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Effect of maturity and variety on the textural quality of green snap beans Martens, Victor Jake 1973

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THE EFFECT OF MATURITY AND VARIETY ON THE TEXTURAL QUALITY OF GREEN SNAP BEANS by VICTOR JAKE MARTENS B.S.A., 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 , 1968 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n the Department o f Food S c i e n c e We a c c e p t t h i s t h e s i s as c o n f o r m i n g to t h e r e q u i r e d s t a n d a r d THE UNIVERSITY OF BRITISH COLUMBIA A p r i l , 1973 In presenting t h i s thesis i n p a r t i a l fulfilment of the requirements for an advanced degree at the University of B r i t i s h Columbia, I agree that the Library s h a l l make i t freely available for reference and study. I further agree that permission for extensive copying of t h i s thesis for scholarly purposes may be granted by the Head of my Department or by his representatives. I t i s understood that copying or publication of t h i s thesis for f i n a n c i a l gain s h a l l not be allowed without my written permission. Department of Food Science The University of B r i t i s h Columbia Vancouver 8, Canada Date A p r i l 25, 1973 i . ABSTRACT R h e o l o g i c a l measurements on i n t a c t f r e s h snap beans ( P h a s e o l u s v u l g a r i s v.) and p u r e e s made f r o m raw beans were u s e d t o a s s e s s t h e e f f e c t o f v a r i e t y and s i e v e s i z e on t h e t e x t u r a l c h a r a c t e r i s t i c s o f g r e e n snap b e a n s . Seed l e n g t h , p e r c e n t a g e d r y m a t t e r and p h y s i c a l f i b e r measurements were u s e d as t e x t u r a l q u a l i t y i n d i c a t o r s . F o u r v a r i e t i e s o f g r e e n snap beans ( T e n d e r c r o p , R a i n i e r , H a r v e s t e r and BBL 290) were t e s t e d i n 1971 and 1972. E ach v a r i e t y was h a r v e s t e d f i v e t i m e s i n each y e a r . A d v e r s e e n v i r o n m e n t a l c o n d i t i o n s i n 1971 c a u s e d bean t e x t u r a l q u a l i t y t o be h i g h e r i n 1972 t h a n i n 1971. The f o u r v a r i e t i e s t e s t e d showed s i g n i f i c a n t d i f f e r e n c e s w i t h R a i n i e r e x h i b i t i n g t h e b e s t t e x t u r a l q u a l i t y w h i l e H a r v e s t e r g e n e r a l l y showed t h e p o o r e s t q u a l i t y . T e s t s i n v o l v i n g t h e r e s i s t a n c e t o s h e a r i n g o f i n t a c t bean pods were c a r r i e d o ut u s i n g t h e O t t a wa T e x t u r e M e a s u r i n g System and t h e Food T e c h n o l o g y C o r p o r a t i o n ' s T e x t u r e T e s t S ystem ( f o r m e r l y t h e Kramer s h e a r p r e s s ) . V i s c o s i t y t e s t s were p e r f o r m e d on p u r e e s composed o f m a c e r a t e d raw g r e e n bean t i s s u e and w a t e r . R e s u l t s were o b t a i n e d from s p r e a d t e s t u s i n g a s i m p l i f i e d Adams-type c o n s i s t o m e t e r and f r o m r o t a t i n g c o a x i a l c y l i n d e r t e s t s u s i n g a B r o o k f i e l d RVT S y n c h r o - L e c t r i c V i s c o m e t e r f i t t e d w i t h a s m a l l sample a d a p t e r . The B r o o k f i e l d d a t a were t h e n f i t t e d t o t h e power-law e q u a t i o n . R h e o l o g i c a l p a r a m e t e r s showed h i g h l y s i g n i f i c a n t i n t e r r e l a t i o n s h i p s i n most i n s t a n c e s . V i s c o u s p r o p e r t i e s o f p u r e e s ( s p r e a d , m, n_ and y i e l d s t r e s s ) were h i g h l y c o r r e l a t e d w i t h p e r c e n t a g e d r y m a t t e r o f t h e b e a n s . Peak f o r c e r e a d i n g s o f t h e Kramer s h e a r p r e s s and t h e O t t a w a T e x t u r e M e a s u r i n g System were s i g n i f i c a n t l y c o r r e l a t e d w i t h a l l t e x t u r a l q u a l i t y and v i s c o m e t r i c p a r a m e t e r s . i i i . TABLE OF CONTENTS PAGE L I S T OF TABLES v -L I S T OF ILLUSTRATIONS v i . ACKNOWLEDGEMENTS v i i i . INTRODUCTION 1 LITERATURE REVIEW 3 T e x t u r a l a t t r i b u t e s 3 O b j e c t i v e t e x t u r e t e s t s 4 Q u a l i t y d e t e r m i n a t i o n 5 S t r u c t u r a l c h a r a c t e r i s t i c s i n f l u e n c i n g b e a n t e x t u r e 6 F a c t o r s a f f e c t i n g v i s c o m e t r i c b e h a v i o r o f p u r e e s 8 P o w e r - l a w f l o w model 10 TEST PROCEDURES 11 H a r v e s t i n g p r o c e d u r e s 11 Q u a l i t y t e s t i n g p r o c e d u r e s 11 R h e o l o g i c a l t e s t s 12 D a t a t r a n s f o r m a t i o n 14 A n a l y t i c a l methods 14 RESULTS AND DISCUSSION 16 Bean t e x t u r a l q u a l i t y 16 Y e a r 17 V a r i e t y 17 S i e v e S i z e 20 V i s c o m e t r i c d a t a 32 i v. RESULTS AND DISCUSSION CONTINUED PAGE F a c t o r s a f f e c t i n g bean p u r e e v i s c o s i t y 34 O t t a w a T e x t u r e M e a s u r i n g System and Kramer s h e a r p r e s s r e s u l t s 40 F a c t o r s a f f e c t i n g s h e a r i n g f o r c e o f g r e e n beans 40 SUMMARY 4 2 L I S T OF REFERENCES 44 APPENDIX A 50 APPENDIX B 56 L I S T OF TABLES TABLE I Means and s t a n d a r d d e v i a t i o n s f o r s e l e c t e d m a t u r i t y and r h e o l o g i c a l p a r a m e t e r s o f f r e s h g r e e n b eans as a f f e c t e d by y e a r I I Means and s t a n d a r d d e v i a t i o n s f o r s e l e c t e d m a t u r i t y and r h e o l o g i c a l p a r a m e t e r s o f f r e s h g r e e n beans f o r f o u r v a r i e t i e s I I I Means and s t a n d a r d d e v i a t i o n s f o r s e l e c t e d m a t u r i t y and r h e o l o g i c a l p a r a m e t e r s o f f r e s h g r e e n beans i n f o u r s i e v e s i z e s IV D e t e r m i n a t i o n o f p a r t i c l e s i z e and d i s t r i b u t i o n o f s c r e e n e d raw g r e e n b e a n p u r e e FIGURE 1 2 3 4 5 6 7 8 L I S T OF ILLUSTRATIONS The e f f e c t o f s i e v e s i z e on t h e s e e d l e n g t h o f g r e e n snap beans i n T e n d e r -c r o p , R a i n i e r , H a r v e s t e r and BBL 290 v a r i e t i e s The e f f e c t o f s i e v e s i z e on t h e d r y m a t t e r c o n t e n t o f g r e e n snap beans i n T e n d e r c r o p , R a i n i e r , H a r v e s t e r and BBL 290 v a r i e t i e s The e f f e c t o f s i e v e s i z e on t h e ash c o n t e n t o f g r e e n snap beans i n T e n d e r -c r o p , R a i n i e r , H a r v e s t e r and BBL 290 v a r i e t i e s The e f f e c t o f s i e v e s i z e on t h e p h y s i c a l f i b e r c o n t e n t o f g r e e n snap b e a n s i n T e n d e r c r o p , R a i n i e r , H a r v e s t e r and BBL 290 v a r i e t i e s The e f f e c t o f s i e v e s i z e on t h e peak f o r c e v a l u e s o f t h e O ttawa T e x t u r e M e a s u r i n g System on whole g r e e n snap b e ans i n T e n d e r c r o p , R a i n i e r , H a r v e s t e r and BBL 290 v a r i e t i e s The e f f e c t o f s i e v e s i z e on t h e peak f o r c e v a l u e s o f t h e Kramer s h e a r p r e s s on whole g r e e n snap b e a n s i n T e n d e r c r o p , R a i n i e r , H a r v e s t e r and BBL 290 v a r i e t i e s The e f f e c t o f s i e v e s i z e on t h e s p r e a d v a l u e s o f t h e Adams-type c o n s i s t o m e t e r t e s t s on bean p u r e e s i n T e n d e r c r o p , R a i n i e r , H a r v e s t e r and BBL 290 v a r i e t i e s The e f f e c t o f s i e v e s i z e on t h e y i e l d s t r e s s v a l u e s o f t h e B r o o k f i e l d v i s c o -m e t e r on bean p u r e e s i n T e n d e r c r o p , R a i n i e r , H a r v e s t e r and BBL 290 v a r i e t i e s The e f f e c t o f s i e v e s i z e on t h e c o n s i s -t e n c y c o e f f i c i e n t (m) o f bean p u r e e s i n T e n d e r c r o p , R a i n i e r , H a r v e s t e r and BBL 290 v a r i e t i e s The e f f e c t o f s i e v e s i z e on t h e f l o w b e h a v i o r i n d e x (n) o f bean p u r e e s i n T e n d e r c r o p , R a i n i e r , H a r v e s t e r and BBL 290 v a r i e t i e s S h e a r s t r e s s vs r a t e o f s h e a r i n g as meas u r e d by B r o o k f i e l d v i s c o m e t e r on raw BBL 290 bean p u r e e P h o t o m i c r o g r a p h s o f s c r e e n e d m a c e r a t e d g r e e n bean t i s s u e on s c r e e n s o f : a) 28 mesh, b) 48 mesh, c) '100 mesh d) 200 mesh v i i i ACKNOWLEDGEMENTS The a u t h o r w i s h e s t o e x p r e s s h i s a p p r e c i a t i o n t o the f o l l o w i n g R e s e a r c h Committee Members f o r a s s i s t a n c e and a d v i c e i n t h i s s t u d y : P r o f e s s o r E . L. W a t s o n , my t h e s i s s u p e r v i s o r , Mr. A. R. M a u r e r , Canada D e p a r t m e n t o f A g r i c u l t u r a l R e s e a r c h S t a t i o n , A g a s s i z , who p r o v i d e d t h e g r e e n beans and t h e r e s e a r c h f a c i l i t i e s and w i t h h i s s t a f f , T. Watson and F . Swannee, c a r r i e d o u t some o f t h e t e s t s , D r . M. A. T u n g , t o g e t h e r w i t h L . R o b i n s o n , who a s s i s t e d i n t h e s t a t i s t i c a l a n a l y s i s o f t h e d a t a , D r . E. 0 . N y b o r g , D e p a r t m e n t o f A g r i c u l t u r a l E n g i n e e r i n g and D r . J . F . R i c h a r d s , D e p a r t m e n t o f Food S c i e n c e , f o r s e r v i n g on t h e c o m m i t t e e and r e v i e w i n g t h i s p a p e r . 1. INTRODUCTION G r e e n snap beans a r e t h e t h i r d most i m p o r t a n t p r o -c e s s i n g v e g e t a b l e c r o p i n B r i t i s h C o l u m b i a and i n C a n a d a , b e i n g e x c e e d e d o n l y by g r e e n peas and sweet c o r n i n p l a n t e d a c r e a g e and v a l u e . The a c r e a g e p l a n t e d t o g r e e n beans i s i n c r e a s i n g s l i g h t l y w h i l e c o r n a c r e a g e r e m a i n s r e l a t i v e l y c o n s t a n t and p e a a c r e a g e d e c l i n i n g . The B l u e Lake p o l e bean h a s , f o r many y e a r s , been t h e p r e d o m i n a n t snap bean v a r i e t y grown i n t h e P a c i f i c N o r t h w e s t . Bush bean v a r i e t i e s , s u i t a b l e f o r m e c h a n i c a l , h a r v e s t i n g , a r e i n c r e a s i n g l y p o p u l a r i n a r e a s where l a b o r c o s t s a r e h i g h . When compared w i t h t h e q u a l i t y o f B l u e Lake p o l e b e a n s , b u s h bean q u a l i t y has g e n e r a l l y been l o w e r a l t h o u g h i m p r o v e d bush bean v a r i e t i e s have been d e v e l o p e d r e c e n t l y . T h e s e new v a r i e t i e s must be t e s t e d t o d e t e r m i n e t h e i r s u i t a b i l i t y f o r m e c h a n i c a l h a r v e s t i n g and p r o c e s s i n g as w e l l as t h e i r consumer a p p e a l . Government q u a l i t y s t a n d a r d s f o r p r o c e s s e d g r e e n b e ans a r e g e n e r a l and r e q u i r e e x p e r i e n c e d j u d g e s f o r a c c u r a t e and s p e c i a l i n t e r p r e t a t i o n . R e g u l a t i o n s r e q u i r e t h a t Canada F a n c y g r e e n beans " p o s s e s s a v e r y good f l a v o r t y p i c a l o f young and t e n d e r b e a n s " w i t h young and t e n d e r b e i n g d e f i n e d as b e i n g " f u l 1 - b o d i e d f o r t h e v a r i e t y , t e n d e r and n o t f i b r o u s ; t h a t t h e s e e d s a r e i n t h e e a r l y s t a t e o f m a t u r i t y ; and t h a t n o t more t h a n 5%, by c o u n t , show e v i d e n c e o f s t r i n g s " ( C a n a d a , 1 9 6 3 ) . Q u a l i t y s t a n d a r d s f o r U n i t e d S t a t e s g r e e n beans a r e s i m i l a r l y d e f i n e d i n terms o f t e n d e r -n e s s , s e e d m a t u r i t y , and t o u g h s t r i n g c o u n t ( U n i t e d S t a t e s , 1 9 6 1 ) . Tough s t r i n g s and s e e d m a t u r i t y c a n be r e a d i l y d e t e r m i n e d by o b j e c t i v e means. However, t e n d e r n e s s i s t h e s u b j e c t i v e e v a l u a t i o n o f i n t e r a c t i o n s among numerous p h y s i c a l c h a r a c t e r i s t i c s . I f t h e s e c h a r a c t e r i s t i c s and t h e d e g r e e o f t h e i r i n t e r a c t i o n s a r e e s t a b l i s h e d , t e n d e r n e s s can be d e f i n e d q u a n t i t a t i v e l y . T h i s s t u d y was u n d e r