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UBC Theses and Dissertations

Some physico-chemical characteristics of dietary fiber Lapsley, Karen Gail 1980

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SOME PHYSI CO-CHARACTERISTICS OF CHEMICAL DIETARY FIBER by KAREN GAIL LAPSLEY B . S c ( F . S c ) Honours, M c G i l l U n i v e r s i t y , 1974 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n THE FACULTY OF GRADUATE STUDIES (Department o f 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 March, (c) Karen G a i l BRITISH COLUMBIA 1980 Lapsley, 1980 I n p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t o f t h e r e q u i r e m e n t s f o r an a d v a n c e d d e g r e e a t t h e U n i v e r s i t y o f B r i t i s h C o l u m b i a , I a g r e e t h a t t h e 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 a n d s t u d y . I f u r t h e r a g r e e 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 p u r p o s e s may be g r a n t e d by t h e Head o f my D e p a r t m e n t o r by h i s r e p r e s e n t a t i v e s . I t i s u n d e r s t o o d t h a t 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 n o t be a l l o w e d w i t h o u t my w r i t t e n p e r m i s s i o n . D e p a r t m e n t Of Food S r i pnr.p The U n i v e r s i t y o f B r i t i s h C o l u m b i a 2075 W e s b r o o k P l a c e V a n c o u v e r , C a n a d a V6T 1W5 D a t e March 19, 19 80 i i ABSTRACT P a r t i c l e s i z e d i s t r i b u t i o n , chemical composition, water b i n d i n g and water h o l d i n g c a p a c i t i e s , m i c r o s t r u c t u r e , and T h e o l o g i c a l p r o p e r t i e s of d i e t a r y f i b e r residues of American A s s o c i a t i o n of C e r e a l Chemists c e r t i f i e d food grade wheat bran, apple mesocarp and pomace, cabbage and c a r r o t ( e d i b l e p o r t i o n ) were determined. The semiauto-mated Tecator FiberTec system and the e x t r a c t i o n techniques of D.A.T. Southgate and of P.J. Van Soest were used f o r d i g e s t i o n and c o l l e c t i o n of d i e t a r y f i b e r r e s i d u e s . The a b i l i t y o f various f i b e r r e s i d u e s , of d i f f e r e n t s i z e ranges, to i n t e r a c t with water was assessed by two methods. Water h o l d i n g c a p a c i t y was estimated as the amount of water remaining w i t h i n a hydrated sample s u b j e c t e d to compaction by a standard c e n t r i f u g a t i o n technique. This method c l o s e l y resembles c o n d i t i o n s i n the body, but i s an i n a c c u r a t e technique, s i n c e supernatant water i s not e a s i l y separated from the sample. A new method, c a l l e d f i l t r a f u g a t i o n , was developed to obtain i n f o r m a t i o n on water b i n d i n g which Mas d e f i n e d as the amount of water adhering to the f i b e r p a r t -i c l e when water i s allowed to d r a i n from the sample during c e n t r i f u g a t i o n . The amounts of water remaining with the f i b e r i n c e n t r i f u g a t i o n and f i l t r a f u g a t i o n t e s t s d i f f e r e d s i g n i f i c a n t l y f o r each f i b e r source, the d i f f e r e n c e being the water h e l d w i t h i n the f i b e r matrix i n t e r s t i c e s . Although the f r u i t and vegetable f i b e r sources had greater water binding and holding c a p a c i t i e s on a d r i e d weight b a s i s , wheat bran held and bound more water on a fresh weight basis because of higher f i b e r content and percent dry matter. Scanning e l e c t r o n microscopy of the d i f f e r e n t f i b e r sources and t h e i r f i b e r residues confirmed the p r o g r e s s i v e l y erosive a c t i o n of the solvent e x t r a c t i o n treatments and elu c i d a t e d subsequent d i f f e r e n c e s i n water binding and holding capaci-t i e s . Since bran i s a senescent and l i g n i f i e d p lant t i s s u e , i n v i t r o d i g e s t i o n changed the p a r t i c l e appearance, but the s t r u c t u r a l matrix, and the water binding and holding capaci-t i e s were maintained throughout. Micrographs of the f r u i t and vegetable f i b e r sources and the f i b e r residues confirmed that the i n i t i a l s t r u c t u r e s were able to bind and hold large amounts of water but with d i g e s t i o n the d e l i c a t e s t r u c t u r e s were t o t a l l y d i s r u p t e d , thus p r o v i d i n g a weak compact matrix c h a r a c t e r i z e d by low water binding and holding c a p a c i t i e s . Dispersions of the f i b e r residues were evaluated viscomet-r i c a l l y at human body temperature i n order to el u c i d a t e t h e i r behavior i n f l u i d systems. When aqueous dispersions were prepared at low concentrations the s o l i d materials gradually s e t t l e d except f o r the apple pomace dispersions. Steady shear flow behavior studies using 60% w/w sucrose s o l u t i o n as the continuous phase revealed large v i s c o s i t y increases at higher concentrations of the di e t a r y f i b e r residue. TABLE OF CONTENTS ABSTRACT LIST OF TABLES LIST OF FIGURES ACKNOWLEDGEMENTS INTRODUCTION LITERATURE REVIEW A. Background B. Solvent Treatments C. Microstructure D. Physical Properties E. Rheological Properties MATERIALS AND METHODS A. Experimental Plan B. Sample Preparation C. Solvent Treatments D. Physical Property Tests 1. Water binding capacity 2. Water holding capacity E. Microstructure F. Rheological Properties G. S t a t i s t i c a l Analyses V Page RESULTS AND DISCUSSION A. Preliminary- Experiments 23 B. D i e t a r y F i b e r Composition 32 1. AACC bran 34 2. Apple mesocarp 36 3. Cabbage 36 4. Carrots 37 C. P h y s i c a l Property Tests 1. AACC bran 38 2. Apple mesocarp 42 3. Cabbage 46 4. Carrots 48 5. Summary 52 D. M i c r o s t r u c t u r e 54 E. R h e o l o g i c a l P r o p e r t i e s 62 !« AACC bran 6 7 2 . Apple pomace 67 3. Carrots 69 4. Summary 69 CONCLUSIONS 73 LITERATURE CITED 75 v i LIST OF' TABLES Table Page I Comparison o f n o n - c e l l u l o s i c p o l y s a c c h a r i d e 7 v a l u e s f o r d i f f e r e n t f i b e r sources and p r e p a r a t i o n t e c h n i q u e s by Southgate's method o f f i b e r a n a l y s i s . I I E f f e c t o f w e i g h i n g procedure on AACC bran 24 treatmen t s i n p r e l i m i n a r y experiments. I l l Mean f i l t r a f u g a t i o n v a l u e s f o r AACC bran 26 and f i b e r r e s i d u e s i n p r e l i m i n a r y experiments (g H 20/g dw). IV Mean v a l u e s f o r water b i n d i n g and h o l d i n g 28 t e s t s on AACC bran and f i b e r r e s i d u e s i n p r e l i m i n a r y experiments (g H^O/g dw). V Mean v a l u e s f o r water b i n d i n g and h o l d i n g 29 t e s t s on apple pomace and f i b e r r e s i d u e s i n p r e l i m i n a r y experiments (g H 2o/g dw). VI Mean v a l u e s f o r water b i n d i n g and h o l d i n g 30 t e s t s on macerated c a r r o t s and f i b e r r e s i d u e s i n p r e l i m i n a r y experiments (g H^O/g dw). VII D i e t a r y f i b e r a n a l y s i s f o r d i f f e r e n t sources 33 and p a r t i c l e s i z e ranges (mean + S.E.). V I I I Water b i n d i n g and h o l d i n g c a p a c i t i e s o f 39 AACC bran and f i b e r r e s i d u e s o f d i f f e r e n t p a r t i c l e s i z e s (mean + S.E.). IX A n a l y s i s o f v a r i a n c e o f water b i n d i n g and 41 h o l d i n g c a p a c i t i e s o f AACC bran and f i b e r r e s i d u e s . X Water b i n d i n g and h o l d i n g c a p a c i t i e s o f macerated apple mesocarp and f i b e r r e s i d u e s o f d i f f e r e n t p a r t i c l e s i z e s (mean + S.E.). 44 v i i Table XI A n a l y s i s o f v a r i a n c e o f water b i n d i n g and h o l d i n g c a p a c i t i e s o f macerated apple mesocarp and f i b e r r e s i d u e s . Page 45 X I I Water b i n d i n g and h o l d i n g c a p a c i t i e s o f macerated cabbage and f i b e r r e s i d u e s o f d i f f e r e n t p a r t i c l e s i z e s (mean + S.E.). 47 X I I I A n a l y s i s o f v a r i a n c e o f water b i n d i n g and water h o l d i n g c a p a c i t i e s o f macerated cabbage and f i b e r r e s i d u e s . 48 XIV Water b i n d i n g and h o l d i n g c a p a c i t i e s f o r macerated c a r r o t and f i b e r r e s i d u e s o f d i f f e r e n t p a r t i c l e s i z e s (mean + S.E.). 50 XV A n a l y s i s o f v a r i a n c e of water b i n d i n g and water h o l d i n g c a p a c i t i e s o f macerated c a r r o t and f i b e r r e s i d u e s . 51 XVI C a l c u l a t i o n of water b i n d i n g and h o l d i n g c a p a c i t i e s o f the .50-1.0 mm p a r t i c l e s i z e range o f the f i b e r sources on a f r e s h weight b a s i s (g H O/g f r e s h m a t e r i a l ) . 53 XVII Power-law parameters f o r steady shear f l o w o f aqueous apple pomace d i s p e r s i o n s at 37°C, 70 v i i i LIST OF FIGURES Figure Page 1 Diagrammatic representation of f r e e , i n t e r - 25 p a r t i c l e and surface bound water i n r e l a t i o n to the f i b e r matrix i n c e n t r i f u g a t i o n and f i l t r a f u g a t i o n t e s t s , 2 Scanning e l e c t r o n micrographs of methanol- 31 acetone t r e a t e d AACC bran and macerated carrot residues. 3 Scanning e l e c t r o n micrographs of AACC bran 57 and f i b e r residues. 4 Scanning e l e c t r o n micrographs of macerated 59 apple mesocarp and f i b e r residues. 5 Scanning e l e c t r o n micrographs of apple pomace 61 and f i b e r residues. 6 Scanning e l e c t r o n micrographs of macerated 64 cabbage and f i b e r residues. 7 Scanning e l e c t r o n micrographs of macerated 66 car r o t and f i b e r residues. 8 R e l a t i v e v i s c o s i t y of dispersions of native 68 bran (.12-.50 mm) i n 601 (w/w) sucrose at 37°C. The mean and standard e r r o r are shown at the concentrations te s t e d . 9 Rheogram f o r flow behavior of aqueous disper- 71 sions of apple pomace at 37°C. P a r t i c l e s i z e s are . 25-. 50 mm at concentrations of 2, 3 and 41. 10 Rheograms f o r r e l a t i v e v i s c o s i t y of dispersions 72 of macerated ca r r o t i n 60% w/w sucrose s o l u t i o n s at 37°C. P a r t i c l e s i z e s are .25-.50 mm ( s o l i d ) and .12-. 25 mm (open) at concentrations of 1, 2 and 3% . ACKNOWLEDGEMENTS The author wishes to express her s i n c e r e a p p r e c i a t i o n to Dr. M. Tung f o r h i s advice and encouragement through a l l the t r i a l s and t r i b u l a t i o n s of t h i s research p r o j e c t . The capable a s s i s t a n c e and patience of Mrs. L. Jones were a l s o i n v a l u a b l e f o r the s u c c e s s f u l completion of th scanning e l e c t r o n micrographs. She i s a l s o t h a n k f u l to the members of her committee: Drs. W.D. Powrie and J . Vanuerstoep of the Department of Food Science, and Dr. J . S h e l f o r d , Department of Animal Science, f o r t h e i r i n t e r e s t i n and review of t h i s t h e s i s INTRODUCTION 1 In recent years i t has become apparent that d i e t a r y f i b e r i s not j u s t an u n a v a i l a b l e source of energy with a l a x a t i v e e f f e c t . During passage through the human gut i t forms a swollen, sponge-like matrix with s p e c i f i c physicochemical p r o p e r t i e s which are l a r g e l y dependent on the s t r u c t u r e and composition of the f i b e r components. Bran and c e r e a l grains are the most e f f e c t i v e i n treatment of c o n s t i p a t i o n and c o l o n i c problems s i n c e they are r e l a t i v e l y non-ferment-able, maintain s t r u c t u r e , and form a supporting matrix and bulk i n the lower i n t e s t i n e . F r u i t s and vegetables, due to t h e i r h i g h e r p e c t i n and h e m i c e l l u l o s e content are more fermentable and u n l i k e l y to r e t a i n t h e i r s t r u c t u r e but do form gels while i n the upper i n t e s t i n a l t r a c t , thereby a l t e r i n g glucose and c h o l e s t e r o l absorption (Eastwood, 1978). The f i b e r theory i s simple, a t t r a c t i v e and based on common sense but when sub j e c t e d to human research s t u d i e s , the s i t u a t i o n appears more complex than expected. One of the main reasons c i t e d i s the absence o f d e t a i l e d i nformation on the p h y s i c a l and chemical p r o p e r t i e s of each f i b e r source. (Hwang et a l . , 1978) Much of the misinformation about f i b e r has r e s u l t e d from the continued use of the crude f i b e r term which i s s t i l l the A.O.A.C. procedure r e q u i r e d i n any l e g a l contest over the composition of food. It i s i n the i n t e r e s t s of food researchers to examine more c l o s e l y d i e t a r y f i b e r composition and p r o p e r t i e s i n a range of food products i n order to be able to make p r e d i c t i o n s of the e f f e c t s of changes i n the d i e t . U n f o r t u n a t e l y there i s l i t t l e agreement between research groups concerning a d e f i n -i t i o n f o r d i e t a r y f i b e r , terminology to be used, or a n a l y f 2 i c a l methods f o r i s o l a t i o n . There i s no d e f i n i t i o n t h a t i s c o n c i s e y e t conveys f u l l y the concept o f f i b e r i n human n u t r i t i o n . The problem o f a c l e a r u n d e r s t a n d i n g o f pre-c i s e l y what c o n s t i t u t e s f i b e r has been m a g n i f i e d by the d i f f i c u l t i e s a s s o c i a t e d w i t h the c h e m i c a l a n a l y s i s o f so complex a substance. This t h e s i s d e s c r i b e s a study to e v a l u a t e d i e t a r y f i b e r f r a c t i o n s as r e s i d u e s o f v a r i o u s s o l v e n t treatments o f a p p l e , cabbage, c a r r o t , and wheat bran i n o r d e r to e l u c i -date t h e i r f u n c t i o n a l p r o p e r t i e s . Scanning e l