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Some physical chemical and histological characteristics of ripening bananas Charles, Ronald John 1972

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SOME PHYSICAL CHEMICAL AND HISTOLOGICAL CHARACTERISTICS OF RIPENING BANANAS by RONALD JOHN CHARLES B . S c . ( A g r i c ) U n i v e r s i t y o f B r i t i s h Columbia 1970 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF . THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n the Department of FOOD SCIENCE  We accept t h i s t h e s i s as conforming required  to the  standard  THE UNIVERSITY OF BRITISH COLUMBIA September, 1972.  In presenting this thesis in partial  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 shall make it freely available for reference a n d s t u d y . I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the Head of my Department or by his representatives.  It  is understood that copying or publication  of this thesis for financial gain shall 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  S e p t e m b e r 15.  1972  ii  ABSTRACT  A study 16  ±  1°C  ated  and  25  o f changes  ± 1°C  subjectively  i s described.  and by  Theological  properties  viscometry;  selected  tests  and  light  microscopy.  temperature  rate  was  due  to-peel of  ratio  roughly  ripened  color as  index, as  maximum  generally  ture.  Reducing  lower  at the h i g h e r  the  reducing sugar  color  index  6.  On  properties  1 kg  a  t o be  lower  force.  linear  increased  the basis  yellow Also  pulp-  than  that  limit  by  a  linear  o f the  of the  essentially color  ripen-  temperature  constant index,  puree  tempera-  throughout  at the lower  peel  tissue  at the h i g h e r  linearly  of peel  fruits  For a given  coefficient  while  was  Higher  full  reflected  ripening  temperature  by  at the higher  i n the p e e l .  a n d was  during  and  appropriate  temperature-ripened  and  evalu-  temperature.  consistency  content  by  at the lower.  tended  under  force  sugars  ing  fruits  was  compression  d i d not develop  softer  a power-law  change  retention  of high  of deformation  plate  that  at the lower  progressively  well  were  pulp  color  properties  color  ripening at  spectrophotometry;  histological  twice  fruits  f o r such  The  increase  and  to chlorophyll  fruits  became  chemical  of peel  temperature-ripened color  parallel  during  Peel  reflectance  by  histochemical  The  i n bananas  beyond  total  iii  sugar  and  moisture  levels  were  ture.  Ripening  relations  lower  content  were  in fruits  ripened  temperature  of color  index  higher  while  at  starch  the higher  therefore influences  to mechanical  and  and  AIS  temperathe  chemical  prope r t i es. Ripening rigidity in  as w e l l  as  over-ripe pulp  but  d i d not  not  detected  amounts steadily  color  apparent  tissue.  i n hard  during  ripening. color  f o r both and  index  o f b an an as .  was  chemical  remained  chart  3,  then  overall  p r o p e r t i e s at  higher  i s used  however,  be  of  were  substantial decreased  a given  (P < 0 . 0 1 ) . into  to estimate  ripening  o f stage  of  Although  temperatures,  taken  wall  pectins  index  temperatures.  ripening  loss  during  Esterified  index  the best  temperatures  a gradual  decreased  fruit;  color  ripening  f o r t h e two  ripening  Tannins  green  by  t h i c k e n i n g o f the c e l l  completely.  at p e e l  correlations that  characterized  appeared  rheological differed  an  disappear  Peel ripeness  was  color  these It is  account  the stage  index  interrecommended, when  of  the  ripeness  iv  TABLE OF CONTENTS PAGE LIST OF TABLES  vii  LIST OF FIGURES  viii  ACKNOWLEDGEMENTS  x  INTRODUCTION  1  LITERATURE REVIEW  4  Banana R i p e n i n g  4  Commercial methods  4  F a c t o r s which a f f e c t r i p e n i n g  4  Temperature  4  Humidity  6  Ethylene  6  Changes A s s o c i a t e d w i t h R i p e n i n g  8  Color  8  Texture  9  Carbohydrates  12  Acidity  13  Moisture Anatomy and H i s t o l o g y  '  13 14  EXPERIMENTAL METHODS  17  Sampling Procedures  17  Materials  17  Ripening  17  Sampling  18  V  PAGE EXPERIMENTAL METHODS (Continued) Physical Properties  18  Length  18  Pulp-to-peel r a t i o  18  Color  18  Rheological Properties . Force-deformation  19  behavior  19  Flow b e h a v i o r  20  Chemical P r o p e r t i e s  23  Moisture  23  pH  23  Alcohol insoluble solids  23  Reducing sugars  24  Total,sugars  25  Starch  25  Titrable  acidity  Histochemical  26  Properties  26  Starch  27  E s t e r i f i e d pectins  27  Tannins  27  Histological  Properties  «'  Sample p r e p a r a t i o n S e c t i o n i n g and s t a i n i n g RESULTS AND DISCUSSION Changes During  Ripening  28 28  -  29 31 31  vi  PAGE RESULTS AND DISCUSSION  (Continued)  Physical properties  31  Fruit size  31  Pulp-to-peel r a t i o  31  Color  34  Rheological properties  34  Force-deformation behavior  34  Flow b e h a v i o r  37  Chemical p r o p e r t i e s  40  Moisture  40  Acidity  40  Alcohol insoluble solids  „  40  Sugars  42  Starch  42  Histochemical properties  47  Histological properties  49  E f f e c t o f R i p e n i n g Temperature  51  Physical properties  52  Rheological properties  52  Chemcial p r o p e r t i e s  54  R e l a t i o n s h i p s Among P r o p e r t i e s  58  CONCLUSIONS  64  LITERATURE CITED  66  vii  LIST OF TABLES TABLE  PAGE Simple c o r r e l a t i o n s among s i z e c h a r a c t e r i s t i c s of bananas (pooled n = 195)  data,  31  Means, s t a n d a r d d e v i a t i o n s and t - t e s t r e s u l t s f o r s i z e c h a r a c t e r i s t i c s of bananas  32  Simple c o r r e l a t i o n s among s e l e c t e d p h y s i c a l , r h e o l o g i c a l and c h e m i c a l p r o p e r t i e s o f bananas r i p e n e d at 16 + 1°C. (n = 110).  59  Simple c o r r e l a t i o n s among s e l e c t e d p h y s i c a l , r h e o l o g i c a l and c h e m i c a l p r o p e r t i e s o f bananas r i p e n e d at 25 + 1°C. (n = 85)  60  Simple c o r r e l a t i o n s among s e l e c t e d p h y s i c a l , r h e o l o g i c a l and c h e m i c a l p r o p e r t i e s o f r i p e n i n g bananas. (Pooled d a t a , n = 195).  61  viii  LIST OF FIGURES FIGURE  PAGE  1  B i o c h e m i c a l changes i n bananas d u r i n g r i p e n i n g (Simmonds 1966)  10  2  Typical force-deformation banana p u l p t i s s u e  21  curve f o r  3  Changes i n p u l p - t o - p e e l r a t i o o f bananas during ripening  33  4  Changes i n c o l o r index o f bananas d u r i n g ripening  35  5  R e f l e c t a n c e curves f o r the p e e l of bananas r i p e n e d at 16 i 1 C  36  R e f l e c t a n c e curves f o r the p e e l o f bananas r i p e n e d at 25 ± 1°C  36  Changes i n l i n e a r l i m i t of banana p u l p tissue during ripening  38  Changes i n c o n s i s t e n c y c o e f f i c i e n t o f banana puree d u r i n g r i p e n i n g  39  Changes i n m o i s t u r e content pulp during r i p e n i n g  41  6 7 8 9 10 11. 12  Changes i n AIS content during ripening  of banana  o f banana p u l p 43  Changes i n t o t a l sugar c o n t e n t pulp during r i p e n i n g  o f banana 44  Changes i n r e d u c i n g sugar content o f banana pulp d u r i n g r i p e n i n g .  45  13  Changes i n s t a r c h content during ripening  46  14  S e c t i o n s o f banana p u l p t i s s u e tannin d i s t r i b u t i o n ,  15 16  o f banana p u l p showing  48  P h o t o m i c r o g r a p h s o f banana p u l p t i s s u e d u r i n g r i p e n i n g at 16 ± 1°C (X 320)  50  E f f e c t o f r i p e n i n g temperature on p u l p t o - p e e l r a t i o o f bananas  53  ix  E f f e c t o f r i p e n i n g t e m p e r a t u r e on deformation of banana.pulp tissue u n d e r 1 kg f o r c e E f f e c t o f r i p e n i n g t e m p e r a t u r e on t o t a l sugar content of banana pulp tissue  X  ACKNOWLEDGEMENTS  The a u t h o r wishes t o express h i s a p p r e c i a t i o n f o r a s s i s t a n c e by Dr. M.A. Tung, Food S c i e n c e who d i r e c t e d t h i s r e s e a r c h  Department,  project.  