t a k e n t o i n v e s t i g a t e some e f f e c t s o f m a t u r i t y and v a r i e t y on t h e t e x t u r a l q u a l i t y o f g r e e n snap beans as m e a s u r e d by o b j e c t i v e t e s t s . Rheo-l o g i c a l t e s t s were u s e d t o a s s e s s t h e i n t e r a c t i o n o f p h y s i c a l c h a r a c t e r i s t i c s r e l a t e d t o t e x t u r e . S h e a r i n g t e s t s were p e r f o r m e d on i n t a c t pods w h i l e v i s c o m e t r i c methods were a p p l i e d t o m a c e r a t e d bean t i s s u e . LITERATURE REVIEW Food q u a l i t y c an be c o n s i d e r e d i n terms o f a p p e a r -a n c e , f l a v o r and k i n e s t h e t i c s o r t e x t u r e ( K r a m e r , 1 9 7 2 ) . T h e s e p r o p e r t i e s , w h i c h a r e p e r c e i v e d i n d i v i d u a l l y , a r e i n t e g r a t e d by t h e b r a i n i n t o an o v e r a l l i m p r e s s i o n o f q u a l i t y . W h i l e a l l t h r e e p r o p e r t i e s a r e i m p o r t a n t i n d e t e r m i n i n g q u a l i t y , t h i s s t u d y w i l l c o n s i d e r o n l y t e x t u r a l a t t r i b u t e s . T e x t u r a l a t t r i b u t e s T e x t u r e i s a m e a n i n g f u l c o n c e p t o n l y when i n t e r -p r e t e d as an i n t e r a c t i o n o f t h e human b e i n g w i t h t h e m e c h a n i c a l p r o p e r t i e s o f t h e m a t e r i a l ( C o r e y , 1 9 7 0 ) . A b b o t t (1972) d e s c r i b e s t h e G e n e r a l Foods T e x t u r e P r o f i l e i n terms o f t h e t h r e e s t a g e s o f i n g e s t i o n : i n i t i a l , m a s t i c a t o r y and r e s i d u a l . The i n i t i a l s t a g e ( t h e f i r s t 1 t o 5 chews, d e p e n d i n g on t h e p r o d u c t ) i n v o l v e s t h e m e c h a n i c a l p r o p e r t i e s o f h a r d n e s s , b r i t t l e n e s s and v i s c o s i t y . The m a s t i c a t o r y s t a g e ( e x t e n d i n g t o t h e t i m e when t h e f o o d i s r e a d y t o be s w a l l o w e d ) may i n v o l v e gumminess, c h e w i n e s s and a d h e s i v e n e s s , i n a d d i t i o n t o t h e p r o p e r t i e s a s s e s s e d i n t h e i n i t i a l s t a g e . In t h e r e s i d u a l s t a g e , t h e f i n a l c o n d i t i o n o f t h e r e s i d u e and t h e d e g r e e o f p r o d u c t change d u r i n g m a s t i c a t i o n i s e v a l u a t e d . S p e c i f i c a t t r i b u t e s o f q u a l i t y c an be a s s o c i a t e d w i t h o b j e c t i v e p h y s i c a l o r c h e m i c a l c r i t e r i a . O b j e c t i v e t e s t s g e n e r a l l y have a h i g h e r d e g r e e o f a c c u r a c y , p r e c i s i o n 4. and r e p r o d u c i b i l i t y t h a n human j u d g e s who a r e o f t e n s u b j e c t t o d r i f t ( K r a m e r , 1 9 6 9 ) . However, t h e s u i t a b i l i t y o f an o b j e c t i v e t e s t ( e . g . t e x t u r e m e a s u r i n g d e v i c e ) can be d e t e r m i n e d o n l y by i t s d e g r e e o f c o r r e l a t i o n w i t h t h e human s e n s e s ( S z c z e s n i a k , 1 9 6 6 ) . O b j e c t i v e t e x t u r e t e s t s O b j e c t i v e t e x t u r e measurements can be c l a s s i f i e d as f u n d a m e n t a l , e m p i r i c a l and i m i t a t i v e ( S z c z e s n i a k 1 9 6 6 ) . Of t h e s e , t h e e m p i r i c a l t e s t s , w h i c h measure r h e o l o g i c a l c h a r a c t e r i s t i c s r e l a t e d t o t e x t u r a l q u a l i t y , a r e p o t e n t i a l l y u s e f u l . R h e o l o g i c a l p r o p e r t i e s o f a m a t e r i a l a r e t h o s e w h i c h a l l o w d e f o r m a t i o n and f l o w r e s u l t i n g f r o m a p p l i e d f o r c e s ( M o h s e n i n , 1 9 7 0 ) . Numerous e m p i r i c a l i n s t r u m e n t s have b e e n d e v e l o p e d t o measure v a r i o u s r h e o l o g i c a l b e h a v i o r . The S o c i e t y o f R h e o l o g y has d e f i n e d c o n s i s t e n c y as " t h a t p r o p e r t y o f a m a t e r i a l by w h i c h i t r e s i s t s perman-e n t change o f shape and i s d e f i n e d by t h e c o m p l e t e f l o w -f o r c e r e l a t i o n " ( S c o t t B l a i r , 1 9 6 9 ) . S z c z e s n i a k (1972) p l a c e s e m p i r i c a l cons i s t o m e t e r s , u s e d f o r e v a l u a t i n g t h e c o n s i s t e n c y o f s o f t f o o d s s u c h as p u d d i n g s and p u r e e s ( F i n n e y , 1972) i n t o two g e n e r a l s u b c l a s s e s : d e v i c e s w h i c h measure d i s t a n c e o f s p r e a d ( e . g . Adams c o n s i s t o m e t e r , B o s t w i c k c o n s i s t o m e t e r ) , and d e v i c e s w h i c h measure r e s i s t a n c e t o a r o t a t i n g s p i n d l e ( e . g . B r o o k f i e l d v i s c o m e t e r , Haake v i s c o m e t e r ) . 5. M u l t i - p u r p o s e u n i t s a r e u s e d t o p e r f o r m a v a r i e t y o f t e x t u r e t e s t s . By u s i n g d i f f e r e n t t e s t c e l l s , t h e Kramer s h e a r p r e s s and t h e Ottawa T e x t u r e M e a s u r i n g System a r e c a p a b l e o f s h e a r i n g , e x t r u d i n g and c r u s h i n g t e s t s among o t h e r s . I n s t r u m e n t s u s e d t o a s s e s s t e x t u r e do n o t a l l measure t h e same p r o p e r t y (Sherman, 1 9 7 0 ) . S i n c e t e x t u r e i s a c o m b i n a t i o n o f r h e o l o g i c a l p r o p e r t i e s , t h e d e c i s i o n as t o whi c h p a r a m e t e r s h o u l d be measured i s e x t r e m e l y i m p o r t a n t . D e c i s i o n s c an be b a s e d on i n t u i t i o n , e x p e r i e n c e o r r e s e a r c h . I f b a s e d on r e s e a r c h , t h e d e c i s i o n w i l l r e v e a l how t e x t u r a l c h a r a c t e r i s t i c s a r e a f f e c t e d by f a c t o r s i n f l u e n c i n g t h e p r o d u c t q u a l i t y , s u c h as t h e g r o w i n g c o n d i t i o n s , v a r i e t y , c h e m i c a l c o n s t i t u e n t s and p r o c e s s i n g ( S z c z e s n i a k , 1 9 6 6 ) . Q n a l i t y d e t e r m i n a t i o n Snap bean q u a l i t y i s d e t e r m i n e d by v a r i e t a l c h a r a c -t e r i s t i c s , t h e s t a g e o f m a t u r i t y and c l i m a t i c c o n d i t i o n s (Kramer e t a l . 1 9 4 9 ) . S e v e r a l government q u a l i t y s t a n d a r d s f o r g r e e n snap beans - - p e r c e n t a g e f i b e r , p e r c e n t a g e s e e d by w e i g h t , t o u g h s t r i n g s -- a r e d i r e c t l y r e l a t e d t o m a t u r i t y ( s e e A p p e n d i x A ) . Some r e s e a r c h e r s have i n v e s t i g a t e d bean q u a l i t y u s i n g p e r c e n t a g e s e e d as a m a t u r i t y c r i t e r i o n ( G o u l d , 1950b; G u y e r and K r a m e r , 1 9 5 2 ) . Seed l e n g t h i s a l s o a good i n d i c a t o r o f m a t u r i t y ( F a r k a s , 1967; M a u r e r , 1 9 7 1 ) . O t h e r s have e v a l u a t e d beans as t o f i b e r c o n t e n t and 6. t o u g h s t r i n g c o u n t . Ross e_t a l _ . (1956) f o u n d t h a t f i b e r c o n -t e n t and t o u g h s t r i n g s were d e p e n d e n t on v a r i e t y , s i z e and g r o w i n g c o n d i t i o n s . Bundy and Kramer (1959) s t a t e d t h a t p e r c e n t a g e f i b e r was n o t a good i n d i c a t o r o f c a n n e d o r f r o z e n g r e e n b e a n q u a l i t y i n 1958. Payment t o bean g r o w e r s i s b a s e d on s i e v e s i z e s e p a r a t i o n w h i c h does n o t t a k e f i b r o u s n e s s i n t o a c c o u n t . P r o c e s s o r s may snap a few beans t o a s s e s s s t r i n g i n e s s o r s e l e c t a sample f o r s e n s o r y e v a l u a t i o n . However, no r a p i d o b j e c t i v e q u a l i t y t e s t s have been a d o p t e d o f f i c i a l l y , a l t h o u g h r e s e a r c h has d e v e l o p e d numerous t e s t s w h i c h c o u l d be u s e d . K a t t a n and S h a r p (1970) u s e d f l o t a t i o n i n v a r y i n g a l c o h o l c o n c e n t r a t i o n s t o g r a d e snap beans and f o u n d t h a t a p p a r e n t d e n s i t y was i n v e r s e l y r e l a t e d t o s i e v e s i z e , s h e a r r e s i s t a n c e , f i b e r c o n t e n t and s e e d p e r c e n t a g e . Kramer (1951) d e v e l o p e d a r a p i d f i b e r t e s t c o r r e l a t e d c l o s e l y w i t h t h e o f f i c i a l U n i t e d S t a t e s Food and Drug A d m i n i s t r a t i o n method f o r f i b e r d e t e r m i n a -t i o n ( U n i t e d S t a t e s , 1 9 5 7 ) . Bundy and Kramer ( 1 9 5 9 ) , Kramer (1961) d e s c r i b e t h e s h e a r p r e s s as a t o o l f o r t h e r a p i d d e t e r m i n a t i o n o f t e x t u r e i n g e n e r a l and f i b e r c o n t e n t i n p a r t i c u l a r . Some t e s t s u s i n g t h e e x t r u s i o n p r i n c i p l e have been a t t e m p t e d b u t t e n d e r raw g r e e n beans have r e q u i r e d 3,000 t o 4,000 kg f o r c e f o r e x t r u s i o n (Bourne and M o y e r , 1 9 6 8 ) . S t r u c t u r a l c h a r a c t e r i s t i c s i n f l u e n c i n g bean t e x t u r e The t e x t u r e o f v e g e t a b l e t i s s u e i s i n f l u e n c e d by a b a l a n c e o f f a c t o r s u n i q u e f o r e a c h t i s s u e (Van B u r e n , 1 9 7 0 ) . 7. Beans a r e composed o f h e t e r o g e n e o u s c e l l s bound t o g e t h e r by c e r t a i n s u b s t a n c e s . The c o m p o s i t i o n o f t h e s e c e l l s and c e l l masses have c e r t a i n q u a l i t i e s w h i c h a f f e c t t e x t u r e . The f i r m n e s s o f t h e t i s s u e i s i n f l u e n c e d b y : (1) t h e m e c h a n i c a l s t r e n g t h and r i g i d i t y due t o s t r u c t u r a l e l e m e n t s and s u p p o r -t i n g members i n t h e c e l l w a l l i t s e l f , (2) t h e i n t e r c e l l u l a r f o r c e s c a u s i n g t h e c e l l s t o a d h e r e t o each o t h e r , and (3) t h e c e l l t u r g i d i t y r e s u l t i n g f rom t h e o s m o t i c p r e s s u r e o f t h e c y t o p l a s m ( M a t z , 1962; F i n n e y , 1969; M e y e r , I 9 6 0 ) . Somers (1965) assumes t h a t t h e c e l l w a l l s , composed e s s e n t i a l l y o f 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 amor-phous m a t r i x , a r e t h e p r i n c i p a l v i s c o e l a s t i c e l e m e n t s o f p l a n t t i s s u e . S t r i n g i n e s s and f i b r o u s n e s s a r i s e f rom t h e t h i c k e n e d c e l l w a l l s i n x y l e m , s c l e r e n c h y m a and c o l l e n c h y m a c e l l s . S c l e r e n c h y m a f i b e r s a p p e a r t o be e l a s t i c when s t r e t c h e d m e c h a n i c a l l y , w h i l e c o l l e n c h y m a f i b e r s t e n d t o e x h i b i t permanent d e f o r m a t i o n ( Sherman, 1 9 7 2 ) . The c e l l s f o r m a n e t w o r k w h i c h , by i n t e r a c t i o n w i t h c e l l c o n t e n t s , g i v e s t h e t i s s u e s t h e i r o v e r a l l v i s o c e l a s t i c p r o p e r t i e s . P e c t i c s u b s t a n c e s a r e o f t e n components o f t h e c e m e n t i n g s u b s t a n c e s between c e l l s . As s u c h , t h e y p l a y a r o l e i n c e l l u l a r a d h e s i o n w h i c h may be d e c r e a s e d s i g n i f i c a n t l y by a v e r y s m a l l change i n t h e p e c t i c s u b s t a n c e s p r e s e n t (Van B u r e n , 1 9 7 0 ) . T h i s may be t h e r e a s o n why r e s e a r c h e r s have n o t f o u n d a good r e l a t i o n s h i p between t e x t u r a l q u a l i t y and p e c t i n f r a c t i o n s i n b eans ( G o u l d , 1 9 5 0 c ) . S u b s t a n c e s o t h e r 8. t h a n p e c t i n may be i n v o l v e d . S t a r c h e s and c a l c i u m , a l t h o u g h n o t b e a r i n g a s i g n i f i c a n t r e l a t i o n s h i p t o t i s s u e t e x t u r e i n th e raw s t a t e , g e n e r a l l y i n f l u e n c e t h e t e x t u r a l p r o p e r t i e s o f c o o k e d v e g e t a b l e s (Van B u r e n , 1970; Sherman, 1 9 7 2 ) . A l t h o u g h f o o d s have p r o p e r t i e s w h i c h v a r y from one p o i n t t o a n o t h e r w i t h i n t h e i r mass ( F i n n e y , 1 9 6 9 ) , many f o o d s b e h a v e i n a p r e d i c t a b l e manner b u t w i t h c e r t a i n i n h e r e n t v a r i a b i l i t y . Kramer (1961) m e n t i o n s t h a t v a r i a b i l i t y between r e p l i c a t e s o f s h