l e t a l . (1970). The authors p o s t u l a t e d t h a t the p o s t - r i g o r r e l a x a t i o n of sarcomeres occurs through weakened actin<-myosin i n t e r a c t i o n s and Z - l i n e d e g e n e r a t i o n . The gross s t r u c t u r a l changes o c c u r r i n g i n Z - l i n e d e g r a d a t i o n were e x p l a i n e d as a consequence of C a + + r e l e a s e from the s a r c o p l a s m i c r e t i c u l u m a f t e r death. Henderson e t a l * (1970) agreed w i t h these o b s e r v a t i o n s and showed t h a t the Z - l i n e of bovine, p o r c i n e and r a b b i t muscle l o s t i t s i n t e g r i t y d u r i n g post-mortem s t o r a g e . The weaken-i n g of the actin-myosin i n t e r a c t i o n , f i r s t observed by F u j i m a k i et a l . (1965) may be e f f e c t e d by a very s p e c i f i c and l i m i t e d p r o t e o l y s i s of myosin, a c t i n and/or one of the r e g u l a t o r y p r o t e i n s , ( G o l l , 1968). Thaw Ri g o r During r a p i d . f r e e z i n g and thawing of p r e - r i g o r muscles, g l y c o l y s i s occurs a t a r a p i d r a t e a t temperatures around ^2° to -4°C, s h o r t e n i n g i s severe and the water holding capacity i s reduced s u b s t a n t i a l l y (deFremery, 1966; Marsh et a l . 1968) . This behaviour i s known as thaw r i g o r . Thaw r i g o r d i f f e r s from normal r i g o r i n that i t s time of onset depends only on the rate of thawing. I t i s always character ized by a more or l e s s powerful contracture , the e f f e c t of which i s d i r e c t l y r e l a t e d to the ATP content of the muscle. For t h i s reason, muscle frozen p r e - r i g o r contracts to a greater extent on thawing than those which have been frozen with an already; depleted ATP l e v e l , although l i m i t e d thaw contracture can occur even at very low l e v e l s — for example, when muscle i s frozen a f t e r the r e s o l u t i o n of normal r i g o r . When muscle i s frozen on the bone, however, the r i g i d structure prevents a large proport ion of the shortening from taking place (Bendall , 1960). Slow f reezing or slow thawing may p a r t i a l l y over-come the d r a s t i c shortening e f f e c t , s ince the muscle may remain p a r t i a l l y frozen for extended periods at temperatures just below i t s f reezing p o i n t . Marsh et a l . (1968), B e n d a l l , (1960), Jones and Murray (1961) and Behnke et a l . (1973) found that at these temperatures, g l y c o l y s i s occurs at an extremely r a p i d rate but shortening cannot occur because the muscle i s f i x e d i n s i z e and shape by the presence of i ce c r y s t a l s . Processing and i t s E f f e c t on Muscle Tenderness P o s t - r i g o r t e n d e r i z a t i o n can occur before f reez ing or a f t e r thawing. The processor can most inf luence the tenderness o f cooked p o u l t r y muscle d u r i n g the aging p e r i o d p r i o r to f r e e z i n g . However, the f r e e z i n g r a t e , the l e n g t h and temperature of f r o z e n storage and the thawing r a t e may a l s o i n f l u e n c e the tenderness o f the f i n a l p roduct. Aging The red and white muscle of p o u l t r y r e q u i r e d i f f e r e n t aging p e r i o d s to al l o w them to pass through r i g o r p r i o r to f r e e z i n g (van den Berg e t a l . , 1964). T h i s should be taken i n t o account when c o n s i d e r i n g adequate aging times f o r p o u l t r y , a) Time of Aging As e a r l y as 1948, Lowe demonstrated t h a t c h i c k e n s ( r o a s t e r s ) f r o z e n w i t h i n 2 hours of k i l l i n g were l e s s tender than those aged 24 hours b e f o r e f r e e z i n g . Stewart et: a l . (1948) i n a study o f t e n d e r i z a t i o n o f New York-dressed f r y e r s a t 35°F found t h a t tenderness developed r a p i d l y a f t e r the p a s s i n g o f r i g o r . Maximum tenderness was found w i t h i n 24 hours w i t h most of the t e n d e r i z a t i o n t a k i n g p l a c e w i t h i n the f i r s t 8 hours. Hanson e t a l . (1942) r e p o r t e d t h a t tenderness i n New York-dressed c h i c k e n b r o i l e r s i n c r e a s e d r a p i d l y d u r i n g the f i r s t 3 hours o f h o l d i n g a t 35°F. Holdi n g beyond t h i s time r e s u l t e d i n continued, g r a d u a l , r e l a t i v e l y s m a l l and d i m i n i s h i n g i n c r e a s e s i n tenderness. In experiments w i t h f r o z e n b r o i l e r s Stewart e t a l . (1945) found no d i f f e r e n c e i n tenderness between groups g i v e n p r e - f r e e z i n g c h i l l i n g p e r i o d s o f 2 hours and 18 hours r e s p e c t i v e l y , but a 48 hour thawing period p r i o r to cooking may have el iminated any d i f f e r e n c e that was o r i g i n a l l y present . C a r l i n et ILk* (1949) studied the extent of t e n d e r i z a t i o n i n roasters and fowl as a funct ion of hours of holding at r e f r i g e r a t e d temperatures and the a d d i t i o n a l e f f e c t of f reezing and thawing. For b i r d s aged l e s s than 6 hours, f reez ing resul ted i n increased tenderness although i t was c l e a r l y recognized by C a r l i n that t h i s may have been due whol ly , or i n p a r t , to the thawing and a d d i t i o n a l aging at thawing temperatures (24 hours at 3 9 ° F ) rather than the f reezing i t s e l f . Aging , f reezing and other processing fac tors were evaluated by Koonz et aJL. (1954) for t h e i r e f f e c t on the tenderness of the p r i n c i p a l muscles i n the chicken b r o i l e r carcass . Ultimate tenderness was reached w i t h i n 16 to 24 hours of aging at 40°F. Freezing and holding at 2 0 ° F for 24 hours e s s e n t i a l l y arrested any t e n d e r i z a t i o n that would otherwise have occurred during that p e r i o d . The authors concluded that f reezing during the ear ly post - . mortem period f ixed the state of tenderness e x i s t i n g at that time and complete t e n d e r i z a t i o n was delayed u n t i l the t issues were d e f r o s t e d . Dawson et a l . (1956) reported progressive increases i n the t e n d e r i z a t i o n of f r y e r s cooked from the frozen s ta te , as the i n t e r v a l between slaughter and f reez ing was increased from 40 minutes to 3, 6 and 24 hours r e s p e c t i v e l y . 8. b) Temperature of Aging Aging temperature i n the range from 0°C to average room temperature was shown by Lowe (1948) to have l i t t l e e f f e c t on the r a t e of post-mortem changes. In fowl cooked 6 hours a f t e r s l a u g h t e r t h e r e was no d i f f e r e n c e i n shear f o r c e o r p a l a t a b i l i t y between those c h i l l e d i n i c e and those h e l d f o r 6 hours at room temperature. Pool e t a l . (19 59) found t h a t t e n d e r i z a t i o n of c h i c k e n b r o i l e r muscle took p l a c e w i t h i n 4 hours a t c h i l l temperatures. Very l i t t l e t e n d e r i z a t i o n took p l a c e a f t e r 12 hours. No a p p r e c i a b l e t e n d e r i z a t i o n o c c u r r e d a t 0°F over a 4 month p e r i o d , but s i g n i f i c a n t i n c r e a s e s i n tender-ness o c c u r r e d i n f r o z e n c a r c a s s e s h e l d a t 25° to 27°F f o r s e v e r a l days. T e n d e r i z a t i o n a r r e s t e d by f r e e z i n g proceeded at a normal r a t e on thawing. The authors recommended an adequate aging p e r i o d which p o t e n t i a l l y c o u l d be imposed e i t h e r i n the c h i l l i n g , f r o z e n s torage o r thawing p e r i o d s . K l o s e e t a l . (.1961) found t h a t a slow t e n d e r i z a -t i o n o c c u r r e d a t 25° to 27°F when o n l y 70% of the water c o n t a i n e d i n the muscle was f r o z e n out. A l l r e a c t i o n s were found by the authors to be a r r e s t e d a t 0°F. Marion and Goodman (1967) and Welbourne e t a l . (1968) s t u d i e d the e f f e c t s o f aging time and c h i l l i n g treatments on the tenderness o f turkey muscle. From r e s u l t s o b t a i n e d , the authors suggested t h a t i f post-mortem t e n d e r i z a t i o n was not complete p r i o r to f r e e z i n g , a d d i t i o n a l i n c r e a s e s i n t e n d e r n e s s • c o u l d occur i n l a r g e turkeys d u r i n g f r e e z i n g and thawing. F r e e z i n g Rate Attempts to determine the e f f e c t of f r e e z i n g r a t e on the tenderness of frozen-thawed muscle have not r e s u l t e d i n complete agreement owing to the f a c t t h a t other v a r i a b l e s such as p r e f r e e z i n g h i s t o r y , depth of f r e e z i n g and l e n g t h of storage o f t e n i n f l u e n c e r e s u l t s . Dubois e t a l . (1940) found t h a t beef and p o u l t r y muscles f r o z e n i n moving a i r a t -40°F were more tender than samples f r o z e n i n moving a i r a t -18° and 23°F. However, Stewart et a l . (1945) were unable to d e t e c t a s i g n i f i c a n t d i f f e r e n c e i n the p a l a t a b i l i t y o f b r o i l e r muscle f r o z e n i n r a p i d l y moving a i r a t e i t h e r -68°F or -4 6°F as compared to b r o i l e r muscle f r o z e n i n sl o w l y moving a i r a t -21°F. S i m i l a r l y , Marion and Stadelman (1958) and M i l l e r and May (1965) found no s i g n i f i c a n t d i f f e r e n c e i n the tenderness o f p o u l t r y muscle f r o z e n a t 0°F, -30°F or -90°F.-B a r r i e e t a l . (1964), P i c k e t t and M i l l e r (1967) and S t r e e t e r and Spencer (1973) compared 'cryogenic' and c o n v e n t i o n a l methods of f r e e z i n g p o u l t r y . No d e t e c t a b l e d i f f e r e n c e s i n tenderness were found by any of the authors d e s p i t e the d i f f e r e n c e i n f r e e z i n g r a t e s . 10. Thawing Rate P o o l jet a l . (1959) showed t h a t t e n d e r i z a t i o n a r r e s t e d by f r e e z i n g proceeded a t about a normal r a t e upon thawing. Many methods of thawing have been r e p o r t e d . K l o s e e t _ a l . (1961) showed t h a t wide d i f f e r e n c e s i n the r a t e of thawing o f turkeys f r o z e n p r e - r i g o r had no adverse e f f e c t on the u l t i m a t e tenderness achieved by aging the b i r d s a f t e r thawing. A s i g n i f i c a n t d i f f e r e n c e i n tenderness was found, however, between turkeys cooked a f t e r thawing and those cooked w h i l e s t i l l f r o z e n . The authors suggested t h a t h o l d i n g f r o z e n turkeys f o r a s h o r t p e r i o d i n the i n t e r m e d i a t e thawing range (20 to 30°F) o f f e r e d promise of p r o v i d i n g tenderness i n b i r d s n e i t h e r c h i l l e d long enough nor h e l d long enough i n the thawed c o n d i t i o n to p r o v i d e the d e s i r e d degree of tenderness. C a r l i n et _ a l . (.194 9) r e c o g n i z e d t h a t u s i n g a thawing temperature of 4°C f o r 24 hours may have i n c r e a s e d the tenderness of c h i c k e n b r o i l e r s f r o z e n 6 hours p o s t -mortem by i n c r e a s i n g the aging p e r i o d upon thawing. Brodine and C a r l i n (1968) found no s i g n i f i c a n t d i f f e r e n c e i n the tenderness of turkeys thawed f o r 4 days a t r e f r i g e r a t o r temperatures and those thawed f o r 10 hours i n running water. H o f f e r t e t a l . (1952) found no d i f f e r e n c e i n the tenderness of b r o i l e r s thawed i n a r e f r i g e r a t o r a t 11. 5°C, i n a i r a t 21°C, i n water a t 24°C or i n an oven a t 150°C. Korslund and E s s a r y (.1971), however, found t h a t turkeys thawed by immersion i n c o l d water were s i g n i f i c a n t l y more tender than those thawed i n warm tap water, i n a low temperature oven, i n a r e f r i g e r a t o r o r a t room temperature. Temperature of Frozen Storage The temperature o f f r o z e n storage i s a major f a c t o r i n f l u e n c i n g the r a t e o f t e x t u r a l d e t e r i o r a t i o n . As the temperature of storage i s lowered, the ext e n t o f tender-ness l o s s (when i t occurs) i s decreased. The t e x t u r a l s t a b i l i t y o f f r o z e n c h i c k e n muscle was found by M i l l e r and May (1965) to be g r e a t e r a t -37°C than a t e i t h e r -28°C or -32°C over a storage p e r i o d o f 6 months. Other workers ( W i l l s jet al. , 1948 and K l o s e e t a l . , 1950) have observed t h a t c h i c k e n and turkey muscles became l e s s tough as the temperature o f f r o z e n storage was lowered t o -5°F. Length of Frozen Storage S t u d i e s o f the e f f e c t s o f v a r y i n g l e n g t h s o f f r o z e n storage on the tenderness o f muscle, have l e d to c o n f l i c t i n g r e s u l t s . Some i n v e s t i g a t o r s have r e p o r t e d t h a t p o s t - r i g o r muscle of p o u l t r y , beef, lamb and f i s h decrease i n tenderness d u r i n g f r o z e n s t o r a g e , (Guerrant e t a l . , 1953). M i l l e r and May (1965) i n t h e i r study on c h i c k e n muscle, found t h a t tenderness g e n e r a l l y decreased w i t h 12. increased time of storage at - 2 8 ° C or - 3 2 ° C . Although the d i f f e r e n c e i n tenderness of chicken muscles stored for 1 week and 1 month was not s i g n i f i c a n t , both of these muscles (stored at - 2 8 ° C ) were somewhat more tender than those stored at the same temperature for e i ther 3 or 6 months. Stewart et a l . (1945) stored b r o i l e r s at - 2 3 ° C for periods of time up to 79 days. Using taste panel assessment of texture , he found that the a c c e p t a b i l i t y l e v e l decreased as storage time increased. The large v a r i a t i o n i n the r e s u l t s obtained from studies of the