A p p r e c i a t i o n i s a l s o extended t o Dr. W.D. and Dr. J.F. R i c h a r d s ,  Food S c i e n c e  Nyborg, A g r i c u l t u r a l E n g i n e e r i n g Jolliffe,  Plant Science  Department;  Dr. E.O.  Department and Dr. P.A.  Department f o r t h e i r  as members o f the r e s e a r c h  Powrie,  assistance  committee.  The w r i t e r i s g r a t e f u l f o r the use o f a Rotary Microtome i n the P l a n t S c i e n c e This research  Department.  was f i n a n c e d , i n p a r t , by the  Canadian I n t e r n a t i o n a l Development  Agency.  1. INTRODUCTION Bananas are grown e x c l u s i v e l y i n the t r o p i c s they are consumed i n p r a c t i c a l l y every c o u n t r y .  but  In a d d i t i o n  to b e i n g a major i t e m of i n t e r n a t i o n a l t r a d e , the banana i s the most i m p o r t a n t t r o p i c a l  f r u i t on the w o r l d market.  A r t h u r et aj_. (1968) s t a t e d t h a t w i t h o u t doubt the banana i s the w o r l d ' s most w i d e l y consumed In 1969, m i l l i o n tons  (FAO  fruit.  t o t a l banana e x p o r t s amounted to 1971).  5.93  T h i s exceeded the amount of c i t r u s  f r u i t s and apples t r a d e d d u r i n g the same y e a r , l e a v i n g  the  banana as the most i m p o r t a n t f r e s h f r u i t i n i n t e r n a t i o n a l trade.  P r e l i m i n a r y FAO  e s t i m a t e s i n d i c a t e t h a t 199,000 tons  of bananas were imported i n t o Canada i n 1970. commencing January  1969  to January  1972,  For the p e r i o d  the t o t a l  o f bananas i n t o Canada was  v a l u e d at $7.11  ( S t a t i s t i c s Canada 1972).  In B r i t i s h Columbia,  account  28.3  million,  f o r a s u b s t a n t i a l amount of a l l imported  Banana i m p o r t s through  B.C.  m i l l i o n t o n s , (B.C.  customs i n 1970  Dept. Ind. Dev.  continuous  fresh  fruit.  amounted to  the y e a r , but  because of t h e i r p e r i s h a b l e n a t u r e , p r o l o n g e d Weekly shipments  bananas  Trade $ Comm. 1971).  Bananas are marketed throughout  not p o s s i b l e .  import  storage i s  of green bananas ensure  s u p p l y of f r e s h f r u i t -at r e t a i l  outlets.  a  However,  f l u c t u a t i o n s i n s u p p l y and demand make i t n e c e s s a r y f o r commercial  r i p e n i n g e s t a b l i s h m e n t s to adopt v a r i o u s r i p e n i n g  s c h e d u l e s i n o r d e r to meet the market  requirements.  2.  The r i p e n i n g p e r i o d ( S e e l i g 1969).  can be v a r i e d from 4 to 10 days  The p r i n c i p a l f a c t o r s used i n the r e g u l a t i o n  of r i p e n i n g are t e m p e r a t u r e , h u m i d i t y , v e n t i l a t i o n and e t h y l e n e gas.  Two  of those f a c t o r s -- temperature and  e t h y l e n e -- are perhaps the most i m p o r t a n t . ripeners  use e t h y l e n e to s t i m u l a t e  Most commercial  or " t r i g g e r " the r i p e n i n g  p r o c e s s w h i l e the r a t e of r i p e n i n g i s c o n t r o l l e d by ture  tempera-  regulation. F r u i t q u a l i t y i s known to be a f f e c t e d by s t o r a g e  and r i p e n i n g temperatures (Simmonds 1966).  Prolonged  exposure to h i g h temperatures d u r i n g r i p e n i n g may  l e a d to  " b o i l e d " f r u i t , w h i l e low temperatures g i v e r i s e to c h i l l i n g injury  ( H a l l 1967):  Under normal commercial  such forms of i n j u r y r a r e l y o c c u r . several reports  ( H a l l 1967 ;  N i e v a e_t a_l_. 1969;  conditions,  However, t h e r e have been  D a l a i e_t a_l_. 1969;  Sanchez  Murata 1970) of d i f f e r e n c e s  in fruit  q u a l i t y , o b t a i n e d w i t h i n the range of normal  ripening  procedures. Many of the s t u d i e s  i n v o l v i n g bananas r i p e n e d  under  d i f f e r e n t c o n d i t i o n s , have f o c u s s e d on major c h e m i c a l constituents changes  and used p a n e l e v a l u a t i o n o f q u a l i t y .  i n physical properties  The  of the f r u i t have been  c o n s i d e r e d l a r g e l y i n d e s c r i p t i v e , terms, a l t h o u g h t h e i r importance i n f r u i t q u a l i t y i s r e c o g n i z e d ( S e e l i g 1969). T h i s study was u n d e r t a k e n to i n v e s t i g a t e some p h y s i c a l , r h e o l o g i c a l and c h e m i c a l p r o p e r t i e s  of the banana  during and  ripening.  A  study  h i s t o l o g i c a l changes  microscopy.  The the  rheological  properties upon  relationships  the  of  also  i n the  o v e r a l l aim  standing' of  dependency  was  the  was  made o f  ripening to  ripening  temperature  of  histochemical  fruit,  obtain  among the  the  using  a better  major fruit  ripening.  under-  chemical and  light  their  and  4.  LITERATURE REVIEW Banana R i p e n i n g Commercial  methods  The c o n t r o l l e d r i p e n i n g o f bananas i s c a r r i e d out by v a r i o u s methods.  In temperate c o u n t r i e s , r i p e n i n g i s  c a r r i e d out i n s p e c i a l l y c o n s t r u c t e d r i p e n i n g rooms i n which t e m p e r a t u r e , h u m i d i t y and a i r c i r c u l a t i o n  are c a r e f u l l y  controlled. Modern r i p e n i n g methods have been reviewed by vonLoesecke Seelig  ( 1 9 5 0 ) , Haarer (1964) and Simmonds (1966).  (1969) reviewed the r e q u i r e m e n t s f o r r i p e n i n g rooms  w i t h p a r t i c u l a r r e f e r e n c e to those adapted f o r boxed The major companies  i n v o l v e d i n the banana t r a d e p r o v i d e  customers w i t h r i p e n i n g recommendations  which a l l o w the  r i p e n i n g p e r i o d to be v a r i e d from 4 to 8 days S a l e s Corp. 1970;  fruit.  (United  Fruit  S t a n d a r d F r u i t and Steamship Co. 1964).  F a c t o r s which a f f e c t Temperature:  ripening.  D u r i n g r i p e n i n g , bananas produce a  c o n s i d e r a b l e amount o f heat as a r e s u l t o f r e s p i r a t o r y activity. at  The amount o f heat g i v e n o f f by green bananas  54°F (12.2°C) i s a p p r o x i m a t e l y 140 B t u / t o n h r  (USDA 1954).  Simmonds (1966) c a l c u l a t e d the heat p r o d u c t i o n  of p r e c l i m a c t e r i c f r u i t  at 53°F (I1.7°C) t o be a p p r o x i m a t e l y  150 B t u / t o n h r . At 68°F (20°C) heat p r o d u c t i o n i n c r e a s e s from 348 B t u / t o n h r at p r e c l i m a c t e r i c to 386 B t u / t o n h r  d u r i n g the c l i m a c t e r i c  (USDA 1954).  These c a l c u l a t i o n s are  based on the amount o f carbon d i o x i d e e v o l v e d . To o b t a i n a r i p e f r u i t  o f e x c e l l e n t q u a l i t y the  p u l p temperature s h o u l d be kept between 58°F (14.3°C) and 64°F (17.6°C) depending on the r a t e of r i p e n i n g ( U n i t e d F r u i t S a l e s Corp. 1970).  desired  The maintenance  o f con-  s t a n t p u l p temperatures r e q u i r e s t h a t heat be withdrawn from the box a t l e a s t as f a s t as i t i s produced by the f r u i t . The a i r temperature must be lower s i n c e the c a r d b o a r d acts as an i n s u l a t o r . listed  In o r d e r t o m a i n t a i n the p u l p temperatures  above, a i r temperatures between 52°F (11.1°C) and  58°F (14.3°C) are recommended ( U n i t e d F r u i t S a l e s Corp. 1964). At t h e c l i m a c t e r i c , p u l p temperature tends to i n c r e a s e very r a p i d l y and room temperature i s u s u a l l y lowered t o m i n i m i z e the i n c r e a s e .  