e c t r o n micro-scopy was used to e l u c i d a t e the m i c r o s t r u c t u r a l d e t a i l s o f the d i f f e r e n t f i b e r r e s i d u e s . Newly developed e x p e r i m e n t a l t e c h n i q u e s were used to determine water b i n d i n g and water h o l d i n g c a p a c i t i e s . Aqueous f i b e r s l u r r i e s were viscomet-r i c a l l y e v a l u a t e d to study v i s c o s i t y m o d i f y i n g p r o p e r t i e s o f the f i b e r r e s i d u e s . REVIEW OF LITERATURE A. Background The importance of the low l e v e l of the western world's d i e t a r y f i b e r intake i n r e l a t i o n to h e a l t h and disease has been the subject of s p e c u l a t i o n ( B u r k i t t and T r o w e l l , 1975). The r o l e of d i e t a r y f i b e r i n human h e a l t h i s b e l i e v e d to be r e l a t e d to i t s water h o l d i n g and absorp-t i v e p r o p e r t i e s , s i n c e one of the main f u n c t i o n s of f i b e r i s to r e t a i n water i n the col o n . Studies by Eastwood and M i t c h e l l (1976), H e l l e r and Hackler (1977) have i n d i c a t e d water h o l d i n g c a p a c i t y v a r i e s depending on f i b e r source. Other recent metabolic s t u d i e s a l s o suggest that f i b e r q u a l i t y and not j u s t f i b e r q u a n t i t y may be the key f a c t o r i n the p r o p h y l a c t i c r o l e of d i e t a r y f i b e r i n human n u t r i -t i o n . It i s hypothesized that the c i r c u l a t o r y diseases are a b s o r p t i o n r e l a t e d i n that c e r t a i n f i b e r sources "bin d " b i l e acids and t h e i r subsequent e x c r e t i o n stimu-l a t e s conversion of c h o l e s t e r o l to b i l e a cids thereby lowering serum c h o l e s t e r o l l e v e l s ( L e v e i l l e , 1977). The a d d i t i o n of generous amounts of gel-forming poly-saccharides to a high f i b e r , low f a t d i e t seems to improve glucose ab s o r p t i o n and i n s u l i n response, thereby lowering the i n s u l i n requirement f o r some d i a b e t i c s . K r i t c h e v s k y (1977) i n d i c a t e s more long term human metabolic s t u d i e s are needed with i n d i v i d u a l f i b e r components i d e n t i f i e d i n order that observed e f f e c t s may be a t t r i b u t e d to appropria t e c o n s t i t u e n t s . It was known i n the Middle Ages that some part of the food from p l a n t s , p a r t i c u l a r l y c e r e a l s , was i n d i g e s t i b l e and had d e f i n i t e e f f e c t s on bowel f u n c t i o n . The term f i b e r has been used f o r over two hundred vears, with 4 the i d e a f i b e r s were chemically r e s i s t a n t i n s o l u b l e substances. I t was not u n t i l the beginning of the nine-teenth century that attempts were made to define the . f i b e r component of the d i e t . The i n i t i a l work came from the developing science of animal n u t r i t i o n , since by e s t i -mating the i n d i g e s t i b l e f r a c t i o n of the d i e t the n u t r i -t i o n a l value was p r e d i c t e d . The crude f i b e r procedure was developed since i t was f e l t s e q u e n t i a l e x t r a c t i o n with ether, a c i d and a l k a l i y i e l d e d the purest carbohydrate r e s i d u e s , but i t was mainly c e l l u l o s e . (Van Soest, 1978a). By 1887 the A.O.A.C. had s t a n d a r d i z e d the crude f i b e r method f o r o f f i c i a l feed a n a l y s i s . Later other c e l l w a l l c o n s t i t u e n t s such as h e m i c e l l u l o s e . and l i g n i n were found to be important i n a s s e s s i n g the q u a l i t y and d i g e s t i b i l i t y of f o o d s t u f f s . U n f o r t u n a t e l y , today crude f i b e r i s s t i l l the term o f l e g a l standing and reported i n food composi-t i o n t a b l e s , although the h e m i c e l l u l o s e s losses are about 851 and l i g n i n 50-90% (Van Soest, 1973). B Solvent Treatments The a n a l y s i s o f d i e t a r y f i b e r , which i s def i n e d as the sum o f the l i g n i n and p o l y s a c c h a r i d e s not dige s t e d by endogenous s e c r e t i o n s o f the human d i g e s t i v e t r a c t , (Southgate et a l . , 19 78) presents problems to an ana l y s t . Dietary f i b e r i s a mixture o f substances derived from the s t r u c t u r a l m a t e r i a l o f the p l a n t c e l l w a l l ( c e l l u l o s e , h e m i c e l l u l o s e s , p e c t i c substances, l i g n i n ) and a range of p o l y s a c c h a r i d e s o f n o n - s t r u c t u r a l nature (gums, muci-lages, c u t i n , M a i l l a r d browning products) (Southgate, 1976). Over the past 50 years attempts have been made to develop improved f i b e r methods, none of which, have managed to o f f i c i a l l y dislodge the crude f i b e r method. The meth-odology i t s e l f must be d i r e c t e d towards two separate goals that are not e n t i r e l y compatible; f o r research purposes 5 one needs a d e t a i l e d system of s t r u c t u r a l a n a l y s i s that c h a r a c t e r i z e s i n d i v i d u a l f i b e r sources; f o r surveys or q u a l i t y c o n t r o l work the method must be r a p i d and con-ven i e n t , with some d e t a i l s a c r i f i c e d . Since f i b e r s are v a r i a b l e i n t h e i r composition, i t i s not p o s s i b l e to d e s c r i b e the c h a r a c t e r i s t i c s and amount of f i b e r i n a s i n g l e value. The detergent system appears to o f f e r some answers f o r r a p i d yet p r e c i s e measurements of i n -s o l u b l e d i e t a r y f i b e r components (Goering and Van Soest, 1970) . The n e u t r a l detergent f i b e r (NDF) method i s based on the assumption that d i g e s t i b l e components of a food sample can be q u a n t i t a t i v e l y and s p e c i f i c a l l y removed by b o i l i n g with sodium l a u r y l s u l f a t e at n e u t r a l pH, the f i b e r res-idue being separated by f i l t r a t i o n . This method r e s u l t s i n the l o s s of an i n d e f i n i t e amount of hot water s o l u b l e p e c t i c substances and h e m i c e l l u l o s e s , and incomplete removal of s t a r c h from s t a r c h r i c h t i s s u e s ( B a i l e y , et a l . , 1978). Several references (McQueen and N i c h o l s o n , 1979, S c h a l l e r , 1978, Baker et a l . , 1979) recommend enzymatic removal of the s t a r c h . The a c i d detergent f i b e r (ADF) i s a measure of the c e l l u -l o se and l i g n i n present. The main d i f f i c u l t y with t h i s method i s that some r e s i d u a l p e c t i n s and pentosans may also remain (Robertson, 1978). Baker et a l . (1979) has suggested a b u f f e r e d ADF procedure. Southgate (1976) i n d i c a t e d h i s u n a v a i l a b l e carbohydrate f r a c t i o n a t i o n method analyzed a l l the water-soluble and w a t e r - i n s o l u b l e n o n - c e l l u l o s i c p o l y s a c c h a r i d e s , c e l l u l o s e and l i g n i n . The polymers are s e q u e n t i a l l y hydrolyzed to t h e i r c o n s t i t u e n t monosaccharides which are then measured c o l o r i m e t r i c a l l y . Table I shows the i n c o n s i s t e n c i e s which 6 e x i s t f o r the n o n - c e l l u l o s i c p o l y s a c c h a r i d e v a l u e s from two o f h i s r e f e r e n c e s . S e l v e n d r a n e t a l . (19 79) r e p o r t e d on drawbacks to Southgate's methodology which would e x p l -a i n the range o f v a l u e s shown. They i n d i c a t e e x t r a c t i o n o f p l a n t t i s s u e w i t h methanol, e t h a n o l o r acetone r e s u l t s . i n the c o p r e c i p i t a t i o n o f a number o f i n t r a c e l l u l a r compo-unds ( c y t o p l a s m i c p r o t e i n s , n u c l e i c a c i d , p o l y p h e n o l s ) w i t h the c e l l w a l l m a t e r i a l , w i t h c o n t a m i n a t i o n h i g h e s t i n immature m a t e r i a l . Some o f t h i s m a t e r i a l and s t a r c h then supposedly cannot r e a d i l y be s o l u b i l i z e d i n the next f r a c -t i o n a t i o n s t e p . They a l s o c l a i m the h y d r o l y s i s o f the w a t e r s o l u b l e m a t e r i a l s l i b e r a t e s the b u l k o f the n e u t r a l s u g a r s , but not the a c i d ones. These d i s c r e p a n c i e s would be r e f l e c t e d by a v a r y i n g r a t i o o f the t h r e e component sugar groups, as i s shown i n Table I f o r two s t u d i e s u s i n g i d e n t i c a l methodology. S e l v e n d r a n et a l . (1979) recommend m e t h y l a t i o n a n a l y s i s o f the c e l l w a l l p o l y s a c c h a r i d e s to e l u c i d a t e the main g l y c o s i d i c l i n k a g e s . Rasper (19 79b) a l s o suggests t h i s , as w e l l as examining a l t e r n a t i v e meth-ods to c o l o r i m e t r i c a n a l y s i s o f s u g a r s . R e c e n t l y , t h e r e has been i n c r e a s e d i n t e r e s t i n enzymatic procedures which t r e a t the food sample w i t h p r o t e o l y t i c and a m y l o l y t i c enzymes to remove the p r o t e i n and s t a r c h , and s i m u l a t e d i g e s t i o n (Asp, 19 79 , S c hweizer and Wursch, 1979). These r e s e a r c h e r s both c i t e the importance o f t echniques to determine w a t e r - s o l u b l e f i b e r components. Asp (19 79) found h a l f the d i e t a r y f i b e r assayed i n the mixed d i e t s t u d i e d was w ater s o l u b l e . C. M i c r o s t r u c t u r e Most o f the d e t a i l e d s t u d i e s on the development, morph-o l o g y , and u l t r a s t r u c t u r e o f p l a n t c e l l w a l l s has been on woody c e l l s r a t h e r than on c e l l w a l l s o f food p l a n t s . Recent s t u d i e s on the p r i m a r y c e l l w a l l s o f algae and s u s p e n s i o n - c u l t u r e d c e l l s have p r o v i d e d i n s i g h t s i n t o the 7 TABLE I . Comparison o f n o n - c e l l u l o s i c p o l y s a c c h a r i d e v a l u e s f o r d i f f e r e n t f i b e r sources and pre-p a r a t i o n t e c h n i q u e s by Southgate's method of f i b e r a n a l y s i s . N o n - c e l l u l o s i c p o l y s a c c h a r i d e s , % P r e p a r a t i o n F i b e r Technique Hexoses Pentoses U r o n i c A c i d s Apple f l e s h none methanol/ acetone 20 56 35 14 45 30 Bran none methanol/ acetone 32 24 58 72 11 3 Cabbage none methanol/ acetone 9 26 47 38 43 36 C a r r o t none methanol/' acetone 20 28 35 26 45 46 Southgate (1978a) and Southgate et a l . (1978) 8 general features of p l a n t c e l l w a l l s , but how d i f f e r e n t polymers are attached and d i s t r i b u t e d i s s t i l l not f u l l y understood (Theander and Aman, 1979b). The concept o f the p l a n t c e l l w a l l as a network of c e l l u l o s e m i c r o f i b r i l s embedded i n an amorphous matrix of d i s c r e t e h e m i c e l l u l o s e polymers and l i g n i n with a p e c t i n cement between adjacent w a l l s i s an o v e r s i m p l i f i c a t i o n . I t i s now evident that many of the polymer f r a c t i o n s are l i n k e d by both convalent and noncovalent bonds , with covalent bonds predominant i n young t i s s u e s ( B a i l e y et a l . , 1978). Scanning e l e c t r o n microscopy (SEM) has only r e c e n t l y been used to study the f u n c t i o n a l p r o p e r t i e s of d i f f e r e n t food f i b e r sources (Southgate, 1978b). Pomeranz et a l . , (19 77) p u b l i s h e d scanning e l e c t r o n micrographs o f d i f f e r e n t c e r e a l f i b e r sources i n r e l a t i o n to f u n c t i o n a l p r o p e r t i e s i n bread making. Baked wheat bran p a r t i c l e s were c u r l e d and twisted. Neukom et a l . , (1978) and Saunders (1978) used SEM to e l u c i d a t e the gross morphology of untreated wheat bran. D i n t z i s et a l . , (1979a,b) adopted SEM to show the morphological d i f f e r e n c e s o f wheat bran a f t e r baking and human g a s t r o i n t e s t i n a l a c t i o n . The excreted bran was r e t r i e v e d as i d e n t i f i a b l e p a r t i c l e s with the endosperm and aleurone c e l l l a y e r s removed. Rasper (19 79b) has p u b l i s h e d SEM micrographs of e n z y m a t i c a l l y d i g e s t e d c e r e a l d i e t a r y f i b e r r e s i d u e s . The s k e l e t a l s t r u c t u r e o f the p a r t i c l e s i s s t i l l evident. To date, there i s no known l i t e r a t u r e on the use of SEM with f r u i t or vegetable f i b e r s t u d i e s . D. P h y s i c a l P r o p e r t i e s The p r i n c i p a l p h y s i c a l p r o p e r t i e s of d i e t a r y f i b e r are p a r t i c l e s i z e , h y d r a t i o n c a p a c i t y and ion-exchange c a p a c i t y . They w i l l vary with the age, anatomy, chemical composition and f i b e r source (Eastwood, 1973). I n i t i a l l y p l a n t m a t e r i a l must be prepared i n a manner that allows 9 b i o l o g i c a l comparison. To achieve c e l l u l a r d i s r u p t i o n of vegetable f i b e r , maceration i n a blender with water, followed by f r e e z i n g and free ze-dry ing i s recommended (Eastwood and M i t c h e l l , 1976). Cereal f i b e r s r e q u i r e minimal p r e p a r a t i o n aside from g r i n d i n g . Grinding f i b e r i through a screen of s p e c i f i e d s i z e may produce a spectrum of s i z e s dependent on the g r i n d i n g equipment and f i b e r source. Excessive heat generated during g r i n d i n g may also a f f e c t the p a r t i c l e ' s f u n c t i o n a l p r o p e r t i e s (Van Soest and Robertson, 1976). P a r t i c l e s i z e range i s determined with a s t a n d a r d i z e d s i e v i n g procedure ( H e l l e r et a l . , 19 77). Eastwood and M i t c h e l l (1976) have developed ion-exchange c a p a c i t y t e s t s to determine the extent o f " i n v i t r o " min-e r a l b i n d i n g . A mechanism of water absorption by f i b e r components was also d e s c r i b e d by Eastwood (1973). He s t a t e d that each f i b e r has a f i n i t e c a p a c i t y to h o l d water (which he c a l l e d the f i b e r s a t u r a t i o n p o i n t ) and t h i s i s determined by the chemistry of the macromolecule, e l e c t r o l y t e c o n c e n t r a t i o n and pH of surrounding l i q u i d . He e x p l a i n e d that with h y d r a t i o n , water i s i n i t i a l l y t i g h t l y bound through hydrogen bonds, then t h i s s t r u c t u r e becomes surrounded by loosely-bound water h e l d by d i p o l e a t t r a c t i o n and adhesion, and f i n a l l y as the polymer swells the spaces i n the macromolecule are f i l l e d by bulk water. Surface areas and i n t e r n a l pore s i z e s were c a l c u l a t e d . Water h o l d i n g c a p a c i t y was d e f i n e d as the amount o f water that could be taken up by a u n i t weight of dry f i b e r and was the p o i n t at which there was no fre e water. C e n t r i -f u g a t i o n at 14,000 xg was used to remove the free water, s i n c e t h i s speed separated a normal from a d i a r r h e a l s t o o l (Eastwood and M i t c h e l l , 1976). H e l l e r and Hackler (1977) showed Eastwood's group had m i s c a l c u l a t e d t h e i r p u b l i s h e d water h o l d i n g c a p a c i t i e s f o r a range of foods. 