e f f e c t o f , v a r i o u s aging, f reezing and thawing techniques on the tenderness of the f i n a l cooked product prompted the research presented i n t h i s t h e s i s . Methods of Measuring Muscle Tenderness  Object ive and Subjective Methods There are a large number of procedures used to measure meat tenderness. Marion (1967) recognized the need to standardize mechanical and sensory methodology so that comparisons of data obtained by d i f f e r e n t techniques can be made. Relat ionships between objec t ive and subject ive measurements of meat tenderness have been widely s t u d i e d , (Deatherage and Garnatz, 1952; Klose et a l . , 1961; White et a l . , 1964; Pangborn et a l . , 1965; Sharrah et a l . , 1965 a , b ; Pool and K l o s e , 1969; Szczesniak et a 1 . , 1970; Larmond and P e t r a s o v i t s , 1972). Bouton and H a r r i s (1972) have g i v e n a comprehensive comparison of some of the o b j e c -t i v e methods used to measure meat tenderness. Most of the o b j e c t i v e methods of measuring tenderness use some form of s h e a r i n g d e v i c e and r e c o r d the f o r c e r e q u i r e d to shear or compress a g i v e n amount of sample. O b j e c t i o n s to such techniques have been put forward by s e v e r a l authors (Sharrah e t a l . , 1965b; Pool and K l o s e , 1969; Szczesniak e t a l . , 1970). Many ot h e r methods of measuring meat tenderness have been used such as measurements of the t e n s i l e s t r e n g t h of muscle f i b r e s used by Nakamura (19.72) and measurement of the e l e c t r i c a l impedance of p o u l t r y muscle c a r r i e d out by Zachariah e t a l . (1971) . S t a n l e y e t a l . (1972) concluded from t h e i r r e s u l t s t h a t there are two major s t r u c t u r a l c o n t r i b u t i o n s of raw muscle to cooked meat tenderness — a c o n n e c t i v e t i s s u e f a c t o r and a c o n t r a c t i o n f a c t o r — and t h a t d i f f e r e n t o b j e c t i v e methods are b e s t s u i t e d f o r t h e i r e v a l u a t i o n . Measurement of Sarcomere Length. Since the r e p o r t by Locker (1960) t h a t tenderness i n beef i s i n f l u e n c e d by the degree of muscular c o n t r a c t i o n i n the post-mortem muscle, a number of workers have i n v e s t i g a t e d the c o r r e l a t i o n between sarcomere l e n g t h , as a measure of the c o n t r a c t i l e s t a t e , and tenderness. The i n f l u e n c e of c o n t r a c t i l e s t a t e on t e x t u r e i s demonstrated i n the phenomenon of V c o l d s h o r t e n i n g ' (Locker and Hagyard, 1963; Marsh and L e e t , 1966), and i n the e f f e c t of the con-f i g u r a t i o n of the c a r c a s s d u r i n g r i g o r m o r t i s on a number of muscles, (Herring e t a l . 1965b H o s t e t l e r e t a l . 1970). Many methods have been developed f o r measuring sarcomere l e n g t h and these are e x c e l l e n t l y reviewed i n The Meat Research I n s t i t u t e , (England) B u l l e t i n 546 (1972). A method c u r r e n t l y i n use a t the Meat Research I n s t i t u t e (Voyle, 1971) d e r i v e s i n i t i a l l y from o b s e r v a t i o n s made i n 1874 t h a t a s t r a i t e d muscle a c t s as a t r a n s m i s s i o n g r a t i n g when p l a c e d i n a beam of l i g h t . D i f f r a c t i o n p a t t e r n s are formed on a screen, the s e p a r a t i o n of the l a t e r a l o r d e r s being determined by the c o n t r a c t i l e s t a t e of the muscle. A r e c e n t development i n t h i s technique i s the use of a gas l a s e r as a source of coherent, monochromatic l i g h t . T h i s has been d e s c r i b e d by Rome (1967) and Cleworth and Edman (1969). I s o m e t r i c Tension Measurement The f i r s t s t u d i e s i n the use of i s o m e t r i c t e n s i o n measurements were r e p o r t e d by Busch e t a l . (19 67) and Jungk e t a l . (1967). Before t h i s time, e x t e n s i b i l i t y measurements were used i n order to q u a n t i t a t i v e l y f o l l o w r i g o r m o r t i s . ' Busch e t a l . (1972) o u t l i n e d the advantages of i s o m e t r i c t e n s i o n measurements over e x t e n s i b i l i t y measure-ments, the most important of which was the a b i l i t y to d e t e c t changes which correspond to both onset and r e s o l u t i o n of r i g o r . Busch et a l . (1972a) recommended some improvements i n the procedure for measuring post-mortem isometric t e n s i o n . Jungk and Marion (1970) demonstrated isometric tension development and d e c l i n e i n turkey muscle and establ ished a l i n e a r r e l a t i o n s h i p between temperature and tension development i n breast muscle. CHAPTER*II. THE TENDERNESS OF CHICKEN BROILER MUSCLE FROZEN AT VARIOUS POSTMORTEM AGING TIMES -METHODS OF FREEZING, COOKING AND TENDERNESS EVALUATION. INTRODUCTION The e f f e c t of f r e e z i n g on p o u l t r y tenderness has been w i d e l y s t u d i e d . V a r i o u s authors have shown t h a t the tenderness of chi c k e n b r o i l e r muscle i s dependent on the l e n g t h of aging time p r i o r to f r e e z i n g but r e p o r t e d r e s u l t s v ary c o n s i d e r a b l y and, i n many i n s t a n c e s , are d i f f i c u l t t o i n t e r p r e t . With young chickens aged i n i c e s l u s h , most of the t e n d e r i z i n g e f f e c t (determined from the cooked f l e s h ) was found to occur w i t h i n 5 hours (Hanson e t a l . , 1942; Koonz e t a l . , 1954; Dodge ' and Stadelman, 1959; Pool e t a l . , 1959 .) In a study by Palmer e t a l . (1965) u n t r a i n e d judges' f r e q u e n t l y d e t e c t e d u n d e s i r a b l e toughness i n cooked c h i c k e n f r y e r s when a c h i l l i n g - a g i n g time of l e s s than 4 hours was used p r i o r to f r e e z i n g . Stewart e t al.'.- (1945) f r o z e b i r d s a t 2 and 18 hours postmortem and found no d i f f e r e n c e s i n the tenderness of b i r d s s u b j e c t e d to the two treatments. Any d i f f e r e n c e s may have been o b v i a t e d , however, s i n c e a 48 hour thawing time was used p r i o r t o cooking,and subsequent tenderness e v a l u a t i o n . C a r l i n e t a l . (1949) found t h a t f o r b i r d s 17. aged l e s s than 6 hours, f r e e z i n g enhanced the tenderness, although, again, r e s u l t s may have been i n f l u e n c e d by a 24 hour aging p e r i o d upon thawing. Shrimpton (19 60) s t u d i e d 11-week o l d chickens weighing 3 - 4 l b each and found t h a t c h i l l i n g - a g i n g times ranging from 0 to 24 hours had no important i n f l u e n c e on the tenderness of the cooked product. ' .deFremery and P o o l (1960) r e p o r t e d t h a t f r e e z i n g and thawing of muscle be f o r e the normal onset of r i g o r induced a very r a p i d "thaw-rigor" which e f f e c t e d a s i g n i f -i c a n t i n c r e a s e i n the toughness of the cooked meat. Muscles which had passed through r i g o r p r i o r to f r e e z i n g showed no corresponding i n c r e a s e i n toughness. The authors concluded t h a t the toughening observed was due to the a c c e l e r a t e d onset of r i g o r upon thawing. Reasons f o r the v a r i a t i o n s and the d i f f i c u l t y of i n t e r p r e t a t i o n of p u b l i s h e d r e s u l t s c o u l d be the l a c k of s t a n d a r d i z e d methods f o r aging, f r e e z i n g , thawing, cooking and tenderness e v a l u a t i o n . In view of the d i v e r s i t y found i n the p u b l i s h e d r e s u l t s , i t was decided to re-study the e f f e c t of v a r i o u s p r e - f r e e z i n g aging times on the u l t i m a t e tenderness of c h i c k e n b r o i l e r muscle. Experiments were a l s o c a r r i e d out to i l l u s t r a t e t h e ' f a c t t h a t v a r i a t i o n s i n the methods used f o r aging, thawing and storage time c o u l d s i g n i f i c a n t l y a l t e r the r e s u l t s o b t a i n e d . 18. T h i s chapter t h e r e f o r e d e s c r i b e s the e s t a b l i s h m e n t of standard methods of. f r e e z i n g , cooking and tenderness e v a l u a t i o n used throughout t h i s t h e s i s . MATERIALS AND METHODS Experiment 1 - A Comparison of S u b j e c t i v e and O b j e c t i v e  Methods of Tenderness E v a l u a t i o n . Muscle Source The b r o i l e r s . u s e d throughout these s t u d i e s were obtained from a l o c a l p r o c e s s i n g p l a n t . The b i r d s had been k i l l e d by normal packing house procedures and were removed from the p r o c e s s i n g l i n e b e f o r e they reached the c h i l l e r a t approximately 20 minutes postmortem. The c a r c a s s e s were packed i n i c e and t r a n s p o r t e d t o the U n i v e r s i t y where they were kept i n i c e water a t approximately 0°C u n t i l used f o r f r e e z i n g . A l l b i r d s used were commercial b r o i l e r s and were approximately 8 weeks o l d a t the time of s l a u g h t e r . Method of F r e e z i n g and Muscle P r e p a r a t i o n . Three groups of 8 c a r c a s s e s each were s e p a r a t e l y packed and s e a l e d i n polyethylene.bags and f r o z e n i n an a i r b l a s t a t - 3 l°C. W i t h i n each group of 8, two b i r d s were f r o z e n a t 1, 3, 6 and 10 hours postmortem, r e s p e c t i v e l y . A f t e r storage f o r one week a t -31°C, the c a r c a s s e s were thawed f o r 4 hours i n running water a t 25°C. The temperature of the water was checked every 30 minutes throughout the thawing procedure. The P. major muscles were then e x c i s e d and clamped between two aluminum p l a t e s spaced 0.7 cm ap a r t and cooked f o r 10 minutes i n b o i l i n g water (deFremery and P o o l , 1960). 20. When cooking was completed, samples were c o o l e d i n running tap water f o r 5 minutes. A f t e r removal from the p l a t e s , the muscle samples were i n d i v i d u a l l y wrapped i n Saran wrap u n t i l needed. S u b j e c t i v e Method of Tenderness E v a l u a t i o n . A f i v e member sensory panel was used. Tenderness was e v a l u a t e d f o r each treatment u s i n g rank a n a l y s i s . Sensory a n a l y s i s was- c a r r i e d out i n a t a s t e panel room s e a t i n g f i v e people and equipped w i t h i n d i v i d u a l c u b i c l e s . Samples were presented i n red l i g h t from a 20 W. f l u o r e s c e n t tube above each c u b i c l e . T r i a l s were h e l d around 10:30 a.m. and 2:30 p.m. on three days. For each judge a t each panel s i t t i n g s i x s m a l l c o n t a i n e r s were coded with 3 - d i g i t random numbers. Three p i e c e s of cooked P. major muscle obtained from each of the four treatment groups were coded and p l a c e d i n the c o n t a i n e r s . Thus, the s i x r e q u i s i t e p a i r s were formed f o r treatment comparison; i e . , 1:3, 1:6, 1:10, 3:6, 3:10 and 6:10. Samples . 2 . presented were approximately 2.5 cm i n s i z e and were c u t from the same area of each P. major muscle. A l l samples were served a t room temperature.. Code numbers were recorded and the p a i r s were presented to the judges i n a random order , t ogether w i t h score sheets. Judges e v a l u a t e d each sample f o r tenderness and, f o r each p a i r presented, recorded* a score of 1 f o r the tougher sample and 2 f o r the more tender sample. Space was provided on the score sheet f o r w r i t t e n comments. Thus s i x panel s e s s i o n s were conducted f o r the twenty-four b r o i l e r s used. The treatment sums of ranks were obtained f o r a l l the panel s e s s i o n s . O b j e c t i v e Method of Tenderness E v a l u a t i o n Measurements of shear were c a r r i e d out u s i n g the Allo-Kramer shear p r e s s . S t r i p s of p a r a l l e l f i b r e s , 1.5 cm wide were cut from samples of the P. major muscle which remained a f t e r the panel samples had been removed. A minimum of 8 shear measurements per b i r d was o b t a i n e d u s i n g a s i n g l e blade shear c e l l , 250 l b r i n g and 9 cm/min c r o s s -head speed. In a l l cases, a t t e n u a t i o n was s e t a t the 10 per cent l e v e l . Experiment 2 - L i q u i d N i t r o g e n B l a s t F r e e z i n g T e s t s were c a r r i e d out, u s i n g thermocouples, to f i n d the l e n g t h of time r e q u i r e d to f r e e z e whole chi c k e n b r o i l e r c a r c a s s e s to an i n t e r n a l temperature of approximately -60°C i n a l i q u i d n i t r o g e n b l a s t f r e e z e r . The b l a s t f r e e z e r c o n s i s t e d of an i n s u l a t e d c a b i n e t , d i v i d e d i n t o four compartments, each compartment separated from the other three by wire mesh. A whole ca r c a s s was p l a c e d i n t o each of the four s e c t i o n s . A copper constantan thermocouple was i n s e r t e d i n t o the b r e a s t muscle of each 22. b i r d a t approximately the same p o s i t i o n , so t h a t i t p e n e t r a t e d to a d i s t a n c e of 0.5 cm from the sternum a t the a n t e r i o r end of the c a r c a s s . A telethermometer was used to r e c o r d the temperature of the i n s i d e of the f r e e z i n g c a b i n e t . The c a b i n e t was then c l o s e d , and l i q u i d n i t r o g e n , under p r e s s u r e was pumped i n v i a i n s u l a t e d copper t u b i n g . A f a n s i t u a t e d i n the base of the c a b i n e t caused a r a p i d flow of n i t r o g e n t o c i r c u l a t e throughout the fou r c a b i n e t s . Temperature readings of the b r e a s t muscle of each b i r d and the i n s i d e of the c a b i n e t were taken a t r e g u l a r i n t e r v a l s . The e n t i r e system used i n t h i s and subsequent s t u d i e s i s shown i n P l a t e I. 2 3 . P l a t e I . A p p a r a t u s used f o r l i q u i d n i t r o g e n b l a s t f r e e z i n g . RESULTS AND DISCUSSION Experiment I Analyses of v a r i a n c e were c a r r i e d out on the data o b t a i n e d from the s u b j e c t i v e and o b j e c t i v e methods of tender-ness e v a l u a t i o n . R e s u l t s of these analyses are shown i n Table 1. TABLE 1. ANALYSES OF VARIANCE FOR SUBJECTIVE AND OBJECTIVE TENDERNESS EVALUATION. Source df Mean Squares (Subj.) Mean Squares (Obj.) Treatment 3 1.97*** 150.86* E r r o r 20 0.24 41.36 T o t a l 23 * p < 0.05 *** p < 0.001 From t h i s t a b l e i t i s seen t h a t i n both cases there i s a s i g n i f i c a n t treatment e f f e c t . T h i s i s p a r t i c u l a r l y so i n the s u b j e c t i v e e v a l u a t i o n s . The treatment means and the r e s u l t s of Duncan's New M u l t i p l e Range T e s t s are shown i n Table IT. S u b j e c t i v e e v a l u a t i o n means are expressed i n terms of panel tenderness scores and have no ab s o l u t e u n i t s ; o b j e c t i v e e v a l u a t i o n means are expressed as Allo-Kramer shear press r e c o r d e r v a l u e s o b t a i n e d when the instrument was f i t t e d w i t h a 250 l b r i n g and attenuationvwas s e t a t the 10 per cent l e v e l . In t h i s case, each u n i t i s e q u i v a l e n t to pounds of f o r c e m u l t i p l i e d by a f a c t o r of 4. TABLE I I . DUNCAN'S NEW MULTIPLE RANGE TEST ON SIGNIFICANT TREATMENT MEANS FROM TENDERNESS EVALUATIONS -EXPERIMENT 1. Time of F r e e z i n g Postmortem, hours 1 3 6 1.0 Panel Scores 4.70 a* 4.07 b 4.03 b 5.23 a Shear Value ' 2 4 . 