e a r p r e s s t e s t s on g r e e n beans i s 5% o r even g r e a t e r . F a c t o r s a f f e c t i n g v i s c o m e t r i c b e h a v i o r o f p u r e e s P u r e e s a r e composed o f two d i s t i n c t p h a s e s -- t h e p a r t i c l e s and t h e serum c o n t a i n i n g t h e s o l u b l e s o l i d s . The s u s p e n d e d p a r t i c l e s g r e a t l y a f f e c t t h e p u r e e v i s c o s i t y . Van Buren (1970) d e s c r i b e s v i s c o m e t r i c b e h a v i o r as p o s s i b l e i n t e r a c t i o n s i n v o l v i n g v a r i o u s m o l e c u l a r f o r c e s , s i m p l e m e c h a n i c a l c o l l i s i o n and o v e r l a p p i n g between p a r t i c l e s . Mason and B a r t o k (1959) o b s e r v e d t h e a c t i o n s o f v a r i o u s p a r t i c l e s i z e s and t y p e s s u s p e n d e d i n a l i q u i d and s u b j e c t e d t o r o t a -t i o n a l movements i n a c o a x i a l c y l i n d e r v i s c o m e t e r . I f l a r g e , i r r e g u l a r p a r t i c l e s a r e p r e s e n t , t h e s m a l l p a r t i c l e s may a c t as f l u i d s i n t h e v i c i n i t y o f t h e l a r g e r p a r t i c l e s . Some s m a l l p a r t i c l e s l i k e l y become e n t r a p p e d i n t h e s u r f a c e c a v i t i e s o f t h e l a r g e p a r t i c l e s t o m o d i f y t h e f l o w . The l a r g e p a r t i c l e s t e n d t o a l i g n t h e m s e l v e s i n t h e l a m i n a r f l o w and may a l s o u n d e r g o r o t a t i o n a l and t r a n s l a t i o n a l movements (Mason and B a r t o k , 1 9 5 9 ) . I r r e g u l a r i t i e s i n t h e p a r t i c l e s u r f a c e s may a l s o c a u s e t u r b u l e n c e i n t h e c o n t i n u o u s p h a s e (serum) o r i m m o b i l i z e some o f t h e serum w i t h i n t h e i n d e n t a t i o n s (Sherman 1 9 7 0 ) . In t h e s t a t i o n a r y s t a t e , f i b r o u s p a r t i c l e s may form a n e t w o r k w h i c h e x h i b i t s v i s c o e l e a s t i c b e h a v i o r ( C o r e y , 1970) When t h e s u s p e n s i o n o r d i s p e r s e d s y s t e m i s s u b s e q u e n t l y s u b j e c t e d t o s h e a r , t h e s t r u c t u r e b e g i n s t o b r e a k down w i t h t h e w e a k e s t bonds between t h e p a r t i c l e s b e i n g d i s r u p t e d f i r s t . The c o n t i n u o u s p h a s e a l s o a f f e c t s t h e r h e o l o g i c a l b e h a v i o r o f t h e p u r e e . Numerous s o l u b l e c e l l and c e l l w a l l c o n s t i t u e n t s , i n c l u d i n g p e c t i n s , s u g a r s , s t a r c h e s and c a l c i u m ( W a t s o n , 1968; M i z r a h i and B e r k , 1970; Van B u r e n , 1 9 7 0 ) , a f f e c t serum v i s c o s i t y t o v a r y i n g d e g r e e s . The v i s c o s i t y o f t h e d i s p e r s e d s y s t e m i s d i r e c t l y p r o p o r t i o n a l t o t h e v i s c o s i t y o f t h e c o n t i n u o u s p h a s e (Sherman, 1 9 7 0 ) . The c o n s i s t o m e t e r s u t i l i z e t h e h y d r o s t a t i c head o f t h e e n c l o s e d p u r e e t o i n i t i a t e f l o w down an i n c l i n e d p l a n e , o r o v e r a f l a t p l a t e . The l o w e r t h e s u r f a c e t e n s i o n o f a m a t e r i a l a p p l i e d t o a h o r i z o n t a l s u r f a c e , t h e g r e a t e r t h e s p r e a d i n g w i l l be (Charm, 1 9 6 2 ) . In t h e c a s e o f p u r e e s , t h e r e i s a l s o a c e r t a i n amount o f f l u i d and p a r t i c l e f r i c t i o n a s s o c i a t e d w i t h b o t h m o l e c u l a r and macro s t r u c t u r e (Charm, 1 9 6 2 ) . The f a c t o r s a f f e c t i n g t h e v i s c o s i t y o f a d i s p e r s i o n o f t e n o p e r a t e s i m u l t a n e o u s l y w i t h t h e n e t e f f e c t u s u a l l y b e i n g d i f f e r e n t i n m a g n i t u d e from t h e sum o f t h e i n d i v i d u a l c o n t r i b u t i o n s ( Sherman, 1 9 7 0 ) . Power-law f l o w model F r u i t and v e g e t a b l e p u r e e s a r e n o n - N e w t o n i a n i n t h e i r f l o w b e h a v i o r . Numerous models have been u s e d t o d e s c r i b e t h e v i s c o m e t r i c b e h a v i o r o f s u c h f l u i d s , c o n s i d e r e d to be p s e u d o p l a s t i c i n n a t u r e . The power-law e q u a t i o n b e s t d e s c r i b e s t h e b e h a v i o r o f p u r e e s ( W a t s o n , 1968; M i z r a h i and B e r k , 1970) : n T my where T s h e a r s t r e s s (dynes/cm ) s h e a r r a t e ( s e c ) m n f l o w b e h a v i o r i n d e x . TEST PROCEDURES T h i s study was c a r r i e d out i n c o - o p e r a t i o n with A. R. Maurer, vegetable r e s e a r c h s c i e n t i s t at the Canada Department of A g r i c u l t u r e Research S t a t i o n , A g a s s i z , B.C. H a r v e s t i n g procedure The green snap beans were grown at the Canada Department o f A g r i c u l t u r e Research S t a t i o n , A g a s s i z , B.C. Four v a r i e t i e s -- Tendercrop, R a i n i e r , H a r v e s t e r and BBL 290 -- were m e c h a n i c a l l y p l a n t e d i n adjacent p l o t s i n 1971 and 1972. Each v a r i e t y was h a r v e s t e d at f i v e d i f f e r e n t times over a three-week p e r i o d (approximately two h a r v e s t s per week) to ensure a n a t u r a l p r o g r e s s i o n of m a t u r i t y . Each h a r v e s t c o n s i s t e d of a l l pods from a 5 0 - f t l e n g t h of row ( r e p l i c a t e d three times) f o r each v a r i e t y . The pods were sep a r a t e d i n t o f o u r s i e v e s i z e groups: 2, 3+4, 5 and 6. Subsequent weight measurements of each s i e v e s i z e were used to determine y i e l d . Q u a l i t y t e s t i n g procedures Seed l e n g t h was determined f o r each s i e v e s i z e by measuring three developed seeds on each of 25 pods s e l e c t e d at random. A 25-g sample of i n t a c t bean pods was f o r c e d -a i r - d r i e d at 70°C to determine percentage dry matter. Another 25-g sample was f r o z e n f o r subsequent ash determina-t i o n . One-hundred grams of beans were a l s o f r o z e n f o r l a t e r a n a l y s i s of p h y s i c a l f i b e r by the blen d o r method (Kramer, 1 9 5 1 ) . R h e o l o g i c a l t e s t s T h r e e 150-g s a m p l e s o f i n t a c t bean pods were t e s t e d i n t h e O t t a w a . T e x t u r e M e a s u r i n g System (OTMS; V o i s e y , 1971) u s i n g a w i r e e x t r u s i o n c e l l and a 10 cm/min c r o s s h e a d s p e e d . The peak f o r c e r e a d i n g was s e l e c t e d f o r c o m p a r a t i v e p u r p o s e s . T h i s t e s t and o t h e r s m e n t i o n e d p r e v i o u s l y ( s e e d l e n g t h , p e r c e n t a g e d r y m a t t e r , p e r c e n t a g e ash and p e r c e n t a g e p h y s i c a l f i b e r ) were c a r r i e d out by Canada D e p a r t m e n t o f A g r i c u l t u r e p e r s o n n e l u n d e r t h e s u p e r v i s i o n o f A. R. M a u r e r . The f o l l o w i n g t e s t s were done i n d u p l i c a t e by t h e a u t h o r . The Food T e c h n o l o g y C o r p o r a t i o n ' s T e x t u r e T e s t System ( f o r m e r l y known as t h e Kramer s h e a r p r e s s ) o p e r a t i n g a t a downward c r o s s h e a d s p e e d o f 10 cm/min was u s e d w i t h 100-g s a m p l e s ( c u t t o 6.5 cm l e n g t h ) p l a c e d p e r p e n d i c u l a r t o t h e 10 b l a d e s i n t h e Kramer u n i v e r s a l t e s t c e l l . The peak f o r c e r e a d i n g was r e c o r d e d . S l u r r i e s were p r e p a r e d by b l e n d i n g 150 grams o f b e a n s , c u t i n 1 cm l e n g t h s , w i t h 50 grams o f w a t e r f o r f i v e m i n u t e s a t h i g h s p e e d i n a 4 - b l a d e W a ring B l e n d o r a t 15,000 rpm ( n o - l o a d s p e e d ) . The m a j o r p o r t i o n o f t h e s l u r r y (200 ml) was t h e n i m m e d i a t e l y p o u r e d i n t o an Adams-type c o n s i s -t o m e t e r ( D a v i s e t a l _ . , 1954) c o n s i s t i n g o f a p l a s t i c t r u n c a t e d cone c e n t e r e d on a p i e c e o f s h e e t g l a s s . The cone was t h e n l i f t e d m a n u a l l y f r o m t h e s u r f a c e and t h e s l u r r y a l l o w e d t o s p r e a d f o r 30 s e c o n d s . Two d i a m e t e r measurements were t a k e n a t r i g h t a n g l e s t o e a c h o t h e r and t h e a v e r a g e v a l u e r e c o r d e d as t h e " s p r e a d " . The s l u r r y was t h e n p l a c e d i n a b e a k e r and a l l o w e d t o r e m a i n a t room t e m p e r a t u r e f o r 10 m i n u t e s . A t h o r o u g h l y - m i x e d 10-ml sample was p l a c e d i n t o t h e s m a l l - s a m p l e a d a p t e r (SC4-13) o f a B r o o k f i e l d RVT S y n c h r o -L e c t r i c V i s c o m e t e r w i t h S p i n d l e #27 (gap w i d t h = 0.364 cm) and a l l o w e d t o r e a c h t h e r m a l e q u i l i b r i u m f o r 5 m i n u t e s . The s m a l l - s a m p l e a d a p t e r was k e p t a t 2 0 ° C . R e a d i n g s were t a k e n at 5 0 , 20, 10, 5, 2.5 and 1 rpm ( c o r r e s p o n d i n g t o s h e a r r a t e s o f 10.5 t o 0.21 s e c *) i n a d e c r e a s i n g s e r i e s . The f l u i d y i e l d s t r e s s was e s t i m a t e d from t h e d i a l r e a d i n g a t t a i n e d by s h e a r s t r e s s r e l a x a t i o n 2 m i n u t e s a f t e r t h e v i s c o m e t e r had been t u r n e d o f f f o l l o w i n g a measurement a t 1 rpm. R e a d i n g s were t h e n t a k e n i n an i n c r e a s i n g s e r i e s o f s h e a r r a t e s up t o 10.5 s e c-* . A l l r e a d i n g s were t a k e n by p l a c i n g t h e b r a k e on a f t e r a s p e c i f i e d number o f r e v o l u t i o n s f o r e a c h s p e e d and t h e n s w i t c h i n g o f f t h e motor f o r about 5 s e c o n d s between e a c h s p e e d . S u p p l e m e n t a r y s t u d i e s were c a r r i e d o u t on s e v e r a l p u r e e s t o d e t e r m i n e p a r t i c l e s i z e d i s t r i b u t i o n by wet s i e v i n g . S t a n d a r d s i e v e s u s e d were 28, 4 8 , 100, 150 and 200 mesh s c r e e n s . The f r a c t i o n s were c o l l e c t e d f rom e a c h s c r e e n and th e m a j o r i t y o f t h e s a m p l e s w e i g h e d a f t e r d r y i n g a t 7 0° C i n a vacuum oven t o d e t e r m i n e s i z e d i s t r i b u t i o n . The mean d i a m e t e r s o f p a r t i c l e s on a s c r e e n were c a l c u l a t e d u s i n g t h e f o l l o w i n g e q u a t i o n : 14. D 2 = / S x x S 2 where D 2 = p a r t i c l e d i a m e t e r on s c r e e n 2 S j = o p e n i n g s i z e i n s c r e e n 1 S 2 = o p e n i n g s i z e i n s c r e e n 2 S e v e r a l s a m p l e s were o b s e r v e d m i c r o s c o p i c a l l y t o d e t e r m i n e p a r t i c l e shape and s i z e . D a t a t r a n s f o r m a t i o n S h e a r s t r e s s and a p p a r e n t v i s c o s i t y v a l u e s were d e t e r m i n e d f o r t h e B r o o k f i e l d v i s c o m e t r i c r e a d i n g s . The Power-law c o n s t i t u t i v e e q u a t i o n , x = my" ( M o h s e n i n , 1970) was f i t t e d t o s h e a r s t r e s s and s h e a r r a t e v a l u e s . The f l o w c u r v e was e s t a b l i s h e d by t h e l e a s t - s q u a r e s - f i t method t o d e t e r m i n e m and n_ v a l u e s . A n a l y t i c a l methods D a t a was a n a l y z e d s t a t i s t i c a l l y u s i n g 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 ' s IBM 360/67 c o m p u t e r . Means and s t a n d a r d d e v i a t i o n s were o b t a i n e d f o r a l l t e s t s . S t u d e n t ' s t - t e s t was u s e d t o d e t e r m i n e w h e t h e r s i g n i f i c a n t d i f f e r e n c e s e x i s t e d among means o f d a t a t o a s s e s s t h e e f f e c t o f y e a r ( v a r i e t i e s and s i z e s p o o l e d ) , v a r i e t y ( a l l s i z e s f r o m b o t h y e a r s p o o l e d ) and s i e v e s i z e ( a l l v a r i e t i e s f rom b o t h y e a r s p o o l e d ) w h i l e t h e F - t e s t was u s e d t o a s s e s s d i f f e r e n c e s among v a r i a n c e s . S i m p l e l i n e a r c o r r e l a t i o n c o e f f i c i e n t s among a l l t e s t p a r a m e t e r s were a l s o o b t a i n e d and t e s t e d f o r s i g n i f i c a n c e a t t h e 1% and 5% l e v e l s ( S n e d e c o r and C o c h r a n , 1 9 6 7 ) , w i t h i n v a r i e t i e s , s i z e s , y e a r s as w e l l as on p o o l e d d a t a . A n a l y s i s of v a r i a n c e was n o t a p p l i e d t o t h e d a t a b e c a u s e t h e d a t a had numerous m i s s i n g v a l u e s and c o n t a i n e d e x t r e m e l y u n e q u a l sample s i z e s ( r a n g e from 0 t o 2 7 ) . 