A f t e r t h e f r u i t has  "sprung" -- i . e . i n the p o s t c l i m a c t e r i c p e r i o d -- the a i r temperature may a g a i n be r a i s e d g r a d u a l l y as heat subsides.  evolution  Changes i n a i r temperature r e s u l t i n a g r a d u a l  change i n p u l p t e m p e r a t u r e , and because o f t h i s i t i s recommended t h a t p u l p t e m p e r a t u r e s be r e c o r d e d at l e a s t t w i c e a day ( U n i t e d F r u i t S a l e s Corp.  1970).  Temperature a f f e c t s the r a t e o f r i p e n i n g as w e l l as the q u a l i t y o f r i p e f r u i t . difficult  The p r e c i s e e f f e c t s are  t o e v a l u a t e because o f i n t e r a c t i o n w i t h  factors  such as v e n t i l a t i o n , h u m i d i t y and the  fruit.  Other f a c t o r s  p r o d u c t i o n and  the p h y s i o l o g i c a l  age  such as v a r i e t y , c o n d i t i o n s  pre-ripening  s t o r a g e may  be  of  of of  considerable  significance . Humidity:  The  s k i n of a mature banana c o n t a i n s 2  a l a r g e number very a c t i v e  480/cm ) of stomata and  (Palmer 1971).  transpiration is  Simmonds (1966) summarized  r e s u l t s of e a r l i e r r e s e a r c h which showed t h a t ripening  by  a s t e a d y s t a t e i n which  i s h i g h e r than i n the p r e c l i m a c t e r i c water l o s s o c c u r r i n g fungal  during  t r a n s p i r a t i o n i n c r e a s e s r a p i d l y at the  This i s followed  attack.  The  stage.  at advanced r i p e n i n g  climacteric.  transpiration Increased  is related  to  r a t e of t r a n s p i r a t i o n i s l a r g e l y  dependent upon temperature and  humidity.  In o r d e r to ensure p r o p e r water r e l a t i o n s  during  ripening  a h i g h r e l a t i v e h u m i d i t y must be m a i n t a i n e d .  general,  r e l a t i v e h u m i d i t y of 85  the b e g i n n i n g of r i p e n i n g .  As  h u m i d i t y i s reduced to 75 Ethylene:  - 95%  the  Burg and  "breaks" color  vonLoesecke (1950) r e v i e w e d the  have examined  endogenous e t h y l e n e and  the  P r a t t and  the  Goeschl  develop  of e t h y l e n e i n banana ( B i a l e et al_. the  has  1954;  r e l a t i o n s h i p between  respiratory  r o l e of e t h y l e n e i n f r u i t r i p e n i n g a n a l y z e d by  i s recommended at  fruit  S i n c e then o t h e r workers Burg 1965)  In  85%.  ments which l e d to w i d e s p r e a d use ripening.  the  climacteric. been  (1969) and  The  recently  by McGlasson  (1970)  7. while  Palmer (1971) has  discussed  e t h y l e n e i n commercial t r a n s p o r t The still  the and  s i g n i f i c a n c e of r i p e n i n g of bananas.  mechanism of e t h y l e n e a c t i o n i n f r u i t s  unresolved, despite  extensive  research.  is  McGlasson  (1970) observed t h a t s e v e r a l hypotheses have been p r e s e n t e d which attempt to e x p l a i n the a c t i o n of e t h y l e n e i n terms of i t s e f f e c t s on enzyme a c t i v i t i e s , i n t e r a c t i o n s w i t h n u c l e i c acids  and  metallo-enzymes and  p r o t e i n membranes. a d e q u a t e l y , but  e f f e c t s on  These hypotheses can be  they f a i l  lipo-  supported  to e s t a b l i s h the n a t u r e of  the  p r i m a r y a c t i o n of e t h y l e n e i n f r u i t t i s s u e . B i a l e ejt a_l_. (1954) r e p o r t e d b y - p r o d u c t of r i p e n i n g . found t h a t p r e c 1 i m a c t e r i c  Burg and  a few  ethylene w i l l differences  hours b e f o r e the  - 0.2  climacteric.  ethylene treatment.  among f r u i t s  Endogenous due  to  the  in a lot,  e n c o u n t e r e d i n the absence of  Supplementary e t h y l e n e enables a l l  f r u i t i n a l o t to a t t a i n the t h r e s h p l d  r i p e n i n g at about the  ppm  increases  induce r i p e n i n g i n the banana, but  uneven r i p e n i n g i s f r e q u e n t l y  the  0.1  that t h i s l e v e l  i n p h y s i o l o g i c a l age  a  Burg (1965) have s i n c e  bananas c o n t a i n  e t h y l e n e i n t h e i r t i s s u e , and dramatically  t h a t e t h y l e n e was  same t i m e .  level,  for  Ethylene production  in  the banana i s temperature s e n s i t i v e (Palmer 1971), thus  low  temperature r i p e n i n g i s not p o s s i b l e i n the absence of applied  ethylene. In commercial p r a c t i c e e t h y l e n e i s a p p l i e d at  the  8.  r a t e of one  c u b i c f o o t per 1000  c u b i c f e e t of r i p e n i n g  space ( U n i t e d F r u i t S a l e s Corp. 1964). t i o n s do not p r o v i d e  Higher  additional benefits.  u s u a l l y a p p l i e d as soon as the green f r u i t the r i p e n i n g room.  Treatment may  d u r i n g a 24 - 36 hour p e r i o d Changes A s s o c i a t e d w i t h  i s stacked  Recently  in  be s i n g l e or m u l t i p l e  (Hall  1967).  of b i o c h e m i c a l  changes i n  c a r r i e d out by vonLoesecke  Simmonds (1966) summarized the more c o n s p i c u o u s f e a t u r e s of r i p e n i n g .  gas i s  Ripening  An e x t e n s i v e review the r i p e n i n g banana was  The  concentra-  These are p r e s e n t e d  Palmer (1971) has  reviewed  the  (1950).  biochemical  i n Figure  1.  compositional  changes d u r i n g r i p e n i n g , as w e l l as the enzymes i n v o l v e d . In t h i s s e c t i o n o n l y those the study w i l l be  changes which are r e l e v a n t to  discussed.  Color During  r i p e n i n g the banana p e e l changes i n c o l o r  from green to y e l l o w .  Y e l l o w i n g of the p e e l begins  at or  f o l l o w s the c l i m a c t e r i c peak (Palmer 1971), w h i l e the r a t e of y e l l o w i n g i s dependent upon the r i p e n i n g c o n d i t i o n s . Peel c o l o r i s probably stage  the most w i d e l y used index of  the  of r i p e n e s s . vonLoesecke (1950) summarized i n f o r m a t i o n on  pigment c o m p o s i t i o n and  carotene  During  of banana p e e l .  the  Chlorophyll, xanthophyll  are the major pigments i n green banana p e e l .  r i p e n i n g c h l o r o p h y l l i s reduced from 50 - 100  ug/g  f r e s h p e e l t o near z e r o , carotene constant  remains  approximately  at 1.5 - 3.5 ug/g f r e s h p e e l and x a n t h o p h y l l  remains c o n s t a n t Patterson  at 5 - 7 yg/g f r e s h p e e l .  also  Looney and  (1967) r e p o r t e d t h a t ch1orophy11ase a c t i v i t y i n  Gros M i c h e l p e e l reached a maximum at the c l i m a c t e r i c peak. I t was suggested t h a t c h l o r o p h y l l d e s t r u c t i o n was due t o the' l o s s o f s t r u c t u r a l i n t e g r i t y i n the ch 1 orop 1 as t s . The a b i l i t y of ethylene  to s t i m u l a t e r i p e n i n g i n d i c a t e s that  i t may have a d i r e c t e f f e c t on c h l o r o p h y l l d e s t r u c t i o n . E t h y l e n e - t r e a t e d bananas r i p e n w i t h u n i f o r m l y peels  colored  (vonLoesecke 1950; U n i t e d F r u i t S a l e s Corp. 1964). C o l o r measurement i n bananas has r e c e i v e d  attention.  G o t t r e i c h e_tj al_.  little  (1969) r e p o r t e d t h a t e a r l y  attempts t o determine s t a t e o f r i p e n e s s on the b a s i s o f pulp c o l o r f a i l e d because o f d i f f i c u l t i e s stable standard tance  colors.  Finney  e_t a_l_. (1967) used  spectrophotometry to evaluate  between p e e l c o l o r and f i r m n e s s  i n preparing reflec-  the r e l a t i o n s h i p  i n V a l e r y bananas.  They  r e p o r t e d t h a t l o s s o f c h l o r o p h y l l a s s o c i a t e d w i t h the change i n c o l o r from green t o y e l l o w was r e l a t e d t o the change i n r e f l e c t a n c e a t 675 nm. Texture S o f t e n i n g i n f r u i t s can be a t r i b u t e d t o the i n t e r conversions  o f s e v e r a l s t r u c t u r a l p o l y s a c c h a r i d e s . McCready  and McComb (1954) demonstrated t h a t p e c t i c substances p l a y a major r o l e i n the l o s s o f f i r m n e s s  in fruit  tissue.  