10 Brodribb and Groves (1978) found t h i s t e s t was not completely s a t i s f a c t o r y , as samples d i d not always form coherent p e l l e t s on c e n t r i f u g a t i o n . S c h a l l e r (1977) and P a r r o t t and T h r a l l (1978) proposed m o d i f i c a t i o n s . Van Soest and Robertson (1976) i n d i c a t e d that the amount of water that i s adsorbed and entrapped w i t h i n f i b e r i s dependent on bulk volume, surface and p a r t i c l e s i z e , and other i n t r i n s i c p r o p e r t i e s of i n d i v i d u a l f i b e r s . They s t a t e d that vegetable f i b e r s have higher bulk volumes and water h o l d i n g c a p a c i t i e s i n i t i a l l y , but proposed the h o t e l theory to e x p l a i n reduced values upon d i g e s t i o n or g r i n d i n g . They compared the s t r u c t u r e of the d i g e s t i n g p l a n t f i b e r . t o a l a r g e c i t y h o t e l i n the process of being demolished. Considerable weight of the s t r u c t u r e could be removed without a l t e r i n g inherent volume. The only mech-anism f o r reducing volume of the s t r u c t u r e was d i g e s t i n g connecting p a r t s , crushing or g r i n d i n g . Van Soest used a standard s o i l t e s t method f o r e v a l u a t i n g bulk volume and h y d r a t i o n c a p a c i t y (Van Soest and Robertson, 1976). Rasper (1979a) c i t e d s i m i l a r techniques and a modified p r o t e i n f u n c t i o n a l i t y t e s t . Recently Stephen and Cummings (1979) have proposed a new i n v i t r o water h o l d i n g technique which may overcome the methodology problems with water-soluble f i b e r components. The f i b e r m a t e r i a l i s enclosed i n a sack of d i a l y s i s tubing, hydrated i n simulated i l e a l s o l u t i o n and a g i t a t e d , a f t e r 24 and 48 hours the bag i s removed, b l o t t e d dry and weighed, then polyethelene g l y c o l added to simulate c o l o n i c absorption and the bag reweighed a f t e r 24 hours. They c i t e d comparable r e s u l t s to the c e n t r i f u g a t i o n technique and found a c l o s e r e l a t i o n s h i p between water uptake and u r o n i c a c i d content. S p i l l e r (1978) s t a t e d that i n v i t r o s t u d i e s c o u l d be very 11 important in gaining an understanding of the f a e c a l bulking mechanism, but cautioned these physical proper-t i e s of dietary f i b e r may or may not be an indication of their behavior in the human gut. Many be n e f i c i a l effects attributed to dietary fiber have been linked to this a b i l i t y to increase faecal output in man. The metabolic study by Cummings et a l . (1978) showed a 20g/day f i b e r supplement increased faecal weight by 127% with wheat bran, 69% with cabbage powder, 59% for carrot powder, 40% for apple powder and 20% with guar gum. These changes in faecal weight were correlated with an increased intake of pentose-containing polysaccharides. Brodribb and Groves (1978) indicated stool weight was also s i g n i f i c a n t l y greater after feeding 20g/day coarse bran supplement than with ah equal amount of fine bran. Kirwan et a l . (1974) has also concluded that in vivo water holding capacity was influenced by the capacity of i n t e r s t i c e s to hold water, with larger bran p a r t i c l e s having larger and more numerous i n t e r p a r t i c l e spaces. E. Rheological Properties Jenkins et a l . , (1978) conducted a major human study evaluating dietary f i b e r supplements, their rheological properties and subsequent metabolic effe c t s . Guar gum had been shown to lower the post-prandial glucose and i n s u l i n responses i n both normal and diabetic subjects. They compared guar gum with other unabsorbable poly-saccharides and found the greatest flattening of the glucose response was seen with guar gum supplements, but this effect was abolished when hydrolyzed non-viscous guar was used. The reduction in the mean peak r i s e in blood glucose concentration was p o s i t i v e l y cor-related with v i s c o s i t y and delayed t r a n s i t time. They concluded this action was related to the a b i l i t y of guar gum to increase the v i s c o s i t y of aqueous solutions. Eastwood and Kay (1979) in their hypothesis for the 12 a c t i o n o f d i e t a r y f i b e r along the g a s t r o i n t e s t i n a l t r a c t c i t e d the importance o f g e l formation as w e l l as water adsorption f o r a l t e r e d metabolic e f f e c t s i n the sm a l l i n t e s t i n e . Anderson and L i n Chen (1979) suggested a g e l f i l t r a t i o n system s i m i l a r to that used i n column chromatography may be e s t a b l i s h e d i n the small i n t e s t i n e before b a c t e r i a l degradation of these s o l u b l e substances i n the colon. For obvious reasons the changing Theolog-i c a l p r o p e r t i e s o f d i e t a r y f i b e r components would be very d i f f i c u l t to evaluate i n v i v o . There was no l i t e r a t u r e a v a i l a b l e on T h e o l o g i c a l s t u d i e s of i n v i t r o i s o l a t e d d i e t a r y f i b e r residues but s e v e r a l s t u d i e s have evaluated the r o l e of the p l a n t c e l l w a l ls i n r e l a t i o n to the v i s c o s i t y o f f l u i d foods. Character-i z a t i o n and a n a l y s i s o f flow behavior o f f l u i d f r u i t products ( j u i c e s , concentrates, purees, sauces and nectars) has been used i n engineering a n a l y s i s or q u a l i t y c o n t r o l . Much o f the e a r l y data on v i s c o s i t y o f j u i c e s and purees was obtained using instruments o p e r a t i n g at one rate of sh e a r i n g . S i n g l e p o i n t measurements cannot adequately describe non-Newtonian f l u i d s . Whittenberger and N u t t i n g , (1958) reported that v i s c o s i t y o f tomato j u i c e was governed by the c e l l w a l l s . Removal of s o l u b l e substances caused t h i s suspended m a t e r i a l s to thi c k e n to a semi-gel. Foda and McCollum (1970) found a s i g n i f i c a n t c o n t r i b u t i o n by the water-s o l u b l e c o n s t i t u e n t s to the v i s c o s i t y of tomato j u i c e , when i n a s s o c i a t i o n with the i n s o l u b l e d i e t a r y f i b e r . I f there was a d i s r u p t i o n i n bonding ( i . e . by c e n t r i f u g a t i o n ) the v i s c o s i t y would not return when the serum and suspended p a r t i c l e s were remixed. Holdsworth (1971) and Harper and E l S a h r i g i (1965) both found tomato concentrates were p s e u d o p l a s t i c , non-Newton-ian systems, agreeing reasonably with the power law model. Holmes and Rha (1978) c i t e d work on the Theological p r o p e r t i e s of cranberry c e l l w a l l m a t e r i a l . 13 They examined p a r t i c l e s i z e , chemical composition and sedimentation properties in an attempt to elucidate the thickening mechanism of the suspensions. They concluded the primary c e l l wall polysaccharides-cellulose, pectin and hemicelluloses were the major contributors to increased v i s c o s i t y . Recently researchers have emphasized the need to study the physice-chemical properties of the system constitu-ents to understand the rheological mechanism (Mi-s-r-ahi, 1979). U n c l a r i f i e d f l u i d f r u i t products consist of a dispersing medium (serum) and suspended pa r t i c l e s (pulp). The clear serum contains low and high molecular-weight solutes. Removal of the l a t t e r leaves a "basic medium" which i s a solution of sugars, s a l t s , and organic acids and has Newtonian flow properties (Mizrahi, 1979). Mizrahi and his co-workers have shown the soluble pectic substances in orange concentrate serum impart non-Newton-ian behavior, a f i n i t e y i e l d stress and time-dependent flow behavior. They suggested there were polymer-polymer interactions and in 1972 published a rheological equation based on the model of a suspension of interacting part-i c l e s in a pseudoplastic medium (Mizrahi and Berk, 1972). They noted in practise two or more factors operate simul-taneously and the net effect is different from the sum of individual contributions. Mizrahi (1979) indicated add-i t i o n of sucrose and elevated temperature would also reduce i n t r i n s i c v i s c o s i t y by i n h i b i t i n g molecular hydr-ation. He also stated the physicochemical character-ization of the suspended p a r t i c l e s should include con-centration, size d i s t r i b u t i o n , p a r t i c l e shape, e l e c t r i c a l and surface properties and mode of interaction, but no quantitative analysis of these properties has been attem-pted due to lack of suitable methodology. Corey (1970) made use of an analogy beteen the flow 14 b e h a v i o r o f an e x p e r i m e n t a l model ( c e l l u l a r f i b e r i n a su c r o s e s o l u t i o n ) and a commercial model (tomato ketchup) i n an attempt to e x p l a i n t e x t u r a l p r o p e r t i e s o f f l u i d food systems. U n f o r t u n a t e l y h i s data were not p u b l i s h e d . He d i d c i t e work on a model system o f v a r i o u s c o n c e n t r a -t i o n s o f i n e r t asbestos f i b e r s , d i s p e r s e d i n 61% su c r o s e s o l u t i o n s . He found an i n c r e a s i n g c o n s i s t e n c y w i t h i n c r e a s i n g c o n c e n t r a t i o n and at a f i n i t e c o n c e n t r a t i o n v i s c o s i t y became temperature independant. He p o s t u l a t e d t h a t around each f i b e r , molecules o f suspending l i q u i d form i n t o a r i g i d envelope which i s i n v a r i a n t w i t h s hear r a t e , c o n c e n t r a t i o n and i n i t i a l l y t e m p e r a t u r e , and pro-posed a crowding f a c t o r e q u a t i o n to e x p l a i n t h i s r e l a t i o n -s h i p . He a l s o c o n c l u d e d t h e r e was l i t t l e hope f o r a g e n e r a l t h e o r y to p r e d i c t v i s c o m e t r i c beha\ rior o f suspen-s i o n s o f a l l c o n c e n t r a t i o n s o f suspended p a r t i c l e s . 15 MATERIALS AND METHODS A. Experimental Plan P r e l i m i n a r y experiments were c a r r i e d out on American A s s o c i a t i o n o f Cereal Chemists (AACC) standard c e r t -i f i e d food grade wheat bran o f four d i f f e r e n t p a r t i c l e s i z e ranges. Four s o l v e n t e x t r a c t i o n treatments were used. A comparative study followed with AACC bran, commercial apple pomace (residue of apple parenchyma c e l l s a f t e r p r e s s i n g f o r j u i c e e x t r a c t i o n ) and c a r r o t s . F i l t r a f u g a t i o n , c e n t r i f u g a t i o n , r h e o l o g i c a l experiments and scanning e l e c t r o n microscopy e v a l u a t i o n s were- done. The f i n a l comprehensive study i n v o l v e d four food f i b e r sources; AACC bran, apple mesocarp, cabbage and c a r r o t s ( e d i b l e p o r t i o n ) , of three p a r t i c l e s i z e ranges (0.12-0.25 mm, 0.25-0.50 mm, 0.50-1.00 mm) with two s o l v e n t treatments ( n e u t r a l detergent and a c i d d e t ergent). The p h y s i c a l property t e s t s ; f i l t r a f u g a t i o n at 1^000 xg, c e n t r i f u g a t i o n at 1,000 xg and 14,000 xg, and scanning e l e c t r o n micro-scopy were conducted on these d i e t a r y f i b e r r e s i d u e s . B. Sample P r e p a r a t i o n The AACC wheat bran mixture at 10.4% moisture r e q u i r e d no p r e l i m i n a r y treatment, whereas the f r u i t and vegetable f i b e r sources with 90-95% moisture d i d . The p r e p a r a t i o n methods of Eastwood and M i t c h e l l (1976) were modified and used. They s t r e s s that p l a n t m a t e r i a l should be prepared i n a manner to allow b i o l o g i c a l comparison, such as c e l l -u l a r d i s r u p t i o n by maceration, f r e e z i n g and thawing; and advocate the thawed m a t e r i a l be washed with water to remove water-soluble m a t e r i a l . There has been c r i t i c i s m of the 16 washing s i n c e water-soluble f i b e r components may a l s o be removed ( H e l l e r and Ha.ckler, 1977) , thus t h i s washing step was omitted i n the present study. The apple pomace was donated by Sunland Company, Summer-land, B.C., i n a wet s l u r r y form ready f o r freeze d r y i n g . The apple mesocarp was obtained from Spartan apples picked at optimum maturity (October 8-9, 1978) at the A g r i c u l t u r e Canada Research S t a t i o n , Summerland, B.C. They were h e l