16. RESULTS AND DISCUSSION Bean t e x t u r a l q u a l i t y C a n a d i a n g r e e n bean r e g u l a t i o n s ( C a n a d a , 1963) do not a l l o w q u a l i t y t o be e x p r e s s e d i n n u m e r i c a l q u a n t i t i e s . The U n i t e d S t a t e s D e p a r t m e n t o f A g r i c u l t u r e q u a l i t y s t a n d a r d s f o r c a n n e d o r f r o z e n g r e e n beans ( U n i t e d S t a t e s , 1961) a l l o t 40 o u t o f 100 p o s s i b l e p o i n t s t o c h a r a c t e r . C h a r a c t e r r e f e r s t o m a t u r i t y as r e f l e c t e d i n s e e d d e v e l o p m e n t , f l e s h i n e s s o f th e pod and l a c k o f f i b r o u s n e s s • Seed l e n g t h , p e r c e n t a g e d r y m a t t e r and p e r c e n t a g e p h y s i c a l f i b e r ( M a u r e r , 1971) b e i n g r e l a t e d t o t h e m a t u r i t y o f g r e e n beans ( s e e A p p e n d i x A) were s e l e c t e d as q u a l i t y i n d i c e s . T h e r e were h i g h l y s i g n i f i c a n t c o r r e l a t i o n s ( r = 0.46 t o 0.77) among a l l t h e s e q u a l i t y i n d i c e s when t h e e f f e c t o f y e a r was e v a l u a t e d ( s e e T a b l e B l ) . When e f f e c t o f v a r i e t y was t e s t e d , t h e q u a l i t y p a r a m e t e r s were s i g n i f i c a n t l y i n t e r c o r r e l a t e d ( r = 0.61 t o 0.83) e x c e p t f o r p e r c e n t a g e p h y s i c a l f i b e r and p e r c e n t a g e d r y m a t t e r i n BBL 290 w h i c h were n o t r e l a t e d (P > 0.05) t o e a c h o t h e r ( s e e T a b l e s B3 and B4) . T h e r e were no s i g n i f i c a n t c o r r e l a t i o n s among t h e s e p a r a m e t e r s w i t h s i e v e s i z e s 2 and 3+4 a l t h o u g h the l a r g e r s i z e s p r o d u c e d h i g h l y s i g n i f i c a n t c o r r e l a t i o n s among a l l q u a l i t y p a r a m e t e r s ( s e e T a b l e s B5 and B 6 ) . In t h i s s t u d y , good t e x t u r a l q u a l i t y i s a s s o c i a t e d w i t h low v a l u e s o f s e e d l e n g t h , p e r c e n t a g e d r y m a t t e r and p e r c e n t a g e p h y s i c a l f i b e r . S h o r t s e e d s i n d i c a t e young beans and h i g h m o i s t u r e c o n t e n t s r e f l e c t t e n d e r and f l e s h y b e a n s . Low p h y s i c a l f i b e r c o n t e n t d e n o t e s t h e l i m i t e d d e v e l o p m e n t o r o c c u r r e n c e o f f i b e r s h e a t h c e l l s w h i c h a f f e c t bean t e x t u r e a d v e r s e l y . Y e a r The e f f e c t o f t r e a t m e n t y e a r on t e s t p a r a m e t e r s was d e t e r m i n e d u s i n g p o o l e d v a r i e t i e s and s i e v e s i z e s ( s e e T a b l e 1 ) . T h e r e was a s i g n i f i c a n t d i f f e r e n c e between 1971 and 1972 f o r a l l p a r a m e t e r s e x c e p t y i e l d s t r e s s v a l u e s . The mean y i e l d s t r e s s v a l u e s v a r i e d w i d e l y i n 1971, r e s u l t i n g i n a l a r g e s t a n d a r d d e v i a t i o n . Mean v a l u e s f o r s e e d l e n g t h , p e r c e n t a g e d r y m a t t e r , p e r c e n t a g e p h y s i c a l f i b e r , m, s h e a r p r e s s f o r c e and Ottawa T e x t u r e M e a s u r i n g System f o r c e were s i g n i f i c a n t l y h i g h e r i n 1971 t h a n i n 1972. P e r c e n t a g e a s h , s p r e a d and n v a l u e s were s i g n i f i c a n t l y l o w e r i n 1971. T h i s i n d i c a t e d t h a t beans grown i n 1972 e x h i b i t e d b e t t e r t e x t u r a l q u a l i t y t h a n 1971 b e a n s . H i g h e r mean t e m p e r a t u r e s and p o s s i b l e i n c r e a s e d s o i l m o i s t u r e s t r e s s e x p e r i e n c e d i n 1971 a f f e c t e d t h e q u a l i t y o f g r e e n snap b eans as r e p o r t e d by D r i j f h o u t ( 1 9 7 0 ) , K a l d y ( 1 9 6 6 ) , and M a u r e r e t a l . , ( 1 9 6 9 ) . V a r i e t y When s i e v e s i z e s were p o o l e d t o a s s e s s t h e e f f e c t o f v a r i e t y , s i g n i f i c a n t d i f f e r e n c e s i n a l l p a r a m e t e r s were d e t e c t e d among s e v e r a l v a r i e t i e s ( s e e T a b l e I I ) . Mean v a l u e s f o r p e r c e n t a g e d r y m a t t e r , p e r c e n t a g e f i b e r , y i e l d s t r e s s , peak s h e a r p r e s s f o r c e and Ottawa T e x t u r e M e a s u r i n g System 18. Table I. Means and standard deviations for selected maturity and rheological parameters of fresh green snap beans as affected by year. Parameters 1971 1972 Pooled Years Mean S. D. Mean S. D. Mean S.D. Seed Length (mm) 8. 38a 3. 19 6.88b 2. 53 7.58 2.95 Dry Matter ' (%) 10.5la 2. 59 7.77b 0. 98 8 .80 2. 21 Fiber (%) 0.97a 0. 44 0.69b 0. 25 0 . 82 0 . 38 Spread Test (cm) 17.7a 4. 0 21 . 2b 1. 7 20.4 2.8 Yield Stress (dynes/cm2) 30.9a 25. 2 19.3a 6. 7 20.0 8.8 m fdynes-secn _ -j cm* •) 117.5a 48. 5 52. 8b 14 . 0 63. 8 33.9 n 0. 186a 0 . 016 0.245b 0 . 024 0. 235 0. 032 Shear Press Force (lb) 919.a 135 . 831 . b 122. 898. 137. OTMS Force (lb) 706.a 99. 557 . b 64 . 624. 110. * Means within a particular parameter followed by the same letter are not significantly different (P < 0.05). 19. T a b l e I I . Means and s t a n d a r d d e v i a t i o n s f o r s e l e c t e d m a t u r i t y and r h e o l o g i c a l p a r a m e t e r s o f f r e s h g r e e n snap beans f o r f o u r v a r i e t i e s P a r a m e t e r s V a r i e t i e s T e n d e r c r o p R a n i e r H a r v e s t e r BBL 290 Mean S. D. Mean S. D. Mean S. D. Mean S. D. Seed L e n g t h (mm) 6. a * 8 8 a 2. 84 7 . 3 6 a b 2. 44 7 . 8 5 b c 3. 24 8.23 C 3. 10 Dry M a t t e r (%) 8. 9 7 a 2. 08 7.90 b 1. 59 8 . 8 0 a 2 . 18 9.58 a 2. 61 F i b e r (%) 0. 8 i a 0. 34 0 . 6 7 b 0. 25 1 . 0 5 c 0. 39 0 . 8 1 a 0 . 43 S p r e a d T e s t (cm) 20 . l a 2. 0 2 2 . 2 b 2. 2 18. 6 C 2. 9 20 . 6 a 2. 8 Y i e l d S t r e s s (dynes/cm^) 19 . 2 a 4. 9 13. 3 b 5 . 0 24 . 9a 12. 5 23. 2 C 5 . 5 m(dynes - s e c n ) cm z 58 . 4 a 24. 6 46 . 5 a 22 . 3 7 9 . 2 b 48. 7 7 1 . 4 b 24. 6 n 0. 2 4 4 a 0. 033 0 . 2 5 3 a 0 . 032 0.220 b 0. 025 0.223 b 0. 023 S h e a r P r e s s F o r c e ( l b ) 899. a 109. 7 8 7 b 76. 9 6 7 . c 180. 9 3 6 . a c 90. OTMS F o r c e ( l b ) 628. a 95. 5 4 8 . b 65 . 703. C 119 . 638. a 105. Means w i t h i n a p a r t i c u l a r p a r a m e t e r f o l l o w e d by t h e same l e t t e r a r e n o t 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). 20. f o r c e were s i g n i f i c a n t l y l o w e r w i t h s i g n i f i c a n t l y h i g h e r mean v a l u e s f o r s p r e a d , n_ and p e r c e n t a g e ash f o r R a i n i e r t h a n f o r o t h e r v a r i e t i e s . R e s u l t s f o r H a r v e s t e r beans showed t h a t p e r c e n t a g e f i b e r , m, s h e a r p r e s s and Ottawa T e x t u r e M e a s u r i n g System f o r c e v a l u e s were s i g n i f i c a n t l y g r e a t e r t h a n o t h e r v a r i e t i e s ; h o w e v e r , t h e s p r e a d i s l o w e r . T h i s w o u ld i m p l y t h a t R a i n i e r i s a more s u c c u l e n t and l e s s f i b r o u s v a r i e t y w h i l e H a r v e s t e r i s more f i b r o u s t h a n t h e o t h e r s t e s t e d . S i e v e s i z e S i e v e s i z e g e n e r a l l y r e f l e c t s t h e s t a g e o f m a t u r i t y o f g r e e n b e a n s . T h i s s t u d y showed t h a t t h e r e was a s i g n i f i c a n t i n c r e a s e i n mean s e e d l e n g t h , p e r c e n t a g e d r y m a t t e r and p e r c e n t a g e p h y s i c a l f i b e r w i t h i n c r e a s i n g s i e v e s i z e f o r p o o l e d v a r i e i t i e s ( s e e T a b l e I I I ) . Peak s h e a r p r e s s and O t t a wa T e x t u r e M e a s u r i n g System f o r c e v a l u e s and p e r c e n t a g e ash g e n e r a l l y i n c r e a s e d w i t h i n c r e a s i n g s i e v e s i z e . However, s i e v e s i z e does n o t a l w a y s r e f l e c t t h e q u a l i t y w h i c h may v a r y w i t h h a r v e s t d a t e and v a r i e t y ( M a u r e r , 1 9 7 1 ) . T h e r e were no s i g n i f i c a n t d i f f e r e n c e s i n s p r e a d t e s t and i n t h e c o n s i s t e n c y c o e f f i c i e n t (m) means o b t a i n e d f r o m B r o o k f i e l d v i s c o m e t r i c r e a d i n g s . S l i g h t d e c r e a s e s were o b s e r v e d i n y i e l d s t r e s s and f l o w b e h a v i o r (n_) v a l u e s w i t h i n c r e a s i n g s i e v e s i z e . The e f f e c t s o f v a r i e t y and s i z e on t h e v a r i o u s p a r a m e t e r s a r e s u m m a r i z e d i n F i g u r e s 1 t h r o u g h 10. The g e n e r a l p a t t e r n o f r e s p o n s e ( i . e . e f f e c t o f s i z e ) f o r t h e f o u r v a r i e t i e s was q u a l i t a t i v e l y s i m i l a r i n s e e d l e n g t h , p e r c e n t a g e d r y m a t t e r , p e r c e n t a g e a s h , p e r c e n t a g e p h y s i c a l 21 . T a b l e I I I . Means and s t a n d a r d d e v i a t i o n s f o r s e l e c t e d m a t u r i t y and r h e o l o g i c a l p a r a m e t e r s o f f r e s h g r e e n b e a n s by s i e v e s i z e s P a r a m e t e r s S i e v e S i z e 2 3+4 5 6 Mean S. D. Mean S. D . Mean S. D. Mean S. D. Seed L e n g t h (mm) 4 . 4 9a 0 . 58 6.46b 1. 50 8. 8 0c 1 . 90 11 .03d 2 . 38 Dry M a t t e r (%) 7. 7 1a 0 . 92 8. 3 0b 1. 77 9. 2 6c 2. 33 10 . 2 9d 2 . 76 F i b e r (%) 0 . 4 7a 0. 17 0 . 7 0b 0. 26 0 . 9 3c 0. 34 1.14d 0. 39 S p r e a d T e s t (cm) 20 . 3a 1 . 6 20 . 8a 2 . 6 2 0 . 6a 3. 6 19 . 8a 3. 5 Y i e l d S t r e s s (dynes/cm^) 23. 9a 7. 5 1 9 . 9a b 8 . 7 17 . 2b 10. 5 1 5 . 9b 5 . 8 m (dynes - s e cn cm2 ) 6 2 . 6a 13. 6 64. 8a 28 . 9 62 . la 45 . 2 65. 9a 4 9 . 1 n 0 . 2 4 3a 0. 020 0.230b 0 . 032 0.237 a b0 . 039 0. 231 a b0 . 03' S h e a r P r e s s F o r c e ( l b ) 8 1 6 .a 70. 8 4 6 .a 115 959 .b 124 1019 . c 137. OTMS F o r c e ( l b ) 5 7 7 .a 73. 6 0 7 .b 90. 655 . c 119. 6 7 6 .C 136. Means w i t h i n a p a r t i c u l a r p a r a m e t e r f o l l o w e d by t h e same l e t t e r a r e n o t s i g n i f i c a n t l y d i f f e r e n t (P < 0 . 0 5 ) . 22. 15 s e +J 60 C . - J T3 <D CO 10 5 . • T e n d e r c r o p A R a i n i e r + H a r v e s t e r X BBL 290 2 3+4 5 6 S i e v e S i z e F i g . l . The e f f e c t o f s i e v e s i z e on t h e s e e d l e n g t h o f g r e e n snap beans i n T e n d e r c r o p , R a i n i e r , H a r v e s t e r and BBL 290 v a r i e t i e s . 23. 12 11 10 -9 -6 . 0 t T e n d e r c r o p A R a i n i e r + H a r v e s t e r X BBL 290 2 3+4 5 6 S i e v e S i z e F i g . 2. The e f f e c t o f s i e v e s i z e on t h e d r y m a t t e r c o n t e n t o f g r e e n snap beans i n T e n d e r c r o p , R a i n i e r , H a r v e s t e r and BBL 290 v a r i e t i e s . O T e n d e r c r o p A R a i n i e r + H a r v e s t e r X BBL 290 - i — 2 — i — 3+4 ~r 6 F i g S i e v e S i z e The e f f e c t o f s i e v e s i z e on t h e ash c o n t e n t o f g r e e n snap beans i n T e n d e r c r o p , R a i n i e r , H a r v e s t e r and BBL 290 v a r i e t i e s . X BBL 290 — i 1 1 1— 2 3+4 5 6 S i e v e S i z e The e f f e c t o f s i e v e s i z e on t h e p h y s i c a l f i b e r c o n t e n t o f g r e e n snap beans i n T e n d e r c r o p , R a i n i e r , H a r v e s t e r and BBL 290 v a r i e t i e s . 26. 800 w <a 3 cS > o u o t L , M ca a> Cu c/) H O F i g 700 600 -500 -« T e n d e r c r o p A R a i n i e r + H a r v e s t e r X BBL 290 2 3+4 5 6 S i e v e S i z e The e f f e c t o f s i e v e s i z e on t h e peak f o r c e v a l u e s o f t h e Ottawa T e x t u r e M e a s u r i n g System on whole g r e e n snap beans i n T e n d e r c r o p , R a i n i e r , H a r v e s t e r and BBL 290 v a r i e t i e s . 27. o O 1300 1200 _ 1100 Xi in © 5 IOOO > rt a> a. u e rt 1*5 9 0 0 . 800 700. • T e n d e r c r o p A R a i n i e r + H a r v e s t e r X BBL 290 F i g - i 1 — 1 • 2 3 + 4. 5 6 S i e v e S i z e The e f f e c t o f s i e v e s i z e on t h e peak f o r c e v a l u e s o f t h e Kramer S h e a r P r e s s on whole g r e e n snap beans i n T e n d e r c r o p , R a i n i e r , H a r v e s t e r and BBL 290 v a r i e t i e s . 