10 Pre-climacteric  Climacteric j  Postclimacteric  colouring anthracnose sprung eating ripe rotting  firm green Internal O?  h  u JQ  GASES  Respiration ( C Q ) 2  |  C  c  Internal C O , eo  c  •H 3  TRANSPIRATION  § 2 >-.  rt C  ca  i_  (TJ I_  -  _o  c rt  I 1  </> o  0  Dry matter  o_30 Q_  oo  c • rt  «»  SOLIDS  J3 vO  Starch  f-H  (J O •—I  rt  O 10 •H E C  | 20 c 10  (D  u  o  j= e o s  l_  O -H •H CO  30  Skin  c  >. 20-  0  'ACTIVE TANNIN'  Pulp  100  Chlorophyll  (0 . C (A  W  50  _  PIGMENTS  L.  V D_  E  ~a  Carotenes and xanthophylls  0  vonLoesecke (1950) i n d i c a t e d t h a t d u r i n g r i p e n i n g , s o l u b l e p e c t i c s u b s t a n c e s i n the pulp of Gros M i c h e l bananas i n c r e a s e d from 0.3 0.5  to 0.2%  to 4.0%  w h i l e p r o t o p e c t i n d e c r e a s e d from  on a f r e s h weight b a s i s .  The  r o l e of c e l l u l c s e and h e m i c e l l u l o s e i n t e x t u r a l  change i n the r i p e n i n g banana was (1943).  i n v e s t i g a t e d by B a r n e l l  He r e p o r t e d t h a t c e l l u l o s e remained c o n s t a n t  hemice1lulose  d e c r e a s e d from 8 - 10% i n the pulp of green  f r u i t s to about 1 - 2% i n r i p e f r u i t s . content  while  f l u c t u a t e d d u r i n g r i p e n i n g and  him  t h a t i t a c t e d as a form of. r e s e r v e  was  concluded  that hemice1lulose  s u b s t a n c e s which may Sarkissian  was  Hemice1lulose t h i s suggested to carbohydrate.  hydrolyzed  to g i v e  serve as s u b s t r a t e s f o r r e s p i r a t i o n . (1965) used a m o d i f i e d C h a t i l l o n  and V e g e t a b l e T e s t e r to determine t e x t u r e - f i r m n e s s banana f r u i t t i s s u e .  It  This device i s a pressure  i n t e s t i n g s o f t f r u i t s such as s t r a w b e r r i e s . a p p l i e d at r i g h t angles  Fruit  in ripe  t e s t e r used  Pressure  was  to the cut s u r f a c e of 2 i n c h  unpeeled c r o s s s e c t i o n s of f r u i t .  He r e p o r t e d t h a t at  advanced p e e l c o l o r s the p u l p of V a l e r y bananas was  much  f i r m e r than t h a t of Gros M i c h e l . Finney  e_t a_l_. (1967) used a s o n i c t e c h n i q u e  measure changes i n f i r m n e s s ripened.  of V a l e r y bananas as  to  they  C y l i n d r i c a l s e c t i o n s of pulp were v i b r a t e d l o n g i -  t u d i n a l l y and  the resonant  f r e q u e n c i e s were used to c a l c u l a t e  Young's modulus of e l a s t i c i t y which i s d e f i n e d as the of s t r e s s to s t r a i n . f o r c e and  ratio  I t i s a measure of r e s i s t a n c e to  t h e r e f o r e , of f i r m n e s s .  They found t h a t s o f t e n i n g  of the banana d u r i n g r i p e n i n g was  a s s o c i a t e d w i t h a decrease  i n Young's-modulus of e l a s t i c i t y from 272 X 10 5 2 i n l i g h t green f r u i t to 85 X 10 ye 11 ow  dynes/cm  dynes/cm  i n the  full  stage. Carbohydrates S t a r c h i s the predominant c a r b o h y d r a t e  bananas.  During  ripening i t i s hydrolyzed  to  sugars.  vonLoesecke (1950) r e p o r t e d the s t a r c h c o n t e n t banana pulp as 20 - 25% and The  peel contains  ripening.  i n green  of green  t h a t of r i p e f r u i t as 1 -  3% s t a r c h which i s a l s o h y d r o l y z e d  Sugars n o r m a l l y  2%. during  i n c r e a s e from 1 - 2% i n green  f r u i t to 15 - 20% i n the pulp of r i p e f r u i t . There i s some disagreement i n the l i t e r a t u r e  with  r e g a r d to the form of the d i f f e r e n t sugars i n r i p e bananas. Eheart  and Mason (1966) a n a l y z e d  wholesale  bananas bought on  market i n Washington D.C.  sugars were p r e s e n t  and  found t h a t  at 10.34% w h i l e sucrose  U n i t e d F r u i t S a l e s Corp. ( 1 9 6 4 ) ' l i s t s the  content  of a f u l l y r i p e banana as f o l l o w s :  Poland  ( f r u c t o s e ) 3.7%  and  dextrose  reducing  content  8.54%.  levulose  the  sugar  sucrose  (glucose)  was  12.7%,  4.8%.  et_ a_l_. (1938) r e p o r t e d t h a t d u r i n g r i p e n i n g , g l u c o s e ,  f r u c t o s e and  sucrose  maintain nearly constant  proportions.  Acidity A c i d i t y o f banana p u l p r i s e s t o a maximum a t o r soon a f t e r the c l i m a c t e r i c and may show a s l i g h t as r i p e n i n g p r o g r e s s e s  (vonLoesecke 1950).  from 5.0 - 5.8 f o r the p u l p o f green f r u i t in post-climacteric f r u i t  decrease  The pH ranges t o 4.2 - 4.8  (Simmonds 1966).  Titrable  a c i d i t y o f Gros M i c h e l p u l p changes from 2.96 i n the p r e c l i m a c t e r i c s t a t e to 4.95 f o l l o w i n g the c l i m a c t e r i c to  3.66 m.equiv/lOOg f r e s h p u l p at f u l l  ripeness.  and Mason (1966) r e p o r t e d the a c i d i t y o f f u l l y  then Eheart  r i p e banana  p u l p as 0.27% m a l i c a c i d ['4.03 m . e q u i v / 1 OOg ] . S t u d i e s by Stewart  e_t_ al_. (1960) and M i l l e r and  Ross (1963) i n d i c a t e t h a t L - m a l i c  and c i t r i c  a c i d s are the  predominant a c i d s i n banana p u l p a t a l l stages  of ripeness.  Moisture In content  s p i t e o f t r a n s p i r a t i o n l o s s e s , the m o i s t u r e  o f banana p u l p i n c r e a s e s d u r i n g r i p e n i n g .  vonLoesecke  (1950) gave v a l u e s f o r f i v e c l o n e s r a n g i n g from 63 - 74% t o 68 77%.  Palmer (1971) suggested  moisture  t h a t the net i n c r e a s e i n p u l p  i s the combined e f f e c t o f r e s p i r a t i o n and osmosis.  Sugar i n c r e a s e s more r a p i d l y i n the p u l p than i n the p e e l and t h i s c r e a t e s an osmotic from p e e l t o p u l p .  g r a d i e n t c a u s i n g water t o move  S t r a t t o n and vonLoesecke (1931) found  that d u r i n g r i p e n i n g the osmotic  pressure  o f Gros M i c h e l  p e e l i n c r e a s e s from 6 t o 11.5 atmospheres and t h a t o f the  p u l p i n c r e a s e s from 6 t o 25 - 27 atmospheres. Osmotic t r a n s f e r o f water r e s u l t s i n changes o f p u l p - t o - p e e l r a t i o on a f r e s h weight b a s i s .  Simmonds  observed t h a t the r a t i o i s about 1.2 - 1.6 i n green  (1966)  fruit  and r i s e s w i t h normal r i p e n i n g to 2.2 - 2.4 at advanced ripening.  M i c r o b i a l i n v a s i o n and d e h y d r a t i o n g i v e r i s e to  f u r t h e r i n c r e a s e s i n the p u l p - t o - p e e l r a t i o .  vonLoesecke  (1950) suggested t h a t p u l p - t o - p e e l r a t i o c o u l d be u s e f u l as an i n d e x o f r i p e n e s s . Anatomy and H i s t o l o g y Bananas  are a r r a n g e d i n n o d a l c l u s t e r s or "hands"  which are borne on a n o d a l base o r " c u s h i o n " a t t a c h e d to a stalk.  This e n t i r e s t r u c t u r e i s roughly c y l i n d r i c a l i n  shape and i s known c o m m e r c i a l l y as a bunch or "stem". The f r u i t i s v e g e t a t i v e l y p a r t h e n o c a r . p i c ; i . e . i t d e v e l o p s a mass o f e d i b l e t i s s u e w i t h o u t p o l l i n a t i o n . The p u l p c o n s i s t s o f r e l a t i v e l y u n d i f f e r e n t i a t e d d i v i d e d i n t o 3 segments  tissue  by the c a r p e l l a r y m a r g i n s .  The  degenerated o v u l e s are a r r a n g e d c e n t r i p e t a l l y i n each segment.  Wolfson (1928) has s t u d i e d the anatomy o f the f r u i t ,  and h i s work forms the b a s i s f o r subsequent o b s e r v a t i o n s by vonLoesecke  (1950).  