4 8 a b 29.35 b 30.60 b 19.62 a ( l b s x 4) * Means i n the same row w i t h s i m i l a r s u p e r s c r i p t s do not d i f f e r s i g n i f i c a n t l y (p < 0.05). The p a n e l and shear data both i n d i c a t e t h a t an i n c r e a s e i n toughness occurs i n b i r d s f r o z e n between 1 and 6 hours postmortem. In both cases, maximum tenderness i s shown to occur i n b i r d s f r o z e n 10 hours a f t e r death although the d i f f e r e n c e i n the tenderness of b i r d s f r o z e n a t 1 and at 10 hours postmortem i s not s i g n i f i c a n t . Both s u b j e c t i v e and o b j e c t i v e methods of tenderness e v a l u a t i o n , t h e r e f o r e , show t h a t i n t h i s experiment, the l e n g t h of p r e - f r e e z i n g aging time has an e f f e c t on the u l t i m a t e tenderness of b r o i l e r muscle. These r e s u l t s are i n agreement w i t h those of Palmer e t a l . (1965) and deFremery and P o o l (I960).. I t i s probable t h a t the b i r d s used i n t h i s experiment, when f r o z e n a t 1, 3 and, i n some cases, 6 hours postmortem, were e i t h e r f r o z e n p r i o r t o , or d u r i n g , the normal onset of r i g o r such t h a t a very r a p i d "thaw r i g o r " , e f f e c t i n g a s i g n i f i c a n t i n c r e a s e i n the tough-ness of the cooked meat, was induced d u r i n g r a p i d thawing. B i r d s f r o z e n a t 10 hours postmortem (and, i n c e r t a i n i n s t a n c e s , 6 hours postmortem) had p r e v i o u s l y passed through r i g o r and t h e r e f o r e showed no co r r e s p o n d i n g i n c r e a s e i n toughness. F i g u r e s 1. and 2 i l l u s t r a t e these e f f e c t s . The standard d e v i a t i o n s of the shear v a l u e s and panel scores are shown i n these f i g u r e s and i l l u s t r a t e a r e l a t i v e l y l a r g e v a r i a t i o n i n the r e s u l t s o b t ained f o r b i r d s f r o z e n a t each postmortem time. V a r i a t i o n i n r e s u l t s i s p a r t i c u l a r l y n o t i c e a b l e f o r b i r d s f r o z e n a f t e r 3 or 6 hours of aging. S e v e r a l f a c t o r s may be the cause of t h i s v a r i a t i o n . Apart from p h y s i o l o g i c a l v a r i a t i o n among the b i r d s used, one cause c o u l d be the r e l a t i v e l y slow method of f r e e z i n g used i n t h i s experiment. 27 . 2-5 : , ; F i g u r e 1. S u b j e c t i v e assessment of toughness of b r o i l e r muscle f r o z e n a f t e r v a r i o u s postmortem a g i n g p e r i o d s . F i g u r e 2. O b j e c t i v e a s s e s s m e n t o f t o u g h n e s s o f b r o i l e r m u s c l e f r o z e n a f t e r v a r i o u s p o s t m o r t e m a g i n g p e r i o d s . Stewart e t a l . (1945) were unable to d e t e c t a s i g n i f i c a n t d i f f e r e n c e i n the p a l a t a b i l i t y of b r o i l e r muscle f r o z e n i n r a p i d l y moving a i r a t e i t h e r -55.5° or -43°C as compared to b r o i l e r muscle f r o z e n i n slow moving a i r a t 29.5°C. S i m i l a r r e s u l t s were ob t a i n e d by Marion and Stadelman,. (1958) , and M i l l e r and May, (1965) . However, i n a l l these examples, . p o u l t r y were f r o z e n a f t e r aging p e r i o d s s u f f i c i e n t to ensure t h a t the muscles had passed through r i g o r m o r t i s and were t h e r e f o r e no l o n g e r s u b j e c t to the toughening e f f e c t s of 'thaw r i g o r ' . In t h i s experiment, b i r d s f r o z e n a f t e r 1, 3 and o c c a s i o n a l l y , 6 hours of aging were approaching the s t a t e of r i g o r a t the time of e n t e r i n g the f r e e z e r . The r a t e of g l y c o l y s i s has been shown to g r a d u a l l y i n c r e a s e i n c h i c k e n P. major muscle as the temperature i s lowered from 0° to -3° or -4°C. and to decrease s h a r p l y from -4° to -10°C (Behnke e t a l . 1973) . The r a t e i n c r e a s e was thought by the authors to be due to a f r e e z e - c o n c e n t r a t i o n e f f e c t . A i r b l a s t f r e e z i n g a t -31°C i s a r e l a t i v e l y slow method of f r e e z i n g whole b r o i l e r c a r c a s s e s and may have l e d to a l a r g e v a r i a t i o n i n the ex t e n t of postmortem g l y c o l y s i s throughout the muscle t i s s u e o f b i r d s i n the p r e - r i g o r and r i g o r s t a t e . Both the p o s i t i o n of the b i r d i n the a i r b l a s t and the r e l a t i v e l y l a r g e mass of the c a r c a s s may have caused p a r t 30. of the muscle t i s s u e to remain unfrozen or p a r t i a l l y f r o z e n f o r extended p e r i o d s a t temperatures j u s t below the f r e e z i n g p o i n t , where g l y c o l y s i s can occur at a r a p i d r a t e . Thus, w h i l e the s u r f a c e muscle l a y e r became f r o z e n and thus ' f i x e d ' i n i t s postmortem s t a t e , g l y c o l y s i s and the develop-ment of r i g o r may have continued a t a r a p i d r a t e i n the i n n e r t i s s u e s . Such a v a r i a t i o n i n the postmortem s t a t e of the muscle t i s s u e c o u l d have a f f e c t e d the tenderness of the cooked product and thus may be a p o s s i b l e reason f o r the l a r g e v a r i a t i o n found i n the r e s u l t s of the tenderness a n a l y s e s . A simple l i n e a r c o r r e l a t i o n a n a l y s i s was performed on the data from the s u b j e c t i v e and o b j e c t i v e tenderness t e s t s . The c o r r e l a t i o n matrix i s presented i n T a b l e I I I . I t can be seen t h a t there are s i g n i f i c a n t c o r r e l a t i o n s between the two methods of tenderness e v a l u a t i o n p a r t i c u l a r l y when b i r d s f r o z e n a f t e r 1 and 10 hours of aging are e v a l u a t e d . TABLE I I I . CORRELATION MATRIX FOR SUBJECTIVE AND OBJECTIVE METHODS OF TENDERNESS EVALUATION AT EACH TIME OF FREEZING, POSTMORTEM. Time of F r e e z i n g Postmortem (hours) O v e r a l l C o r r e l a t i o n 1 . 3 6 10 S u b j e c t i v e O b j e c t i v e .87*** .71* .74* .77** .53**** * P = < .. 1 ** p = <. .05 *'** p = < .02 * * * * p = <.0 31. R e l a t i o n s h i p s between o b j e c t i v e and s u b j e c t i v e measurements of meat tenderness have been widely s t u d i e d by many authors. S t a n l e y . e t a l . (1972), d i d not o b t a i n h i g h l y s i g n i f i c a n t c o r r e l a t i o n s between panel e v a l u a t i o n s of tenderness and shear v a l u e s i n t h e i r s t u d i e s of p o r c i n e muscle. S i m i l a r l y o b j e c t i o n s to the use of the Allo-Kramer shear press as an adequate means of determining meat tenderness, have been r a i s e d by Sharrah e t a l . (1965b), Pool and K l o s e , (1969) and Szczes n i a k e t a l . (1970). The b a s i s of the o b j e c t i o n s i n v o l v e s an exact d e f i n i t i o n of the q u a l i t i e s t h a t the Allo-Kramer shear press measures. S u b j e c t i v e assessment of tenderness i n v o l v e s c u t t i n g , s h e a r i n g , t e a r i n g , g r i n d i n g and squeezing. Compression, t e n s i o n and s h e a r i n g s t r e s s e s are simulated by t h i s instrument. In a d d i t i o n , c e r t a i n experimental, v a r i a b l e s must a l s o be c o n t r o l l e d i n order to o b t a i n r e l i a b l e r e s u l t s from the Allo-Kramer shear p r e s s . However, i n view of the s i g n i f i c a n t and r e l a t i v e l y s t r o n g c o r r e l a t i o n s between the s u b j e c t i v e and o b j e c t i v e methods of tenderness e v a l u a t i o n used i n t h i s experiment, and the obvious treatment e f f e c t shown by both methods, i t was concluded t h a t e i t h e r method of tenderness assessment c o u l d be used i n f u t u r e experiments of t h i s type. Experiment 2 As p r e v i o u s l y mentioned, i t was thought t h a t the slow r a t e of f r e e z i n g of whole b r o i l e r c a r c a s s e s used i n Experiment 1 may have p a r t i a l l y caused the r e l a t i v e l y l a r g e v a r i a t i o n i n the tenderness v a l u e s o b t a i n e d f o r b i r d s r f r o z e n p r i o r t o or d u r i n g the onset of r i g o r . In an attempt to d i s c o u n t any p o s s i b l e v a r i a t i o n i n tenderness throughout the P. major muscle caused by a slow f r e e z i n g method, l i q u i d n i t r o g e n b l a s t , f r e e z i n g was t e s t e d as a p o s s i b l e method f o r r a p i d l y f r e e z i n g the whole c a r c a s s , and thus r a p i d l y ' f i x i n g ' the postmortem s t a t e of the muscle. R e s u l t s of t h i s experiment showed t h a t the i n t e r n a l temperature of the P. major muscle on the b r o i l e r c a r c a s s c o u l d be lowered to -60°C - a temperature f a r below t h a t a t which any g l y c o l y t i c changes can occur i n the muscle -w i t h i n 20 minutes. Very l i t t l e v a r i a t i o n was found i n the r a t e of f r e e z i n g of c a r c a s s e s p l a c e d i n each of the f o u r compartments i n s i d e the f r e e z e r c a b i n e t . T h i s i s shown i n F i g u r e 3. I t was decided to continue u s i n g t h i s method of r a p i d f r e e z i n g i n the f o l l o w i n g experiments. cabinet •air temperature CHAPTER I I I . THE TENDERNESS OF CHICKEN BROILER MUSCLE FROZEN AT VARIOUS POSTMORTEM AGING TIMES -THE EFFECT OF VARYING AGING, THAWING AND FROZEN STORAGE TECHNIQUES. INTRODUCTION As p r e v i o u s l y s t a t e d , p o s s i b l e reasons f o r the v a r i a t i o n s and the d i f f i c u l t y o f i n t e r p r e t a t i o n o f many of the p u b l i s h e d r e s u l t s p e r t a i n i n g to the q u a l i t y of f r o z e n p o u l t r y , c o u l d be the l a c k of s t a n d a r d i z e d methods of aging, f r e e z i n g , thawing, cooking and tenderness e v a l u -a t i o n . Experiment 1 has shown t h a t f r e e z i n g a f t e r v a r i o u s postmortem aging times up to 10 hours a f t e r death, has the e f f e c t of causing a d e t e c t a b l e i n c r e a s e i n toughness up to 6 hours postmortem when the p r e v i o u s l y d e s c r i b e d methods of f r e e z i n g , thawing, cooking and tenderness e v a l u a t i o n are used. A d i f f e r e n c e i n the r a t e of thawing of the c a r c a s s may have a s i g n i f i c a n t e f f e c t on the u l t i m a t e tenderness of the cooked muscle. Pool e t a l . (1959), have shown t h a t t e n d e r i z a t i o n of p o u l t r y muscle, a r r e s t e d by f r e e z i n g w i l l proceed a t a normal r a t e on thawing. Thus i t i s c o n c e i v a b l e t h a t a long thawing time a t low temperatures w i l l have a t e n d e r i z i n g e f f e c t on muscle f r o z e n p r e - r i g o r . Postmortem g l y c o l y s i s proceeds r a p i d l y a t temperatures j u s t below the f r e e z i n g p o i n t (Behnke e t a l . , 1973) and i t i s t h e r e f o r e p o s s i b l e t h a t h o l d i n g c a r c a s s e s i n t h i s i n t e r m e d i a t e thawing range d u r i n g slow thawing, c o u l d g r e a t l y i n c r e a s e the u l t i m a t e tenderness of the muscle. T h i s f a c t was r e c o g n i z e d by C a r l i n e t a l . (1949), who concluded t h a t a thawing temper-ature of 40°C f o r 24 hours may have i n c r e a s e d the tenderness of c h i c k e n muscle f r o z e n 6 hours postmortem. S i m i l a r r e s u l t s were r e p o r t e d by Klose e t a l . (1961) . The method of thawing used i n Experiment 1 was r a p i d , such t h a t the c a r c a s s passed through the i n t e r -mediate thawing range - the temperature range a t which postmortem g l y c o l y s i s i s most r a p i d - i n a very s h o r t time. The f o u r hour thaw was not s u f f i c i e n t f o r s i g n i f i c a n t t e n d e r i z a t i o n of the p r e - r i g o r f r o z e n muscle to o c c u r . The next three experiments t h