23 rt <D U &, CO F i g 22 . 21 20 19 18 17 16 . 9 T e n d e r c r o p A R a i n i e r + H a r v e s t e r X BBL 290 —i r 3 + 4 5 S i e v e S i z e —r -6 The e f f e c t o f s i e v e s i z e on t h e s p r e a d v a l u e s o f t h e Adams-type c o n s i s t o m e t e r t e s t s on bean p u r e e s i n T e n d e r c r o p , R a i n i e r , H a r v e s t e r and BBL 290 v a r i e t i e s . 8 J 6 4 2 J 0 9 T e n d e r c r o p A R a i n i e r + H a r v e s t e r X BBL 290 "T T F i g . 8 2 3+4 5 6 S i e v e S i z e The e f f e c t o f s i e v e s i z e on t h e y i e l d s t r e s s v a l u e s o f t h e B r o o k f i e l d v i s c o m e t e r on bean p u r e e s i n T e n d e r c r o p , R a i n i e r , H a r v e s t e r and BBL 290 v a r i e t i e s . 6 C o o in i to <u c X 100 90 -80 30. 70 60 50 40 30 S 0 • T e n d e r c r o p A R a i n i e r + H a r v e s t e r x BBL 290 T 3 + 4 S i e v e S i z e F i g . 9. The e f f e c t o f s i e v e s i z e on t h e c o n s i s t e n c y c o e f f i c i e n t (m) o f bean p u r e e s i n T e n d e r c r o p , R a i n i e r , H a r v e s t e r and BBL 290 v a r i e t i e s . 0. 27 0.26 . 0.25 31 0. 24 . 0. 23 0.22 0. 21 0. 20 -0.0 • T e n d e r c r o p + H a r v e s t e r A R a i n i e r * BBL 290 « r 3+4 5 S i e v e S i z e T " 6 F i g . 1 0 . The e f f e c t o f s i e v e s i z e on t h e f l o w b e h a v i o r i n d e x (n) o f bean p u r e e s i n T e n d e r c r o p , R a i n i e r , H a r v e s t e r and BBL 290 v a r i e t i e s . 32. f i b e r , s h e a r p r e s s and O t t a wa T e x t u r e M e a s u r i n g System r e a d -i n g s , whereas t h e r e s p o n s e p a t t e r n f o r s p r e a d t e s t , y i e l d s t r e s s , m and n_ v a l u e s d i f f e r e d q u a n t i t a t i v e l y and q u a l i t a -t i v e l y f o r t h e f o u r v a r i e t i e s b e c a u s e o f p o s s i b l e i n t e r -a c t i o n s among q u a l i t y p a r a m e t e r s . V i s c o m e t r i c d a t a The B r o o k f i e l d v i s c o m e t r i c d a t a were a c c u r a t e l y d e s c r i b e d by t h e power-law e q u a t i o n w i t h an a v e r a g e c o e f f i c i e n t o f d e t e r m i n a t i o n ( r2) o f 0.98 ( r a n g e : 0.930 - 0 . 9 9 7 ) . The B r o o k f i e l d d a t a a r e p r e s e n t e d i n T a b l e s I , I I and I I I as y i e l d s t r e s s , m and n v a l u e s , t o g e t h e r w i t h t h e s p r e a d d i a m e t e r t e s t r e s u l t s u s i n g an Adams-type c o n s i s t o m e t e r . The p u r e e s made f r o m t h e raw g r e e n beans were non-N e w t o n i a n ( s e e F i g u r e 11) w i t h a f l o w b e h a v i o r i n d e x l e s s t h a n 1 (mean n = 0 . 2 3 5 ) . Thus t h e p u r e e s can be c o n s i d e r e d p s e u d o p l a s t i c ( M o h s e n i n , 1970; Sherman, 1970) a c c o m p a n i e d by a d e f i n i t e y i e l d s t r e s s v a l u e i n e v e r y i n s t a n c e . The d e g r e e o f c o r r e l a t i o n between t h e r h e o l o g i c a l d a t a and t h e q u a l i t y i n d i c e s v a r i e d g r e a t l y . S t r e s s r e l a x a -t i o n v a l u e s were c o r r e l a t e d (P < 0.05) w i t h s e e d l e n g t h and p e r c e n t a g e f i b e r f o r R a i n i e r and BBL 290 and h i g h l y c o r r e l a -t e d (P < 0.01) w i t h p e r c e n t a g e d r y m a t t e r f o r H a r v e s t e r . Y i e l d s t r e s s was c l o s e l y r e l a t e d t o p e r c e n t a g e d r y m a t t e r f o r s i z e s 3+4 and 5, and t o p e r c e n t a g e p h y s i c a l f i b e r i n s i z e 5. The m v a l u e s were h i g h l y c o r r e l a t e d w i t h s o l i d s c o n t e n t i n a l l v a r i e t i e s and s i z e s ( p o o l e d d a t a r = 0 . 7 5 ) . 10 01 600 loo -Y e a r : 1972 loo 6~00 V a r i e t y : BBL 290 A00 S i z e : 2 200 H a r v e s t : 11/8/72 loo -m = 67.1 d y n e s - s e c /cm n = 0.236 loo 90 8o 70 A J^^^ io s-o A, ' ' • 40 36 20 A i n c r e a s i n g s e r i e s 9 d e c r e a s i n g s e r i e s 10 1 L_ i_ .1 t_ _L i i i i • • • i i i t •01 -2 -3 -4 S b -1 8 9 10 Z 3 4 J 6 T 8 9 /0 Rate o f s h e a r i n g ( s e c-* ) 11. S h e a r s t r e s s vs r a t e o f s h e a r i n g as m e a s u r e d by B r o o k f i e l d v i s c o m e t e r on raw BBL 290 bean p u r e e . The f l o w b e h a v i o r i n d e x (n) d e c r e a s e d w i t h i n c r e a s i n g d r y m a t t e r p e r c e n t a g e ( p o o l e d d a t a r = - 0 . 5 6 ) , a g r e e i n g w i t h H o l d s w o r t h (1971) and was h i g h l y c o r r e l a t e d t o a l l q u a l i t y p a r a m e t e r s i n s i z e s 3+4 and 5 and i n a l l v a r i e t i e s e x c e p t T e n d e r c r o p . S p r e a d v a l u e s were h i g h l y r e l a t e d w i t h s o l i d s c o n t e n t f o r e v e r y v a r i e t y and s i z e e x c e p t s i z e 2 ( p o o l e d d a t a r = - 0 . 7 8 ) . T h i s a g r e e s w i t h t h e f i n d i n g s o f Watson (1968) and M i z r a h i and Berk (1970) t h a t v i s c o u s p r o p e r t i e s o f p u r e e s a r e s i g n i f i c a n t l y c o r r e l a t e d w i t h s o l i d s c o n t e n t . Some o f t h e v i s c o m e t r i c d a t a showed s i g n i f i c a n t i n t e r r e l a t i o n s h i p s . S p r e a d v a l u e s were c l o s e l y r e l a t e d w i t h a l l t h r e e B r o o k f i e l d p a r a m e t e r s - - y i e l d s t r e s s ( p o o l e d d a t a r = - 0 . 7 0 ) , m ( p o o l e d d a t a r = -0.84) and n ( p o o l e d d a t a r = 0 . 6 3 ) . However, t h e r e were i n d i c a t i o n s t h a t c o n s i s t e n c y c o u l d f a i l t o p r e d i c t t h e f l o w b e h a v i o r i n d e x i n s e v e r a l o f t h e s i z e s and v a r i e t i e s . Y i e l d s t r e s s v a l u e s showed e x c e l l e n t c o r r e l a t i o n ( p o o l e d d a t a r = 0.95) w i t h m. S p r e a d , y i e l d s t r e s s and m v a l u e s showed a h i g h i n t e r r e l a t i o n s h i p as t h e s e f a c t o r s a r e i n v o l v e d w i t h t h e d e f o r m a t i o n o f p u r e e s t r u c t u r e a t v e r y low r a t e s o f s h e a r . F a c t o r s a f f e c t i n g bean p u r e e v i s c o s i t y The v i s c o m e t r i c b e h a v i o r o f raw g r e e n bean p u r e e s was i n f l u e n c e d by numerous f a c t o r s d e a l i n g p r i m a r i l y w i t h p u r e e c o m p o s i t i o n . The p u r e e c o n s i s t e d o f m a c e r a t e d , b l e n d e d bean t i s s u e and w a t e r . P r e l i m i n a r y s t u d i e s showed t h a t 25% added w a t e r would f a c i l i t a t e b l e n d i n g and would n o t c a u s e the s e t t l i n g - o u t o f t h e s u s p e n d e d , d i s p e r s e d p a r t i c l e s as w o uld be t h e c a s e f o r l a r g e r volumes o f added w a t e r . Some s a m p l e s , w h i c h were r e l a t i v e l y f i b r o u s and c o n t a i n e d h i g h amounts o f d r y m a t t e r r e q u i r e d some a s s i s t a n c e i n t h e i n i t i a l s t a g e o f b l e n d i n g due t o u n m a c e r a t e d bean t i s s u e b r i d g i n g o v e r t h e b l e n d o r k n i v e s . With t h e s e s a m p l e s a d e c r e a s e i n b l e n d o r s p e e d was o f t e n n o t e d w h i c h may have c a u s e d a v a r i a t i o n i n t h e d e g r e e o f m a c e r a t i o n and p a r t i c l e s i z e d i s t r i b u t i o n . T h i s r e s u l t e d i n h i g h e r v i s c o s i t y and l o w e r s p r e a d r e a d i n g s . The b l e n d e d bean t i s s u e c o n t a i n e d c o n s i d e r a b l e a i r w h i c h u n d o u b t e d l y c o n t r i b u t e d t o t h e t h i c k -n e s s o f t h e s l u r r y ( W i l e y , 1 9 5 9 ) . The b l e n d i n g p r o c e d u r e was t h e r e f o r e k e p t u n i f o r m t o m i n i m i z e v a r i a t i o n i n t h e amount o f i n c o r p o r a t e d a i r . The p u r e e s a r e composed o f two s e p a r a t e p h a s e s --t h e d i s p e r s e d p a r t i c l e s and t h e serum c o n t a i n i n g t h e s o l u b l e s o l i d s . The p a r t i c l e s v a r y i n s i z e d i s t r i b u t i o n , shape and c o n c e n t r a t i o n among p u r e e s . S e v e r a l p u r e e s were w e t - s i e v e d u s i n g v a r i o u s s t a n d a r d s i e v e s . The g r e a t e r p e r c e n t a g e (by d r y w e i g h t ) o f t h e p a r t i c l e s were r e t a i n e d on t h e 48 and 100 mesh s c r e e n s (mean p a r t i c l e d i a m t e r s = 416um and 208ym r e s p e c t i v e l y - see T a b l e IV) w i t h t h e amount on t h e 28 mesh s i e v e v a r y i n g d i r e c t l y w i t h r e s p e c t t o t h e amount o f p h y s i c a l f i b e r i n t h e sample as d e t e r m i n e d by t h e b l e n d o r method ( K r a m e r , 1 9 5 1 ) . The b l e n d o r method f o r p h y s i c a l f i b e r d e t e r m i n a t i o n u s e d a h i g h e r p r o p o r t i o n o f w a t e r t o T a b l e I v . D e t e r m i n a t i o n o f p a r t i c l e s i z e and d i s t r i b u t i o n o f s c r e e n e d raw g r e e n bean p u r e e . P a r t i c l e s i z e (pm) P a r t i c l e d i s t r i b u t i o n S c r e e n Mesh No. M i c r o s c o p e C a l c u l a t e d Weight % o f T o t a l m 28 825 832 0.389 14.7 48 443 416 0.606 22.9 100 262 208 0.710 26.8 200 186 104 0.288 10.9 < 200 0.648 24.6 \ 37. f a c i l i t a t e b l e n d i n g t h a n was u s e d i n p u r e e p r e p a r a t i o n , t h e r e b y r e s u l t i n g i n a l o w e r p e r c e n t a g e o f p a r t i c l e s r e t a i n e d on t h e 28 mesh s c r e e n b e c a u s e o f more e f f i c i e n t m a c e r a t i o n . P a r t i c l e s h a p e , as e xamined m i c r o s c o p i c a l l y , v a r i e d w i t h p a r t i c l e s i z e ( s e e F i g u r e 1 2 ) . The l a r g e r p a r t i c l e s were v e r y i r r e g u l a r and a n g u l a r w h i l e t h e s m a l l e r p a r t i c l e s were q u i t e r o u n d e d and u n i f o r m . The l a r g e r p a r t i c l e s r e s u l t e d f r o m i n c o m p l e t e m a c e r a t i o n due t o t h e p r e s e n c e o f f i b e r and t h i c k e n e d c e l l w a l l s and c o n s i s t e d o f l a r g e c e l l m a s ses. M e d i u m - s i z e p a r t i c l e s c o n s i s t e d o f one o r more c e l l s w i t h t h e s m a l l p a r t i c l e s b e i n g c e l l w a l l f r a g m e n t s and i n s o l u b l e c e l l u l a r c o n t e n t s . The s h a p e s and s i z e s o f t h e s e p a r t i c l e s a l l i n t e r a c t e d i n t h e v i s c o m e t r i c b e h a v i o r o f t h e p u r e e . The s u s p e n d e d p a r t i c l e s g r e a t l y a f f e c t t h e v i s c o s i t y o f t h e p u r e e s (Sherman, 1 9 7 0 ) . The p a r t i c l e s c o n s i s t o f i n t a c t c e l l masses o r i n d i v i d u a l c e l l s w h i c h v a r y g r e a t l y i n shape and s i z e b e c a u s e o f f i b e r c o n t e n t . F i b r o u s d i s p e r s i o n s t e n d t o form t h r e e - d i m e n s i o n a l n e t w o r k s e x h i b i t i n g v i s c o 1 e l a s t i c b e h a v i o r ( C o r e y , 1970) . T h i s may e x p l a i n t h e y i e l d s t r e s s o b t a i n e d f o r e v e r y p u r e e . Under t h e i n f l u e n c e o f s h e a r , t h e l i n k s i n t h e n e t w o r k may be s t r e t c h e d , d i s t o r t e d and r u p t u r e d (Sherman, 1970). The bean p u r e e s e x h i b i t e d p s e u d o p l a s t i c i t y . Sherman (1970) s u g g e s t s t h a t i n p s e u d o -p l a s t i c f l o w p a r t o f t h e s h e a r i n g f o r c e i s u s e d t o b r e a k down t h e f l o c c u l a t e d s t r u c t u r e w h i l e t h e r e m a i n d e r i s u s e d 38. c) 100 Mesh d) 200 Mesh e) U n s c r e e n e d F i g . 