The p e e l c o n s i s t s o f an e p i d e r m a l  l a y e r which i s u n d e r l a y e d by parenchyma with f i b r o v a s c u l a r bundles. o u t e r l a y e r o f parenchyma  cells  interspersed  C h l o r o p l a s t s are found i n the  known as the chlorenchyma.  The e p i d e r m a l c e l l s are s l i g h t l y  convex on the  15 . upper s u r f a c e and  s l i g h t grooves appear where the edges of  a d j o i n i n g c e l l s meet, g i v i n g a s t r i a t e d appearance to the peel surface.  T r a n s p i r a t i o n and  p l a c e through stomata and the e p i d e r m i s  gaseous exchange  take  a t h i n l a y e r of c u t i n p r o t e c t s  from d e s i c c a t i o n and  o t h e r forms of  injury.  Parenchyma c e l l s make up the b u l k of the p e e l tissue.  They are l a r g e and  away from the  thin walled, increasing in size  epidermis.  A t h i n l a y e r of cytoplasm  c o n t a i n i n g numerous  p l a s t i d s , l i n e the i n s i d e of the c e l l w a l l .  In the i n n e r -  most c e l l s of the p e e l the p l a s t i d s become c e n t e r s starch accumulation.  A s a p - f i l l e d vacuole  c e n t e r of the c e l l . c o n s i s t s mainly compounds and The  to  occupies  c e l l sap i s a c l e a r f l u i d  of d i s s o l v e d s u g a r s ,  the which  organic acids, phenolic  water. f i b r o v a s c u l a r bundles are s c a t t e r e d throughout  the parenchyma and the f r u i t .  The  of  run p a r a l l e l to the l o n g i t u d i n a l a x i s of  In a d d i t i o n to i m p a r t i n g s t r e n g t h and  the p e e l they serve  as conveyors of water and  I n d i v i d u a l f i b e r c e l l s are l o n g , narrow and  rigidity metabolites.  thick walled.  Inner bundles are l e s s f i b r o u s but more, complex.  They are  surrounded by a r i n g of l a t i c i f e r o u s t i s s u e i n t e r s p e r s e d w i t h parenchyma c e l l s  (Ram  et_ a_l_.. 1962).  elements of the f r u i t  a l l converge and  The  vascular  anastomose i n the  r e g i o n of the p e d i c e l . The  l a t e x system i s found i n both the p e e l  and  the p u l p ,  and c o n s i s t s o f l a r g e t h i n - w a l l e d , b a r r e l shaped  c e l l s which are j o i n e d end to end i n s i n g l e l i n e s . peel  they are g e n e r a l l y  a l t h o u g h they f r e q u e n t l y Barnell two  associated  with vascular  o c c u r by t h e m s e l v e s .  bundles,  B a r n e l l and  (1945) noted t h a t l a t e x c e l l s i n the p e e l  well-defined  types.  Most o f the t a n n i n  In the  are o f  i n the f r u i t  i s found i n the l a t e x ( B a r n e l l and B a r n e l l 1945). The p u l p - p e e l of parenchyma c e l l s w i t h  boundary c o n s i s t s o f a few l a y e r s l a r g e i n t e r c e l l u l a r -spaces.  D u r i n g r i p e n i n g t h i s r e g i o n becomes more porous w i t h the r e s u l t that peeling  o f the f r u i t  i s made e a s i e r .  Upon  removal o f the p e e l prominent l o n g i t u d i n a l bundles are seen a d h e r i n g to the p e e l .  These b u n d l e s g i v e r i s e to the  c h a r a c t e r i s t i c d e p r e s s i o n s on the s u r f a c e Pulp c e l l s are t h i n w a l l e d isodiametric.  o f the p u l p .  and may be long or  The i n n e r c e l l s are a r r a n g e d i n rows  r a d i a t i n g from the s e p t a e .  These c o n s i s t l a r g e l y of paren  chyma c e l l s and v a s c u l a r bundles which pass i n t o the placental axis.  The p l a c e n t a l a x i s c o n s i s t s c h i e f l y o f  spongy parenchymatous t i s s u e s . bananas t h e r e  In green as w e l l as r i p e  are few o r no i n t e r c e l l u l a r  During r i p e n i n g , c e l l  spaces.  s i z e remains c o n s t a n t w h i l  s t a r c h g r a n u l e s decrease i n s i z e and number (vonLoesecke 1950). but  Latex tubes are p r e s e n t i n the p u l p o f r i p e  they c o n t a i n  no l a t e x .  c o n d e n s a t i o n ( B a r n e l l 1943). cell  This  fruit,  i s a t t r i b u t e d to tannin  The r i p e n i n g b e h a v i o r of the  w a l l and i t s components has not been  studied.  EXPERIMENTAL METHODS Sampling P r o c e d u r e s Materials Hard green V a l e r y bananas ( C h i q u i t a brand) were p u r c h a s e d from a l o c a l w h o l e s a l e e s t a b l i s h m e n t . The  fruits  had been brought i n by t r u c k from the docks at S e a t t l e , 3  Washington  and were t r e a t e d w i t h e t h y l e n e (approx. 1 f t 3  per 1000 f t  s t o r a g e space) f o r 24 h r b e f o r e b e i n g used i n  the e x p e r i m e n t s . Ripening A c l o s e d - c y c l e heated a i r d r y e r equipped w i t h a cooling c o i l  a t t a c h e d t o a r e f r i g e r a t i o n u n i t was used as  a r i p e n i n g chamber.  T h i s apparatus i s d e s c r i b e d i n d e t a i l  by Bhargava  F r u i t s were r i p e n e d at 16 ± 1°C and  25 ± 1°C.  (1970).  A r e l a t i v e h u m i d i t y of 85 - 95% was m a i n t a i n e d  d u r i n g r i p e n i n g , by i n j e c t i n g steam i n t o the u n i t . Temperature  and r e l a t i v e h u m i d i t y i n the r i p e n i n g  ment were r e c o r d e d by a hygrometer  compart-  (Hydrodynamics I n c .  Model 15-4050 E) and a hygrothermograph. A 40 l b c a r t o n of f r u i t was used f o r each trial.  ripening  Upon r e c e i v i n g the f r u i t s the "hands" were broken  up and i n d i v i d u a l f r u i t s were r e p l a c e d at random i n the carton,  which was then p l a c e d i n the r i p e n i n g chamber. Each t e m p e r a t u r e t r e a t m e n t was r e p l i c a t e d t h r e e  times.  Groups 1, 2 and 3 were r i p e n e d at 16 ± 1°C and  groups 4, 5 and 6 at 25 ± 1°C.  Experiments were t e r m i n a t e d  18 .  when the f r u i t s  a c q u i r e d a p e e l c o l o r index of 8.  Sampling E i g h t f r u i t s were sampled every r i p e n i n g at 16 ± 1°C, and  every day  of l e n g t h , p u l p - t o - p e e l r a t i o ,  tion  behavior.  The  collectively solids  i n the  c o l o r and  p u l p from these f r u i t s was  used to study f l o w b e h a v i o r .  The  days d u r i n g  d u r i n g r i p e n i n g at 25  ± 1°C. F i v e f r u i t s were used i n d i v i d u a l l y tion  2-3  determina-  force-deformapooled  and  other three f r u i t s  were  used i n the d e t e r m i n a t i o n of a l c o h o l i n s o l u b l e  ( A I S ) , s u g a r s , m o i s t u r e , pH and t i t r a b l e  acidity.  Physical Properties Length A vinyl  m e t r i c tape was  used to measure the  d i s t a n c e from the trimmed stem end to the d i s t a l the f r u i t .  T h i s was  sides.  mean of these two measurements was  The  l e n g t h of the  end  done along both the convex and  of concave  taken as  the  fruit.  Pulp-to-peel  ratio  Whole and p e e l e d f r u i t s were weighed to o b t a i n gross and p u l p w e i g h t . d i f f e r e n c e and  P e e l weight  was  the p u l p - t o - p e e l r a t i o  q u o t i e n t o f p u l p and p e e l  then d e r i v e d by  was  c a l c u l a t e d as  the  weights.  Color A banana r i p e n i n g c h a r t w i t h c o l o r p l a t e s used to e v a l u a t e the c o l o r index Fruit  S a l e s Corp.  1964).  The  (CI) of f r u i t s ,  CI f o r a g i v e n day  was  (United represented  19 .  the  mean  f o r the e i g h t  fruits  sampled.  Spectrophotometric carried fruit in  out on two 35 mm  at the d i s t a l  a plastic  black  backing.  