d i n c o l d storage at 0°C f o r two months. Each apple was a u t o m a t i c a l l y peeled and decored, cut i n t o s l i c e s and macerated i n a C u i s i n a r t Food Processor ( a l l press type) f o r 60 seconds. The cabbage was purchased from a l o c a l farmer i n Richmond, B.C. The outer leaves and core were removed,, the e d i b l e p o r t i o n macerated i n the C u i s i n a r t f o r 60 seconds, then an equal amount of d i s t i l l e d , d e i o n i z e d water added to f a c i l i t a t e chopping, followed by 60 seconds maceration. C a r r o t s , S c a r l e t Mantis No. 2 v a r i e t y , were harvested at optimum maturity (October, 1978) at the A g r i c u l t u r e Canada Research S t a t i o n , A g a z z i z , B.C. They were washed, peeled, and the e d i b l e p o r t i o n macerated i n a manner s i m i l a r to the cabbage. A l l samples were frozen at -20°C f o r at l e a s t 48 hours, then freeze d r i e d i n ten pound batches i n a Thermovac I n d u s t r i e s Corporation freeze d r i e r (Model FDC-10-DR) at a s h e l f temperature of 50°C and 0.1 Torr pressure. Since research had shown s p e c i f i c p a r t i c l e s i z e to be very important to p h y s i c a l property t e s t r e s u l t s , p a r t i c l e s i z e d i s t r i b u t i o n was determined on a l l samples, with a s i e v i n g procedure s i m i l a r to H e l l e r et a l . (1977). A known weight of sample was p l a c e d on the l a r g e s t s i e v e of the f o l l o w i n g s e r i e s of U.S. standard s i e v e s with the designated a p e r t u r e s ; 10 (2.00- mm), 18 (3..00 mm), 35 (0.50 mm), 60 (0.25 mm), 120 (0.12 mm), and 230. (Q.Q6 mm). The "nested" s e r i e s of s i e v e s were brass, 17 20 cm diameter, 5 cm height, and f i t t e d with pan and -cover. They were v i b r a t e d f o r 30 minutes on a Ro-Tap sieve shaker. The sample p a r t i c l e s i z e range r e t a i n e d on each sieve was c o l l e c t e d and s t o r e d i n glass j a r s i n a d e s i c c a t o r . The AACC bran mixture d i d not provide a s u f f i c i e n t amount of the s m a l l e s t p a r t i c l e s i z e range, •0.12-0.25 mm by s i e v i n g , thus" ra water-cooled Janke and Kunkel high-speed micro shearing m i l l was used to g r i n d 0.25-0.50 mm m a t e r i a l with the r e s u l t a n t m a t e r i a l s i e v e d '. tp o b t a i n p a r t i c l e s i n the s i z e range d e s i r e d . C. Solvent Treatments It was necessary to s e l e c t d i e t a r y f i b e r a n a l y s i s tech-niques which y i e l d e d p h y s i o l o g i c a l l y r e l e v a n t f i b e r residues on which to conduct f u r t h e r t e s t s . Southgate's complete f r a c t i o n a t i o n procedure provides a n a l y t i c a l data on a l l the d i e t a r y f i b e r components, but no f i n a l residues are obtained (Southgate, 1976). His p r e l i m i n a r y methanol e x t r a c t i o n and acetone-drying treatments were adopted i n an attempt to obtain unaltered, t o t a l d i e t a r y f i b e r , i n c l u d i n g water-soluble components (Cummings et a l . , 1978). A standard l a b o r a t o r y r e f l u x setup and Buchner funnel f i l t r a t i o n system was employed. When the o u t l i n e d proced-ure (Greenberg, 1976) was found inadequate f o r s t a r c h removal an a d d i t i o n a l r e f l u x i n g with methanol, followed by acetone, was used (Southgate, 1978b). Van Soest's n e u t r a l detergent and a c i d detergent d i e t a r y f i b e r residues were prepared using the Tecator semi-automated FiberTec system. This u n i t permits simultan-eous d i g e s t i o n , f i l t r a t i o n and d r y i n g of s i x 1-3 gram samples without h a n d l i n g , under c o n s i s t e n t and reproduc-i b l e c o n d i t i o n s . D i e t a r y f i b e r residue c o l l e c t i o n i n v o l -ved 10 to 20 d i g e s t i o n s of each f i b e r source and p a r t i c l e s i z e range to o b t a i n s u f f i c i e n t sample f o r f u r t h e r t e s t s . 18 The samples were preweighed on a S a r t o r i u s e l e c t r o n i c balance to the nearest centigram, d r i e d i n an oven (37°C) f o r one hour a f t e r d i g e s t i o n , and s t o r e d i n a i r -t i g h t c o n t a i n e r s . As the d i e t a r y f i b e r components are hydroscopic and open s i n t e r e d glass c r u c i b l e s are used, the "hot" weighing techniques of Goering and Van Soest (1970) and Mongeau (1978) were used f o r the q u a n t i t a t i v e d i e t a r y f i b e r a n a l y s i s . For "hot" weighing, dry, clean c r u c i b l e s were p l a c e d i n a f o r c e d - d r a f t oven set at 100°C ( F i s h e r Isotemp Oven Model 301) f o r a minimum of two hours before weighing. They were removed one at a time f o r weighing on a M e t t l e r H35 s i n g l e pan automatic balance ( p r e c i s i o n +_ 0.05 mg) . This weight was a t t a i n e d and recorded 20 to 30 seconds a f t e r p l a c i n g the c r u c i b l e on the balance pan. A f t e r removal of the c r u c i b l e any de-f l e c t i o n of the balance zero s e t t i n g was recorded. This d e f l e c t i o n due to temperature change was s u b t r a c t e d from each weight. A f t e r the minimum weight was recorded f o r the numbered c r u c i b l e s , 1 gram samples were q u a n t i t a t i v e l y weighed i n t o the t a r e d c r u c i b l e s , d i g e s t i o n followed, then the "hot" weighing technique employed again a f t e r the d i e t a r y f i b e r residues were d r i e d 24 hours at 100°C (Goering and Van Soest, 1970). D. P h y s i c a l Property Tests The a b i l i t y of the various f i b e r r e s i d u e s , of the d i f f e r -ent s i z e ranges, to i n t e r a c t with water was assessed by two methods, as shown i n Figure 1. F i l t r a f u g a t i o n was a method developed to l e a r n more about the i n t r i n s i c nature of water bi n d i n g . The c e n t r i f u g a t i o n method more c l o s e l y resembled c o n d i t i o n s i n the body but i t i s an inaccurate technique (Brodribb and Groves 1978). The f i l t r a f u g a t i o n technique appears/more p r e c i s e and provides i n f o r m a t i o n about the bound water within*, the p a r t i c l e s themselves. 19 1. Water Bindi n g Capacity D u p l i c a t e and r e p l i c a t e 0.25^-0,50 g samples of each f i b e r source and p a r t i c l e s i z e range were d i s p e r s e d with. 25 ml of d i s t i l l e d , d e i o n i z e d water on top of a m i l l i p o r e f i l t e r d i s k (.22 mm pore s i z e ) and screen w i t h i n polycarbonate f i l t e r i n g c e n t r i f u g e tubes ( M i l l i p o r e XX62 025 50). These tubes were p l a c e d i n 250 ml screw cap adaptor c e n t r i f u g e b o t t l e s , covered, allowed to hydrate 24 hours at 25°C, then c e n t r i f u g e d at 1000 xg at 25°C i n the GSA r o t o r of a S o r v a l Super-speed RC2-B c e n t r i f u g e f o r one hour. The p e l l e t was t r a n s f e r r e d to pre-weighed aluminum weighing dishes, d r i e d i n the f o r c e d - a i r oven at 100°C f o r 24 hours, then f i n a l weight of the p e l l e t determined using the "hot" weighing techniques f o r hygroscopic m a t e r i a l s . The water b i n d i n g c a p a c i t y was expressed as g r^O h e l d by 1 g dry weight of sample. 2. Water Holding Capacity A l l samples were s i m i l a r l y d i s p e r s e d i n 25 ml of d i s -t i l l e d , d e i o n i z e d water w i t h i n pre-weighed 50 ml poly-carbonate c e n t r i f u g e tubes. The tubes were s e a l e d with p a r a f i l m , allowed to hydrate 24 hours at 25°C, p l a c e d i n the SS-34 r o t o r of S o r v a l Superspeed RC2-B c e n t r i -fuge, and c e n t r i f u g e d at 1000 or 14,000 xg f o r one hour at 25°C. The fre e water was poured o f f , with tubes p l a c e d open end down at a 45° angle f o r 15 min-utes to d r a i n , then excess water d r o p l e t s removed by cotton swabs. The weights of the tube plus p e l l e t were determined with the M e t t l e r a n a l y t i c a l balance before and a f t e r drying f o r 24 hours i n the 100°C oven. The water h o l d i n g c a p a c i t y was expressed as g H ?0 h e l d by 1 g dry weight of sample. 20 Micros t r u c t u r e P a r t i c l e s o f the 0.25-0.50 mm s i z e range of the AACC bran, apple mesocarp and pomace, cabbage and c a r r o t s (various d i e t a r y f i b e r residues) were mounted on 9 mm aluminum d i s c specimen stages with double s t i c k pressure s e n s i t i v e tape, coated " i n vacuo" with a gold/palladium a l l o y i n a s p u t t e r c o a t i n g device, and examined i n e i t h e r an ETEC Autoscan scanning microscope operated at 20 kV a c c e l e r -a t i o n v o l t a g e , or a H i t a c h i 5500 SEM. Images were record-ed on P o l a r o i d p o s i t i v e / n e g a t i v e 10.2 cm x 12.7 cm f i l m with the ETEC system. With the H i t a c h i microscope a Pentax camera and I l f o r d Pan F 35 mm f i l m were used. R h e o l o g i c a l P r o p e r t i e s D u p l i c a t e d i s p e r s i o n s of the untreated and two detergent t r e a t e d f i b e r residues of the two s m a l l e r p a r t i c l e s i z e ranges (0.12-0.25 mm and 0.25-0.50 mm) of the AACC bran, apple pomace and c a r r o t s were added to Newtonian l i q u i d s ( d i s t i l l e d d e i o n i z e d water or 60% w/w sucrose s o l u t i o n ) at concentrations of 1-12%. Dispersions were prepared as f o l l o w s : the sample was added to 100 ml of the s e l e c t e d l i q u i d at 25°C, m a g n e t i c a l l y s t i r r e d f o r 30 minutes, allowed to hydrate f o r 24 hours, then the d i s p e r s i o n q u a n t i t a t i v e l y t r a n s f e r r e d to the A2 cup (83 ml volume) of the Brabender viscometer. The steady shear flow behavior of these d i s p e r s i o n s were evaluated with the Brabender rheotron c o a x i a l c y l i n d e r viscometer. The A2 cup and s p i n d l e with a gap width of 3.0 mm p r o v i d e d the maximum distance between the s t a t i o n -ary s p i n d l e and r o t a t i n g cup over a range of shear rates from 2.05 to 1000 s " 1 . A l l t e s t s were made at a sample temperature of 37°C which was maintained by a thermostat-i c a l l y controlled water jacket surrounding the cup and spindle. Each sample was subjected to a stepwise shear rate increase, then decrease with the shear stress signal read from the meter, for each gear setting. Calibration constants were obtained for the A2 spindle/cup combin-ation using o i l v i s c o s i t y standards (Cannon Instrument Co., State College, PA.). Shear stress (_a dyne/cm) and shear rate (y , s'*) were calculated from the meter reading (S) and cup rotational speed (N, rpm) using the equations: a - AS ( 1 ) f = BN ( 2 ) where A i s the torsion constant for the spring used with the A2 fixtures (0.312 dyne/cm ) and B i s the shear rate constant for the A2 fixtures (1.034 s */rpm). Apparent v i s c o s i t y (n , poise) was calculated from the equation: n = ( 3 ) Relative v i s c o s i t y (n Te^) was expressed as the quotient of the dispersion apparent v i s c o s i t y and continuous phase apparent v i s c o s i t y at each shear rate when the fiber dis-perions were prepared with 601 w/w sucrose solution. The viscometric data were organized by f i t t i n g the Power-Law flow model to the data by the method of least squares using a power function program with an HP-65 calculator. The Power-Law relates shear stress or apparent v i s c o s i t y to shear rate by the equations: o = m Y n C 4 ) n = my11*1 ( 5 ) Where m i s the consistency c o e f f i c i e n t (dyne sn/cm^) and n is the flow behavior index (no u n i t s ) . 22 G. S t a t i s t i c a l Analyses S t a t i s t i c a l a n a l y s i s began on a Hewlett Packard program-mable c a l c u l a t o r (HP-65) with a s t a t i s t i c s program package. Programs were used to c a l c u l a t e standard e r r o r of means and the 2 - t a i l e d Student's-t t e s t f o r unpaired data f o r comparison of the f i b e r composition and water b i n d i n g and h o l d i n g data. A n a l y s i s of v a r i a n c e followed using the UBC computer (Amdahl 470 V/6 Model II) and a UCLA Health Sciences general l i n e a r r e g r e s s i o n program (BMD 10V) f o r uneven data s e t s . .Duncan's m u l t i p l e range t e s t was used to compare the means of the main e f f e c t s (chemical treatment and p a r t i c l e s i z e ) . 23 RESULTS AND DISCUSSION A. P r e l i m i n a r y E xpe riments P a r t i c l e s i z e d i s t r i b u t i o n determinations of the AACC bran mixture as r e c e i v e d i n d i c a t e d p a r t i c l e s of 0.25-0.50 mm, 0.50-1". 00 mm and 1. 