12. P h o t o m i c r o g r a p h s o f s c r e e n e d m a c e r a t e d g r e e n bean t i s s u e on s c r e e n s o f a) 28 mesh b) 48 mesh c ) 1 0 0 mesh d)200 mesh e) U n s c r e e n e d 39. t o p r o d u c e f l o w a t t h e h i g h e r s h e a r r a t e s . The t h i x o t r o p i c n a t u r e o f t h e p u r e e s i s shown by t h e h y s t e r e s i s e x h i b i t e d i n F i g u r e 11. The h i g h i n i t i a l s h e a r r a t e l i k e l y c a u s e d w i d e s p r e a d d e s t r u c t i o n o f t h e n e t w o r k s t r u c t u r e so t h a t s u b s e q u e n t s h e a r s t r e s s v a l u e s were l o w e r i n t h e d e c r e a s i n g s h e a r r a t e s e r i e s w h i l e h i g h e r v a l u e s were o b t a i n e d f o r t h e i n c r e a s i n g s e r i e s a f t e r t h e s t r u c t u r e had t i m e t o r e f o r m . R e l a t i v e l y low s h e a f r a t e s were u s e d (10.5 s e c * maximum) w i t h t h e B r o o k f i e l d v i s c o m e t e r . The c o n s i s t e n c y o r s p r e a d o f t h e bean p u r e e w i l l be a f f e c t e d by t h e amount o f f r e e w a t e r , t h e c o n c e n t r a t i o n and t y p e o f d i s s o l v e d s o l i d s , t o g e t h e r w i t h t h e s i z e d i s t r i b u -t i o n and c o n c e n t r a t i o n o f t h e s o l i d p a r t i c l e s . The c o n t i n -uous p h a s e forms a t h i n f i l m a r o u n d each p a r t i c l e due t o v a r i o u s a t t r a c t i v e f o r c e s . As t h e p r o p o r t i o n o f f r e e l i q u i d i n c r e a s e s , t h e f i l m s t a r t s a c t i n g as a l u b r i c a n t between the p a r t i c l e s and c a u s e s a h i g h e r s p r e a d v a l u e . The q u a n t i t y o f f r e e w a t e r i s d e p e n d e n t on t h e d e g r e e o f c e l l r u p t u r e , t u r g i d i t y and volume o f c e l l c o n t e n t s . C e l l r u p t u r e i s , i n t u r n , a f f e c t e d by t h e r e s i s t a n c e o f c e l l w a l l s t o c u t t i n g and s h e a r i n g a c t i o n s o f t h e b l e n d o r b l a d e s . The s i z e d i s t r i b u -t i o n and shape o f t h e p a r t i c l e s i s d e p e n d e n t on t h e c e l l s t r e n g t h as w e l l b e c a u s e f i b e r i s r e l a t i v e l y r e s i s t a n t t o m a c e r a t i o n . The s p r e a d o f t h e p u r e e i s , t h e r e f o r e , r e l a t e d t o t h e t e x t u r a l q u a l i t y o f t h e g r e e n b e a n . 40. O t t a w a T e x t u r e M e a s u r i n g System and Kramer s h e a r p r e s s r e s u l t s The O t t a w a T e x t u r e M e a s u r i n g System f o r c e v a l u e s showed h i g h e r c o r r e l a t i o n s w i t h a l l q u a l i t y and v i s c o m e t r i c p a r a m e t e r s t h a n d i d t h e Kramer s h e a r p r e s s f o r c e v a l u e s e x c e p t f o r s e e d l e n g t h w h i c h was c o r r e l a t e d h i g h e r w i t h t h e s h e a r p r e s s . The two s y s t e m s were c l o s e l y r e l a t e d ( p o o l e d d a t a r = 0 . 7 8 ) . However, t h e r e was a s i g n i f i c a n t d i f f e r e n c e b e tween s y s t e m s i n 1971 ( r = 0.92) and 1972 ( r = 0.42) due t o a m a l f u n c t i o n i n g t r a n s d u c e r (LVDT) i n t h e Kramer s h e a r p r e s s p r o v i n g r i n g i n 1972. The peak f o r c e r e a d i n g s o f b o t h the Kramer s h e a r p r e s s and t h e Ottawa T e x t u r e M e a s u r i n g System were h i g h l y c o r r e l a t e d (P < 0.01) t o t h e t h r e e q u a l i t y i n d i c e s w i t h c e r t a i n v a r i e t a l d i f f e r e n c e s . However, Kramer r e a d i n g s were n o t s i g n i f i c a n t l y c o r r e l a t e d w i t h p e r c e n t a g e p h y s i c a l f i b e r i n 1972. Peak f o r c e r e a d i n g s on b o t h i n s t r u m e n t s showed low c o r r e l a t i o n w i t h p e r c e n t a g e f i b e r i n s i e v e s i z e 2. T h i s was e x p e c t e d b e c a u s e f i b e r i s g e n e r a l l y low i n t h e beans o f s i z e 2 and i s not t h e o n l y f a c t o r a f f e c t i n g t h e s h e a r i n g r e s i s t a n c e o f g r e e n b e a n s . F a c t o r s a f f e c t i n g s h e a r i n g f o r c e o f g r e e n b eans T h e r e a r e numerous f a c t o r s w h i c h a f f e c t t h e peak f o r c e r e a d i n g s and t h e t o t a l work done by t h e t e x t u r e t e s t i n g i n s t r u m e n t s . The s h e a r t e s t s were r u n u s i n g pods c u t t o l e n g t h w i t h i n t a c t s e e d s w h i l e Bundy and Kramer (1960) u s e d d e s e e d e d p o d s . The r e a s o n f o r u s i n g i n t a c t bean pods was t o a s c e r t a i n t h e c o m b i n e d e f f e c t o f s e e d s and f i b e r on t h e 41 . s h e a r i n g f o r c e r e q u i r e d . The r e s u l t s o f Bundy and Kramer (1959) were g e n e r a l l y h i g h e r . However, t e s t c o n d i t i o n s were n o t i d e n t i c a l ( e . g . d i f f e r e n t v a r i e t i e s u s e d ) so t h a t a c c u r a t e c o m p a r i s o n s c o u l d n o t be made. The t u r g i d i t y o f t h e c e l l s w i l l a l s o a f f e c t t h e peak f o r c e r e a d i n g s by m i n i m i z i n g the d e g r e e o f e l a s t i c d e f o r m a t i o n b e f o r e s h e a r i n g o c c u r s . The shape o f t h e t e s t c e l l and p l u n g e r d e t e r m i n e s the f o r c e r e q u i r e d t o s h e a r and e x t r u d e t h e b e a n s . S i n c e most o f t h e s e f a c t o r s a r e r e l a t e d t o t e x t u r a l q u a l i t y , t h e Kramer s h e a r p r e s s and O t t a w a T e x t u r e M e a s u r i n g System s h o u l d be c o n s i d e r e d as s u i t a b l e t e x t u r a l q u a l i t y m e a s u r i n g d e v i c e s . 4 2 . SUMMARY The e f f e c t o f m a t u r i t y and v a r i e t y on t e x t u r a l q u a l i t y o f g r e e n snap beans i n e a c h o f two y e a r s was a n a l y z e d u s i n g v a r i o u s r h e o l o g i c a l t e c h n i q u e s . V i s c o m e t r i c and s h e a r -i n g t e s t s were u s e d t o a s s e s s t h e e f f e c t o f m a t u r i t y ( d e s i g -n a t e d by s i e v e s i z e ) and o f v a r i e t y ( T e n d e r c r o p , R a i n i e r , H a r v e s t e r and BBL 290) on t e x t u r a l q u a l i t y ( d e f i n e d by s e e d l e n g t h , p e r c e n t a g e d r y m a t t e r and p e r c e n t a g e p h y s i c a l f i b e r ) . 1. T h e r e were h i g h l y s i g n i f i c a n t d i f f e r e n c e s (P < 0.05) i n a l l p a r a m e t e r means between 1971 and 1972 due t o v a r i a t i o n s i n g r o w i n g c o n d i t i o n s . Beans grown i n 1972 g e n e r a l l y e x h i b i t e d s u p e r i o r t e x t u r a l q u a l i t y t h a n b eans s u b j e c t e d t o h i g h e r mean t e m p e r a -t u r e s i n 1971. 2. The f o u r v a r i e t i e s t e s t e d showed h i g h l y s i g n i f i c a n t d i f f e r e n c e s i n t e x t u r a l q u a l i t y . R a i n i e r e x h i b i t e d t h e h i g h e s t q u a l i t y (low v a l u e s f o r t o t a l s o l i d s and f i b e r c o n t e n t , s h e a r f o r c e ) w h i l e H a r v e s t e r had t h e l o w e s t q u a l i t y ( h i g h v a l u e s o f f i b e r c o n t e n t and s h e a r f o r c e r e a d i n g s w i t h low s p r e a d v a l u e s ) . T e n d e r c r o p and BBL 290 were i n t e r m e d i a t e i n q u a l i t y . 3. S i e v e s i z e e x e r t e d a marked e f f e c t on most v i s c o m e t r i c and s h e a r i n g t e s t s due t o i n c r e a s i n g m a t u r i t y . 4. The power-law c o n s t i t u t i v e e q u a t i o n x = m y " , - a c c u r a t e l y d e s c r i b e d t h e p s e u d o p l a s t i c v i s c o m e t r i c d a t a from 4 3 . raw g r e e n bean p u r e e . Raw g r e e n bean p u r e e a c t e d as a t h i x o t r o p i c f l u i d e x h i b i t i n g a d e f i n i t e y i e l d s t r e s s . V i s c o u s p r o p e r t i e s o f bean p u r e e showed h i g h l y s i g n i f i -c a n t c o r r e l a t i o n s w i t h p e r c e n t a g e d r y m a t t e r and s e e d l e n g t h when v a r i e t i e s were p o o l e d t o t e s t t h e e f f e c t o f m a t u r i t y . In most i n s t a n c e s , p e r -c e n t a g e f i b e r was p o o r l y c o r r e l a t e d w i t h v i s c o s i t y p a r a m e t e r s (m, n and y i e l d s t r e s s v a l u e s t o g e t h e r w i t h s p r e a d d i a m e t e r ) . The Kramer s h e a r p r e s s and t h e Ottawa T e x t u r e M e a s u r i n g System f o r c e v a l u e s were b o t h s i g n i f i c a n t l y c o r r e l a t e d w i t h a l l t e x t u r a l q u a l i t y and v i s c o m e t r i c p a r a m e t e r s ( a l t h o u g h t o v a r y i n g d e g r e e s ) . The s y s t e m s were more c l o s e l y r e l a t e d i n 1971 ( r = 0.91) t h a n i n 1972 ( r = 0 . 4 2 ) . L I S T OF REFERENCES A b b o t t , J . A . 1972 " S e n s o r y a s s e s s m e n t o f f o o d t e x t u r e " . Food T e c h n o l o g y 26_ ( 1 ) , 40-49. B o u r n e , M.C. and M o y e r , J . C . 1968 "The e x t r u s i o n p r i n c i p l e i n t e x t u r e measurement o f f r e s h p e a s " . Food T e c h n o l o g y 2_2 ( 8 ) , 1013-1017. Bundy, O.M. and K r a m e r , A. 1959 "The p r a c t i c a l a p p l i c a t i o n o f t h e s h e a r p r e s s i n d e t e r m i n i n g q u a l i t y and g r a d e s o f g r e e n b e a n s " . M a r y l a n d P r o c e s s o r s R e p o r t 5_ ( 6 ) , 3-7. Canada. D e p a r t m e n t o f A g r i c u l t u r e . 1963. " P r o c e s s e d F r u i t and V e g e t a b l e R e g u l a t i o n s , S c h e d u l e A, Canned Beans ( g r e e n o r w a x ) , and S c h e d u l e B, F r o z e n Beans ( g r e e n o r wax)"." Canada A g r i c u l t u r a l P r o d u c t s S t a n d a r d s A c t , O t t a w a . C a r r , D . J . and S k e n e , K.G.M. 1961 " D i a u x i c g r o wth c u r v e s o f s e e d s w i t h s p e c i a l r e f e r e n c e t o F r e n c h beans ( P h a s e o l u s v u l g a r i s ) " . A u s t r a l i a n J o u r n a l o f B i o l o g i c a l S c i e n c e 14., 1-12. Charm, S.E. 1962 "The n a t u r e and r o l e o f f l u i d c o n s i s t e n c y i n f o o d e n g i n e e r i n g a p p l i c a t i o n s " . In A d v a n c e s i n Food  R e s e a r c h 11, 355-435. New Y o r k : A c a d e m i c P r e s s . C o r e y , H. 1970 " T e x t u r e i n f o o d s t u f f s " . CRC C r i t i c a l Reviews i n Food T e c h n o l o g y 1_ (2) , 161-198. C u l p e p p e r , C.W. 1936 " E f f e c t o f s t a g e o f m a t u r i t y o f t h e snap bean on i t s c o m p o s i t i o n and use as a f o o d p r o d u c t " . Food R e s e a r c h 1, 357-376. D a v i s , R.B., DeWeese, D. and G o u l d , W.A. 1954 " C o n s i s t e n c y measurements o f tomato p u r e e " . Food T e c h n o l o g y 8 ( 7 ) , 330-334. 4 5 . D r i j f h o u t , E . 1970. " I n f l u e n c e o f t e m p e r a t u r e on s t r i n g f o r m a t i o n o f beans ( P h a s e o l u s v u l g a r i s ) " . E u p h y t i c a 1 9 , 145-151. F a r k a s , D.F. 1967 "Use o f s e e d s i z e f o r c o n t r o l l i n g snap bean q u a l i t y f o r p r o c e s s i n g " . Food T e c h n o l o g y 21_, (5) , 789-791. F i n n e y , E . E . 1969 " O b j e c t i v e measurements f o r t e x t u r e i n f o o d s " . J . T e x t u r e S t u d i e s 1_, 19-37. 1972 " E l e m e n t a r y c o n c e p t s o f r h e o l o g y r e l e v a n t t o f o o d t e x t u r e s t u d i e s " . Food T e c h n o l o g y 26_ ( 2 ) , 68-77. G o u l d , W.A. 1950a " F i b e r c o n t e n t o f snap beans e v a l u a t e d by v a r i e t y , m a t u r i t y " . Food P a c k e r 31_ ( 7 ) , 42-44. 1950b "Seed l e n g t h i s a good measure o f m a t u r i t y f o r snap b e a n s " . Food P a c k e r 31_ ( 8 ) , 54-55. 1950c " R e s u l t s from c h e m i c a l a n a l y s e s o f snap b e a n s " . Food P a c k e r 3_1_ ( 9 ) , 26-27 , 54-55. G u y e r , R.B. and K r a m e r , A.1952 " S t u d i e s o f f a c t o r s a f f e c t i n g t h e q u a l i t y o f g r e e n and wax b e a n s " . B u l l e t i n A 6 8 , U n i v e r s i t y o f M a r y l a n d A g r i c u l t u r a l E x p e r i m e n t S t a t i o n , C o l l e g e P a r k , M a r y l a n d . H o l d s w o r t h , S.D. 1971 " A p p l i c a b i l i t y o f r h e o l o g i c a l models t o t h e i n t e r -p r e t a t i o n o f f l o w and p r o c e s s i n g b e h a v i o r o f f l u i d f o o d p r o d u c t s " . J . T e x t u r e S t u d i e s 2_, 393-424. J o n e s , L.H. and C o r n e r , J . J . 1962 " P h y s i o l o g i c a l a s p e c t s o f d w a r f bean m a t u r i t y " . F i r s t I n t e r n a t i o n a l C o n g r e s s on Food S c i e n c e and T e c h n o l o g y 2, 137-147. K a l d y , M.S. 1966 " F i b e r c o n t e n t o f g r e e n snap beans as i n f l u e n c e d by v a r i e t y and e n v i r o n m e n t " . P r o c . Amer. S o c . H o r t . S c . 