sample  holder  recording peel  tissue  discs  and stem culture  The d i s h  the v i s i b l e  Fresh  instrument  for  470  ment  from t h e was  placed  with a  and clamped  to the  o f a Unicam  S P 800  Diffuse  reflectance  of the  scale oxide  (450 to 800 nm) was at a scan  was u s e d  values  rate  o f 200  to c a l i b r a t e t h e  at 470, 672 and 730 nm were  the s p e c t r a  and t h e mean constituted  Reflectance  ratios  The Index o f V a r i a n c e  reflectance  then  calculated  data f o r  computed f o r  as 730 and 672 nm  Reflectance  ejt a^. (1953) as a c r i t e r i o n  i n f r u i t s , was  obtained  the r e f l e c t a n c e were  and 672, 672 and 470 as w e l l  Powers  and f l a t t e n e d  Reflectance  fruit.  tively.  disc  was  a t 100% r e f l e c t a n c e .  t h e two s e c t i o n s  each  by  magnesium  removed  color  unit  spectrum  nm/min.  of peel  Each  covered  o f the r e f l e c t a n c e  on a l o g a r i t h m i c  from  dish  spectrophotometer.  within  of peel  ends.  was  recorded  read  measurement  using  respec-  (IVR) p r o p o s e d  for color  measure-  the f o l l o w i n g  formula: IVR  Rheological  -  !zi°__!iZl 672  cn  Properties Force-deformation  A cylindrical  behavior  specimen  o f t i s s u e was p r e p a r e d by  20 . c u t t i n g a s e c t i o n o f the p e e l e d f r u i t parallel  s t r i n g s l i c i n g device.  2.5 cm l o n g , u s i n g a  Cross s e c t i o n a l area a t  each c y l i n d e r end was c a l c u l a t e d from the average measured w i t h v e r n i e r c a l i p e r s .  diameter  The mean o f these measure-  ments was d e s i g n a t e d as the c r o s s s e c t i o n a l a r e a o f the specimen. The compression  s e c t i o n was s u b j e c t e d t o p a r a l l e l  plate  along the l o n g i t u d i n a l a x i s u s i n g an I n s t r o n  Model TMM u n i v e r s a l t e s t i n g machine.  Loading  r a t e was 0.5  cm/min and c h a r t speeds o f 2 and 5 cm/min were used. Force-deformation  curves o f the type shown i n F i g u r e 2 were  o b t a i n e d f o r f i v e f r u i t s on each sampling day.  From these  curves v a l u e s were o b t a i n e d f o r maximum f o r c e , l i n e a r deformation  at one kg o f f o r c e and the energy  the sample from i n i t i a l l i m i t energy).  absorbed by  l o a d i n g t o the l i n e a r l i m i t  (linear  To compensate f o r d i f f e r e n c e s i n c r o s s  s e c t i o n a l a r e a - o f the c y l i n d r i c a l and  limit,  samples,  maximum f o r c e  l i n e a r l i m i t were d i v i d e d by the c r o s s s e c t i o n a l  area  and the one kg d e f o r m a t i o n was m u l t i p l i e d by t h a t a r e a . Flow b e h a v i o r Pulp from the f r u i t s used i n ' t h e study o f f o r c e deformation 25%  c h a r a c t e r i s t i c s was s l i c e d and b l e n d e d  with  (W/W) water i n a h i g h speed -Waring b l e n d o r f o r 8 min.  Preliminary t r i a l s  i n d i c a t e d t h i s amount o f water was  optimum f o r s l u r r y p r e p a r a t i o n s i n c e green p u l p c o u l d be macerated t o a smooth c o n s i s t e n c y w h i l e the p a r t i c u l a t e  21 .  D e f o r m a t i o n ,  FIGURE  2  m m  Typical f o r c e - d e f o r m a t i o n curve f o r banana pulp t i s s u e . M F , maximum f o r c e ; LL, l i n e a r limit; U l , d e f o r m a t i o n due t o 1 k g force.  22 . matter i n o v e r - r i p e puree d i d not s e t t l e sion.  A f t e r b l e n d i n g , the puree was  out of the suspen-  a l l o w e d to s t a n d at  room temperature f o r 30 min. About tion.  100 ml of puree was used f o r each d e t e r m i n a -  A l l measurements were o b t a i n e d w i t h a Haake R o t o v i s k o  c o n c e n t r i c c y l i n d e r v i s c o m e t e r equipped w i t h an MV1 (gap w i d t h 0.96  mm).  spindle  The sample was kept at 20°C u s i n g a  Kryomat c o n s t a n t temperature b a t h connected to the water j a c k e t t h a t surrounded the sample  holder.  During each d e t e r m i n a t i o n the s p i n d l e speed was  v a r i e d s t e p w i s e from maximum to minimum.  v i s c o m e t e r t r a n s m i s s i o n was s t r e s s r e l a x a t i o n was attained. the  rotation The  then disengaged and the shear  r e c o r d e d u n t i l a c o n s t a n t v a l u e was  T h i s measurement was used as a y i e l d s t r e s s f o r  sample.  The sample was  then t e s t e d from low to h i g h  shear r a t e s to complete the v i s c o m e t r i c measurements. Shear r a t e s ranged from 8.5  to 1370 sec '''. -  The t o r q u e due to  v i s c o u s drag i n the f l u i d at known shear r a t e s was by a Moseley A u t o g r a f s t r i p c h a r t  sensed  recorder.  Flow b e h a v i o r curves were c o n s t r u c t e d u s i n g shear r a t e , shear s t r e s s and y i e l d s t r e s s dat'a d e r i v e d from the viscometric tests.  Two  forms of the w i d e l y used  power-law  f l o w model were f i t t e d to these d a t a . . mt"  [2]  23.  and  x  =  where  T  = shear  ray  +  11  T  [3]  y  stress  (dynes  cm  _ 2  )  -2  The  flow  using  Ty  = yield  stress  (dynes  Y  = shear  rate  ( s e c *)  m  = a parameter,  the consistency  n  = a parameter,  the flow-behavior  parameters  t h e method  fitting  of least  technique.  statistical which  m a n d _n w e r e  parameters  the flow  Chemical  This  models  cm  evaluated  squares  index.  with  included  would  fitted  coefficient  a  computer  and a n o n - l i n e a r  procedure  that  )  indicate  curve  evaluation of the accuracy  with  the data.  Properties Moisture A  duplicate 103°C the on  modified  AOAC  5 g samples  f o r 18 h r .  dried  samples  a fresh  weight  (1965)  were  After were  dried  cooling weighed  method  was  used  i n which  i n a h o t a i roven  a t 100 -  i n a d e s i c c a t o r f o r 30 m i n , and p e r c e n t  moisture  computed  basis.  P'H A amount with  40% s l u r r y  of puree  an  with  Instrument Alcohol  of  based puree  Laboratory Insoluble  on an AOAC were  Extraction  was  made  distilled  Determination was  was  carried  water pH  an  appropriate  a n d t h e pH was  measured  meter.  Solids  of alcohol  (1965)  extracted  by m i x i n g  method.  insoluble  solids  Duplicate  i n 250 ml b o i l i n g  5 g  (AIS) samples  80% e t h y l  o u t f o r 30 m i n i n a w a t e r  bath  alcohol. at  24 . about 85°C.  The hot s o l u t i o n was v a c u u m - f i l t e r e d  Whatman No.2 f i l t e r paper i n a Buchner f u n n e l .  through  The r e s i d u e  was washed w i t h an equal volume o f hot 80% e t h y l a l c o h o l , then d r i e d , i n a hot a i r oven a t 100 - 103°C f o r 2 h r . A f t e r c o o l i n g i n a d e s i c c a t o r f o r 15 min, the samples were weighed and AIS c a l c u l a t e d as a p e r c e n t a g e o f f r e s h weight.  Dried  AIS m a t e r i a l was p l a c e d i n sample b o t t l e s and s t o r e d i n a d e s i c c a t o r to be used l a t e r f o r d e t e r m i n a t i o n o f s t a r c h . Reducing  sugars  These were measured by t h e method o f T i n g  (1956)  w i t h some m o d i f i c a t i o n s by Furuholmen e_t al_. (1964). method i s based on the r e d u c t i o n o f a l k a l i n e which i s then c o n v e r t e d complex.  to a blue-green  The  ferricyanide,  arsenomolybdate  The absorbance o f t h i s complex at 515 nm i s then  measured w i t h a s p e c t r o p h o t o m e t e r .  A l l reagents  t h i s method were as d e s c r i b e d by Ting The  filtrate  used i n  (1956).  o b t a i n e d d u r i n g AIS d e t e r m i n a t i o n was  c o o l e d t o room temperature and made up t o 1000 ml w i t h distilled  water.  At t h i s c o n c e n t r a t i o n e t h a n o l d i d not  i n t e r f e r e w i t h the t e s t .  A one ml a l i q u o t o f t h i s  dilute  e x t r a c t was t r a n s f e r r e d by p i p e t t e t o a' 100 ml v o l u m e t r i c f l a s k and 5 ml f e r r i c y a n i d e reagent s w i r l e d then heated  added.  i n a b o i l i n g "water bath  The f l a s k was f o r 10 min.  