00- 2.00 mm diameter c o n s t i t u t e d 99% of the samples by weight. The i n i t i a l s o l v e n t treatments (acetone d r y i n g , methanol-acetone e x t r a c t i o n ) and f i l t r a -f u g a t i o n t e s t s were conducted on these p a r t i c l e s i z e ranges as w e l l as the bran mixture. Table II shows the e f f e c t of the weighing procedure on these hygroscopic f i b e r residues using the t r a d i t i o n a l c o l d weighing and the "hot" weighing technique of Goering and Van Soest (1970). Based on these r e s u l t s the "hot" weighing technique was adopted. Figure 1 i s a diagrammatic r e p r e s e n t a t i o n of the f r e e , i n t e r p a r t i c l e and surface bound water i n r e l a t i o n to the c e n t r i f u g a t i o n and f i l t r a f u g a t i o n t e s t s . The c e n t r i -f u g a t i o n ' o r water h o l d i n g t e s t i s a measure of the amount of water the f i b e r matrix holds by b i n d i n g to the sur-faces of the f i b e r , as w e l l as that trapped i n spaces between f i b e r p a r t i c l e s . In the f i l t r a f u g a t i o n or water bindin g t e s t the matrix i s s t r e s s e d , t h e r e f o r e only the s u r f a c e bound water remains i n the matrix. The f i l t r a f u g a t i o n r e s u l t s of the AACC bran f o r a pre-l i m i n a r y experiment are shown i n Table I I I . The water bi n d i n g values of the untreated samples of i n c r e a s i n g p a r t i c l e s i z e decreased s l i g h t l y (1.72-1.18 g U^O/g dw). This trend i s expected s i n c e an i n c r e a s e d number of f i n e l y ground p a r t i c l e s w i l l have a g r e a t e r exposed surface area to bind water than w i l l a s m a l l e r number TABLE I I . E f f e c t of weighing procedure on AACC bran treatments i n p r e l i m i n a r y experiments. S o l v e n t t r eatment P a r t i c l e s i z e range, mm % Dry mat t e r Hot weight b a s i s C o l d w e ight b a s i s Acetone .25-.50 88.1 93.3 .50-1.0 88.2 93.9 1.0-2.0 90.0 94.4 composite 88.1 92.6 Methanol/ .25-.50 81.9 86.5 Acetone .50-1.0 30.9 36.1 1.0-2.0 84.5 85.1 composite 82.7 84.7 D u p l i c a t e values obtained f o r each t e s t . CENTRIFUGATION FILTRAFUGATION F i g u r e 1, Diagrammatic r e p r e s e n t a t i o n of f r e e , i n t e r p a r t i c l e and s u r f a c e bound water i n r e l a t i o n t o the f i b e r m a t r i x i n c e n t r i f u g a t i o n and f i l t r a -f u g a t i o n t e s t s . 26 1 TABLE I I I . Mean f i l t r a f u g a t i o n values f o r AACC bran and f i b e r residues i n p r e l i m i n a r y e x p e r i -ments (g H ?0/g dw). Solvent treatment P a r t i c l e s i z e range, mm composite .25-.50 .50-1.0 1.0-2.0 None 1.19 1. 72 1. 24 1.18 Acetone 1.30 1. 34 1.40 1.32 Methanol/ acetone 1.40 1.66 1. 36 1.33 Neutral detergent 2.47 2. 70 3.47 1.00 A c i d detergent 3.10 3.32 4.50 1.15 Dupl i c a t e values obtained f o r each t e s t . 27 of l a r g e r p a r t i c l e s ( S c h a l l e r , 1978). The v a r i a b i l i t y i n the r e s u l t s f o r the s o l v e n t t r e a t e d samples was a t t r i b u t e d to e x c e s s i v e oven d r y i n g which had been used d u r i n g the i n i t i a l sample p r e p a r a t i o n and caused s t r u c -t u r a l damage (Eastwood, 1978). S i n c e Southgate's methanol/acetone e x t r a c t i o n removed more s o l u b l e m a t e r i a l than the acetone treatment of Eastwood and M i t c h e l l (1976), (see Table I ) , i t was c o n c l u d e d South-gate's method would be more u s e f u l f o r o b t a i n i n g the w a t e r - s o l u b l e and i n s o l u b l e components i n t a c t . I t was a l s o c o n c l u d e d the 1.00-2.00 mm p a r t i c l e s were too l a r g e and t h a t i t would be more p h y s i o l o g i c a l l y r e l e v a n t to i n c l u d e e v a l u a t i o n s of 0.12-0.25 mm diameter p a r t i c l e s . Based on these f i n d i n g s the i n i t i a l comparative study f o l l o w e d , w i t h the water b i n d i n g and water h o l d i n g r e s u l t s f o r AACC b r a n , apple pomace, and c a r r o t shown i n Tables IV-VI. The untreate'd c a r r o t showed the expected i n c r e a s e d water b i n d i n g v a l u e s f o r the s m a l l e r p a r t i c l e s and decreased water h o l d i n g v a l u e s . These decreased v a l u e s are expected due to the p a c k i n g f a c t o r o f s m a l l e r p a r t i c l e s i n a m a t r i x upon c e n t r i f u g a t i o n ( B r o d r i b b and Groves, 1978). The u n t r e a t e d bran and apple pomace v a l u e s d i d not show the same c l e a r t r e n d , p o s s i b l y due to g r e a t e r i n t e r f e r e n c e o f p r o t e i n s , waxes, l i p i d s and water s o l u b l e compounds which are a b l e to b i n d and h o l d water themselves (Southgate, 1976). The removal of some of these compounds by the methanol/acetone e x t r a c t i o n may be the reason these c a r r o t and apple pomace water b i n d i n g v a l u e s were lower than f o r the u n t r e a t e d , and water h o l d i n g v a l u e s h i g h e r . The e l e c -t r o n micrographs i n F i g u r e 2 and p o s i t i v e i o d i n e t e s t s i n d i c a t e t h i s treatment was i n e f f e c t i v e f o r s t a r c h removal. 28 TABLE IV. Mean values f o r water b i n d i n g and h o l d i n g t e s t s on AACC bran and f i b e r residues i n p r e l i m i n a r y experiments (g H 0/g dw).} Solvent treatment P a r t i c l e s i z e range. mm F i l t r a f u g e 1,0.00 xg Ce n t r i f u g e 14,000 xg None 0.12-0.25 0.25-0.50 0.50 - 1.00 1.61 1. 73 1. 77 3. 99 4.54 5.85 Methanol/ acetone 0.12-0.25 0.25-0.50 0.50-1.00 1.62 1.66 1. 73 4.12 4. 90 5.62 Neut r a l •detergent 0.12-0.25 0.25-0.50 0.50-1.00 3. 56 3. 30 3.47 9. 91 9. 80 12.02 A c i d • • detergent 0.12-0.25 0. 25-0.50 0.50-1.00 3, 3 4, 35 32 52 10.42 12.37 12. 26 "Duplicate values obtained f o r each t e s t . 29 TABLE V. Mean values f o r water b i n d i n g and h o l d i n g t e s t s on apple pomace and f i b e r residues i n p r e l i m i n a r y experiments Cg H^O/g dw], F i l t r a f u g e Centrifuge Solvent P a r t i c l e size — treatment range, mm . 1,000 xg 14,000 xg None 0 .12-0". 25 9.73 13.02 0.25-0.50 7.41 12.16 0.50-1.00 9.42 13.53 Methanol/ 0.12-0.2 5 5.99 40.16 ace tone 0.25-0.50 5.73 35.67 0.50-1.00 6.50 38.43 Neutral 0 .12-0 . 25 10. 06 56.00 detergent 0.25-0.50 11.44 58.93 0.50-1.00 12.01 65.62 A c i d 0.12-0.25 6.82 18.05 detergent 0.25-0.50 7.47 19.56 0.50-1.00 4.50 17.10 D u p l i c a t e values obtained f o r each t e s t . 30 TABLE V I . Mean v a l u e s f o r water b i n d i n g and h o l d i n g t e s t s on macerated c a r r o t s and f i b e r r e s i d u e s i n p r e l i m i n a r y experiments (g H 0/g dw) . S o l v e n t t r e a t m e n t P a r t i c l e s i z e range, mm F i l t r a f u g e C e n t r i f u g e 1,000 xg 14,000 xg None 0.12-0.25 0.25-0.50 0.50-1.00 10.23 8.40 7.64 12.25 15.34 21.01 Methanol/ acetone 0.12-0.25 0.25-0.50 0.50-1.00 5.73 4.95 5.92 26.42 32.09 31.19 N e u t r a l d e t e r g e n t 0.12-0.25 0.25-0.50 0-50-1.00 9.70 10.32 12.61 27.58 38.58 38.52 A c i d d e tergent 0.12-0.25 0-25-0.50 0-50-1. 00 3.03 4.41 2.71 12.85 13.24 14.79 D u p l i c a t e v a l u e s o b t a i n e d f o r each t e s t . 31 macerated c a r r o t FIGURE 2 . Scanning e l e c t r o n micrographs o f methanol/ acetone t r e a t e d AACC bran and macerated c a r r o t r e s i d u e s . 32 A m o d i f i c a t i o n of the methanol/acetone treatment was attempted (Southgate, 1978b), but was u n s u c c e s s f u l , t h e r e f o r e t h i s treatment was abandoned s i n c e i n t r o -duction of an enzyme f o r s t a r c h removal i n an aqueous system would also remove water s o l u b l e d i e t a r y f i b e r components. Recently p u b l i s h e d work by Selvendran et a l . (1979) c i t e drawbacks to Southgate's treatment, s t a t i n g c o p r e c i p i t a t i o n of i n t r a c e l l u l a r compounds, i n c l u d i n g s t a r c h , i s a problem p a r t i c u l a r l y f o r immature m a t e r i a l . The n e u t r a l detergent f i b e r (NDF) water h o l d i n g values of 9.8 g f^O/g dw f o r the AACC bran were comparable to 9.5 g H^O/g dw s u p p l i e d by AACC. There was no d e f i n i t e p a t t e r n f o r the NDF or ADF values of the d i f f e r e n t p a r t i c l e s i z e ranges and f i b e r sources. L i g h t microscopy l a t e r showed the n e u t r a l and a c i d detergent treatments cause clumping of p a r t i c l e s which explained the v a r i e d r e s u l t s f o r these residues (Robertson, 1978). I t was decided a d d i t i o n a l s i e v i n g of the f i b e r residues a f t e r d i g e s t i o n , before use i n p h y s i c a l p r o p e r t i e s t e s t s might e l i m i n a t e some of the v a r i a b i l i t y evident i n the i n i t i a l r e s u l t s . Since d u p l i c a t e readings only were taken, und a l l these metholology problems were encountered, no f u r t h e r s t a t i s t i c a l a n a l y s i s was done on the p r e l i m i n a r y data. B. D i e t a r y F i b e r Composition The d i e t a r y f i b e r a n a l y s i s r e s u l t s f o r the AACC bran, apple mesocarp, cabbage and c a r r o t s are shown i n Table VII. I t should be noted that the composition of p l a n t f i b e r w i l l vary with age, s p e c i e s , stage of growth (Eastwood and Robertson, 1978), and that the d i e t a r y f i b e r content of wheat bran on a f r e s h weight ba s i s i s much higher than f o r the other f i b e r sources due to TABLE VII. Dietary f i b e r a n a l y s i s f o r d i f f e r e n t sources and p a r t i c l e s i z e ranges (Mean + S.E.) S amp1e Dry matter, % P a r t i c l e s i z e range, mm F i b e r r e s i d u e , % d.w. NDF ADF Hemicellulose AACC bran 90.6 compos i t e 37. 53+0.48 a 3 10.59+0.05 a 26. 94 0.12-0.25 34. 21+0.25a 15.27-0.13 b 18. 94 0.25-0.50 35. 71+0.18a 9.65+0.07c 26. 06 0.50-1.00 42. 28+0.39b 11.04+0.02 a 31. 24 Apple 8.0 0.12-0.25 7. 82 + 0.12rn 4.95+0.08m 2.87 mesocarp 0.25-0.50 7. 66+0.29 m 4.88+0.08m 2.78 0.50-1.00 8. 09+0.39m 4.20+0.20n 3.89 Cabbage 9.5 0.12-0.25 8. 89+0.08r 7.21+0.05r 1.68 0.25-0.50 11. 61+0.17s 10.20+0.08 s 1. 41 0. 50- 1.00 12. 95+0.IO* 10.46+0.01 s 2.49 Carrot 10.6 0.12-0.25 7. 42+0.02X 8.24+0.09x 0.25-0.50 10. 12+0.37 y 11.03+0.44 y - - -0. 50-1.00 11. 17+0.28Z 11.39-0.27 y — D u p l i c a t e and r e p l i c a t e r e s u l t s obtained f o r each a n a l y s i s . Hemicellulose c a l c u l a t e d as d i f f e r e n c e NDF-ADF Values sharing a common s u p e r s c r i p t l e t t e r w i t h i n a column are not s i g n i f i c a n t l y d i f f e r e n t . (p>0. 05) . 34 g r e a t l y d i f f e r i n g water contents. 1. AACC bran The NDF value (37.5%) and the ADF value (10.6%) f o r the bran mixture as r e c e i v e d are lower than the AACC data p r o v i d e d (NDF 40.21, ADF 11.9%). Saunders and Hautala (1979) found the AACC bran to be 45.4% NDF. Mongeau (1978) found t h i s s t a n d ardized bran was 42.01. D i n t z i s et a l . (1979) c i t e d 44% i n s o l -ube d i e t a r y f i b e r f o r AACC bran by modified t e c h n i -ques and 12.2% ADF. None of these workers used a FiberTec system, a l l encountered s t a r c h removal problems with NDF a n a l y s i s and obtained s l i g h t l y higher values. The Tecator equipment appears cap-able of a more complete d i g e s t i o n with no enzyme step necessary f o r s t a r c h removal (Mossberg, 1979). Southgate et a l . (1978) reported the water s o l u b l e components of wheat bran were minimal and that the NDF technique a c c u r a t e l y measured the t o t a l d i e t a r y f i b e r content of wheat bran. Jeltema and Zabik (1979) found s i m i l a r r e s u l t s f o r these components of commer-c i a l wheat bran; 0.44% water s o l u b l e h e m i c e l l u l o s e s , 0.61% p e c t i n . Schweizer and Wursch (1979) used modi-f i e d enzymatic methods to show wheat bran was 39.2% i n s o l u b l e f i b e r and 7,4% s o l u b l e components, (compr-i s e d mainly of arabinose and xylose u n i t s ) . No data were a v a i l a b l e on the e f f e c t of p a r t i c l e s i z e on the f i b e r a n a l y s i s of the AACC sta n d a r d i z e d bran although t h i s research found p a r t i c l e s i z e range had a s i g n i f i c a n t e f f e c t on the NDF and ADF a n a l y s i s . The NDF values f o r the composite and the two smaller p a r t i c l e s i z e ranges were not s i g n i f i c a n t l y d i f f e r e n t from each other, but were 7% lower than the l a r g e s t 35 s i z e range. This i s i n general agreement with Butcher (1975), and H e l l e r et a l . (19 77) f i n d i n g s f o r wheat bran. T h e i r re'duced NDF values f o r more f i n e l y ground bran were a t t r i b u t e d to the greater release of t i g h t l y bound h e m i c e l l u l o s e s and p r o t e i n s due to g r i n d i n g and t h e r e f o r e i n c r e a s e d contact with the detergent s o l u t i o n . The ADF a n a l y s i s showed the opposite trend. The value f o r the l a r g e s t p a r t i c l e s i z e range (11.0%) was s i g n i f i c a n t l y greater than the next s i z e (9.61) but the ADF value f o r the s m a l l e s t p a r t i c l e s (15.3%) was s i g n i f i c a n t l y g r e a t e r than the l a r g e r s i z e ranges or the composite. Van Soest (19 73) s t a t e d that ADF may r e t a i n up to 15% r e s i s t a n t m i c e l l a r pentosans which should be more a v a i l a b l e i n a f i n e l y ground sample. B a i l e y et a l . (1978) and Robertson et a l . (1979) found ADF may contain r e s i d u a l p e c t i n s which would al s o more l i k e l y be present with a n a l y s i s of a f i n e l y ground sample since c e l l u l a r contents are more d i s -rupted. Robertson (1978) a l s o i n d i c a t e d these ADF sources of e r r o r which may augment values and reco-mmended s e q u e n t i a l NDF, ADF a n a l y s i s . The water i n s o l u b l e h e m i c e l l u l o s e content may be est-imated as the d i f f e r e n c e between the NDF and A£>F values (Robertson, 1978). The AACC bran composite contained 26.9% water i n s o l u b l e h e m i c e l l u l o s e s , which i s i n agreement with the 28.3% value AACC data c i t e d . This research found the 0.15-0.25 mm p a r t i c l e s contain-ed 18.9%, 0.25-0.50 mm contained 26.1%, and the 0.50-1.00 mm contained 31.2% water i n s o l u b l e h e m i c e l l u l o s e s . This trend was due to the more complete NDF and hemi-c e l l u l o s e d i g e s t i o n with s m a l l e r p a r t i c l e s . Jeltema and Zabik (1979) and Schweizer and Wursch (1979) 36 have shown the water i n s o l u b l e h e m i c e l l u l o s e s are gr e a t e r than 90% pentose-containing p o l y s a c c h a r i d e s (arabinose and x y l o s e ) . Cummings et a l . (1978) -p o s i t i v e l y c o r r e l a t e d these pentoses i n wheat bran with i n c r e a s e d f a e c a l b u l k i n g i n humans. Apple Mesocarp The NDF values of 7 . 