e r e f o r e d e s c r i b e v a r i a t i o n s i n the thawing method used f o r p o u l t r y f r o z e n a f t e r v a r i o u s postmortem aging times, i n an attempt to determine an adequate thawing time f o r p r e - r i g o r f r o z e n muscle. The temperature of p r e - f r e e z i n g aging has a l s o been suggested to be a p o s s i b l e f a c t o r i n f l u e n c i n g the r a t e of onset of r i g o r . Lowe (1948), found t h a t the temperature of aging i n the range from 0°C to average room temperature had l i t t l e e f f e c t on the r a t e of postmortem changes i n f o w l . Conversely, Dodge and Stadelman (1959), showed t h a t both the temperature and the media of aging appeared to a f f e c t the p a t t e r n of r i g o r and the l e v e l of tenderness a t a g i v e n time postmortem- Water or i c e s l u s h was shown by the authors to be the b e s t medium f o r aging. Aging i n a i r l e d to some deh y d r a t i o n and consequent toughening of the muscle t i s s u e . More t e n d e r i z a t i o n of muscle o c c u r r e d i n water a t 0° and 12.8°C than i n water a t 22°C or i n a i r a t 3.9° or 12.8°C. Marsh and L e e t (1966), a l s o showed t h a t the u l t i m a t e tenderness of meat i s a f f e c t e d by the temperature d u r i n g the f i r s t few hours postmortem. Experiment 6 d e s c r i b e s a comparative study of two methods of p r e - f r e e z i n g a g ing to f i n d the e f f e c t , i f any, of the temperature and media of aging on the u l t i m a t e tenderness of b r o i l e r muscle. S t u d i e s of the e f f e c t of f r o z e n storage on tender-ness of p o u l t r y muscle have a l s o l e d to c o n f l i c t i n g r e s u l t s . M i l l e r and May (1965) , i n t h e i r study on c h i c k e n muscle found t h a t tenderness g e n e r a l l y decreased with i n c r e a s i n g time of storage. These authors a l s o found t h a t the t e x t u r a l s t a b i l i t y of f r o z e n c h i c k e n muscle was g r e a t e r a t -35°F than at e i t h e r -18° or -26°F over a storage p e r i o d of 6 months. Klose e t a l . . (1950), observed t h a t turkey muscle became l e s s tough as the temperature of f r o z e n storage was lowered to -23°F. Stewart e t a l . (1945) s t o r e d b r o i l e r s a t 37. -10 F f o r p e r i o d s of up to 79 days a f t e r which time, the authors found t h a t the t e x t u r e of the b i r d s had d e t e r i o r a t e d . The e f f e c t of temperature and l e n g t h of f r o z e n storage on the r a t e and p a t t e r n of postmortem g l y c o l y s i s has not been s t u d i e d . Muscle f r o z e n p r e - r i g o r may undergo a s m a l l amount of g l y c o l y s i s , d u r i n g long term f r o z e n storage such t h a t the u l t i m a t e tenderness of the cooked product i s g r e a t e r than t h a t of the same p r e - r i g o r f r o z e n muscle t h a t has not been s t o r e d . Experiment 7 d e s c r i b e s a study of the e f f e c t s of long term storage on the. tenderness of b r o i l e r muscle f r o z e n p r e - r i g o r . 38. MATERIALS AND METHODS Experiment 3 - The E f f e c t of Rapid Thaw on the Tenderness  of Chicken B r o i l e r Muscle Frozen a t V a r i o u s Postmortem  Aging Times. Whole c a r c a s s e s were f r o z e n i n a l i q u i d n i t r o g e n b l a s t f r e e z e r f o r 20 minutes (by the method p r e v i o u s l y described) a f t e r aging i n i c e water f o r 1, 2 , 3 , 4 , 6 , 8 and 10 hours. In each t r i a l , 4 c a r c a s s e s were f r o z e n f o r each aging time. A f t e r f r e e z i n g the c a r c a s s e s were i n d i v i d u a l l y wrapped i n p o l y e t h y l e n e bags and s t o r e d a t -31°C. A f t e r one week, the c a r c a s s e s were thawed i n running water a t 25°C f o r 4 hours. The P. major muscles were e x c i s e d and cooked by the method d e s c r i b e d i n Experiment 1. Tenderness was eva l u a t e d u s i n g the Allo-Kramer shear p r e s s . Nine measure-ments on s t r i p s of p a r a l l e l f i b r e s 1.5 cm wide, were made from each P. major muscle, g i v i n g 18 measurements f o r each c a r c a s s used. T h i s experiment was repeated three times so t h a t , i n t o t a l , 12 c a r c a s s e s were used f o r each aging time s t u d i e d . Experiment 4 - The E f f e c t of a 24 Hour Thaw on the Tenderness  of Chicken B r o i l e r Muscle Frozen a t V a r i o u s Postmortem  Aging Times. Experiment 3 was repeated. However, i n t h i s case, aging times of 1, 2, 3, 4, 6 and 10 hours were used and c a r c a s s e s were thawed a t 4 UC f o r 24 hours p r i o r to cooking and tenderness e v a l u a t i o n . Four b i r d s were used f o r each of the s i x aging times. Experiment 5 - The E f f e c t of a 48 hour Thaw on the Tenderness  of Chicken B r o i l e r Muscle Frozen a t V a r i o u s Postmortem Aging  Times. In t h i s experiment, thawing time a t 4°C was i n c r e a s e d to 4 8 hours. Once again, f o u r b i r d s were used f o r each of the s i x aging times. (1, 2, 3, 4, 6 and 10 hours). Experiment 6 - The E f f e c t of V a r y i n g the P r e - F r e e z i n g Aging  Medium and Temperature on the Tenderness of Chicken B r o i l e r  Muscle Frozen a t V a r i o u s Postmortem Aging Times. F i v e groups of fou r c a r c a s s e s each were aged i n a i r at room temperature (23°C) and then f r o z e n i n a l i q u i d n i t r o g e n b l a s t f r e e z e r a t 1 , 1 1/2, 2, 2 1/2 and 3 hours postmortem, r e s p e c t i v e l y . F r e e z i n g was repeated w i t h a second batch of twenty b i r d s a f t e r aging them f o r 1, 1 1/2, 2, 2 1/2 and 3 hours i n i c e s l u s h a t 0°C . Storage f o r one week a t -31°C Was f o l l o w e d by a fou r hour thaw i n running water a t 25°C. Muscle e x c i s i o n , cooking and tenderness e v a l u a t i o n s were c a r r i e d out on the two groups of samples. Experiment 7 - The E f f e c t of Length of Storage on the  Tenderness of Chicken B r o i l e r Muscle Frozen a t V a r i o u s  Postmortem Aging Times. F i v e groups of fou r b i r d s each were aged i n i c e 40 s l u s h a t 0°C f o r 1, 2, 3, 6 and 10 hours postmortem, respec t i v e l y . A f t e r f r e e z i n g i n a l i q u i d n i t r o g e n b l a s t f r e e z e r , the c a r c a s s e s were i n d i v i d u a l l y wrapped i n p o l y e t h y l e n e bag and s t o r e d i n a f r e e z e r a t -23°C f o r 3 months. At the end of t h i s p e r i o d , the c a r c a s s e s were thawed i n running water a t 25°C f o r 4 hours. Muscle e x c i s i o n , cooking and tenderness e v a l u a t i o n s were c a r r i e d out on each c a r c a s s , by methods p r e v i o u s l y d e s c r i b e d . RESULTS AND DISCUSSION Experiments 3 , 4 arid 5 Experiments 3 , 4 and 5 are s i m i l a r s i n c e they are a l l concerned w i t h thawing r a t e . They w i l l t h e r e f o r e be d i s c u s s e d t o g e t h e r . Experiment 3 d i f f e r e d from Experiment 1 o n l y i n t h a t the method of f r e e z i n g used was' more r a p i d and t h a t tenderness was e v a l u a t e d u s i n g the Allo-Kramer shear p r e s s o n l y . Table IV l i s t s the means, standard d e v i a t i o n s and c o e f f i c i e n t s o f v a r i a t i o n o f the shear v a l u e s o b t a i n e d f o r muscle f r o z e n a t the d i f f e r e n t aging times i n Experiment 3 . I t may be noted from t h i s t a b l e t h a t the mean shear v a l u e s a t each treatment time do not d i f f e r a p p r e c i a b l y from those found i n Experiment 1 . TABLE IV. MEANS, STANDARD DEVIATIONS AND COEFFICIENTS OF VARIATION OF SHEAR VALUES FROM P. MAJOR MUSCLE • THAWED FOR FOUR HOURS - EXPERIMENT 3 . Time of f r e e z i n g (hours) Shear Value (lbs x 4 ) sd C o e f f i c i e n t of V a r i a t i o n (%) 1 . 0 2 3 . 0 1 7 . 0 6 3 0 . 7 0 2 . 0 1 9 . 3 6 5 . 1 0 2 6 . 3 6 3 . 0 2 4 . 5 5 7 . 6 3 3 1 . 0 9 4 . 0 2 8 . 5 4 6 . 8 8 2 4 . 0 9 6.0 2 9 . 1 2 7 . 9 7 2 7 . 3 6 8.0 2 8 . 6 2 6 . 4 1 2 2 . 4 1 I O . O X 1 9 . 1 9 5 . 3 6 2 7 . 9 1 sd = standard d e v i a t i o n When a thawing p e r i o d of 2 4 hours a t 4°C was used i n Experiment 4, the mean shear, v a l u e s were lower than those obtained i n Experiment 3, f o r each time of f r e e z i n g s t u d i e d . However, i n t h i s experiment the c o e f f i c i e n t s of v a r i a t i o n f o r each o b s e r v a t i o n i n c r e a s e d c o n s i d e r a b l y . The means, standard d e v i a t i o n s and c o e f f i c i e n t s of v a r i a t i o n f o r Experiment 4 are shown i n Table V. TABLE V. MEANS, STANDARD DEVIATIONS AND COEFFICIENTS OF VARIATION OF SHEAR VALUES FROM P. MAJOR MUSCLE THAWED FOR 24 HOURS - EXPERIMENT 4. Time of F r e e z i n g (hours) Shear Value (lbs x 4) sd C o e f f i c i e n t of V a r i a t i o n (%) 1.0 21.62 9.14 42.26 2.0 17 .39 7.00 40.27 3.0 18.85 7.39 39.22 4.0 20.72 10 .16 49.06 6.0 24.92 11.90 47.75 10.0 17.85 8.06 45.16 sd = standard d e v i a t i o n When a 48 hour thawing p e r i o d was used i n Experiment 5, the mean shear v a l u e s decreased once more. In t h i s experiment, the c o e f f i c i e n t s of v a r i a t i o n of the o b s e r v a t i o n remains h i g h e r than those found i n Experiment 4. The means, standard d e v i a t i o n s and c o e f f i c i e n t s of. v a r i a t i o n f o r Experiment 5 are shown i n Table V I . TABLE VI. MEANS, STANDARD DEVIATIONS AND COEFFICIENTS OF VARIATION OF SHEAR VALUES FROM P. MAJOR MUSCLE THAWED FOR 4 8 HOURS - EXPERIMENT 5. C o e f f i c i e n t Time of F r e e z i n g Shear Value sd of V a r i a t i o n (hours) (lbs x 4) (%)• 1.0 18.15 8.50 46.81 2.0 15.31. 6.43 41.97 3.0 16.14 4.64 28.72 4.0 16.62 6.07 36.53 6.0 18.01 5.53 30.69 10.0 18.97 6.17 32.50 sd = standard d e v i a t i o n An a n a l y s i s of v a r i a n c e and Duncan' s New M u l t i p l e Range t e s t were performed on the r e s u l t s from each of Experiments 3, 4 and 5. These are presented i n T a bles VII and V I I I . TABLE V I I . ANALYSIS OF VARIANCE OF SHEAR VALUES FROM P. MAJOR MUSCLE THAWED FOR 4, 24 AND 4 8 HOURS. Source df Mean Squares 4 hour 24 hour 4 8 hour 4 hour 24 hour 4 8 hour Thaw Thaw Thaw Thaw Thaw Thaw Treatment 6 5 5 4008.60*** 594.55*** 146.91** Bird/Treatment 77 - 18 18 101.85*** ;31.78 •••. 13.07 E r r o r 1428 408 408 42.12 88.33 40.44 T o t a l 1511 431 431 *** p < 0.001 ** p < 0.01 A l l t h ree experiments show s i g n i f i c a n t v a r i a t i o n i n shear v a l u e s f o r the times of f r e e z i n g s t u d i e d . Only Experiment 3 showed a s i g n i f i c a n t v a r i a t i o n among the b i r d s used f o r each treatment time. I t i s thought t h a t b i r d to b i r d v a r i a t i o n probably e x i s t e d " i n a l l the experiments c a r r i e d out. However, the l a r g e number of b i r d s used i n Experiment 3 r e s u l t e d i n the v a r i a t i o n being d e c l a r e d s i g n i f i c a n t . The r e s u l t s of Duncan's New M u l t i p l e Range T e s t on s i g n i f i c a n t treatment means from Experiment 3, show t h a t two homogenous subsets e x i s t . The mean shear v a l u e s f o r b i r d s f r o z e n a t 2 and 10 hours postmortem and b i r d s f r o z e n a t 4, 6, and 8 hours postmortem do not d i f f e r s i g n i f i c a n t l y from each, o t h e r . The same t e s t c a r r i e d out on r e s u l t s * from TABLE V I I I . DUNCAN'S NEW MULTIPLE RANGE TEST ON SIGNIFICANT TREATMENT MEANS FROM EXPERIMENTS 3,4 AND 5 Time of F r e e z i n g (Hours) 4 Exp 3 hour thaw Exp 4 24 hour thaw Exp 5 48 hour th; 1.0 23.01 21.62 b G be 18.15 c 2.0 a* 19.36 17.39 a 1 5 . 3 l a 3.0 24.55 18.85 a 16.14 a b 4.0. 28.54 b 20.72 a b 16.62 a b 6.0 29.12 b 24.92 C be 18.01 8.0 28.62 b 10.0 19.19 a 17.85 3 18.97 c Means i n the same column wi t h s i m i l a r s u p e r s c r i p t s d i f f e r s i g n i f i c a n t l y (p ^  0.05) do not Experiment 4 shows t h a t three homogenous subsets e x i s t . In t h i s experiment, the mean shear v a l u e s f o r b i r d s f r o z e n a t 2, 3, 4 and 10 hours postmortem, those f r o z e n a t 1 and 4 hours postmortem and those f r o z e n a t 1 and 6 hours postmortem do not d i f f e r s i g n i f i c a n t l y from each o t h e r . Three homogenous subsets a l s o e x i s t i n Experiment 5. B i r d s f r o z e n a t 2, 3 and 4 hours postmortem, those f r o z e n a t 1, 3, 4, and 6 hours postmortem and those f r o z e n a t 1, 6 and 10 hours postmortem do not d i f f e r s i g n i f i c a n t l y from each o t h e r . The mean shear v a l u e s together w i t h standard d e v i a t i o n s f o r each f r e e z i n g time s t u d i e d are shown i n F i g u r e s 4 , 5 and 6. The l e a s t squares c u b i c f i t to the data i s shown i n each f i g u r e . The c o e f f i c i e n t s of determina-2 t i o n , (R ), are 0.64, 0.79 and 0.67 r e s p e c t i v e l y . Experiment 3 shows s i m i l a r r e s u l t s to those found i n Experiment 1. However, a l a r g e r number of p r e - f r e e z i n g aging times were s t u d i e d i n t h i s experiment and a decrease i n toughness was demonstrated i n c a r c a s s e s f r o z e n between 1 and 2 hours postmortem. T h i s i s f o l l o w e d by an i n c r e a s e to maximum toughness i n b i r d s f r o z e n between 4 and 8 hours postmortem. I n c r e a s i n g tenderness occurs i n b i r d s f r o z e n between 8 and 10 hours postmortem. The r e s u l t s of Duncan's New M u l t i p l e Range T e s t on s i g n i f i c a n t treatment means -from Experiment 3 imply t h a t c a r c a s s e s f r o z e n a f t e r 2 and 10 hours ° - 5 2-0 3.5 5 T 0 6 ^ 5 B~Q oT POSTMORTEM FREEZING TIME (HOURS) F i g u r e 4. The e f f e c t o f a 4 hour thaw on the t e n d e r n e s s o f c h i c k e n b r o i l e r muscle f r o z e n a t v a r i o u s postmortem a g i n g t imes , 1 1 1— I 0.5 2.0 3.5 5.0 6.5 8.0 9.5 POSTMORTEM FREEZING TIME (HOURS) . • i F i g u r e 5. The e f f e c t of a 24 hour thaw on the tenderness of c h i c k e n b r o i l e r muscle f r o z e n a t v a r i o u s postmortem aging times. F i g u r e 6. The e f f e c t o f a 48 hour thaw on the t e n d e r n e s s o f c h i c k e n b r o i l e r muscle f r o z e n a t v a r i o u s postmortem a g i n g t i m e s . 