A f t e r h e a t i n g the f l a s k was q u i c k l y c o o l e d i n a r u n n i n g water b a t h .  The c o n t e n t s were then p a r t i a l l y n e u t r a l i z e d  w i t h 10 ml IM H„S0  and shaken u n t i l gas e v o l u t i o n ceased.  25 . Four ml o f arsenomolybdate was  reagent were added, the m i x t u r e  mixed t h o r o u g h l y and made up t o volume.  The f l a s k was  a l l o w e d t o s t a n d f o r 15 min. Absorbance o f the f e r r o c y a n i d e - a r s e n o m o l y b d a t e complex was measured a t 515 nm and a s l i t w i d t h o f 0.016 mm w i t h a H i t a c h i - P e r k i n Elmer s p e c t r o p h o t o m e t e r .  A reagent  b l a n k w i t h water was used t o s t a n d a r d i z e the s p e c t r o p h o t o meter and g l u c o s e and f r u c t o s e s o l u t i o n s were used t o cons t r u c t a standard curve.  The r e d u c i n g sugar c o n t e n t o f  each a l c o h o l i c e x t r a c t was determined Total  i n duplicate.  sugars  A 5 0 ml sample o f t h e d i l u t e e x t r a c t was p l a c e d i n a 200 ml beaker w i t h 10 ml 6M HC1.  The beaker was  s w i r l e d and a l l o w e d t o s t a n d at room temperature hr.  f o r 18  F o l l o w i n g i n v e r s i o n the m i x t u r e was p a r t i a l l y  n e u t r a l i z e d w i t h 5 ml 10M NaOH and the pH a d j u s t e d between 5 and 7 w i t h IM NaOH.  The s o l u t i o n was then t r a n s f e r r e d t o  a 200 o r 250 ml v o l u m e t r i c f l a s k  and made up t o volume. One  ml o f t h i s s o l u t i o n was t r a n s f e r r e d t o a 100 ml v o l u m e t r i c f l a s k and t o t a l sugars were determined described f o r reducing sugars. c a r r i e d out on each i n v e r t e d  u s i n g the procedure  Two d e t e r m i n a t i o n s were  sample.  St a r c h A m o d i f i e d AOAC (1965) method was used starch.  t o measure  A sample o f d r i e d AIS (<\,0.5g) was added t o a  m i x t u r e o f 200 ml water  and 20 ml 6M HC1.  T h i s was then  refluxed treated 5 - 7  f o r 2.5 h r and a f t e r with  with  solution left  10 ml 10M NaOH.  a t 20°C  i n an i c e b a t h ,  The pH was a d j u s t e d between  IM NaOH and one ml o f s a t u r a t e d l e a d  was added  for clarification.  overnight i n a refrigerator  suspended  particles.  Whatman No.2 f i l t e r transferred  The m i x t u r e  to allow s e t t l i n g  The s u p e r n a t a n t paper  acetate  was f i l t e r e d  using a l i g h t  vacuum,  to volume.  to  determine  A one ml a l i q u o t reducing sugars  calculated  i n duplicate  of this  solution  as o u t l i n e d  was  then  of the through  then  t o a 500 o r 1000 ml v o l u m e t r i c f l a s k  up  was  cooling  and made was  before.  used  Starch  as 0.90 t i m e s  the r e d u c i n g  Titrable  acidity  The  (1965) method was u s e d  to determine  sugar e q u i v a l e n t .  AOAC  titrable  acidity  had  sealed i n p l a s t i c  been  Twenty  g o f puree  distilled  water.  i n samples  was u s e d  of frozen bags  puree.  and k e p t  frozen  t o make a s l u r r y  The s l u r r y  The p u r e e at -37°C.  with  was t i t r a t e d w i t h  100 ml  0.10M  NaOH t o pH 8.1 u s i n g a pH m e t e r  and m a g n e t i c  stirrer.  Titrable  i n duplicate  and e x p r e s s e d  in  acidity  m.equiv/1OOg.  Histochemical  Properties  Fruits 15  was d e t e r m i n e d  used  i n these  - 17°C and 85% r e l a t i v e  sample  of f i v e  histochemical  studies  humidity.  f r u i t s were removed and h i s t o l o g i c a l  were r i p e n e d a t During  every  studies.  ripening  two days f o r Free-hand  a  27 transverse  sections  razor  blade  and  Cross  sections  fruit  were u s e d  of  fresh  tested  for  of pulp to  tissue  starch  5 mm  study  pulp  and  thick  were  cut  esterified  from  the  with  a  pectins.  middle  of  the  "tannin" d i s t r i b u t i o n .  Starch The  method  of Jensen  determination.  An  iodine  and  potassium  tilled  w a t e r was  placed  on  After  2 min  water  and  granules  1.5g  IKI  the  a glass  reagent and  were  stained  dark  was  the  lowered  was  it.  consisting  of  one  part  alcohol  was  added.  was  indicated  under  a  After  flooded  0.1M  HC1. by  0.3g  i n 100  tissue  ml  dis-  section  was  added.  o f f with  distilled  a microscope.  Starch  blue.  t e s t used.  to  slide  of  this  pectins  on  containing  under  in  reagent  washed  hydroxy 1 a m i n e - f e r r i c  reagent  the  of  examined  hydroxylamine  and  3 drops  section  a l . 1959)  ethyl  The  the  The  dissolved  used.  was  used  consisting  iodide  reagent  Esterified  et  solution  slide  excess  (1962) was  Five  placed 5 min  chloride  on  an  with The  a red  10%  equal  of  HC1  FeCl^ of  when, the  an  and  volume and  i n . 60%  a  section  of  solution  ethyl  section  95%  drained  esterified  (Gee  alkaline  2 parts  s o l u t i o n was  presence  color  drops  a slide  concentrated Excess  reaction  off  alcohol pectin  was  examined  microscope. Tannins This  (polyphenols)  t e s t was  adapted  from  the  method  of  Jensen  28 . (1962).  I t i s not s p e c i f i c  phenols as  react  bananas where  polyphenols cut  from  dish in  with  the reagent;  this  test  covered  60% e t h y l  i s useful.  alcohol  containing  sections  and  examined f o r " t a n n i n "  by  a dark  were  blue  Histological  the f r u i t  of  tissue  septae  5 mm  cm  from  the t i s s u e .  and  necessary  175 ml  washed using  cores  a t 0°C  was  distilled  were  to the degenerated  1962)  mixed  chromium  4 mm  i n diameter  tion  5g  cross section  cut into  Tissue  solutions  sections  of pulp  placed i n a  petri  HC1. with  location.  of  chloride  After  5 min  distilled  This  was  water  indicated  preparation  was  close  (Jensen  t h o r o u g h l y washed  group  of f e r r i c  0.1M  such  Properties  2.5  of  poly-  precipitate.  Sample A  were  a 10% s o l u t i o n  the  other  the l a r g e s t  Cross  of the f r u i t  with  since  however, i n f r u i t s  tannins constitute  the middle  and  for tannin  were  from  50 m l  Solution  distilled  of Feder  cores the  ovules. i n Navashin's A  15 m i n  solution  glacial  acetic  and  fixation then  and O ' B r i e n  infiltra-  t o remove a i r  i s made  Solution  After  solution  vacuum  use.  water  middle  cut out w i t h i n  from  two  A consists acid  B i s a" m a x t u r e o f 200  water.  i n cold  the  Cylindrical  at the outset of f i x a t i o n  trioxide,  the schedule  then  f o r 24 h r .  (1:1) b e f o r e  f o r 30 m i n  slices.  fixed  Navashin's  water.  of pulp  and ml  320  (1968).  ml  formalin  the t i s s u e  dehydrated  of  at  was 0°C  The  tissue  (melting  point  material  was  used  p-araffin  was  poured  properly  oriented  lowered  into  surface  ahd  was  56.5°C)  a  for  i n f i l t r a t e d in  using  paper hot  bath  s o l i d i f i e d  completely.  After  it  removed  the  and  stored  in  from a  wooden  removed placed  in  of  blocks  using  jaws  used  to  of  precleaned  a  Haupt's were  obtain  slide  which  the  sections  the  slide  of  xylene.  series  (100,  molten cores  molds  were  were  then  ice.  When  submerged  and  allowed  had  wrapped  completely in  left  10  After  of  u  the  the to  cooled,  aluminum  on  with A  a  f o i l  hot  hydration  50%),  wooden  blocks  microtome  the  which  was  surface  thin  layer  of  of  formalin  drops were  an  4%  floated at  was  the  slides  were  upper  the in  was  The  formaliri  from  attached  paraffin  plate  on  were  Excess  a  few  overnight  removed  tissue  thick.  ribbons  Excess  dry  and  12  the  rotary  1962).  placed  was  and  coated  partial  9 5 , ' 70  -  was  to  spatula.  Spencer  expand.  