82 -8.09% and ADF values of 4.2- •,_ 4.9%, f o r the d i f f e r e n t p a r t i c l e s i z e ranges, were comparable to those—of Van Soest (19 78b), NDF 7.6% and ADF 4.8%. Comparative r e s u l t s on the e f f e c t of apple f l e s h p a r t i c l e s i z e on d i e t a r y f i b e r composition were not a v a i l a b l e i n the l i t e r a t u r e . This study showed p a r t i c l e s i z e had no s i g n i f i c a n t e f f e c t on NDF, but there were s i g n i f i c a n t l y higher ADF values f o r the two s m a l l e r p a r t i c l e s i z e ranges. This follows the same trend as the bran ADF a n a l y s i s . Since apples contain 33% t o t a l p e c t i n (dw) i t i s p o s s i b l e c e r t a i n c e l l w a l l p e c t i n s could be more r e s i s t a n t i n more f i n e l y ground samples ( B a i l e y et a l . 1978). The i n s o l u b l e h e m i c e l l u l o s e content ranged from 2.8-3.9% f o r the d i f f e r e n t p a r t i c l e s i z e ranges as com-pared to 2.8% f o r a composite sample (Van Soest, 1978b). This i s a greater value than obtained f o r cabbage or c a r r o t . Southgate (1978a) l i s t e d apple f l e s h as 33% t o t a l d i e t a r y f i b e r , or approximately 25% water s o l u b l e components, i f the NDF i n s o l u b l e d i e t a r y f i b e r value i s s u b t r a c t e d . As Table I shows h i s p u b l i s h e d r e s u l t s f o r the water s o l u b l e components are i n c o n s i s t e n t . Cabbage The NDF values of 8.89-12.95% f o r the various p a r t -37 i c l e s i z e ranges, were lower than t;h-0se of Van Soest, 1978b (14.0%), and Schweizer and Wursch, 19 79 (14.2%), p o s s i b l y i n d i c a t i n g more complete d i g e s t i o n with the FiberTec system. The ADF r e s u l t s of 7.21-10.46% were a l s o lower; Van Soest (1978b) c i t e d 10.5%, Schweizer and Wursch (1979) 12.2% ADF. Each p a r t i c l e s i z e range of the cabbage had a s i g n i f i c a n t e f f e c t on the NDF a n a l y s i s whereas only the s m a l l e s t to the intermediate and l a r g e s t s i z e ADF residues were s i g -n i f i c a n t l y d i f f e r e n t . These r e s u l t s do f o l l o w the theory of more complete d i g e s t i o n with s m a l l e r p a r t -i c l e s i z e f o r both NDF and ADF analyses. The hemi-c e l l u l o s e content a l s o correspondingly decreases with each s m a l l e r p a r t i c l e s i z e range (2.5-1.7%). These r e s u l t s are i n general agreement with Schwerdtfeger (1979) who s t u d i e d the e f f e c t of p a r t i c l e s i z e on the i n s o l u b l e d i e t a r y f i b e r content of k a l e , using enzymatic techniques. He found the i n s o l u b l e compo-nents decreased by 20% s i n c e the s m a l l e r p a r t i c l e s had i n c r e a s e d contact with the enzyme. Schweizer and Wursch (1979) l i s t white cabbage, anal-yzed e n z y m a t i c a l l y , as 18.5% i n s o l u b l e f i b e r , 13.7% s o l u b l e components, 32.2% t o t a l d i e t a r y f i b e r with minimal (1-2%) i n s o l u b l e h e m i c e l l u l o s e s . B a i l e y et a l . (1978) i n d i c a t e cabbage i s 5.3% (dw) t o t a l p e c t i n , with 66% water s o l u b l e p e c t i c substances. Southgate (1978a) i n d i c a t e s the water s o l u b l e components of cabbage c o n s t i t u t e 15% with up to 50% pentose contain-i n g p o l y s a c c h a r i d e s and 50% p e c t i c substances but these values are not c o n s i s t e n t (see Table I ) . 4. Carrots The c a r r o t NDF r e s u l t s of 7.2-11.2% agreed with Van Soest (1978b), 9.2% f o r a composite sample. Each 38 p a r t i c l e s i z e range was s i g n i f i c a n t l y d i f f e r e n t with more complete d i g e s t i o n of the s m a l l e r p a r t i c l e s . For ADF a n a l y s i s only the s m a l l e s t p a r t i c l e s i z e was s i g n i f i c a n t l y d i f f e r e n t (P< 0.05) and lower, with the r e s u l t a n t 8.2% ADF comparable to the 8.0% ADF o f Van Soest (1978b) . An unexpected f i n d i n g was that ADF values f o r the two s m a l l e r p a r t i c l e s i z e ranges were s i g n i f i c a n t l y d i f f e r e n t from and greater than the corresponding NDF values. The Schweizer and Wursch (1979) composite c a r r o t a n a l y s i s showed the same trend (14.9% ADF, 13.9% NDF). They ex p l a i n e d c a r r o t contained n e g l i g i b l e amounts o f i n s o l u b l e h e m i c e l l u l o s e s and that a r t e f a c t s i n ADF procedure may l e a d to ADF values which are s l i g h t l y h igher than NDF values. Robertson et a l . (19 79) during an i n v e s t -i g a t i o n of the d i e t a r y f i b e r content of d i f f e r e n t v a r i e t i e s and ages o f c a r r o t s found the ADF value was only s l i g h t l y l ess than NDF and the d i f f e r e n c e was not s i g n i f i c a n t , f o r any given age and v a r i e t y . Van Soest (1978b) c i t e s 1.2% i n s o l u b l e h e m i c e l l u l o s e s , Matthee and Appledorf (19 78), 1. 0% and both s t a t e car-r o t i s mainly c e l l u l o s e and l i g n i n by detergent anal-y s i s . Theander and Aman (1979b) found c a r r o t had 2.5% water-s o l u b l e f i b e r components, Schweizer and Wursch (19 79) c i t e 13.5%, and Southgate (1978a) i n d i c a t e s approxi-mately 16%. A l l these researchers used d i f f e r e n t a n a l y t i c a l techniques. C. P h y s i c a l Property Tests 1. AACC bran Table VIII summarizes the r e s u l t s of the water bind-i n g and h o l d i n g t e s t s f o r AACC bran. As expected the f i l t r a f u g a t i o n and c e n t r i f u g a t i o n r e s u l t s d i f -TABLE V I I I . Water binding and holding c a p a c i t i e s of AACC bran and f i b e r residues of d i f f e r e n t p a r t i c l e s i z e s (mean + S.E.). Solvent Treatment P a r t i c l e s i z e , mm F i l t r a f u g e C e n t r i f u g e 1,000 xg 1, 000 xg 14,000 xg None 0.12-0.25 1.78-0.06 a 2 4. 88-0.40 a 5.16-0.29 a 0.25-0.50 1.73-0.08 a 5. 48-0.12 b 5.18-0.25 a 0.50-1.00 1.61-0.05 b 6. 27-0.05 c 5.98-0.31 b NDF 0.12-0.25 3.52-0.20 m 8. 22-0.91 m 8.08-0.501" 0.25-Q.50 3.17-0.01 m 10. 57-0.16 n 10.33-0.31 n 0.50-1.00 2.75-0.10 n 11. 82-0.43? 12.39-0.61? ADF 0.12-0.25 2.49-0.14 x 14. 54-0.47 x 11.68-0.65 x 0.25-0.50 2.6S-0.04 x y 16. 95-0.34 y 12.98-0.80 y 0.50-1.00 2.97-0.23 7 20. 08-0.40 z 12.76-0.48 y Values expressed as g H ?0/g dw. Experiments were repeated 4-8 times. Values sharing a common s u p e r s c r i p t l e t t e r w i t h i n a column are not s i g n i f i c a n t l y d i f f e r e n t (P>0.05). 40 f e r e d c o n s i d e r a b l y , the d i f f e r e n c e b e i n g the water h e l d by the f i b e r m a t r i x between p a r t i c l e s . The f i l t r a f u g a t i o n t e s t s were developed to study the way i n which the p a r t i c l e s bound water, as d i s -cussed e a r l i e r . For a given weight, f i n e l y ground p a r t i c l e s would have a g r e a t e r s u r f a c e area to b i n d water than would l a r g e r p a r t i c l e s ( S c h a l l e r , 1978). T - s t a t i s t i c s on the f i l t r a f u g a t i o n means i n d i c a t e d p a r t i c l e s i z e had a s i g n i f i c a n t e f f e c t between the s m a l l e s t and l a r g e s t p a r t i c l e s i z e ranges, f u r t h e r -more, a n a l y s i s o f v a r i a n c e r e s u l t s i n Table IX showed only treatment has a s i g n i f i c a n t e f f e c t on wheat bran's a b i l i t y to b i n d water. The u n t r e a t e d samples bound the l e a s t amount o f water (1.7-1.8g H 20/g dw) due to the presence o f s o l u b l e s u b s t a n c e s , p a r t i c u -l a r l y s t a r c h , which i n t e r f e r e w i t h d e t e r m i n a t i o n s (Southgate, 1976). The NDF p a r t i c l e s bound up to 3.5g r^O/g dw. When the bulk c a u s i n g pentose c o n t a i n -i n g h e m i c e l l u l o s e s were removed by ADF treatment the same s i z e p a r t i c l e c e l l u l o s e and l i g n i n s k e l e t o n c o u l d only b i n d 2.5g H 20/g dw. Br o d r i b b and Groves (1978) i n d i c a t e d t h a t very coarse wheat bran h e l d 7.3g H"20/g dw, very f i n e bran 3.9g H 20/g dw. This t r e n d , agrees w i t h the u n t r e a t e d c e n t r i f u g e d values (4.9-6.3g H 2o/g dw) although the p a r t i c l e s i z e s and i n i t i a l treatments were not i d e n t -i c a l . The u n t r e a t e d p a r t i c l e s h e l d l e s s water i n the f i b e r m a t r i x than the NDF o r ADF c e n t r i f u g e d r e s i d u e s due to the presence o f s o l u b l e s u b s t a n c e s . The NDF water h o l d i n g values (8.1-12.4g H 20/g dw) agree w i t h the 9.5g H 20/g dw value c i t e d f o r the composite AACC bran (AACC, 1976). There were no data a v a i l a b l e 41 TABLE IX. A n a l y s i s of varia n c e of water b i n d i n g and h o l d i n g c a p a c i t i e s of AACC bran and f i b e r r e s i d u e s , 1 Test Source of v a r i a t i o n Degrees of freedom Mean square F - r a t i o F i l t r a f u g e , l,000xg Treatment 2 P a r t i c l e s i z e 2 TxP 4 Residual 48 T o t a l 56 7.655 0. 615 1. 216 0. 821 9.324 ** 0.749 n.s, 1.481 n.s, C e n t r i f u g e , l,000xg Treatment 2 672.12 41.942 ** P a r t i c l e s i z e 2 85.06 5.295 ** TxP 4 67.83 4.223 ** Residual 48 T o t a l 56 Cent r i f u g e 14,000xg Treatment 2 406.69 P a r t i c l e s i z e 2 5.20 TxP 4 16.74 Residual 48 7.53 T o t a l 56 53.992 ** 0.690 n.s, 2.223 ** "These data are shown i n Table VIII ftft Denotes s i g n i f i c a n c e at P<.01 42 on the e f f e c t of p a r t i c l e s i z e on water h o l d i n g capacity, of so l v e n t t r e a t e d samples i n v i t r o , although human st u d i e s do i n d i c a t e l a r g e r bran p a r t i c l e s have a grea t e r e f f e c t on s t o o l weight (Brodribb and Groves, 1978). The ADF samples were able to h o l d more water than the NDF p a r t i c l e s due t o i t h e more r i g i d , 3-dimensional matrix of non-digest-i b l e c e l l u l o s e - l i g n i n that was maintained. The c e n t r i f u g a t i o n r e s u l t s were more d i f f i c u l t to i n t e r p r e t from the s t a t i s t i c a l analyses. T - t e s t r e s u l t s i n d i c a t e d a s i g n i f i c a n t d i f f e r e n c e between the c e n t r i f u g e speeds f o r the ADF residues only, and s i g n i f i c a n t d i f f e r e n c e s based on p a r t i c l e s i z e . A n a l y s i s of variance showed treatment, p a r t i c l e s i z e , and the i n t e r a c t i o n term were s i g n i f i c a n t f o r the c e n t r i f u g e 1000 xg t e s t . The s i g n i f i c a n t i n t e r a c t i o n term i s d i f f i c u l t to e x p l a i n since no general trend was found when treatment and p a r t i c l e s i z e were p l o t t e d . I t should be noted that t h i s technique gave i n c o n s i s t e n t r e s u l t s and a d d i t i o n a l t e s t s were re q u i -red s i n c e at t h i s low speed water removal was not always complete. Table IX i n d i c a t e s that the c e n t r i -fuge 14,000 xg treatment e f f e c t was s i g n i f i c a n t , p a r t i c l e s i z e was not, but the i n t e r a c t i o n term was s i g n i f i c a n t . There does not appear to be an explan-a t i o n f o r t h i s i n t e r a c t i o n except that uneven data sets were used which can a f f e c t s t a t i s t i c a l a n a l y s i s adversely (Fanous, 1980). 2. Apple Mesocarp Untreated f r e e z e - d r i e d apple contains approximately 301 p e c t i c substances, which are of a charged nature and a f f e c t water b i n d i n g c a p a c i t y ( B a i l e y et a l . 1-978). 43 This property i s very evident i n the water b i n d i n g r e s u l t s shown i n Table X. The untreated p a r t i c l e s bound up to 19.9g ^ O / g dw, whereas the NDF samples bound 6.7-7.7g H^O/g dw. The ADF treatment removed the i n s o l u b l e h e m i c e l l u l o s e s and p e c t i n s , thereby reducing the water b i n d i n g values to 4.3-5.0g H^O/g dw. T - s t a t i s t i c s and a n a l y s i s of v a r i a n c e r e s u l t s i n d i c a t e d that water bindi n g a b i l i t y was not s i g n i -f i c a n t l y a f f e c t e d by p a r t i c l e s i z e . The g e l l i n g a c t i o n of p e c t i c substances i s an impor-tant property of f r u i t s (Van Buren, 1979), but i n t e r -f eres with coherent p e l l e t formation, t h e r e f o r e no r e s u l t s were obtained f o r the untreated c e n t r i f u g e d apple samples, as shown i n Table X. The NDF mat-r i c e s h e l d up to 43.5g H^O/g dw when c e n t r i f u g e d at 1000 xg and 33.3g H 20/g dw when c e n t r i f u g e d at 14,000 xg. These high values may be due to the high l e v e l of arabinose c o n t a i n i n g i n s o l u b l e h e m i c e l l u -loses apples c o n t a i n (Theander and Aman, 1979a), which Van Buren (1979) c i t e s as most e f f e c t i v e i n water absorption. T - s t a t i s t i c s and a n a l y s i s of variance r e s u l t s i n d i c a t e d that p a r t i c l e s i z e d i d not have a s i g n i f i c a n t e f f e c t but NDF treatment and c e n t r i f u g e speed d i d . The ADF r e s u l t s d i d not show the same tr e n d . T - t e s t s i n d i c a t e d c e n t r i f u g a t i o n speed was not a s i g n i f i c a n t f a c t o r whereas p a r t i c l e s i z e was at 14,000 xg. In Table XI a n a l y s i s of variance demonstrates NDF and ADF treatment d i d have a s i g n i f i c a n t e f f e c t but p a r t i c l e s i z e d i d not. The ADF water h o l d i n g values of 14.7-20.4g H 20/g dw were gre a t e r than f o r the other f i b e r sources on a dry weight b a s i s , but the n o n - l i g n i f i e d apple s t r u c -ture i s fermentable and t h e r e f o r e has minimal a f f e c t TABLE X, Water binding and holding c a p a c i t i e s of macerated apple mesocarp and f i b e r residues of d i f f e r e n t p a r t i c l e s i z e s (mean + S.E.). Solvent Treatment P a r t i c l e s i z e , mm F i l t r a f u g e C e n t r i f u g e 1,000 xg 1,000 xg 14,000 xg None 0.12-0.25 18.08-1.69 a 2 0.25-0.50 19.95-2.38 a 0-50-1.00 16.49-1.79 a NDF 0.12-0.25 7 - 51-0.47 m 43.51-3.85 m 32.62-0.75 m 0.25-Q.50 6.68-0.061" 33.58-0.87 m 33.30-1.921" 0.50-1.00 7.74-0.86 m 35.35-2.19 m 29.70-2.15 m ADF 0 .12-0.25 5.03-0.32 x 18.76-1.12 x 19.74-0.90 x 0.25-0.50 4.37-0.19 x 16.65-0.34 x 14.73-0.53y 0 .50-1.00 4.33-0.26 x 20.38 ±2.44 x 16.55-0.30 z Values expressed as g H 20/g dw. Experiments were repeated 4-8 times. Values sharing a common s u p e r s c r i p t l e t t e r w i t h i n a column are not s i g n i f i c a n t l y d i f f e r e n t (P>0.05). 