50. of aging do not d i f f e r s i g n i f i c a n t l y i n tenderness when r a p i d thawing procedures are used. S i m i l a r l y , c a r c a s s e s f r o z e n a f t e r 4 and 8 hours of aging do not d i f f e r s i g n i f i c a n t l y i n toughness. The r e s u l t s of Experiment 4 d i f f e r s l i g h t l y from those found i n the p r e v i o u s experiment i n t h a t the mean shear v a l u e s are l e s s f o r every f r e e z i n g time s t u d i e d and a decrease i n toughness occurs i n c a r c a s s e s f r o z e n between 1 and 4 hours postmortem. Maximum toughness.occurs i n b i r d s f r o z e n between 6 and 8 hours postmortem. When a 4 8 hour thawing time was used, the mean shear v a l u e s were s i g n i f i c a n t l y lower than those found i n Experiment 3. Once again, a decrease i n toughness occurs i n c a r c a s s e s f r o z e n between 1 and 4 hours postmortem f o l l o w e d by an i n c r e a s e to maximum toughness i n b i r d s f r o z e n between 6 and 10 hours postmortem. The r e s u l t s from these experiments appear to show t h a t the l e n g t h of thawing time does have a s i g n i f i c a n t e f f e c t on the u l t i m a t e tenderness of b r o i l e r muscle f r o z e n a f t e r v a r i o u s postmortem aging times. In an attempt to show t h i s e f f e c t more c l e a r l y , a combined a n a l y s i s of v a r i a n c e was c a r r i e d out on the data o b t a i n e d i n Experiments 3, 4 and 5. The r e s u l t s of t h i s a n a l y s i s are shown i n Table IX. The thawing and f r e e z i n g treatments and the i n t e r a c t i o n between . the treatments are a l l shown to be h i g h l y s i g n i f i c a n t . T A B L E I X . C O M B I N E D A N A L Y S I S O F V A R I A N C E O F S H E A R V A L U E S F R O M P. M A J O R M U S C L E ' T H A W E D F O R 4 , 24 A N D 4 8 H O U R S . d f T h a w 2 F r e e z e 5 F r e e z e x T h a w 10 B i r d s / F r e e z e , T h a w 102 E r r o r 2040 T o t a l 2159 M e a n S q u a r e s E r r o r 7 9 9 7 . 3 0 * . * * B i r d / F r e e z e , T h a w 3 4 3 4 . 9 0 * * * B i r d / F r e e z e , T h a w 6 5 7 . 4 7 * * * B i r d / F r e e z e , T h a w 7 5 . 2 6 * * 5 1 . 3 6 * * * P < 0 . 0 0 1 * * P < 0 . 0 1 A Duncan's New M u l t i p l e Range T e s t was performed on the s i g n i f i c a n t t r e a t m e n t i n t e r a c t i o n means. The r e s u l t s o f t h i s t e s t a r e shown i n T a b l e X. TABLE K. DUNCAN'S NEW MULTIPLE RANGE TEST ON SIGNIFICANT TREATMENT INTERACTION MEANS FROM EXPERIMENTS 3, 4, AND 5. Thaw Time (Hours) Times o f F r e e z i n g (Hours) 4 24 48 1 .0 23 . 0 1 F 9 * 21 . 6 2 e f g 18 n c a b c d . Ib 2 .0 19 _ ,cde .36 17 > 3 9 a b c d ]5 . 3 l a 3 .0 24 .55 g 18 . 8 5 b c d 16 .14 a b 4 .0 28 .54h 20 . 7 2 d e f 16 r ~abc 6 .0 29 .12h 24 .92 g 18 . o i a b c d 10 .0 19 . 1 9 c d e 17 _ 8 5 a b c d 18 _ 9 ? b c d e * Means w i t h s i m i l a r s u p e r s c r i p t s 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) From t h i s t a b l e i t can be seen t h a t when c a r c a s s e s ar e f r o z e n a f t e r 1 hour o f a g i n g , a thawing time o f 48 hours i s n e c e s s a r y b e f o r e any s i g n i f i c a n t l a c k o f toughness i s n o t e d . A 24 hour thaw does n o t appear t o a f f e c t t h e toughness i n c a r c a s s e s f r o z e n a t t h i s time.: When f r e e z i n g t a k e s p l a c e a f t e r 2 hours o f a g i n g , a s i m i l a r d e c r e a s e i n toughness t a k e s p l a c e as the thawing time i s i n c r e a s e d . When c a r c a s s e s f r o z e n a t 3 hours postmortmem, are thawed, a s i g n i f i c a n t decrease i n toughness takes p l a c e when thawing time i s i n c r e a s e d to 24 hours. A f u r t h e r decrease i n toughness occurs i n c a r c a s s e s thawed f o r 4 8 hours. Large decreases i n toughness occur i n c a r c a s s e s f r o z e n 4 and 6 hours postmortem, when the thawing time i s i n c r e a s e d from 4 to 24 hours. A f t e r 4 8 hours of thawing, c a r c a s s e s f r o z e n a t t h i s time do not d i f f e r i n toughness with c a r c a s s e s f r o z e n a t 1, 2 or 3 hours postmortem and thawed f o r the same l e n g t h of time. No s i g n i f i c a n t d i f f e r e n c e s are observed i n the toughness of b i r d s f r o z e n a f t e r 10 hours of aging f o r any of the thawing treatments used. The e f f e c t of v a r y i n g the thawing time on the tender-ness of chi c k e n muscle f r o z e n a t v a r i o u s postmortem aging times can be c l e a r l y seen i n F i g u r e 7. Data obtained i n these experiments support the r e s u l t s of Pool e t a l . (1959) , which show t h a t t e n d e r i z a t i o n of p o u l t r y muscle a r r e s t e d by f r e e z i n g w i l l continue upon thawing. The r a p i d thawing method of 4 hours a t 2 5°C used i n Experiment 3 does not appear to be s u f f i c i e n t f o r s i g n i f -i c a n t t e n d e r i z a t i o n of the p r e - r i g o r f r o z e n muscle to occur. The r a p i d f r e e z i n g and thawing of the p r e - r i g o r muscles have l e d to some s h o r t e n i n g of the muscle on the c a r c a s s thereby causing toughening. When.the c a r c a s s e s were h e l d f o r 48 hours a t 4°C, however, the muscle remains a t temperatures j u s t below 0°C f o r a long p e r i o d of time. A t these temperatures, 4 0 36 • ~ • 4 hour thaw o-o 24 hour thaw 4 8 hour thaw 3 2 28 x to CO 24 O Di o 20 16 12 0-5 2-0 3-5 5-0 6-5 8-0 P O S T M O R T E M F R E E Z I N G T I M E (hours) 9-5 F i g u r e 7 The e f f e c t s of a 4, 24 and 48 hour thaw on the t e n d e r n e s s of c h i c k e n b r o i l e r muscle f r o z e n a t v a r i o u s postPiortem a g i n g t i m e s . g l y c o l y s i s occurs a t an extremely r a p i d r a t e but any s h o r t e n -i n g which may occur i n muscle at t a c h e d to the c a r c a s s , cannot take p l a c e because the muscle i s f i x e d i n s i z e and shape by the presence of i c e c r y s t a l s . Thus, p r e - r i g o r f r o z e n muscle which i s thawed sl o w l y i s shown to be l e s s tough than p r e - r i g o r . f r o z e n muscle which has been r a p i d l y thawed. Some l a c k of toughening i s a l s o shown to occur after, thawing f o r 24 hours at 4°C but i t i s debatable whether t h i s l e n g t h of time a t 4°C i s s u f f i c i e n t f o r the muscle to become completely thawed p r i o r to e x c i s i o n and cooking. The f a c t t h a t the i n n e r muscle t i s s u e s may have been p a r t i a l l y f r o z e n when cooked c o u l d e x p l a i n the l a r g e v a r i a t i o n i n the shear v a l u e s f o r each time of f r e e z i n g . Thus, the tenderness of p r e - r i g o r f r o z e n p o u l t r y , i s very dependent on the r a t e of thawing used p r i o r to cooking and t h i s may e x p l a i n the v a r i a b i l i t y and the d i f f i c u l t y of i n t e r p r e t a t i o n of many of the p u b l i s h e d r e s u l t s r e l a t i n g postmortem f r e e z i n g time to tenderness of the cooked product. Experiment 6 The decrease i n toughness which took p l a c e i n c a r c a s s e s f r o z e n between 1 and 2 hours postmortem i n Exper-iment 3 and those f r o z e n between 1 and 4 hours postmortem i n Experiments 4 and 5, i s an i n t e r e s t i n g phenomenon which has not been p r e v i o u s l y r e p o r t e d . I t i s p o s s i b l e t h a t i t c o u l d be caused by the temperature and medium used d u r i n g the aging p e r i o d . F o r t h i s reason, i t was deci d e d to study the e f f e c t of changing the p r e - f r e e z i n g aging temperature and medium on the tenderness of b r o i l e r muscle f r o z e n d u r i n g the f i r s t three hours postmortem. The a n a l y s i s o f v a r i a n c e was performed on the shear v a l u e s obtained i n t h i s study and i s shown i n Tab l e XI. TABLE XI. ANALYSIS OF VARIANCE OF SHEAR VALUES FROM P. MAJOR MUSCLE AGED IN ICE SLUSH AND IN AIR AT ROOM TEMPERATURE. Source df Mean Squares Treatment 4 * * * .1116.10 Temperature 1 *** 137 8.10 Bird/Treatment/Temperature 30 57.57 E r r o r 612 78.23 T o t a l 647 *** p < 0.001 Both the treatment and temperature e f f e c t are h i g h l y s i g n i f i c a n t . The mean shear v a l u e s and standard d e v i a t i o n s f o r each treatment-temperature combination are shown i n Tab l e X I I , to g e t h e r w i t h the r e s u l t s o f Duncan's New M u l t i p l e Range T e s t on the treatment mean shear v a l u e s 57. TABLE X I I . MEANS, STANDARD DEVIATIONS AND DUNCAN'S NEW MULTIPLE RANGE TEST ON COMBINED MEANS OF SHEAR VALUES FROM EXPERIMENT 6. Time of F r e e z i n g Shear Value sd Combined Shear Value (hours) (lbs x 4) ( l b s x 4) 0°C 23°C 0°C 23°C 1.0 23.80 25.00 9 .34 7.84 24.51 C* 1.5 19.58 23.17 7.30 10.58 21.38 b 2.0 17. 40 18.17 6.00 7.50 17.79 a 2.5 16.32 21.06 7.06 11.17 18.69 a 3.0 20.61 26.22 6.93 10.09 23.42 b c * Means with s i m i l a r s u p e r s c r i p t s do not d i f f e r s i g n i f i c a n t l y (p < 0.05) The mean shear v a l u e s together w i t h standard d e v i a t i o n s f o r each f r e e z i n g time s t u d i e d are shown i n g r a p h i c a l form i n F i g u r e s 8 and 9. The c o e f f i c i e n t s of d e t e r m i n a t i o n , (R ), f o r the l e a s t - s q u a r e s q u a d r a t i c f i t shown i n each of the f i g u r e s are 0.833 and 0.644 r e s p e c t i v l e y The f i g u r e s show t h a t c a r c a s s e s aged i n a i r a t room temperature are. tougher a t every f r e e z i n g time than c a r c a s s e s aged i n i c e s l u s h . A l s o , the standard d e v i a t i o n o f the mean a t each time of f r e e z i n g i s g r e a t e r f o r b i r d s aged i n a i r than f o r those aged i n i c e s l u s h . The reason f o r i n c r e a s e d toughness i n the c a r c a s s e s aged i n a i r t h e r e -f o r e may be moisture l o s s from p a r t s of the muscle t i s s u e F i g u r e 8. The e f f e c t of a g i n g i n i c e s l u s h on the t e n d e r n e s s of c h i c k e n b r o i l e r muscle f r o z e n a t v a r i o u s postmortem a g i n g t i m e s . \ I I I I I I O.B 1.2 i . 6 2 . 0 2 . 4 2 . B 3 . POSTMORTEM FREEZING TIME (HOURS) Figure 9. The e f f e c t of aging i n a i r at 23°C on the the tenderness of chicken b r o i l e r muscle frozen at various postmortem aging times. 60. d u r i n g aging. Such a phenomenon would a l s o account f o r the l a r g e v a r i a t i o n of shear v a l u e s a t each f r e e z i n g time. Dodge and Stadelman (1959), have shown t h a t toughening o c c u r r i n g i n muscle t i s s u e aged i n a i r , i s due to dehydra-t i o n . The decrease i n toughness i n b i r d s f r o z e n between 1 and 2 hours postmortem found i n Experiments 3, 4 and 5 a l s o occurs i n t h i s experiment.. The temperature and medium of aging are t h e r e f o r e not r e s p o n s i b l e f o r t h i s i n c r e a s e i n tenderness immediately p r i o r to the onset of r i g o r . The time a t which maximum tenderness i s reached, d i f f e r s s l i g h t l y w i t h the method of aging used. T h i s may be due to the temperature of the aging environment. P h y s i o l o g i c a l v a r i a t i o n s among the b i r d s , however, may a l s o be r e s p o n s i b l e and f u r t h e r experiments u s i n g l a r g e r numbers of p o u l t r y must be c a r r i e d out to determine the e f f e c t of temperature of the aging environment on the tenderness of muscle. I t may be s a i d w i t h reasonable c e r t a i n t y t h a t aging i n a i r a t a h i g h temperature lea d s t o a tougher product than one which i s aged i n i c e s l u s h a t 0°C, due to d e h y d r a t i o n . The temperature and medium o f ' a g i n g do not a f f e c t the i n c r e a s e i n tenderness observed i n b i r d s f r o z e n between 1 and approximately 2 1/2 hours postmortem. Experiment 7 The temperature and l e n g t h of f r o z e n s t o r a g e were shown to have a s i g n i f i c a n t e f f e c t on the tenderness of p o u l t r y f r o z e n p r e - r i g o r . The a n a l y s i s of v a r i a n c e was performed on the shear v a l u e s obtained from p o u l t r y s u b j e c t e d to storage a t -23°C f o r 3 months. The r e s u l t s of t h i s a n a l y s i s are shown i n Tab l e X I I I . TABLE X I I I . ANALYSIS OF VARIANCE.OF SHEAR VALUES FROM P. MAJOR MUSCLE SUBJECTED TO LONG TERM FROZEN STORAGE. Source df Mean Squares Treatment 4 32.03 ns Bird/Treatment 15 121.53 ns E r r o r 340 125.87 T o t a l 359 ns = not s i g n i f i c a n t T h i s a n a l y s i s shows t h a t no s i g n i f i c a n t d i f f e r e n c e e x i s t s between the mean shear v a l u e s of c a r c a s s e s f r o z e n a t any of the f i v e aging times s t u d i e d , a f t e r 3 months of storage a t -23°C. The means, standard d e v i a t i o n s and c o e f f i c i e n t s of v a r i a t i o n f o r the shear values o b t a i n e d i n t h i s experiment are shown i n Table XIV. TABLE XIV. MEANS, STANDARD DEVIATIONS AND COEFFICIENTS OF VARIATION OF SHEAR VALUES FROM P. MAJOR MUSCLE STORED AT -23°C FOR 3 MONTHS. C o e f f i c i e n t Time of F r e e z i n g (hours) Shear Value (lbs x 4) sd of V a r i a t i o n (%.) 