8_, 361-366. K a t t a n , A.A. and S h a r p , C O . 1970 "Mass g r a d i n g o f snap b e a n s " . A r k a n s a s Farm R e s e a r c h _9_ (5) . K r a m e r , A. 1951 " F a s t e r q u a l i t y check f o r snap b e a n s " . Food P a c k e r 32_ ( 6 ) , 32-34. _ _ _ _ _ _ _ 1961 "The s h e a r p r e s s , a b a s i c t o o l f o r t h e f o o d t e c h n o l o g i s t " . The Food S c i e n t i s t 5 ( 1 ) , 7-16. 1969 "The r e l e v a n c e o f c o r r e l a t i n g o b j e c t i v e and s u b j e c -t i v e d a t a " . Food T e c h n o l o g y _3 ( 7 ) , 926-928. 1972 " T e x t u r e , i t s d e f i n i t i o n , measurement and r e l a t i o n t o o t h e r a t t r i b u t e s o f f o o d q u a l i t y " . Food T e c h n o l o g y 26_ ( 1 ) , 34-39. ' , G u y e r , R.B. and I d e , L . E . 1949 "How t o t e l l t h e q u a l i t y o f snap b e a n s " . Food P a c k e r _0 ( 8 ) , 41-44. L o e w e n b e r g , J.R. 1955 "The d e v e l o p m e n t o f bean s e e d s ( P h a s e o l u s v u l g a r i s P l a n t P h y s i o l o g y 30_, 244-250. Mason, S.G. and B a r t o k , W. 1959 "The b e h a v i o r o f s u s p e n d e d p a r t i c l e s i n l a m i n a r s h e a r " . In R h e o l o g y o f D i s p e r s e S y s t e m s , C.C. M i l l ( e d . ) , New Y o r k : Pergamon P r e s s , 16-47. M a t z , S.A. 1962 Food T e x t u r e . W e s t p o r t , Conn: AVI P u b l i s h i n g Co. M a u r e r , A.R. 1971 " Q u a l i t y s t a n d a r d s i n g r e e n snap b e a n s " . P a p e r p r e s e n t e d t o W e s t e r n Food P r o c e s s o r s C o n v e n -t i o n , F e b . 1971. V a n c o u v e r , B.C. M a u r e r , A.R., O r m r o d , D.P. and S c o t t , N . J . 1969 " E f f e c t o f f i v e s o i l w a t e r r e g i m e s on g r o w t h and c o m p o s i t i o n o f snap b e a n s " . Can'. J . P l a n t S c . 4_9_, 271-278. M e y e r , L.H. 1960 Food C h e m i s t r y . New Y o r k : R e i n h o l d Book Co. M i z r a h i , S. and B e r k , Z. 1970 "Flow b e h a v i o r o f c o n c e n t r a t e d o r a n g e j u i c e " . J . T e x t u r e S t u d i e s 1_, .342-355. M o h s e n i n , N.N. 1970 P h y s i c a l P r o p e r t i e s o f P l a n t and A n i m a l M a t e r i a l s . New Y o r k : Gordon and B r e a c h S c i e n c e P u b l i s h e r s . R e e v e , R.M. and Brown, M.S. 1968a " H i s t o l o g i c a l d e v e l o p m e n t o f t h e g r e e n bean pod as r e l a t e d t o c u l i n a r y t e x t u r e . 1. E a r l y s t a g e s o f pod d e v e l o p m e n t " . J . Food S c i e n c e 3_3, 321-325. and . 1968b " H i s t o l o g i c a l d e v e l o p m e n t o f t h e g r e e n bean pod as r e l a t e d t o c u l i n a r y t e x t u r e . 2. S t r u c t u r e and c o m p o s i t i o n a t e d i b l e m a t u r i t y " . J . Food S c i e n c e 3_3_, 326-331. R o s s , E . , B r e k k e , J . E . and M o o r e , J . F . 1956 "The o b j e c t i v e e v a l u a t i o n o f some g r e e n bean v a r i e t i e s i n t h e N o r t h w e s t " . P r o c . Amer. H o r t . S c . 6_7 ( 6 ) , 398-411. S c o t t B l a i r , G.W. 1969 E l e m e n t a r y R h e o l o g y . London: A c a d e m i c P r e s s . S herman, P. 1970 I n d u s t r i a l R h e o l o g y . London: A c a d e m i c P r e s s 1972 " S t r u c t u r e and t e x t u r a l p r o p e r t i e s o f f o o d s " . Food T e c h n o l o g y 26 ( 3 ) , 69-79. S n e d e c o r , G.W. and C o c h r a n , W.G. 1967 S t a t i s t i c a l M e t h o d s . 6 t h e d i t i o n . Ames, Iowa: The Iowa S t a t e U n i v e r s i t y P r e s s . 48. Somers, G.F. 1965 " V i s c o e l a s t i c p r o p e r t i e s o f s t o r a g e t i s s u e s f r o m p o t a t o , a p p l e and p e a r " . J . Food S c i e n c e _0 ( 6 ) , 922-929. S t a r k , F.C. and Mahoney, C H . 1942 "A s t u d y o f the t i m e and d e v e l o p m e n t o f t h e f i b r o u s s h e a t h i n t h e s i d e w a l l o f e d i b l e snap bean pods w i t h r e s p e c t t o q u a l i t y " . P r o c . Amer. S o c . H o r t . Sc. 41_, 353-359. S z c z e s n i a k , A.S. 1966 " T e x t u r e m e a s urements". Food T e c h n o l o g y 2_ ( 1 0 ) , 1294-1298. 1972 " I n s t r u m e n t a l methods o f t e x t u r e measurement". Food T e c h n o l o g y 2_ ( 1 ) , 50-56. Tung, M.A., G a r l a n d , M.R., M a u r e r , A.R. and Watson, T.K. 1973. " R h e o l o g i c a l e v a l u a t i o n o f sweet c o r n m a t u r i t y " . Can. I n s t . Food S c i . T e c h . J . ( i n p r e s s ) . U n i t e d S t a t e s . C o n s u m e r and M a r k e t i n g S e r v i c e . 1 9 6 1 • " U n i t e d S t a t e s S t a n d a r d s f o r (a) g r a d e s o f canned g r e e n beans and canned wax beans (b) g r a d e s o f f r o z e n g r e e n beans and f r o z e n wax b e a n s " . F e d e r a l R e g i s t e r , T i t l e 7, Chap. 1, p a r t 52, W a s h i n g t o n , D.C. U n i t e d S t a t e s . F o o d and Drug A d m i n i s t r a t i o n . 1 9 5 7 " D e f i n i t i o n s and s t a n d a r d s f o r f o o d : c a n n e d g r e e n b e a n s " . F e d e r a l R e g i s t e r , T i t l e 21, Chap. 1, p a r t 51.10, W a s h i n g t o n , D.C. Van B u r e n , J . 1970 " C u r r e n t c o n c e p t s on t h e t e x t u r e o f f r u i t s and v e g e t a b 1 e s " . CRC C r i t i c a l Reviews i n Food T e c h n o l o g y 1 ( 1 ) , 5-24. V o i s e y , P.W. 1971 "The Ottawa T e x t u r e M e a s u r i n g S y s t e m " . Can. I n s t . Food T e c h . J . £ ( 3 ) , 91-95. Watada, A.E. and M o r r i s , L . L . 1967 "Growth and r e s p i r a t i o n p a t t e r n s o f snap bean f r u i t s " P l a n t P h y s i o l o g y 42, 757-761. 49. Watson, E.L. 1968 " R h e o l o g i c a l b e h a v i o r o f a p r i c o t p u r e e s and c o n -c e n t r a t e s " . C a n a d i a n A g r i c u l t u r a l E n g i n e e r i n g 1_0 ( 1 ) , 8-11. W i l e y , R.C. 1959 " S l u r r y v i s c o s i t y measurements as methods t o d e t e r m i n e m a t u r i t y o f l i m a beans and p e a s " . Food T e c h n o l o g y _3 (12) , 694-698. APPENDIX A S t r u c t u r a l D e v e lopment o f t h e Snap Bean F r u i t 1. G e n e r a l growth o f bean ( P h a s e o l u s v u l g a r i s ) The b a s i c p a t t e r n o f bean pod t i s s u e i s l a i d down i n t h e f l o w e r bud s e v e r a l days b e f o r e f l o w e r i n g . Reeve and Brown (1968a) d i s c u s s t h i s i n i t i a l d e v e l o p m e n t e x t e n s i v e l y . The pod b e g i n s t o grow about t h e s e c o n d day a f t e r a n t h e s i s ( i . e . f l o w e r i n g ) a c c o r d i n g t o C a r r and Skene ( 1 9 6 1 ) . A f t e r t h i s s t a g e , g r o w th i s p r i m a r i l y due t o c e l l e n l a r g e m e n t and v a c u o l a t i o n r a t h e r t h a n t o c e l l d i v i s i o n . J o n e s and C o r n e r (1962) summarize t h e growth and d e v e l o p m e n t o f t h e bean f r u i t as t a k i n g p l a c e i n t h r e e s t a g e s . Phase 1 e n t a i l s t h e r a p i d g r o w th o f t h e pod w h i l e t h e s e e d s r e m a i n q u i t e s m a l l and i n s i g n i f i c a n t when compared t o t h e p o d . T h i s p h a s e c o n t i n u e s u n t i l 24 days a f t e r a n t h e s i s . The l a g p h a s e o f s e e d g r owth ( t o be d i s c u s s e d l a t e r ) i s a l s o i n c l u d e d a t t h e end o f t h i s s t a g e . Pod growth c e a s e s a f t e r t h e l a g p h a s e o f s e e d g r o w t h . The s e c o n d p h a s e o f d e v e l o p m e n t o c c u r s when embryo and c o t y l e d o n s ( i . e . t h e s e e d ) grow r a p i d l y . The t h i r d s t a g e i n f r u i t d e v e l o p m e n t i s t h e d r y i n g o u t o f t h e pod w a l l w h i l e t h e s e e d c o m p l e t e s i t s d e v e l o p m e n t . Watada and M o r r i s (1967) d e s c r i b e t h e growth p a t t e r n o f bean f r u i t as s i g m o i d . Maximum pod l e n g t h was a t t a i n e d a b out t h e 1 3 t h day a f t e r a n t h e s i s w h i c h was due 51 . e s s e n t i a l l y t o t h e e n l a r g e m e n t o f t h e f l e s h y e n d o c a r p (up t o 12% s e e d ) -- i d e a l m a t u r i t y . Seed w e i g h t began t o i n c r e a s e m a r k e d l y at t h i s t i m e and c o n t i n u e d t o i n c r e a s e w i t h i n t h e c a v i t y f o r m ed s i m u l t a n e o u s l y by t h e c o l l a p s e o f t h e e n d o c a r p (12 - 16% s e e d ) -- s l i g h t l y o v e r m a t u r e . As t h e s e e d r e a c h e d maximum s i z e , o n l y t h e s k e l e t a l c e l l w a l l s o f t h e e n d o c a r p r e m a i n e d ( o v e r 16% s e e d ) --beyond e d i b l e m a t u r i t y . J o n e s and C o r n e r (1962) a l s o s t a t e t h a t t h e g r o wth o f t h e pods i s i n t i m a t e l y i n v o l v e d w i t h s e e d d e v e l o p m e n t and i s p r o b a b l y c o n t r o l l e d by t h e s e e d from t h e t i m e o f f e r t i l i -z a t i o n o n w a r d s . 2. Pod g r o w t h The e n t i r e snap bean up t o t h e 15-day s t a g e a f t e r a n t h e s i s may be c o n s i d e r e d as pod o r p e r i c a r p a c c o r d i n g t o C u l p e p p e r ( 1 9 3 6 ) . S t a r k and Mahoney (1942) c o n s i d e r t h e pod t o be d i v i d e d i n t o f o u r t i s s u e s . The i n n e r m o s t r e g i o n o f p a r e n c h y m a t i s s u e i s t h e e n d o c a r p . The a d j a c e n t r e g i o n , t h e m e s o c a r p c o n s i s t s o f two l a y e r s . The o u t e r l a y e r o f m esocarp c o n t a i n s t h e v a s c u l a r b u n d l e s w h i l e t h e i n n e r l a y e r has b een c a l l e d t h e " p a r c h m e n t " l a y e r . The o u t e r r e g i o n o f p a r e n chyma t o g e t h e r w i t h t h e e p i d e r m i s can be t e r m e d t h e e x o c a r p . The i n n e r e p i d e r m i s o f t h e f l o w e r bud g i v e s r i s e t o t h e i n n e r s o f t p a r e n c h y m a o f t h e p o d . The e n d o c a r p i s t h e t i s s u e w h i c h s u r r o u n d s t h e chamber where t h e s e e d d e v e l o p s . One o f t h e most i m p o r t a n t a r e a s i n t h e pod t i s s u e s i s t h e i n n e r m e s o c a r p . The f i b e r s h e a t h , as i t i s a l s o 52. named, i s i n v o l v e d i n t h e t e x t u r a l c h a r a c t e r i s t i c s o f bean q u a l i t y . The f i b e r s h e a t h c e l l s a r e o r i e n t e d o b l i q u e l y (45° a n g l e ) t o t h e l e n g t h o f t h e pod. The f i b r o u s s h e a t h o r " f i b e r o f t h e s i d e w a l l " i n young pods c o n s i s t s o f s m a l l , compact, a l m o s t i s o d i a m e t r i c c e l l s w i t h no c e l l w a l l t h i c k e n -i n g . T h e s e young f i b e r s h e a t h c e l l s f r o m a d i s t i n c t b o u n d a r y of v e r y n a r r o w c e l l s a b o u t 3 o r 4 deep between the i n n e r and o u t e r p arenchyma t i s s u e s . Reeve and Brown (1968a) s t a t e t h a t d i f f e r e n c e s i n f i b e r d e v e l o p m e n t between v a r i e t i e s were m a i n l y i n t h e r a t e s o f g r o w t h by c e l l e l o n g a t i o n . As t h e pods become more m a t u r e , t h e f i b e r s c l e r e i d s become much l a r g e r and d e v e l o p e x t e n s i v e t h i c k e n i n g o f t h e w a l l s ( S t a r k and Mahoney, 1942) t o f o r m t h e p a p e r y l a y e r o f t h e o v e r -m a t u r e p o d s . The s e c o n d a r y w a l l t h i c k e n i n g o f t h e c e l l s i n t h e i n n e r m e s o c a r p a p p e a r s t o be a c c e l e r a t e d by c o n d i t i o n s o f h i g h t e m p e r a t u r e s and low r a i n f a l l and does n o t o c c u r e x t e n s i v e l y u n t i l t h e pods a r e i n t h e l a t e r s t a g e s o f e d i b l e m a t u r i t y . However, t h e r e a r e m a j o r d i f f e r e n c e s between v a r i e t i e s i n t h e i r s e c o n d a r y g r o w t h c h a r a c t e r i s t i c s o f t h e f i b e r s h e a t h , b o t h i n t h e i r r e a c t i o n t o e x t e r n a l s t r e s s and i n c o n s e q u e n t c e l l w a l l c o m p o s i t i o n . S t a r k and Mahoney (1942) s t a t e t h a t i n no c a s e was l i g n i n p r e s e n t i n t h e i n n e r m e socarp a l t h o u g h a p o s i t i v e t e s t f o r t h e x y l a n - a r a b a n h e m i c u l l u l o s e s was o b t a i n e d a t v a r y i n g s t a g e s o f pod m a t u r i t y , d e p e n d i n g on