45 TABLE xi. -Analysis of variance of water binding and h o l d i n g c a p a c i t i e s of macerated apple mesocarp and f i b e r r e s i d u e s . Source of Degrees of Mean Test v a r i a t i o n freedom square F - r a t i o F i l t r a f u g e , l.OOOxg Treatment 2 P a r t i c l e s i z e 2 TxP 4 Residual 55 T o t a l 64 1152 . 8 4.27 11. 95 29.322 39.315 ** 0.146n.s, 0.407n.s, C e n t r i f u g e , l,000xg Treatment P a r t i c l e s i z e TxP Residual T o t a l 1 2 2 20 25 1994.4 18. 05 2 . 03 7.77 256.47 ** 2 . 32" n, s , 0.26 n.s C e n t r i f u g e , 14,-000xg Treatment P a r t i c l e s i z e TxP Residual T o t a l 1 2 2 15 20 859. 5 20.26 1. 09 8. 91 96.50 ** 2.27 n.s 1.12 n.s, 'These data are shown i n Table X. Denotes s i g n i f i c a n c e of P<,01 46 on f a e c a l weight (Cummings e t ' a l . 19 78) . „••.-._... 3, Cabbage The water bindi n g and h o l d i n g r e s u l t s are l i s t e d i n Table X I I . Untreated cabbage p a r t i c l e s bound 5.5-7,6g H^O/g dw, f o l l o w i n g the theory of i n c r e a s e d b i n d i n g c a p a c i t y with s m a l l e r p a r t i c l e s , although s o l u b l e p o l y s a c c h a r i d e s i n t e r f e r e d with determina-t i o n s CSchaller, 1978). The NDF p a r t i c l e s had a greater exposed s u r f a c e area of parenchyma c e l l s and v a s c u l a r bundles. The water b i n d i n g values i n c r e a s e d to 14.7-18.5g H 20/g dw. The more s t r i n g e n t ADF t r e a t -ment removed i n s o l u b l e h e m i c e l l u l l o s e s , with the remaining l e a f t i s s u e b i n d i n g 3.0-3.3g H^O/g dw, and p a r t i c l e s i z e no longer had a s i g n i f i c a n t e f f e c t . The a n a l y s i s of variance (Table XIII) of the f i l t r a -f u g a t i o n t e s t s i n d i c a t e d treatment had a s i g n i f i c a n t e f f e c t whereas p a r t i c l e s i z e d i d not, o v e r a l l . The c e n t r i f u g a t i o n r e s u l t s f o r untreated f r e e z e - d r i e d cabbage ranged from 26.5- 39. 2g H 20/g dw depending on c e n t r i f u g e speed and p a r t i c l e s i z e . T - s t a t i s t i c s i n d i c a t e d that p a r t i c l e s i z e only had a s i g n i f i c a n t e f f e c t between the s m a l l e s t and l a r g e s t s i z e range. The NDF water h o l d i n g values (71.6-105g H 20/g dw) show cabbage's s u p e r i o r a b i l i t y f o r matrix formation i n the small i n t e s t i n e . Recent metabolic s t u d i e s i n d i c a t e d cabbage powder was i d e a l f o r fermentation promotion but had minimal water h o l d i n g c a p a c i t y i n the l a r g e i n t e s t i n e (Van Soest, 1978c). These r e s u l t s a l s o i n d i c a t e that the water h o l d i n g c a p a c i t y of ADF was. g r e a t l y reduced (8.8-10. Ig H 20/g dw). T - t e s t s showed c e n t r i f u g a t i o n speed d i d not a f f e c t ADF r e s u l t s and p a r t i c l e s i z e only had a s i g n i f i c a n t e f f e c t at TABLE X I I , Water b i n d i n g and h o l d i n g c a p a c i t i e s of macerated c a b b a g e ^ n d f i b e r r e s i d u e s o f d i f f e r e n t p a r t i c l e s i z e s (mean + S.E.). S o l v e n t P a r t i c l e F i l t r a f u g e C e n t r i f u g e Treatment s i z e , mm : 1,000 xg 1,000 xg 14,000 xg None 0.12- 0.25 7.63' 0.57 a 2 29.67-0.87 a 26. 49-0. 9 6 a 0.25- 0. 50 6. 70-0. 6& 39.18*1.20 b 32. 44-0. 8 5 b 0.50- 1.00 5. 53*0. 20 c 38.27-1.21 b 32. 21-0. 8 2 b NDF 0.12-0.25 18.46-1.00 m 111.96-4.97 m 104. 97-2. 0 3 m 0. 25- 0. 50 14.67-0.16 n 81.05-5.37" 72. 17*1. 9 6 n 0. 50-1.00 16.98-0.32P 83. 36- 2. 0 3 n 71. 60*2. 8 0 n ADF 0.12-0.25 3.26-0.16 x 8.76*0.40 x 8. 99*0. 3 8 x 0.25-0.50 2.99-0.06 x 9.52-0.46 x 10. 15*0. soy 0.50-1.00 3.29-0.22 x 9. 96-0.71 x 9. 85*0. 5 3 ^ *Values expressed as g H^O/g dw... Experiments were repeated 4-8 ti m e s . Values s h a r i n g a common s u p e r s c r i p t l e t t e r w i t h i n a column are not s i g n i f i c a n t l y d i f f e r e n t (P> 0.05). 48 TABLE X I I I . A n a l y s i s of vari a n c e of \vater b i n d i n g and water h o l d i n g c a p a c i t i e s of macer-ated cabbage and f i b e r r e s i d u e s . Test Source of Degrees of v a r i a t i o n freedom Mean square F - r a t i o F i l t r a f u g e , Treatment 2 584.63 67.99 ** l,000xg P a r t i c l e s i z e 2 27.53 3.20 n.s. TxP 4 5. 34 0.62 n.s. Res i d u a l 32 8.59 T o t a l 40 C e n t r i f u g e , Treatment 2 25047.0 900.96 ** l,000xg P a r t i c l e s i z e 2 139.91 5.03 * TxP 4 629.33 22.64 A * Res i d u a l 32 27. 80 T o t a l 40 C e n t r i fuge, Treatment 2 19984.0 1593.6 * A 14,000xg P a r t i c l e s i z e 2 273.07 21. 76 A A TxP 4 692.80 55. 25 A * Res i d u a l 32 12.54 T o t a l 40 These data are shown i n Table XII Aft Denotes s i g n i f i c a n c e o f P<.01 Denotes s i g n i f i c a n c e of P<.05 49 14,000 xg. The a n a l y s i s of v a r i a n c e r e s u l t s f o r cabbage c e n t r i f u g e t e s t s i n Table XII were d i f f i c u l t to evaluate due to s i g n i f i c a n c e at P<.05 of treatment, p a r t i c l e s i z e and i n t e r a c t i o n term f o r both 1000 and 14,000 xg c e n t r i f u g e treatments. I t should be noted great d i f f i c u l t y was experienced with the p r e c i s i o n of the c e n t r i f u g e t e s t s due to cabbage's very high water h o l d i n g c a p a c i t y and the inherent problems with t h i s method. 4. Carrots The c a r r o t water b i n d i n g and h o l d i n g values presented i n Table XIV are s i m i l a r to the cabbage r e s u l t s except that the values f o r c a r r o t are lower. Cabbage has a s i g n i f i c a n t amount o f h e m i c e l l u l o s e s with arabinose si d e chains, which have e x c e l l e n t h y d r o p h i l i c charac-t e r i s t i c s (Van Buren, 1979) whereas c a r r o t i s mainly c e l l u l o s e and l i g n i n . The f i l t r a f u g e r e s u l t s show NDF p a r t i c l e s bound up to 10.2g H^O/g dw. The more s t r i n g e n t ADF treatment reduced the b i n d i n g c a p a c i t y of c a r r o t to 3.5-3.8g ti^O/g dw. T - s t a t i s t i c s demon-s t r a t e d p a r t i c l e s i z e only had a s i g n i f i c a n t d i f f e r -ence i n water b i n d i n g and h o l d i n g c a p a c i t i e s between the s m a l l e s t and l a r g e s t p a r t i c l e s f o r untreated and NDF samples only. The a n a l y s i s of variance f o r c a r r o t f i l t r a f u g a t i o n data (Table XV) i n d i c a t e d that treatment and p a r t i c l e s i z e had a s i g n i f i c a n t o v e r a l l e f f e c t . Table XV a l s o shows treatment had a s i g n i f i c a n t , e f f e c t f o r both c e n t r i f u g e speeds, whereas p a r t i c l e s i z e d i d not. T - s t a t i s t i c s on means f o r each t e s t c o n d i t i o n i n d i c a t e d r e s u l t s were s i g n i f i c a n t l y d i f f e r e n t f o r d i f f e r e n t p a r t i c l e s i z e s . The p a r t i c l e matrices f o r untreated samples h e l d 28.1-32.8g H^o/g dw. With the s o l u b l e p o l y s a c c h a r i d e s removed the NDF residues h e l d TABLE XIV. Water b i n d i n g and h o l d i n g t e s t s f o r m a c e r a t e d c a r r o t and f i b e r r e s i d u e s o f d i f f e r e n t p a r t i c l e s i z e s (mean + S . E . ) 1 S o l v e n t Treatment P a r t i c l e s i z e , mm F i l t r a f u g e C e n t r i f u g e 1,000 xg 1, 000 xg 14,000 xg None 0.12-0.25 7.09- 0. 2 7 a 2 29. 56-0.88 a 28.06-0.84 3 0.25-0. 50 6.96-0.33 a b 32. 84-0.54 b 30.76-0.88 b 0.50-1.00 6.14-0.22 b 29. 3 8 t i . 6 3 a 30.59-0.73 b NDF 0.12-0.25 10.17-0.16 m 48. 00-1.95 m 44.60 t1.89 m 0.25-0.50 9.90-0.10 m 43. 09-0.62" 4 0 . 3 3 - 2 . l l n 0.50-1.00 8.34-0.15 n 38. 07-1.06? 38.99-1.72P ADF 0.12-0.25 3.48^0.18 x 10. 80-1.79 x 10.90-0.82 x 0.25-0.50 3.78-0.07 x 13. 52-0.43 x 12.65-0.44 7 0.50-1.00 3.48-0.18 x 9. 23-1.33 y 7.35-1.12 z Values expressed as g H^O/g dw. Experiments were r e p e a t e d 4-8 times. Values s h a r i n g a common s u p e r s c r i p t l e t t e r w i t h i n a column are not s i g n i f i c a n t l y d i f f e r e n t (P>0.05). 51 TABLE XV. A n a l y s i s of variance of water b i n d i n g and h o l d i n g c a p a c i t i e s of macerated c a r r o t and f i b e r r e s i d u e s . Test Source of v a r i a t i o n Degrees of freedom Mean square F - r a t i o F i l t r a f u g e , 1,OOOxg Treatment 2 P a r t i c l e s i z e 2 TxP 4 Residual 61 T o t a l 69 202.85 18.94 4. 36 2.15 94.42 ** 8.82 ** 2.03 n.s, Ce n t r i f u g e , 1,OOOxg Treatment P a r t i c l e s i z e TxP Res i d u a l T o t a l 2 2 4 61 69 2698.9 26.49 107.55 206.64 13.061 ** .128 n.s .520 n.s C e n t r i fuge, 14,OOOxg Treatment 2 P a r t i c l e s i z e 2 TxP 4 Residual 61 T o t a l 69 1927.6 43.91 164.49 243.93 7.902 ** .180 n.s, .674 n.s, These data are shown i n Table XIV. Denotes s i g n i f i c a n c e at P<.01 52 up to 48.Og H 20/g dw, f o r the smallest p a r t i c l e s i z e range and lowest c e n t r i f u g e speed. The water holding c a p a c i t i e s of ADF matrices were reduced to 7.4-10.8g H 20/g dw. The cabbage values were s i m i l a r , with one important d i f f e r e n c e , carrot's c e l l u l o s e backbone contains 1-21 l i g n i n which would reduce f e r m e n t a b i l i t y and d i g e s t i b i l i t y i n the human colon (Van Soest, 1978a). 5 . Summary Table XVI summaries the water binding and holding r e s u l t s f o r the four f i b e r sources on a fresh weight b a s i s . Although the f r u i t and vegetables had greater water binding and holding c a p a c i t i e s on a d r i e d weight b a s i s , bran by v i r t u e of i t s higher f i b e r content and % dry matter binds and holds more water as measured by i n v i t r o methods ( H e l l e r and Hackler, 1977). The AACC bran 0.50-1.0 mm p a r t i c l e s bound 1.5g H 20/g fr e s h weight (fw) without solvent treatment and l . l g H 20/g fw a f t e r ADF treatment, whereas i n v i t r o d i g e s t i o n reduces the f r u i t and vegetables' water binding capa-c i t y d r a s t i c a l l y . Metabolic studies i n d i c a t e con-centrated f r u i t and vegetable f i b e r sources have a minimal f a e c a l b u l k i n g e f f e c t due to b a c t e r i a l f e r -mentation i n the large i n t e s t i n e , but may have hypo-cholesterolemic p r o p e r t i e s (Jenkins et a l . , 1979). Sources of concentrated f r u i t and vegetable f i b e r could be the wastes of the apple j u i c e industry (Dreyer and Van der Walt, 1979) or carr o t j u i c e pro-duction (Schweizer and Wursch, 1979). The published values on water h o l d i n g c a p a c i t i e s of various-food f i b e r sources by McConnell et a l . (1974) were found to be i n c o r r e c t by H e l l e r and Hackler TABLE XVI. C a l c u l a t i o n of water bi n d i n g and ho l d i n g c a p a c i t i e s of the 0.50-1.0 mm p a r t i c l e s i z e range of the f i b e r sources on a f r e s h weight basis (g H 0/g f r e s h m a t e r i a l ) . 1 Solvent Water bindin g Water h o l d i n g Sample treatment c a p a c i t y c a p a c i t y AACC bran None 1.46 5.42 NDF 1.05 4. 75 ADF 1.14 1.28 Apple None 1. 32 3.00 3 mesocarp NDF 0. 05 0.19 ADF 0.015 0.06 Cabbage None 0 . 53 3.06 NDF 0.21 0.88 ADF 0. 033 0.098 Carrot None 0.65 3.24 NDF 0.099 0.46 ADF 0.041 0.088 WBC or WHC of = WBC or WHC of g f i b e r residue i n % dw raw m a t e r i a l f i b e r residue A 1 g raw m a t e r i a l 100 Cen t r i f u g e 14,000xg values used f o r c a l c u l a t i o n . Estimated value due to p e c t i n i n t e r f e r e n c e . 54 (1977). There were no comparable p u b l i s h e d v a l u e s f o r the w a t e r h o l d i n g c a p a c i t i e s o f the f r u i t and ve g e t a b l e f i b e r s o u r c e s . The r e s u l t s f o r u n t r e a t e d a p p l e , cabbage and c a r r o t i n d i c a t e they may have a s i g n i f i c a n t m a t r i x f o r m a t i o n a b i l i t y w i t h o t h e r foods d u r i n g passage from the stomach through the s m a l l i n t e s t i n e (Holloway e t a l . , 1978). The NDF and ADF treatment reduced t h e i r w a t e r h o l d i n g c a p a c i t y to a minimal l e v e l , f o r example cabbage h e l d 3.1g H^O/g fw, b e f o r e i n v i t r o d i g e s t i o n but O.lg H^O/g fw a f t e r ADF tr e a t m e n t . The AACC b r a n , 0.50-1.0 mm p a r t i c l e s h e l d 5.4g H^O/g fw b e f o r e s o l v e n t treatment and 4.1g H^O/g fw a f t e r methanol-acetone e x t r a c t i o n . These val u e s are h i g h e r than the e s t i m a t e d 2.9g H 20/g raw b r a n , a f t e r acetone d r y i n g o f H e l l e r and H a c k l e r (1977). They s t a t e the val u e w i l l v a ry depen-dent on bran p r o d u c t . AACC c i t e d 3.4g/g fw f o r NDF t r e a t e d , composite, AACC s t a n d a r d i z e d b r a n , but s u p p l i e d no data on the e f f e c t o f p a r t i c l e s i z e on water h o l d i n g c a p a c i t y . The AACC b r a n , NDF r e s i d u e s w ater h o l d i n g c a p a c i t i e s ranged from 2.7-4.7g H 20/g fw f o r the s m a l l e s t t o l a r g e s t p a r t i c l e s i z e ranges. Due to h e m i c e l l u l o s e l o s s e s on ADF treatment the water h o l d i n g c a p a c i t y o f AACC bran was reduced to 1.3g H 20/g fw, but the s k e l e t a l c e l l u l o s e l i g n i n m a t r i x was s t i l l i n d i g e s t i b l e , had a b u l k i n g e f f e c t and i s e x c r e t e d by humans ( D i n t z i s e t a l . , 1979a). D. M i c r o s t r u c t u r e Scanning e l e c t r o n microscopy o f the f i b e r r e s i d u e s con-f i r m e d the e r o s i v e a c t i o n o f the s o l v e n t t r e a t m e n t s and e l u c i d a t e d subsequent d i f f e r e n c e s i n water h o l d i n g c a p a c i t i e s . 