1.0 22.79 11.22 49.24 2.0 23.02 13.09 56.87 3.0 22.94 . 9.7 6 42.53 6.0 22.51 9.47 42.07 10.0 21.37 11.33 53.02 sd = standard d e v i a t i o n The mean shear v a l u e s together w i t h standard d e v i a t i o n s f o r each time of f r e e z i n g postmortem s t u d i e d , are shown i n g r a p h i c a l form i n F i g u r e 10. The l i n e a r f i t to the data shown i n the f i g u r e has a c o e f f i c i e n t of de t e r m i n a t i o n of 0.87. In t h i s experiment, f o u r b i r d s were used f o r each mean shear v a l u e shown. Thus, the l a r g e standard d e v i a t i o n o f each mean shear v a l u e , shows t h a t the r e s u l t s of t h i s experiment do not o f f e r c o n c l u s i v e evidence f o r the t e n d e r i z a t i o n of p r e - r i g o r f r o z e n muscle d u r i n g l o n g -term f r o z e n s t o r a g e . However, i t i s c o n c e i v a b l e t h a t such a phenomenon does occur and s t u d i e s i n v o l v i n g f r o z e n storage f o r longer p e r i o d s of time may o f f e r f u r t h e r evidence f o r the occurrence of t e n d e r i z a t i o n a t very low temperatures . 8 L _ I - ! I ' I I 05 2-0 3-5 5-0 6-5 8-0 9-5 POSTMORTEM FREEZING TIME (hours) F i g u r e 1 0 . The e f f e c t o f f r e e z i n g a t v a r i o u s p o s t m o r t e m a g i n g t i m e s o n t h e t e n d e r n e s s o f c h i c k e n . b r o i l e r m u s c l e s t o r e d f o r 3 m o n t h s . However, the r e s u l t s of t h i s experiment show t h a t the p a t t e r n of tenderness shown i n Experiment 3 i s o b v i a t e d a f t e r 3 months a t -23°C. T h e r e f o r e , t h i s group of experiments.has shown t h a t the r a t e of thawing, the aging medium and p o s s i b l y the temperature of aging and l e n g t h of f r o z e n s torage a l l a f f e c t the tenderness o f muscle f r o z e n p r e - r i g o r . A decrease i n toughness has a l s o been shown to occur p r i o r to the normal onset o f r i g o r . T h i s phenomenon cannot be e x p l a i n e d i n terms of the method of p r e - f r e e z i n g aging used. S i m i l a r l y , a decrease i n the r a t e o f thawing does not appear t o prevent such an i n c r e a s e i n tenderness from o c c u r r i n g although the preceeding i n c r e a s e i n toughness i s delayed f o r s e v e r a l hours when a 4 8 hour thawing method i s used. F u r t h e r s t u d i e s c a r r i e d out i n an attempt to e x p l a i n t h i s phenomenon, are described, i n Chapter 4. CHAPTER IV. THE TENDERNESS OF CHICKEN BROILER MUSCLE FROZEN AT:j VARIOUS, POSTMORTEM AGING TIMES - OTHER' METHODS OF EVALUATING MEAT TENDERNESS. INTRODUCTION There i s a need f o r p r e d i c t i n g t e x t u r e i n cooked meat from the c h a r a c t e r i s t i c s of the uncooked muscle. Many methods of tenderness e v a l u a t i o n have been developed but r e p o r t e d c o r r e l a t i o n s between o b j e c t i v e measurements of muscle tenderness and sensory panel v a l u e s f o r cooked meat show much v a r i a t i o n (Sharrah e t a l . , 1965 a, b ) . In Chapter 2, reasonable c o r r e l a t i o n s were o b t a i n e d between o b j e c t i v e measurements of tenderness performed on cooked muscle u s i n g the Allo-Kramer shear press and sensory panel e v a l u a t i o n s . The r e p o r t e d o b s e r v a t i o n s of an i n c r e a s e i n tenderness i n c h i c k e n muscle f r o z e n between 1 and 2 hours postmortem has not been e x p l a i n e d i n terms of the aging and thawing methods used. Measurements of t e n s i o n developed d u r i n g thaw r i g o r and lengths of sarcomeres a t v a r i o u s postmortem times were t h e r e f o r e made i n an attempt to e x p l a i n t h i s phenomenon and to determine whether or not these methods c o u l d be used f o r adequate p r e d i c t i o n of tenderness i n the cooked meat. Rigor m o r t i s a r r e s t e d by f r e e z i n g , has been shown to proceed a t about the normal r a t e upon thawing. Recent work on turkey and b r o i l e r muscle have used the i s o m e t r i c tension pattern to fo l low the sequence of p h y s i c a l changes i n r i g o r (Jungk and Marion, 1970; Wood, 1973). The pattern has been shown to c l o s e l y p a r a l l e l the tenderness cycle and i l l u s t r a t e s the tendency of muscle to shorten. Measurements of isometric tension development i n muscle frozen before the onset of r i g o r w i l l therefore determine to some extent, the p r e - r i g o r state of the muscle at the time of f r e e z i n g . Such measurements could thus be used for p r e d i c t i n g the tenderness of the cooked meat. Experiment 8 describes the measurement of isometric tension i n muscle frozen p r i o r to the onset of r i g o r . Locker (1960) showed that tenderness i n beef i s inf luenced by the degree of muscular contrac t ion i n the postmortem muscle. . Many workers have since invest igated the c o r r e l a t i o n between sarcomere length, as a measure of the c o n t r a c t i l e s ta te , and tenderness. Herring et al .(1965 a, b have found that taste panel r e s u l t s are inf luenced by the degree of contrac t ion as measured by the sarcomere length . Stanley et a l . (1972 ) d i d not f i n d a s i g n i f i c a n t c o r r e l a t i o n of these v a r i a b l e s although t h i s may have been due to very small d i f ferences i n the mean sarcomere lengths of the muscl samples used. Exper iments describes the use of o p t i c a l d i f f r a c t i o n as a means of determining sarcomere lengths of cooked chicken muscle frozen at various postmortem aging 67. times. Attempts are made to c o r r e l a t e the sarcomere l e n g t h measurements with o b j e c t i v e and s u b j e c t i v e e v a l u a t i o n s of tenderness. 68. MATERIALS AND METHODS Experiment 8 - The E f f e c t of F r e e z i n g a t V a r i o u s Postmortem  Aging Times on the Tension Development i n Muscle S t r i p s . Three groups of f o u r b i r d s each were aged i n i c e s l u s h f o r 1, 2 and 3 hours postmortem. Muscle f o r t e n s i o n measurement was obtained a f t e r each aging p e r i o d by c u t t i n g the b r e a s t s k i n and e x c i s i n g muscle s t r i p s of p a r a l l e l f i b r e s , 5 cm long, weighing approximately l g . , from the a n t e r i o r p o r t i o n of one P. major muscle on each c a r c a s s . S i x s t r i p s were c u t from each b i r d . The remainder of the c a r c a s s , c o n t a i n i n g one complete P. major muscle to be used f o r tenderness e v a l u a t i o n u s i n g the Allo-Kramer shear p r e s s , was f r o z e n w i t h the other three c a r c a s s e s a t the a p p r o p r i a t e aging time u s i n g the l i q u i d n i t r o g e n b l a s t f r e e z e r . At the same time, the twenty-four muscle s t r i p s wrapped i n Saran wrap, were p l a c e d i n an a i r - b l a s t f r e e z e r a t -31°C-A f t e r f r e e z i n g , the c a r c a s s e s were s t o r e d a t -31°C f o r one week bef o r e thawing a t 4°C f o r 4 hours. The one P. major muscle was removed from each b i r d , cooked, and e v a l u a t e d f o r tenderness u s i n g the Allo-Kramer shear p r e s s . Tension development i n the muscle s t r i p s was measured u s i n g an E & M 6-channel physiograph f i t t e d w ith i s o m e t r i c t r a n s d u c e r s . The f r o z e n muscle s t r i p s were removed from the f r e e z e r a f t e r 6 hours and clamped i n a p l e x i g l a s s c y l i n d e r . The f r e e upper clamp, h o l d i n g the f r o z e n muscle s t r i p was attached by f i s h i n g l i n e to an i s o m e t r i c t r a n s d u c e r . A sm a l l amount of phosphate b u f f e r was p l a c e d i n the base of the p l e x i g l a s s c y l i n d e r and the top was covered i n Saran wrap i n an attempt to prevent d e h y d r a t i o n of the muscle s t r i p d u r i n g thawing. The physiograph was c a l i b r a t e d so t h a t a 1 cm pen d e f l e c t i o n was e q u i v a l e n t to 5 g t e n s i o n . The muscle s t r i p s were allowed to thaw i n the c y l i n d e r s and maximum t e n s i o n development i n grams per square cen t i m e t r e of muscle t i s s u e was c a l c u l a t e d . Experiment 9 - The Tenderness of Chicken B r o i l e r Muscle Frozen a t V a r i o u s Postmortem Aging Times - Sarcomere Length Measure-ments as a P r e d i c t i o n of Cooked Meat Tenderness. F i v e groups of fou r b i r d s each were aged i n i c e -s l u s h f o r 1, 2 , 3 , 6 and 10 hours postmortem. F r e e z i n g i n the l i q u i d n i t r o g e n b l a s t f r e e z e r was f o l l o w e d by storage f o r one week a t -31°C. The c a r c a s s e s were thawed f o r 4 hours i n running water a t 25°C a f t e r which time the P. major muscles were removed and cooked by the method p r e v i o u s l y d e s c r i b e d . Taste panel e v a l u a t i o n s were c a r r i e d out u s i n g the method d e s c r i b e d i n Experiment 1. Using the Allo-Kramer 70. shear press, shear values were obtained from the P. major muscle which remained aft e r the taste panel samples had been cut. A minimum of 9 shear values per b i r d were obtained. The sarcomere lengths of the P. major muscle f i b r e s were determined using the o p t i c a l d i f f r a c t i o n method described by the Meat Research I n s t i t u t e , B r i s t o l , England, (1972). The apparatus consisted of a 1-mW helium - neon laser of a wavelength of A = 632.8 nm mounted on an optics bench with a specimen holding device and a screen. The screen consisted of a v e r t i c a l l y mounted white card bearing a central millimetre scale. A small piece of P. major muscle was cut with known orientation of the f i b r e s . Single f i b r e s or small f i b r e bundles were teased out and mounted between two glass cover s l i p s using a. drop of buffered sucrose solution (0.2M sucrose i n a phosphate buffer of pH 7.1 and 0.2M). The f i b r e bundle was then placed v e r t i c a l l y i n r e l a t i o n to the laser beam to give a horizontal array of d i f f r a c t i o n bands on the screen. An example of t h i s i s shown in Plate I I . Sarcomere lengths were calculated using the following formula: -d = (632.8 x 10~ 3) D urn S where d i s equal to the sarcomere length D i s the d i s t a n c e i n m i l l i m e t r e s between the specimen and the s c r e e n . S i s the s e p a r a t i o n between the Oth and the n t h o r d e r d i f f r a c t i o n b a n d . (Throughout t h i s e x p e r i m e n t , D had a c o n s t a n t v a l u e o f 8 4 mm. Twelve sarcomere l e n g t h s were o b t a i n e d f o r each c a r c a s s . Care was taken to ensure t h a t muscle f i b r e s were t a k e n from the same a r e a o f the P . major muscle on each b i r d . E x p e r i m e n t s was r e p e a t e d u s i n g another 20 b r o i l e r s In t o t a l , f o u r t a s t e p a n e l s e s s i o n s were h e l d . Sarcomere Length = 1 -83 urn P l a t e I I . D i f f r a c t i o n p a t t e r n obtained from muscle f i b r e . RESULTS AND DISCUSSION Experiment 8 Analyses of v a r i a n c e were performed on the shear v a l u e s and t e n s i o n measurements obtained i n t h i s experiment. These are shown i n Tables XV. •TABLE XV. ANALYSES OF VARIANCE FOR SHEAR VALUES AND TENSION MEASUREMENTS RECORDED IN EXPERIMENT 8, Source df Mean Squares Shear Value T e n s i o n Treatment 2 E r r o r 9 T o t a l 11 28.58*** 2.00 2374.00* 47 6 .79 * p < 0.0 5 *** p < 0.002 A s i g n i f i c a n t treatment e f f e c t i s observed f o r both measurements although t h i s e f f e c t i s more e v i d e n t i n the shear v a l u e s than~the t e n s i o n measurements. Duncan's New M u l t i p l e Range Te s t s were performed on both s e t s of data. The r e s u l t s of these t e s t s are presented w i t h the means and standard d e v i a t i o n s i n Table XVI. TABLE XVI. STANDARD DEVIATIONS AND DUNCAN'S NEW MULTIPLE RANGE TEST ON THE SIGNIFICANT TREATMENT MEANS FROM EXPERIMENT 8. Time of F r e e z i n g Shear Value sd Tension sd (hours) (lbs x 4) (g/cm 2) 1.0 21.23 a* 5.94 118.35 a b 24.15 2.0 18.15 5.15 136.95 a 34.42 3.0 23.48 a 4.78 88.65 b 27.99 * Means on the same column with s i m i l a r s u p e r s c r i p t s do not d i f f e r s i g n i f i c a n t l y (p < 0.05). One homogeneous subset occurs among the mean shear v a l u e s w h i l e two may be observed among the mean t e n s i o n measurements. F i g u r e 11 shows the e f f e c t of f r e e z i n g a t v a r i o u s postmortem times on the t e n s i o n developed i n muscle s t r i p s . F i g u r e 12 shows shear press v a l u e s from cooked muscle s u b j e c t e d t o the same treatment. A s i g n i f i c a n t simple l i n e a r c o r r e l a t i o n c o e f f i c i e n t of -0.7 appears t o e x i s t between the two s e t s of d a t a . However, i t i s t o be noted t h a t muscle s t r i p s f r o z e n a f t e r 2 hours of aging develop more t e n s i o n upon thawing than muscle s t r i p s which have been f r o z e n a f t e r 1 or 3 hours o f aging. T h i s r e s u l t i s the op p o s i t e of what would be expected , a f t e r o b s e r v i n g i n previous experiments, the i n c r e a s e i n tenderness i n car c a s s e s f r o z e n a f t e r 2 hours. Wood (1973), found no s i g n i f i c a n t r e l a t i o n s h i p between t e n s i o n r e l e a s e and shear val u e s and concluded t h a t the t e n s i o n r e l e a s e observed i n i n d i v i d u a l b i r d s was not i n d i c a t i v e of tenderness. Although a r e l a t i o n s h i p between t e n s i o n development and shear v a l u e s appears to e x i s t i n t h i s experiment, the d e v i a t i o n from the mean t e n s i o n measurements are l a r g e e s p e c i a l l y i n muscle s t r i p s f r o z e n a f t e r 2 hours o f aging. A l s o , the t e n s i o n v a l u e s r e p o r t e d cannot be i n t e r p r e t e d as being e q u i v a l e n t t o va l u e s t h a t would be obtained from muscle l e f t on the ca r c a s s d u r i n g f r e e z i n g and thawing. C o l d s h o r t e n i n g and p o s s i b l e moisture l o s s from the s u r f a c e l a y e r s of the muscle s t r i p s d u r i n g thawing may have l e d to an i n c r e a s e i n the t e n s i o n v a l u e s . Thus, the r e s u l t s of t h i s experiment are not i n agreement with the o b s e r v a t i o n s made i n preceeding experiments Further, s t u d i e s should be c a r r i e d out u s i n g more b i r d s i n an attempt t o decrease the v a r i a t i o n i n t e n s i o n v a l u e s b e f o r e the r e s u l t s r e p o r t e d i n t h i s experiment can be c o n c l u s i v e . 