v a r i e t y . Reeve and Brown (1968b) m e n t i o n e d t h a t t h e w a l l s of t h e f i b e r s h e a t h s c l e r e i d s g i v e a p o s i t i v e r e a c t i o n t o b o t h 53. l i g n i n and p e n t o s a n t e s t s i n c o n t r a s t t o some o f t h e f i n d i n g s o f S t a r k and Mahoney ( 1 9 4 2 ) . A n o t h e r r e g i o n w h i c h can a f f e c t t e x t u r e m a r k e d l y i s t h e o u t e r p a r e n c h y m a o r o u t e r m e s o c a r p . Reeve and Brown (1968a) have d e t e r m i n e d t h a t a l l o f t h e v a s c u l a r t i s s u e s o f t h e pod w a l l d e v e l o p w i t h i n t h e young o u t e r parenchyma d u r i n g f l o r a l and p o s t - f l o r a l g r o w t h . No v a s c u l a r b u n d l e s d e v e l o p i n t h e i n n e r p a r e n c h y m a . A c c o r d i n g t o D r i j f h o u t ( 1 9 7 0 ) , a p r o m i n e n t v a s c u l a r b u n d l e , p r o t e c t e d e x t e r n a l l y by a s h e a t h , o c c u r s b o t h a t t h e d o r s a l and v e n t r a l s i d e o f the pod i n t h e l a r g e - c e l l e d o u t e r p a r e n c h y m a t i s s u e . The s h e a t h , p r o t e c t i n g t h e v a s c u l a r b u n d l e s , c o n s i s t s o f 4 t o 8 l a y e r s o f s m a l l c e l l s and c o n s t i t u t e s t h e " s t r i n g s " f o u n d i n b ean p o d s . The s h e a t h may be composed o f v a r y i n g r a t i o s o f t h r e e k i n d s o f c e l l s : p a r e n c h y m a c e l l s , wood c e l l s and s c l e r e n c h y m a ( f i b e r ) c e l l s . The s c l e r e n c h y m a c e l l s a r e r e s p o n d i b l e f o r t h e s t r e n g t h o f t h e s t r i n g and may c o n s t i t u t e up t o 90% o f t h e s h e a t h c e l l s i n e x t r e m e l y s t r i n g y v a r i e t i e s . In f a c t , a c c o r d i n g t o D r i j f h o u t ( 1 9 7 0 ) , s t r i n g l e s s v a r i e t i e s do n o t e x i s t as i s e v i d e n t from t h e a n a t o m i c a l s t r u c t u r e o f t h e pod w a l l . T e m p e r a t u r e can have a marked e f f e c t on v a r i e t i e s t h a t have no c o m p l e t e s t r i n g i n t h e p o d , w h i l e l i t t l e o r no t e m p e r a t u r e i n f l u e n c e was n o t e d i n pods o f r e l a t i v e l y s t r i n g y v a r i e t i e s . The e x o c a r p i s composed o f t h e o u t e r e p i d e r m i s and t h e u n d e r l y i n g h y p o d e r m a l c e l l s . Reeve and Brown (1968b) 5.4. m e n t i o n t h a t c h l o r o p l a s t s a r e p r e s e n t i n t h e o u t e r p a r e n c h y m a and o c c u r p r i m a r i l y i n t h e e x o c a r p w h i l e t h e i n n e r p a r e n c h y m a c o n t a i n s no c h l o r o p l a s t s . T h e s e s t r u c t u r e s e n s u r e t h a t p h o t o s y n t h e s i s can t a k e p l a c e i n t h e bean pod as i s e v i d e n c e d by t h e f a c t t h a t s m a l l s t a r c h g r a n u l e s a p p e a r i n t h e o u t e r p a r e n c h y m a as t h e pod u n d e r g o e s r a p i d e l o n g a t i o n b e f o r e h a r v e s t m a t u r i t y i s r e a c h e d . The amount o f s t a r c h p r e s e n t v a r i e s p r i m a r i l y w i t h t h e c o n d i t i o n s t h a t i n f l u e n c e t h e r a t e o f p h o t o s y n t h e s i s . Numerous s t o m a t a w i t h e x t e n s i v e sub-s t o m a t a l i n t e r c e l l u l a r s p a c e s a r e e v i d e n t i n t h e u p p e r e p i d e r m i s o f t h e pod a t e d i b l e m a t u r i t i e s . The e x t e n t o f t h e i n t e r c e l l u l a r s p a c e s o f t h e o u t e r e p i d e r m i s and t h e a d h e s i v e p r o p e r t i e s o f t h e m i d d l e l a m e l l a e o f t h e h y p o d e r m a l c e l l s b o t h c o n t r i b u t e t o s l o u g h i n g c h a r a c t e r i s t i c s o f b l a n c h e d and c a n n e d g r e e n b e a n s . The w a l l s o f t h e h y p o d e r m a l c e l l s t h i c k e n d u r i n g e d i b l e m a t u r i t y s t a g e s o f pod g r o w t h and a r e g r e a t l y t h i c k e n e d when the pods a r e o v e r l y m a t u r e . The w a l l s and m i d d l e l a m e l l a e o f t h e h y p o d e r m a l c e l l s g i v e p o s i t i v e r e a c t i o n s f o r p e c t i n s and h e m i c e l l u l o s e s . T h i s w i l l a f f e c t t h e c u l i n a r y q u a l i t i e s o f t h e pod t o a c e r t a i n e x t e n t as we 11. 3. Seed d e v e l o p m e n t C a r r and Skene (1961) d e s c r i b e t h e d e v e l o p m e n t a l s t a g e s o f t h e bean s e e d . The growth c u r v e o f t h e bean s e e d was d i a u x i c , i . e . two p h a s e s o f h i g h g r o wth r a t e s e p a r a t e d by a l a g p h a s e . T h r e e p h a s e s can t h e r e f o r e be n o t e d i n t h e growth o f b e a n s e e d s . In t h e f i r s t , g r o w t h i s e x p o n e n t i a l w i t h t h e f i r s t s t a g e o c c u r r i n g f rom t h e 8 t h t o t h e 2 0 t h day a f t e r a n t h e s i s . In t h e s e c o n d p h a s e ( l a s t i n g o n l y 3 d a y s ) growth i s much l e s s r a p i d t h a n i n t h e f i r s t s t a g e and i s r e f e r r e d t o as t h e l a g p h a s e . In t h e t h i r d p h a s e , growth i s i n i t i a l l y a b o u t as r a p i d as i n t h e e x p o n e n t i a l f i r s t p h a s e , b u t g r a d u a l l y d e c l i n e s t o z e r o as t h e s e e d becomes mature and e n t e r s d o r m a n c y . The l a g p h a s e i n bean s e e d growth can be e x p l a i n e d m o r p h o l o g i c a l l y i n t h a t t h e embryo, i n i t i a l l y s m a l l compared t o t h e embryo s a c i n w h i c h i t i s c o n t a i n e d , grows a t a f a s t e r r a t e t h a n t h e s a c u n t i l i t f i l l s t h e s a c . T h i s p o i n t c o r r e s p o n d s t o t h e s t a r t o f t h e l a g p h a s e . Few c e l l d i v i s i o n s o c c u r i n c o t y l e d o n s o f t h e s e e d o l d e r t h a n 3 weeks a f t e r f l o w e r i n g . Growth i s p r i m a r i l y c e l l e n l a r g e m e n t a f t e r t h i s p o i n t a c c o r d i n g t o Loewenberg ( 1 9 5 5 ) . Dry w e i g h t o f t h e bean s e e d s a t t h i s t i m e i s l e s s t h a n 15% o f t h a t f i n a l l y o b t a i n e d . T a b l e B l . S i m p l e l i n e a r c o r r e l a t i o n c o e f f i c i e n t s among s e l e c t e d q u a l i t y and r h e o l o g i -c a l p a r a m e t e r s o f g r e e n snap beans i n 1971 and 1972 - - p o o l e d v a r i e t i e s and s i z e s . Seed % Dry Leng t h M a t t e r % F i b e r S p r e a d Y i e l d T e s t S t r e s s m n_ S h e a r P r e s s OTMS Seed L e n g t h % Dry M a t t e r % F i b e r S p r e a d T e s t Y i e l d S t r e s s m n_ S h e a r P r e s s OTMS CM cn .772** ,573** 720** .515** 193 -.353** 326** .111 422** .079 136. .132 531** .478** 384** .463** 1971 624** - .633** ~ 7 T I 3 * 459** -.856** .957* -.101 -1.000* .577*' . 737* .636* 216* -.834* -.878* 151 -.695** .997** 252 -.653** .948** 130 .324** -.369** -.308** 321 -.057 -.368 665** -.560** .391** .468* .292** 029 .691** .610** 112 .615** .583** 313 .678** .605** 216 -.598** -.607** 178 .435 .601 353 .726** .670** -.095 -.018 327 .914** 298** .418** S i g n i f i c a n t at P < 0.01 S i g n i f i c a n t a t P < 0.05 T a b l e B2. S i m p l e l i n e a r c o r r e l a t i o n c o e f f i c i e n t s among s e l e c t e d q u a l i t y and r h e o l o g i -c a l p a r a m e t e r s o f g r e e n snap beans -- p o o l e d d a t a . Seed % Dry % F i b e r S p r e a d Y i e l d m n S h e a r OTMS Le n g t h M a t t e r T e s t S t r e s s P r e s s Seed L e n g t h % Dry M a t t e r .729** % F i b e r .692** .230** S p r e a d T e s t -.368** -.778** -.369** Y i e l d S t r e s s -.152 .402** -.197 -.697** m .315** .751** .405** -.837** .946** n -.384** -.562** -.378** .630** -.374** -.631** S h e a r P r e s s .684** .641** .652** -.569** .076 .547** -.503** OTMS .565** .737** .676** -.728** .583** .780** -.636** .779** ** S i g n i f i c a n t a t P < 0.01 * S i g n i f i c a n t at P < 0.05 T a b l e B3. S i m p l e l i n e a r c o r r e l a t i o n c o e f f i c i e n t s among s e l e c t e d q u a l i t y and r h e o l o g i -c a l p a r a m e t e r s o f g r e e n snap beans f o r T e n d e r c r o p and R a i n i e r -- p o o l e d s i z e s Seed L e n g t h % Dry M a t t e r % F i b e r S p r e a d T e s t Y i e l d S t r e s s m n S h e a r P r e s s OTMS TENDERCROP Seed L e n g t h .725** .748** - . 575** - .199 .433* - . 201 .902** . 766** % Dry M a t t e r .658** .607** - . 767** -.079 . 711** - . 231 .718** .763** % F i b e r .759** .785** -.589** - . 113 .431 - . 285 . 600** .672** S p r e a d T e s t DC OJ r H - .134 -.648** -.579** - . 612**- .853** .431* - . 569 -.701** Y i e l d S t r e s s z r H < CC -.706** .021 -.598** -.552** .942** - . 296 .019 .100 m .079 .691** -.490* - .715** .915** - . 377 .436 .677** n -v! 35 7 -.638** . 298 .447* -.136 - .667** - . 230 - .418* S h e a r P r e s s . .694** .624** .685** - . 398 -.635 .220 - .446 .674** OTMS . 310* .721** .494** - .629** .430* .589** - .408* .468** ** S i g n i f i c a n t a t P < 0.01 * S i g n i f i c a n t a t P < 0.05 T a b l e B4. S i m p l e l i n e a r c o r r e l a t i o n c o e f f i c i e n t s among s e l e c t e d q u a l i t y and r h e o l o g i -c a l p a r a m e t e r s o f g r e e n snap beans f o r H a r v e s t e r and BBL 290 v a r i e t i e s --p o o l e d s i z e s . Seed % Dry % F i b e r S p r e a d Y i e l d L e n g t h M a t t e r T e s t S t r e s s m n S h e a r OTMS P r e s s o cn CM Seed L e n g t h % Dry M a t t e r % F i b e r S p r e a d T e s t Y i e l d S t r e s s m CQ m n S h e a r P r e s s OTMS 782' .800** .621** - .001 -.272 -.747** -.480* . 192 -.593** .718** .600** 346 653** 665** 621** 773** HARVESTER 826** -.652' 124 640** -.922** .648** -.585* -.329 461* 839** 402 635' 342 827** -.924** 986' 830** 434* -.384 329 -.769** .722** 549** .470 .277 -.564** 693** .152 .285 703** -.256 -.165 051 809** 815** .653** 766** .706** .831** 548** .645** .565** 779** -.925** 393 .023 .698** 762** .651* .811** -.778** -.840** 013 .770** 781** .688** ** S i g n i f i c a n t at P < 0.01 * S i g n i f i c a n t at P < 0.05 T a b l e B5. S i m p l e l i n e a r c o r r e l a t i o n c o e f f i c i e n t s among s e l e c t e d q u a l i t y and r h e o l o g i -c a l p a r a m e t e r s o f g r e e n snap beans f o r s i e v e s i z e s 2 and 3+4 - - p o o l e d v a r i e t i e s . Seed L e n g t h % Dry % F i b e r S p r e a d Y i e l d M a t t e r T e s t S t r e s s m n S h e a r OTMS P r e s s Seed L e n g t h % Dry M a t t e r % F i b e r S p r e a d T e s t Y i e l d S t r e s s " + to m n CO S h e a r P r e s s OTMS 732** 56 398* 605** 718** 365** 445** .173 098 706** 800** 650** 122 211 -.565** -.841** .029 317 409* 561** SIZE 2 290 234 678** 643** 847** 714** 092 294 001 609' - . 019 930** 377* 440** .364** -.423* .135 620** 570' 616' 554' . 493** 004 626** 940** 690** 521* 867** 220 140 217 109 158 109 237 .471** 055 .530** 233 .114 482 850** 926** .157 .654** .718** -.863**-.048 653** 768** .696** 031 * * S i g n i f i c a n t at P < 0.01 * S i g n i f i c a n t at P < 0.05 T a b l e B6. S i m p l e l i n e a r c o r r e l a t i o n c o e f f i c i e n t s among s e l e c t e d q u a l i t y and r h e o l o g i -c a l p a r a m e t e r s o f g r e e n snap beans f o r s i e v e s i z e s 5 and 6 -- p o o l e d v a r i e t i e s . Seed L e n g t h % Dry M a t t e r % F i b e r S p r e a d T e s t Y i e l d S t r e s s m n S h e a r P r e s s OTMS Seed L e n g t h .820** .534** -.771** SIZE 5 . 494* .709** - . 720** .413** . 592** % Dry M a t t e r .818** .609** - .920** . 863** .893** - . 747** . 392* .670** % F i b e r . 591** .695** -.782** .599** .703** -.631** . 352* . 657** S p r e a d T e s t vO - .682** - .922** -.794** -.760** -.852** .775** -.587 - .896** Y i e l d S t r e s s UJ to r-t i o .124 .572* .557 -.760** .960** -.523* . 863 .889** m .534* . 847** .531 -.872** .964** -.649** .699 .791** n -.501* - , 601* .411 .613** - .478 - . 748** - .488 -.747** S h e a r P r e s s .718** .700** . 772** -.922** .618 .596 - . 132 . 799** OTMS .643** .825** . 759** - .968** .864** .809** - . 525* .813** ** S i g n i f i c a n t at P < 0.01 * S i g n i f i c a n t at P < 0.05 

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