55 The AACC bran micrographs are shown i n Figure 3. Since bran i s a mature and senescent p l a n t t i s s u e , i t i s a h i g h l y ordered s t r u c t u r e with l i g n i f i c a t i o n (Saunders, 1978). The presence of the s t a r c h granules from the adhering endosperm tends to mask the w a l l s t r u c t u r e of the p e r i c a r p l a y e r s i n the untreated sample. These l a y e r s , the epidermis one c e l l l a y e r t h i c k at the outer edge, followed by s e v e r a l t h i n , shrunken ones and then a more r i g i d aleurone l a y e r are more evident with the NDF micrograph. This i n s o l u b l e d i e t a r y f i b e r has the s t a r c h granules and other s o l u b l e substances removed from the endosperm p r o t e i n matrix i n d i c a t i n g areas water may now occupy. This micrograph i s s i m i l a r to one by Rasper (1979b) f o r e n z y m a t i c a l l y prepared hard wheat bran. The ADF micrograph i s s i m i l a r to those of D i n t z i s et a l . (1979) who found the recovered AACC wheat bran from human faeces g r e a t l y changed i n appearance with the p e r i c a r p l a y e r s f o l d e d and c u r l e d , although the bran was able to maintain i t s s t r u c t u r e and has areas i n which water may continue to r e s i d e . A very d i f f e r e n t type of s t r u c t u r e i s evident i n the apple mesocarp micrographs shown i n Figure 4. Since the f r u i t i s the ripened ovary of the p l a n t i t i s l a r g e l y comprised of parenchyma t i s s u e , with a p o o r l y developed v a s c u l a r system as i s evident i n the untreated sample. It should be noted these samples were f r e e z e - d r i e d i n p r e l i m i n a r y treatment t h e r e f o r e some s t r u c t u r a l damage i s evident. With the NDF and ADF micrographs a shrinkage e f f e c t on the d e l i c a t e s t r u c t u r e i s very evident. The untreated p a r t i c l e s bound 19.95g f^O/g dw whereas the ADF m a t e r i a l i s only able to b i n d 4.37g t^O/g dw. The apple pomace micrographs i n Figure 5 are s i m i l a r to the apple mesocarp. In the untreated f r e e z e - d r i e d sample the middle l a m e l l a r e gion between two primary FIGURE 3, Scanning e l e c t r o n micrograph's of AACC bran and f i b e r r e s i d u e s . FIGURE 4. Scanning e l e c t r o n micrographs of macerated apple mesocarp and f i b e r r e s i d u e s . FIGURE 5. Scanning e l e c t r o n micrographs of apple pomace and f i b e r r e s i d u e s , 62 c e l l w a l l s i s more evident. This area i s r i c h i n p e c t i c substances and has the c e l l u l o s e f i b e r s l a i d down ran-domly i n a matrix of h e m i c e l l u l o s e s (Southgate, 1976). The s i z e range of the two untreated apple c e l l s i n d i -cates the s i z e range of apple parenchyma c e l l s (50-500 mm diameter). The cabbage micrographs are shown i n Figure 6. With the l e a f s t r u c t u r e of cabbage there i s a loose arrangement of parenchyma c e l l s i n t e r s p e r s e d with v a s c u l a r bundles which are l i g h t l y l i g n i f i e d and r i c h i n t h i c k walled collenchyma c e l l s . In the untreated sample the primary xylem t i s s u e i s evident as h e l i c a l c y l i n d e r s which maintain s t r u c t u r e w i t h i n expanding t i s s u e . With the removal of the s o l u b l e substances, i n the NDF residue these c o i l e d and open c a v i t i e s are more evident. These p a r t i c l e s themselves are able to bind 18g F^O/g sample and h o l d 80 g/g as a matrix. With the ADF treatment the water h o l d i n g c a p a c i t y i s decreased s i n c e the e r o s i v e a c i d treatment caused c o i l s to u n r a v e l . The c a r r o t micrographs shown i n Figure 7 are very s i m i l a r to cabbage i n that they are both d i c o t p l a n t s consumed at an immature stage of growth, except that t h i s i s a root s t r u c t u r e . The v a s c u l a r bundles are s c a t t e r e d through a matrix of parenchyma t i s s u e i n the untreated f r e e z e - d r i e d sample. This xylem t i s s u e i s l i g h t l y l i g n -i f i e d , s i n c e the c a r r o t i s u s u a l l y eaten before secondary t h i c k e n i n g occurs. In the NDF and ADF micrographs the same type of s t r u c t u r a l c o r r o s i o n i s evident as f o r the cabbage. E. R h e o l o g i c a l Experiments The d i s p e r s i o n s of AACC bran, were evaluated at 37°C, human apple pomace and c a r r o t body temperature, i n order FIGURE 6. Scanning e l e c t r o n micrographs of macerated cabbage and f i b e r residues. FIGURE 7, Scanning e l e c t r o n micrographs o f macerated c a r r o t and f i b e r r e s i d u e s . 67 to be physiologically relevent and elucidate their function in f l u i d systems. When aqueous dispersions of 1-4% concentrations were prepared using these fiber sources the s o l i d materials gradually settled to the bottom except for the apple pomace dispersions. 1. AACC bran The r i g i d bran p a r t i c l e s were d i f f i c u l t to disperse in water, therefore a 60% w/w sucrose solution with a s p e c i f i c gravity of 1.229 was used. Relative v i s c o s i t y was expressed as the quotient of the dis-persion v i s c o s i t y and solvent v i s c o s i t y . These dis-persions gave unusual results for steady shear flow, possibly due to physical adsorption of sucrose by the cellulose of the bran, thereby lowering the v i s c o s i t y of the sucrose solution (Mizrahi, 1979). Despite these interactions some general trends were observed in Figure 8. Increasing the concentration of the bran in the dispersion did result in a s i g n i f i c a n t increase in the r e l a t i v e v i s c o s i t y from 1.1 for a 1% dispersion to 14.0 for a 12% slurry. The quadratic equation n r e l=l.508-0.52c+0.12c 2 (6) was f i t t e d to the pooled data from the two p a r t i c l e size ranges to form the curve observed.. Due to clumping of NDF and ADF p a r t i c l e s these samples could not be evaluated. 2. Apple Pomace A l l aqueous dispersions exhibited time-independent non-Newtonian behavior. Since the flow curve of this type of f l u i d is not l i n e a r , in that the r a t i o of shear stress to shear rate i s not constant, apparent v i s c o s i t y is the term used. The dispersions dis-played shear-thinning flow behavior, in that, 6 8 14 1 2 10 II O u z2 6 > > T— < 4 4 6 8 10 . C O N C E N T R A T I O N , % D. M. 12 Figure 8. R e l a t i v e v i s c o s i t y of d i s p e r s i o n s of n a t i v e bran (.12-.50 mm) i n 60% (w/w) sucrose at 37°C. The mean and standard e r r o r are shown at the concentrations t e s t e d . 69 apparent v i s c o s i t y decreased with i n c r e a s i n g shear rate according to the power-law r e l a t i o n . The power-law parameters f o r the steady shear flow behavior of the apple pomace d i s p e r s i o n s are summarized i n Table XVII. The 0.12-0.25 mm p a r t i c l e s d i s p e r s i o n s gave some unusual m values with the 21 d i s p e r s i o n t h i n n e r than the 1 and 31 at y • 1 s " 1 , although a l l data followed the power-law c l o s e l y . A least-squares f i t o f the power-law f u n c t i o n to the data showed the c o e f f i c i e n t of determination values (r ) a l l greater than 0.9. Figure 9 shows the expected apparent v i s -c o s i t y b u i l d i n g e f f e c t with i n c r e a s i n g c o n c e n t r a t i o n of 0.25-0.50 mm p a r t i c l e s . Carrot Since the f r e e z e - d r i e d , untreated c a r r o t powder was d i f f i c u l t to disperse i n water a 601 w/w sucrose s o l -u t i o n was a l s o used. Figure 10 shows that i n c r e a s i n g the c o n c e n t r a t i o n and s i z e of the p a r t i c l e s d i d have a s i g n i f i c a n t e f f e c t on r e l a t i v e v i s c o s i t y whereas shear rate d i d not. At a shear rate of 100 s " 1 , comparable to those experienced i n mixing or pouring, the v i s c o s i t y of the sucrose s o l u t i o n was 0.3 p o i s e whereas the 1% d i s p e r s i o n had a r e l a t i v e v i s c o s i t y of 1.8-2.2 poise f o r the two p a r t i c l e s i z e ranges. Summary Since none of the NDF or ADF residues of the four f i b e r sources formed s t a b l e d i s p e r s i o n s at low concen-t r a t i o n s , large amounts of d i g e s t e d sample were r e q u i -red, and the untreated d i s p e r s i o n s gave unexpected r e s u l t s , i t was concluded no f u r t h e r i n f o r m a t i o n could be obtained from a d d i t i o n a l r h e o l o g i c a l experiments. TABLE XVIJ. Power-law parameters f o r steady shear flow of aqueous apple pomace d i s p e r s i o n s at 37°C. Dis p e r s i o n cone. p a r t i c l e s i z e , mm Consistency Coef., n - ? dyne sec cm Flow behavior index C o e f f i c i e n t of determination 1 2 3 4 0 .12-0.25 0 .12-0.25 0 .12-0.25 0.12-0.25 5.16 3.17 3. 58 1. 70 0. 42 3.17 0. 30 0. 40 0. 98 0. 96 0. 99 0. 99 2 0.25-Q.50 1.06 3 0.25-0.50 1.54 4 0 . 25-0. 50 4. 71 0.59 0.91 0.36 0.99 0.26 0.99 71 - l i I 10 100 1000 S H E A R R A T E ( s _ 1 ) FIGURE 9. Rheogram f o r f l o w b e h a v i o r o f aqueous d i s p e r s i o n s o f apple pomace a t 37°C. P a r t i c l e s i z e s are .25-.50 mm a t concent-r a t i o n s o f 2, 3 and 4%. 72 10 100 1000 S H E A R R A T E ( s _ 1 ) FIGURE 10. Rheograms f o r r e l a t i v e v i s c o s i t y of d i s p e r -sions of macerated c a r r o t i n 601 w/w sucrose s o l u t i o n s at 37°C. P a r t i c l e s i z e s are .25-.50 mm ( s o l i d ) and .12-.25 mm (open) at concentrations of 1, 2 and 31. 73 CONCLUSIONS This study e l u c i d a t e d f u n c t i o n a l p r o p e r t i e s of four morpho-l o g i c a l l y d i f f e r e n t food f i b e r sources. The wheat bran f i b e r residues by v i r t u e of the lower moisture content and higher i n d i g e s t i b l e d i e t a r y f i b e r content, bound and h e l d the most water. The apple, cabbage and c a r r o t f i b e r residues demonstrated they d i d not exert a s i g n i f i c a n t b u l k i n g e f f e c t a f t e r i n v i t r o d i g e s t i o n . The l i t e r a t u r e i n d i c a t e s f r u i t and vegetable f i b e r sources may be r e s p o n s i b l e f o r other s p e c i f i c p h y s i o l o g i c a l e f f e c t s (Jenkins et a l . 1979). The Van Soest NDF and ADF treatments and the FiberTec extrac-t i o n system produced i n s o l u b l e d i e t a r y f i b e r r e s i d u e s , with e x c e l l e n t r e p r o d u c i b i l i t y , s u i t a b l e f o r p h y s i c a l property t e s t i n g . Southgate's methanol/acetone e x t r a c t i o n s , to o b t a i n the water s o l u b l e and i n s o l u b l e d i e t a r y f i b e r components i n t a c t , were un s u c c e s s f u l and now are not recommended (Selvendran et a l . , 1979). P a r t i c l e s i z e exerted a s i g n i f i -cant e f f e c t on NDF and ADF a n a l y s i s of AACC bran, cabbage and c a r r o t , but not on apple mesocarp. The bran and apple meso-carp contained a g r e a t e r p r o p o r t i o n of b u l k - c o n t r i b u t i n g h e m i c e l l u l o s e s than cabbage or c a r r o t . The water b i n d i n g and h o l d i n g c a p a c i t i e s , as measured by f i l t r a f u g a t i o n and c e n t r i f u g a t i o n , d i f f e r e d s i g n i f i c a n t l y f o r each f i b e r source. The f i l t r a f u g a t i o n technique devel-oped was more p r e c i s e . The c e n t r i f u g a t i o n t e s t had poor r e p r o d u c i b i l i t y , p a r t i c u l a r l y f o r samples c o n t a i n i n g water s o l u b l e h y d r o p h i l i c components. Scanning e l e c t r o n micro-scopy of the d i f f e r e n t residues was an e x c e l l e n t technique, with minimal sample p r e p a r a t i o n , f o r e l u c i d a t i n g the micro-s t r u c t u r a l d e t a i l and areas water might occupy i n a f i b e r residue. 74 The cabbage NDF residues with a l a r g e exposed surface area of parenchyma c e l l s and v a s c u l a r bundles h e l d up to lOOg f^O/g dw sample. A n a l y s i s of variance r e s u l t s i n d i c a t e d p a r t i c l e s i z e d i d not have a s i g n i f i c a n t e f f e c t on the water b i n d i n g c a p a c i t i e s of bran, apple and cabbage, nor on the water h o l d i n g c a p a c i t i e s of bran, apple and c a r r o t . Treat-ment e f f e c t was s i g n i f i c a n t f o r a l l f i b e r sources and water r e l a t i o n t e s t s . This research has c l a r i f i e d the r e l a t i o n s h i p between s t r u c -t u r a l components o f i n s o l u b l e d i e t a r y f i b e r residues and water r e l a t i o n s t u d i e s . In concluding t h i s d i s c u s s i o n i t should be noted that there i s no proven r e l a t i o n s h i p between these i n v i t r o t e s t s and the i n s i t u human a c t i o n they seek to p o r t r a y . LITERATURE CITED 75 American A s s o c i a t i o n of Cerea l Chemists, 19 76. AACC c e r t i -f i e d food grade wheat bran a n a l y t i c a l data. 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