200 7f> 401 L I ' • • I 0-8 1-2 1-6 2-0 2-4 2-8 3-2 P O S T M O R T E M F R E E Z I N G T I M E (hours) F i g u r e 11. The e f f e c t o f f r e e z i n g a t v a r i o u s p o s t m o r t e m a g i n g t i m e s on t e n s i o n d e v e l o p m e n t i n m u s c l e s t r i p s . 16 12 8 1 ' . I fu I— I 0-8 1 -2 1-6 2 - 0 2-4 2-8 3-2 P O S T M O R T E M F R E E Z I N G T I M E (hours) Figure. 12 . The e f f e c t of f r e e z i n g a t v a r i o u s postmortem a g i n g times o n . t e n d e r n e s s i n b r o i l e r P. major muscle. 78. Experiment 9 Analyses of v a r i a n c e were performed on the three groups of data r e s u l t i n g from t h i s experiment. The r e s u l t s of the analyses are presented i n Table XVII. TABLE XVII. ANALYSES OF VARIANCE FOR PANEL SCORES, SHEAR VALUES AND SARCOMERE LENGTHS RECORDED IN EXPERIMENT 9. Source df Mean Squares Panel Scores Shear Value Sarcomere Length Treatment 4 1.34* 16.52** E r r o r 15 0.18 1.35 T o t a l 19 * p < 0.05 ** p < 0.001 *** p < 0.0001 A s i g n i f i c a n t treatment e f f e c t i s observed f o r a l l s e t s of measurements. The s i g n i f i c a n t e f f e c t i s p a r t i c u l a r l y n o t i c e a b l e f o r the sarcomere l e n g t h measurements. Duncan's New M u l t i p l e Range Te s t s were performed a t the 10% l e v e l on a l l s i g n i f i c a n t treatment means. R e s u l t s of these t e s t s are presented i n Table XVIII. The 10% l e v e l of p r o b a b i l i t y was used i n t h i s i n s t a n c e i n an attempt to o f f e r b e t t e r evidence f o r the e x i s t e n c e of s i g n i f i c a n t d i f f e r e n c e s i n an experiment where only l i m i t e d numbers of c a r c a s s e s were used. TABLE XVIII. DUNCAN'S NEW MULTIPLE RANGE TEST ON THE SIGNIFICANT TREATMENT MEANS FROM EXPERIMENT 9 Time of F r e e z i n g Panel Scores Shear Value Sarcomere Length (hours) (lbs x 4) (ym) 1.0 b* 6.20 18.50 1 . 7 la 2.0 6.60 b •' 16.35 a 1.80 3.0 5.40 a 20.15 b 1.63 a 6.0 5.35 a 20.40 b 1.46 10.0 6.40 b 16.10 a 2.08 * Means i n the same column with s i m i l a r s u p e r s c r i p t s do not d i f f e r s i g n i f i c a n t l y (p < 0.1) Table XVIII shows t h a t some s i m i l a r i t y e x i s t s between the three sets of. d ata. The panel scores show t h a t c a r c a s s e s f r o z e n a f t e r 3 and 6 hours of aging are s i g n i f i c a n t l y tougher than those f r o z e n a t 1, 2 or 10 hours postmortem. The panel was t h e r e f o r e unable to d e t e c t any s i g n i f i c a n t d i f f e r e n c e s between the tenderness of b i r d s f r o z e n a f t e r 2 hours of aging and those f r o z e n a t 1 hour postmortem.. The shear and t a s t e panel v a l u e s recorded are somewhat l e s s than those obtained i n e a r l i e r , s i m i l a r e x p e r i -ments. Although every e f f o r t was made to ensure t h a t exper-imental b i r d s were of approximately the same age and s i z e , 80. some v a r i a t i o n i s to be expected. A s i g n i f i c a n t d i f f e r e n c e i s shown to occur between the shear v a l u e s of b i r d s f r o z e n a t 2 and a t 10 hours postmortem and those f r o z e n a f t e r 1, 3 or 6 hours of aging. Once again , b i r d s f r o z e n a t 3 and 6 hours postmortem are tougher than those f r o z e n a f t e r 2 and 10 hours postmortem. Carcasses f r o z e n a f t e r 1 hour of aging, however, are s i g n i f i c a n t l y tougher a t the 10% l e v e l than those f r o z e n a t 2 hours postmortem. Panel members were unable to d e t e c t t h i s d i f f e r e n c e . Sarcomere lengths reach a minimum i n b i r d s f r o z e n a f t e r 6 hours of aging. Again, a s i g n i f i c a n t d i f f e r e n c e e x i s t s between the sarcomere l e n g t h s o f b i r d s f r o z e n a t 2 hours postmortem and those f r o z e n a f t e r 1 hour of aging. However i n t h i s case b i r d s f r o z e n a f t e r 1 and a f t e r 3 hours of aging have sarcomere lengths which are not s i g n i f i c a n t l y d i f f e r e n t . F i g u r e s 13, 14, and 15, i l l u s t r a t e these o b s e r v a t i o n s The c o r r e l a t i o n matrix f o r the three s e t s of data i s presented i n Table XIX. TABLE XIX. CORRELATION MATRIX FOR THE THREE PARAMETERS STUDIED IN EXPERIMENT 9. Shear Value Sarcomere Length Panel Score 0.72** 0.60** Shear Value i - 0 0 .0.56* * p < 0.02 ** p < 0.01 F i g u r e 13. S u b j e c t i v e assessment of toughness of b r o i l e r muscle f r o z e n a f t e r v a r i o u s postmortem a g i n g p e r i o d s . 40 82. 36 F i g u r e 14 . O b j e c t i v e assessment o f toughness o f b r o i l e r muscle f r o z e n a f t e r v a r i o u s postmortem a g i n g p e r i o d s . 83. 2-6 , _ , 24 L 2-2 L ML 1-2L 101 -J I _l I J L 0-5 2-0 3-5 5-0 6-5 8-0 9-5 P O S T M O R T E M F R E E Z I N G T I M E ( h o u r s ) F i g u r e 1 5 . The m e a s u r e m e n t o f s a r c o m e r e l e n g t h s • i n b r o i l e r m u s c l e f r o z e n a f t e r v a r i o u s , p o s t m o r t e m a g i n g p e r i o d s . 84. A c o r r e l a t i o n among the t h r e e methods of t e n d e r n e s s assessment t h e r e f o r e e x i s t s a l t h o u g h , from the r e s u l t s of the Du n can 's New M u l t i p l e Range T e s t s , the s e n s i t i v i t y of each method o f a s s e s s i n g toughness v a r i e s . P a n e l members were u n a b l e to d i s c e r n e d i f f e r e n c e s between the toughness o f b i r d s f r o z e n a t 2 hours postmortem and those f r o z e n a f t e r 1 and 10 hours o f a g i n g . The A l l o - K r a m e r shear p r e s s r e s u l t s show t h a t a s i g n i f i c a n t d i f f e r e n c e i n toughness between b i r d s f r o z e n a t 2 and 10 hours and those f r o z e n a t o t h e r a g i n g t i m e s , does e x i s t , however. S i m i l a r l y , sarcomere l e n g t h s are g r e a t e r i n b i r d s f r o z e n a f t e r 2 hours of a g i n g than i n b i r d s f r o z e n a t 1, 3, and 6 hours of a g i n g , i n d i c a t i n g t h a t muscle f r o z e n a f t e r 2 hours i s more t e n d e r than t h a t f r o z e n 1, 3 o r 6 hours postmortem. From these r e s u l t s i t i s not p o s s i b l e to c o m p l e t e l y e x p l a i n the phenomenon o b s e r v e d i n b i r d s f r o z e n a t 2 hours postmortem. The sarcomere l e n g t h measurements made i n t h i s exper iment o f f e r some e v i d e n c e f o r postmortem changes o c c u r i n g between 1 and 2 hours a f t e r d e a t h which c o u l d l e a d to i n c r e a s e s i n muscle t e n d e r n e s s i m m e d i a t e l y p r i o r to the o n s e t of r i g o r . A l t h o u g h t a s t e p a n e l members were u n a b l e to d e t e c t such a change, o b j e c t i v e measurements o f t e n d e r n e s s o f f e r e d e v i d e n c e t h a t such t e n d e r i z a t i o n t a k e s p l a c e . 85 F u r t h e r work i s o b v i o u s l y necessary to determine what changes c o u l d take p l a c e i n muscle immediately p r i o r to the onset of r i g o r . T h i s experiment does o f f e r evidenc however, t h a t measurements of sarcomere lengths u s i n g the method d e s c r i b e d c o u l d be used as a means of p r e d i c t i n g tenderness i n cooked muscle. 86. SUMMARY AND CONCLUSIONS The r e s u l t s i n the previously described experiments show that the ult imate tenderness of b r o i l e r muscle can be great ly influenced by the i n t e r a c t i o n of p r e - f r e e z i n g aging time and thawing time. When carcasses were frozen at various postmortem times and then r a p i d l y thawed, a c h a r a c t e r i s t i c toughness pattern was observed. The pattern consisted of a d e c l i n e i n toughness i n carcasses frozen between 1 and 2 hours postmortem followed by an increase to maximum toughness i n those frozen between 4 and 8 hours postmortem. Maximum tenderness occurred i n muscle frozen 10 hours af ter death. When the length of thawing time was increased to 4 8 hours t h i s pattern was eradicated with the exception of the d e c l i n e i n toughness i n carcasses frozen a f t e r 2 hours of aging. The aging medium and temperature d i d not e f f e c t the decrease i n toughness observed i n carcasses frozen at 2 hours postmortem. A f t e r a three month storage p e r i o d , a l l carcasses exhibi ted s i m i l a r tenderness l e v e l s and the pat tern of toughness previously observed was no longer evident . Thus, over longer storage p e r i o d s , some postmortem t e n d e r i z a t i o n appears to take place i n the p r e - r i g o r frozen muscle. Measurements of sarcomere lengths of the muscle f i b r e s of carcasses frozen at various postmortem aging times 87. c o r r e l a t e d , w e l l with toughness measurements. Sarcomere len g t h s were observed to i n c r e a s e i n muscle f r o z e n between 1 and 2 hours of aging and decrease i n l e n g t h i n c a r c a s s e s f r o z e n between 4 and 8 hours postmortem. I t may t h e r e f o r e be p o s s i b l e to use the measurement of sarcomere lengths as a method f o r p r e d i c t i n g the tenderness i n cooked meat. The sarcomere l e n g t h measurements o f f e r e d more evidence f o r the observed decrease i n toughness o c c u r r i n g i n muscle f r o z e n between 1 and 2 hours postmortem. T h i s phenomenon has not been p r e v i o u s l y observed and f u r t h e r work i s necessary to determine the changes t h a t take p l a c e i n muscle immediately p r i o r to the onset of r i g o r . The r e s u l t s of t h i s t h e s i s do, however, h e l p to e x p l a i n some of the v a r i a b i l i t y i n the p u b l i s h e d r e s u l t s of work p r e v i o u s l y c a r r i e d out i n t h i s a r ea. 88. LITERATURE CITED B a r r i e , P.J., Goertz, G.E. and F r y , J.L. 1964. A c c e p t a b i l i t y of b l a s t - f r o z e n and l i q u i d - f r o z e n turkey hens and toms. Food Technol. 18:565. Bate-Smith, E.C. and B e n d a l l , J.R. 1949. F a c t o r s determining the time course of r i g o r m o r t i s J . P h y s i o l . 110:47. Behnke, J.R., Fennema, 0. and Cassens, J.R. 1973. Rates of postmortem metabolism i n f r o z e n animal t i s s u e s . Agr. Food Chem. 21:5. B e n d a l l , J.R. 1951. The s h o r t e n i n g of r a b b i t muscles d u r i n g r i g o r m o r t i s : i t s r e l a t i o n to the breakdown of adenosine t r i p h o s p h a t e and c r e a t i n e phosphate and to muscular c o n t r a c t i o n . J . P h y s i o l . 114: 71. B e n d a l l , J.R. 1960. Postmortem changes i n muscle i n S t u c t u r e and F u n c t i o n of Muscle. V o l . 3. Bourne, G.H. (ed.) p.227 Academic Press L t d . , New York. B e n d a l l , J.R. 1969. Muscles, Molecules and Movement. Heinemann E d u c a t i o n a l Books L t d . , London. Bouton, P.E. and H a r r i s , P.V. 1972. A comparison of some o b j e c t i v e methods used to assess meat tenderness. J . Food. S c i . 37:218. B r i s k e y , E . J . 1963. The i n f l u e n c e of ante- and postmortem h a n d l i n g p r a c t i c e s on the p r o p e r t i e s of muscle r e l a t e d to tenderness in. Proceedings Meat Tenderness Symposium, p. 195. Campbell Soup Company. Brodine, M.V. and C a r l i n , A.F. 1968. C h i l l i n g and thawing methods and t h e i r e f f e c t on q u a l i t y of cooked whole t u r k e y s . Food Technol. 22:607. Buck, E.M., S t a n l e y , D.W. and Comissiong, E".A. 1970. P h y s i c a l and chemical c h a r a c t e r i s t i c s of f r e e and s t r e t c h e d r a b b i t muscle. J . Food S c i . 35:100. Busch, W.A., P a r r i s h , F.C. J r . . and G o l l , D.E. 1967. M o l e c u l a r p r o p e r t i e s of postmortem muscle. 4. E f f e c t of temperature on adenosine t r i p h o s p h a t e d e g r a d a t i o n , i s o m e t r i c t e n s i o n parameters and shear r e s i s t a n c e of bovine muscle. J . Food S c i . 32:390 89. Busch, W.A. , G o l l , D.E. and P a r r i s h , F.C. J r . 197 2. M o l e c u l a r p r o p e r t i e s of postmortem muscle-Isometric t e n s i o n development and d e c l i n e i n bovine, p o r c i n e and r a b b i t muscle. J . Food S c i . 37:289. C a r l i n , F., Lowe, B. and Stewart, G.F. 1949. The e f f e c t of aging versus aging, f r e e z i n g and thawing on the p a l a t a b i l i t y o f e v i s c e r a t e d p o u l t r y . Food Technol. 3:156. Cleworth, D. and Edman, K.A.P. 1969. Laser d i f f r a c t i o n s t u d i e s on s i n g l e s k e l e t a l muscle f i b e r s . Science 163:296;. Dawson, L.E., Davidson, J.A., Frang, M. and Walters, S. 1956. The e f f e c t of time i n t e r v a l between s l a u g h t e r and f r e e z i n g on toughness of f r y e r s . P o u l t r y S c i . 35:1140. Deatherage, F.E. and Garnatz, G. 1952. A comparative study of tenderness d e t e r m i n a t i o n by sensory panel and by Shear s t r e n g t h measurements. Food Technol. 6:260. deFremery, D. and P o o l , M.F. 1960. B i o c h e m i s t r y of c h i c k e n muscle as r e l a t e d to r i g o r m o r t i s and t e n d e r i z a t i o n . Food Research 25:73. deFremery, D. and P o o l , M.F. 1963. The i n f l u e n c e of postmortem g l y c o l y s i s on p o u l t r y tenderness. J . Food S c i . 28:173. deFremery, D. and S t r e e t e r , I.V. 1969. T e n d e r i z a t i o n of c h i c k e n muscle: the s t a b i l i t y of a l k a l i - i n s o l u b l e c o n n e c t i v e t i s s u e d u r i n g postmortem aging. J . Food S c i . 34:176. deFremery, D. 1966. Some aspects of postmortem changes i n p o u l t r y muscle i n The P h y s i o l o g y and B i o c h e m i s t r y of Muscle as a Food. B r i s k e y , E . J , , Cassens, R.G. and Trautman, J.C (eds.): p.205. Univ. of Wisconsin,'. ••'/':: 1 Dodge, J.W, and Stadelman, E . J . 1959. Postmortem aging of p o u l t r y meat and i t s e f f e c t on the tenderness of the b r e a s t muscles. Food Technol. 13:81. Dubois, C.W., T r e s s l e r , D.K. and Fenton, F. 1940. The i n f l u e n c e of r a t e of f r e e z i n g and temperature of storage on the q u a l i t y of f r o z e n meat. Conf. I n s t . Food Technol., p. 167. 90. F u j i m a k i , M.f Arakawa, N, , O k i t a n i , A, and T a k a g i , 0. 1965. The changes of "myosin B" ("actomyosin") d u r i n g storage of r a b b i t muscle. I I The d i s s o c i a t i o n of "myosin B" i n t o myosin A and a c t i n , and i t s i n t e r a c t i o n w i t h ATP. J . Food S c i . 30:937. G o l l , D.E. 1968. The r e s o l u t i o n of r i g o r m o r t i s . Proc. 21st Ann. R e c i p r . Meats Conf. p.16. N a t i o n a l L i v e s t o c k and Meat Board, Chicago, I l l i n o i s . G o l l , D.E., Arakawa, N., Stromer, M.H.,.Busch, W.A. and Robson, R.M. 1970. Chemistry of muscle p r o t e i n s as a food. i n The P h y s i o l o g y and B i o c h e m i s t r y of Muscle as a Food. 2. B r i s k e y , E . J . , Cassens R.G. and Marsh, B.B. (eds.) p.755. Univ. of Wisconsin. Gothard, R.H., M u l l i n s , A.M., Boulware, R.F. and Hansard,, S . L. 1966. H i s t o l o g i c a l s t u d i e s of postmortem changes i n sarcomere l e n g t h as r e l a t e d to bovine muscle tenderness. J . Food S c i . 31:825. Guerrant, N.B., H a r t z l e r , E.R., N i c h o l a s , J.E., Perry, J.S., Garey, J.G., Murphy, J.F., Dodds, M.L. and Bennett, G. 1953. Some F a c t o r s A f f e c t i n g the Q u a l i t y of Frozen Foods. Penn. S t a t e Univ. Agr. E x p t l . S t a t i o n B u l l -No. 565. Hanson, H.L. Stewart, G.F. and Lowe, B. 1942. P a l a t a b i l i t y and h i s t o l o g i c a l changes o c c u r r i n g o i n New York dressed b r o i l e r s h e l d a t 1.7 C (35 F) . Food Research 7:148. Henderson, D.W., G o l l , . D . E . and Stromer, M.H. 1970. A comparison of s h o r t e n i n g and Z - l i n e d e g r a d a t i o n i n post-mortem bovine, p o r c i n e and r a b b i t muscle. Amer. J . Anat. 128:117. H e r r i n g , H.K., Cassens, R.G. and B r i s k e y , E . J . 1965a. Sarcomere l e n g t h of f r e e and r e s t r a i n e d bovine muscles a t low temperature as r e l a t e d to tenderness. J . Sci.. Food A g r i c . 16:379. H e r r i n g , H.K., Cassens, R.G. and B r i s k e y , E . J . 1965b. F u r t h e r s t u d i e s on bovine muscle as i n f l u e n c e d by c a r c a s s p o s i t i o n , sarcomere l e n g t h and f i b e r diameter. J . Food Sci,.30:1049.. H o f f e r t , E., Plagge, A.R., Lowe, B. and Stewart G.F. 1952. The d e f r o s t i n g method and p a l a t a b i l i t y of p o u l t r y . Food Technol. 6:337. H o s t e t l e r , R.L., Landmann, W,A, L i n k B.A. and F i t z h u g h , H.A. 1970. I n f l u e n c e of c a r c a s s p o s i t i o n d u r i n g r i g o r m o r t i s on tenderness of beef muscles: a comparison of. two treatments J . Anim. S c i . 31:47.. Jones, N.R. and Murray, J . 1961. N u c l e o t i d e d e g r a d a t i o n i n f r o z e n cod (Gadus C a l l a r i u s ) muscle. Biochem. J . 80:26P. Jungk, R.A., Snyder, H.E., G o l l , D.E. and McConnell, K.G. 1967. I s o m e t r i c t e n s i o n changes and s h o r t e n i n g i n muscle s t r i p s d u r i n g post-mortem aging. J . Food S c i . 32:15.8. Jungk, R.A. and Marion, VI.VI. 1970. Postmortem i s o m e t r i c t e n s i o n changes.and s h o r t e n i n g i n turkey muscle s t r i p s h e l d a t v a r i o u s temperatures. J . Food S c i . 35:143. Kl o s e , A.A., Hanson, H.L. and Lineweaver H. 1950. The f r e e z i n g p r e s e r v a t i o n of turkey meat s t e a k s . Food Technol. 4:71. Klose A.A., Sayre, R.N. and P o o l , M.F. 1971. Tenderness changes a s s o c i a t e d w i t h c u t t i n g up p o u l t r y s h o r t l y a f t e r warm e v i s c e r a t i o n . P o u l t r y S c i . 40:68.3. Klo s e , A.A., Campbell, A.A., Hansen, H.L. and Lineweaver, H 1961. E f f e c t of d u r a t i o n and type of c h i l l i n g and thawing on tenderness of f r o z e n t u r k e y s . P o u l t r y S c i . 40:688. Kl o s e , A.A. Luyet, B.J. and Menz, L . J . 1970. E f f e c t of c o n t r a c t i o n on tenderness of p o u l t r y muscle cooked i n the p r e - r i g o r s t a t e . J . Food S c i . 35:577. Koonz, C.H., Darrow, M.I. and E s s a r y , E.O. 19.54. F a c t o r s i n f l u e n c i n g tenderness of p r i n c i p a l muscles composing the p o u l t r y c a r c a s s . Food Technol. 8:97. Korslund, M.K. and Es s a r y , E.O. 1971. Methods of d e f r o s t i n g t u r k e y s . P o u l t r y S c i . 50:1790. Larmond, E. and P e t r a s o v i t s A. 1972. R e l a t i o n s h i p between Warner-Bratzler and sensory d e t e r m i n a t i o n of beef tenderness by the method of p a i r e d comparisons. Can. I n s t . Food S c i . Technol. J . 5:138. Lawrie, R.A. 1966. Meat Sc i e n c e , Pergamon Press L t d . , Oxford. rLocker, R.H. 1969. Degree of muscular c o n t r a c t i o n as a f a c t o r i n tenderness of beef. Food Research 25:304. Locker, R.H. and Hagyard, C.J. 1963. A c o l d s h o r t e n i n g e f f e c t i n beef muscle. J . S c i . Food A g r i c . 14:787. Lowe, B. 1948. F a c t o r s a f f e c t i n g the p a l a t a b i l i t y of p o u l t r y with emphasis on h i s t o l o g i c a l postmortem changes. Adv. i n Food Research. 1:203. Marion, W.W. 1967. Meat tenderness i n the av i a n s p e c i e s . World's P o u l t r y S c i . J . 23:6. Marion, W.W. 1971. Turkey tenderness and a s s o c i a t e d p h ysio-chemical parameters. F e e d s t u f f s . A p r i l 3, p.24. Marion, W.W. and Stadelman, E . J . 1958. E f f e c t of v a r i o u s f r e e z i n g methods on the q u a l i t y of p o u l t r y meat. Food Technol. 12:367. Marion, W.W. and Goodman, H.M. 1967. I n f l u e n c e of continuous c h i l l i n g on tenderness of turkey. Food Technol. 21:89. Marsh, B.B. 1954. Rigor m o r t i s i n beef. J . S c i . Food A g r i c . 9:417. Marsh, B.B. and Thompson, J.F. 1958. Rigor m o r t i s and thaw r i g o r i n lamb. J . S c i . Food A g r i c . 9:417. Marsh, B.B. and Leet, N.G. 1966. S t u d i e s i n meat tenderness. 3. The e f f e c t s of c o l d s h o r t e n i n g on tenderness. J . Food S c i . 31:450. Marsh, B.B., Woodhams, P.R. and Leet, N.G. 1968.Studies i n meat tenderness. 5. The e f f e c t s on tenderness of c a r c a s s c o o l i n g and f r e e z i n g b e f o r e the onset of r i g o r m o r t i s . J . Food S c i . 33:12. Meat Research I n s t i t u t e , B r i s t o l , England. 1972. Assessment of Meat Texture by O p t i c a l D i f f r a c t i o n . B u l l . 546. M i l l e r , W.O. and May,K.N. 1965. Tenderness of c h i c k e n . as a f f e c t e d by r a t e of f r e e z i n g , storage time and temperature and f r e e z e d r y i n g . Food Technol. 19:1171. Nakamura, R. 1972. Measurement of t e n s i l e s t r e n g t h of muscle f i b e r s and i t s change d u r i n g postmortem aging of c h i c k e n b r e a s t muscle. J . Agr. Food Chem. 20:809. Newbold, R.P. and H a r r i s , P.V. 1972. The e f f e c t of p r e - r i g o r changes on meat tenderness. A review. J . Food S c i . 37 : 337. Palmer, H.H., Klo s e , A.A,, Smith, S. and Campbell, A.A. 1965. E v a l u a t i o n of toughness d i f f e r e n c e s i n chickens i n terms of consumer r e a c t i o n . J . Food S c i . 30:898. Pangborn, R.M., Sharrah, N., Lewis, H. and Brant, A.W. 1965. Sensory and mechanical measurements of turkey tenderness. Food Technol. 19:1268. P i c k e t t , L.O. and M i l l e r , B.F. 1967. The e f f e c t of l i q u i d n i t r o g e n f r e e z i n g on the t a s t e , tenderness and keeping q u a l i t i e s of dressed turkey. P o u l t r y S c i . 46:1148. P o o l , M.F. 1963. E l a s t i c i t y of muscle of ep i n e p h r i n e . t r e a t e d c h i c k e n . P o u l t r y S c i . 42:749. P o o l , M.F., deFremery, D., Campbell, A.A. and Kl o s e , A.A. 1959. P o u l t r y tenderness. 2. I n f l u e n c e of p r o c e s s i n g on tenderness o f c h i c k e n s . Food T e c h n o l . 13:25. P o o l , M.F. and Klo s e , A.A. 1969. The r e l a t i o n of f o r c e to sample dimensions i n o b j e c t i v e measurement of tenderness of p o u l t r y meat. J . Food S c i . 34:524. Rome, E. 1967. L i g h t and X-ray d i f f r a c t i o n s t u d i e s o f the f i l a m e n t l a t t i c e of g l y c e r o l - e x t r a c t e d r a b b i t Psoas muscle. J . Mol. B i o l . 27:591. Sharrah, N., Kunze, M.S. and Pangborn, R.M. 1965a. Beef tenderness - sensory and mechanical e v a l u a t i o n of animals of d i f f e r e n t breeds. Food Technol. -19:233. Sharrah, N. , Kunze, M.S. and Pangborn R.M.. 1965b. Beef tenderness - comparison o f sensory methods w i t h the W a r n e r - B r a t z l e r and L.E.E. Kramer shear p r e s s e s . Food Technol. 10:238. Shrimpton, D.H. 1960. Some causes of toughness i n b r o i l e r s I . Packing s t a t i o n procedure; i t s i n f l u e n c e on the chemical changes a s s o c i a t e d with r i g o r m o r t i s and on the tenderness of the f l e s h . B r i t . P o u l t r y S c i . 1:101. Smith, M.C., Judge, M.D. and Stadelman, W.J. 1969. A " c o l d s h o r t e n i n g " e f f e c t i n av i a n muscle. J . Food Sc 34:42. S t a n l e y , D.W., McKnight, L.M., Hines, W.G.S., Usbourne, W.R. and deMan, J.M. 1972. P r e d i c t i n g meat tenderness from muscle t e n s i l e p r o p e r t i e s . J . Texture S t u d i e s 3:51. Stewart, G.F., Hanson, H.L., Lowe, B. and A u s t i n , J.V. 1945. E f f e c t s of aging, f r e e z i n g r a t e and storage p e r i o d on p a l a t a b i l i t y of b r o i l e r s . Food Research 10:16. Stewart, G.F., Lowe, B. and Morr, M. 1.9 4 8. Postmortem changes i n New York dressed p o u l t r y a t 35 F. U.S. Egg and P o u l t r y Mag. 47:542. S t r e e t e r , E.M. and Spencer, J.V. 1973. Cryogenic and c o n v e n t i o n a l f r e e z i n g of chicken. P o u l t r y S c i . 52:317. Stromer, M.H. and G o l l , D.E. 1968. M o l e c u l a r p r o p e r t i e s of postmortem muscle. 3. E l e c t r o n microscopy of m y o f i b r i l s . J . Food S c i . 32:386. Szczesniak, A.S., Humbaugh, P.R. and Block, H.W. 1970. Behaviour of d i f f e r e n t foods i n the standard shear compression c e l l of the shear press and the e f f e c t of sample weight on peak area and maximum f o r c e . J . Texture S t u d i e s 1:356. Takahashi, K., Fukazawa, T. and Y a s u i , T. 1967. Formation of m y o f i b r i l l a r fragments and r e v e r s i b l e c o n t r a c t i o n of sarcomeres i n c h i c k e n p e c t o r a l muscle. J . Food S c i . 32:409. van den Berg, L., L e n t z , C.P. and Khan, A.W. 1964. Postmortem changes i n tenderness and w a t e r - h o l d i n g and i o n - b i n d i n g p r o p e r t i e s of p o u l t r y l e g and b r e a s t meat. Food T e c h n o l . 18 : 573. V o y l e , C A . 1971. Proceedings of the seventeeth European meeting of Meat Research workers, B r i s t o l , England. Welbourne, J.L., H a r r i n g t o n , R.B. and Stadelman, W.J. 1968. R e l a t i o n s h i p s among shear v a l u e s , sarcomere lengths and c o o l i n g procedures i n t u r k e y s . J . Food S c i . 33:450. White, E.D., Hanson, H.L., K l o s e , A.A. and Lineweaver, H. 1964 E v a l u a t i o n of toughness d i f f e r e n c e s i n t u r k e y s . J . Food S c i . 29:673. W i l l s , R, , Lowe, B, and. Stewart, G . F , 1948, Poul t ry Q s torage at subfreezing temperatures - comparisons at -10 and 10 F . Ref r i g . Eng.. 56:237. Wood, D . F . 1973. Some Postmortem Aspects of B r o i l e r Breast Muscle. PhD. T h e s i s . U n i v e r s i t y of B r i t i s h Colombia. Zachariah, G . L . , Haugh, C . G . and Stadelman, W.J . 1971. Tenderness measurements based on the e l e c t r i c a l propert ies of p o u l t r y . Paper presented at the 1971 annual meeting. American Society of A g r i c u l t u r a l Engineers . A . S . A . E . S t . Joseph, Michigan. 

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:
http://iiif.library.ubc.ca/presentation/dsp.831.1-0099900/manifest

Comment

Related Items