Tissuemat in  same  crushed  containing  hot  (Jensen  then  to  was  The  The  tissue  The  block  tissue  a  segments  was  was  the  slide  and  62°C.  paraffin  staining  a  ribbons  adhesive  added  the  paraffin  around  the  and  needles.  mold  at  tissue.  molds  water,  and  Pieces  from  the  Tissuemat  refrigerator.  Sectioning  to  oven  containing  the  harden was  vacuum  embedding  into  water  a  with  35°C  to  drained  hot  the allow and  plate.  slides ethyl were  on  by  soaking  alcohol  stained  with  safranin-toluidine from  the  (1962).  safranin-fast  (70,  xylene.  and  They were  Permount  drying  95  with  period  Pentax  sections  were p a s s e d and  then  dried  22  o f 24  x 60  mm  h r was light  camera was  staining method  100%)  A W i l d M20 Asahi  The  green  Stained slides  series  in  blue.  schedule  outlined through  finally f o r 24  an  through hours  coverslips  used  to observe  at m a g n i f i c a t i o n s o f 100  and  and  400  alcohol  3 changes  (No.l).  fitted  adapted  Jensen  before  necessary before microscope  by  was  A  of  mounting further  examination. with  a 35  photograph  diameters.  mm the  RESULTS AND Changes  During  Ripening  Physical  related  properties  Fruit  size:  each  other  to  DISCUSSION  A l l v a r i a b l e s examined (Table  1).  Generally  much d i f f e r e n c e among g r o u p s  although  were  the  and  longer gross  mental  showed  geographical  than the  the  bunches  and  was  were s u b j e c t  Pulp  1  and  2). . Length  in a l l experi-  from  different  seasonal  and  SIMPLE CORRELATIONS AMONG SIZE CHARACTERISTICS OF BANANAS ( p o o l e d d a t a , n = 195)  Gross  wt.  Pulp  wt.  0.847  wt. s e c t i o n area  Pulp-to-peel steady  increase  ranged  from  The  not  effects.  wt.  Cross  to  was  considered  were d e r i v e d  Length Gross  not  closely  i n groups  (Table  most v a r i a t i o n  fruits  there  fruits  others  Variation in size  because  " h a n d s " and  1.  heavier  weight  groups.  excessive  TABLE  and  were  results  observations  1.35 of  0.805  0.962  0.489  0.762  ratio:  A l l groups  in pulp-to-peel i n green this  study  fruits are  of vonLoesecke  ratio to  of  (Figure  2.14  fruit  showed  3).  Ratios  in over-ripe  i n agreement  (1950) and  0.831  with  the  Simmonds (1966) .  a  fruits  TABLE  2.  Group  MEANS, STANDARD D E V I A T I O N S AND t - T E S T R E S U L T S S I Z E C H A R A C T E R I S T I C S OF BANANAS.  Length (cm)  1  Gross  (g)  23.22  181.0  a b l  1. 64 2  171.89  C  1.75  2 . 33 5  23.90  191 . 4 6  2. 00 6  22.66  178.29  2.46  1  Means differ  a c d  at P =  sharing  0.05.  7 . 24  a  111 . 6 7  109.58  bc  7 . 06  a  a  a  1.11 7. 0 4  a  6 . 90  a  letter  a  0 .99  22.18  t h e same  a  0 .80  24 . 89  33.02  i n a column  7 . 18  a  0 . 64  119 . 9 3  b d  a  0.48  31 . 2  35.13 b d e  a  31.07  42.57  a  6 . 97  110.87  aC  173.72  c e  114 . 7 3  (cm2)  16.67  31 .07  22 . 0 3  Area  111 . 0 5  c  25 . 36  21 . 2 6  Pulp wt. (g)  14.41  172 . 8 4  c d  1.91  4  ab  17.63  21.76  3  wt.  FOR  0 . 70  do n o t  a  33.  FIGURE  3.  Changes i n p u l p - t o - p e e l during ripening.  ratio  of  bananas  Color: is  The  shown i n F i g u r e  observed  a f t e r one  somewhat-variable  change  in color  4.  In most  day  of  groups  ripening.  although  index  that  of  during  a change  ripening  in color  Rate  of  change  groups  4,  5 and  was  was 6  tended  tobelessso. Typical ripening overall  that  found  occurring  wavelength  that  a change  of  the  in reflectance that  in surface Index  at  675  r i p e n i n g , but  tended  t o have h i g h e r  ripe  Rheological  values  index  or  two  in  able  days  increase  of  2 were h a r d to w i t h s t a n d  the  ripening  in softening.  maximum  force,  with  the  while  in  al_. (1967)  associated  with  Powers  ejt a l .  nm  related  at  678  of  chlorophyll in  was  (IVR)  i n groups  than  changes  reduction  et  was  the  groups  4,  1,  to  lemons.  decreased 5 and  2 and  6 3.  properties  Force-deformation  sections  with  during  an  Reflectance  Reflectance  fruits  was  ripening  Finney  nm  reflectance  of Variance  There  nm.  peel.  concentration  during  color  672  c h l o r o p h y l l i n banana p e e l  (1953) r e p o r t e d changes  at  6.  during  were a s s o c i a t e d  content  o f banana p e e l  5 and  in reflectance  changes  chlorophyll  curves  shown i n F i g u r e s  increase  greatest at  are  reflectance  linear  behavior: and up  of This  brittle to  65  kg  a l l groups was  limit  Green  fruit  with  cylindrical  of  showed  reflected  and  force.  linear  by  with  After  a  one  a marked sudden  limit  changes  energy.  35 .  I 0  I 2  ]  I  4  I  6  ,  8  I  I  L  10  12  14  Time, days FIGURE 4.  Changes i n ripening.  color  index  of  bananas  during  450  500  550  600  650  W a v e I„-e n g t h ,  700  75 0  n m  FIGURE  5.  R e f l e c t a n c e curves f o r the p e e l o f bananas r i p e n e d a t 16 ± 1 ° C . N u m b e r s on t h e curves i n d i c a t e peel c o l o r index.  FIGURE  6.  Reflectance curves f o r the peel o f bananas r i p e n e d a t 25 ± 1 ° C . N u m b e r s on t h e curves indicate peel color index.  Changes i n l i n e a r l i m i t d u r i n g r i p e n i n g are i l l u s t r a t e d i n F i g u r e 7.  When the f r u i t s  from a l l groups a t t a i n e d  ripeness  ( f u l l y e l l o w ) , l i n e a r l i m i t remained  constant  and showed l e s s v a r i a t i o n among groups.  full  relatively  Deformation increased s t e a d i l y during e a r l y ripening.  In groups 1, 2 and 3 the r i p e f r u i t s were not as  r e a d i l y deformed as i n the o t h e r groups.  Linear  limit  energy d e c r e a s e d w i t h r i p e n i n g i n a l l groups w i t h the r a t e of change b e i n g  g r e a t e s t i n groups 4, 5 and 6.  There was  much v a r i a t i o n i n green f r u i t and, to a l e s s e r e x t e n t , i n ripe  fruit. Flow b e h a v i o r :  two  Data from a l l groups f i t t e d the  power-law flow models w e l l .  determination  The mean c o e f f i c i e n t o f  f o r the power-law w i t h y i e l d s t r e s s  [ 3 ] ) was 0.97 and t h a t f o r power-law ( E q u a t i o n 0.96.  (Equation  [ 2 ] ) was  Thus both models a c c u r a t e l y d e s c r i b e the f l o w  behavior  o f banana p u r e e , however the power-law w i t h  yield  s t r e s s was s e l e c t e d f o r d i s c u s s i o n i n t h i s p r e s e n t a t i o n . During consistency.  r i p e n i n g the f r u i t puree d e c r e a s e d i n  The power-law c o n s i s t e n c y c o e f f i c i e n t  decreased and flow b e h a v i o r  index  puree approached Newtonian f l o w .  (m)  (n_) i n c r e a s e d , i . e . the The r a t e o f change i n  m was g r e a t e s t i n groups 4, 5 and- 6 (Figure. 8 ) , w h i l e values  f o r n_ tended to be l a r g e r i n the same groups. The  deformation  parameter m c o r r e l a t e d w e l l (Table  3) w i t h  v a r i a b l e s as w e l l as w i t h s t a r c h and sugar  force  Time, days FIGURE  7.  Changes i n l i n e a r l i m i t during ripening.  o f banana  pulp  tissue  39  400  2 FIGURE  8.  4  6 8 Time , days  10  Changes i n c o n s i s t e n c y c o e f f i c i e n t puree d u r i n g r i p e n i n g .  12 o f banana  14  content.  Y i e l d s t r e s s values  decreased d u r i n g  270 - 350 dynes/cm 2 i n green f r u i t s over-ripe  fruits.  r i p e n i n g from  to 10 - 25 dynes/cm 2 i n  Decrease i n y i e l d s t r e s s f o l l o w e d a  p a t t e r n s i m i l a r to t h a t o f the parameter m. Chemical  properties  Moisture:  Moisture  content increased  from 71.3  to 76.0% i n groups, 1, 2 and 3 and from 72.6 to 78.7% i n groups 4, 5 and 6 ( F i g u r e 9 ) . range o f t a b u l a t e d v a l u e s  Increases  were w i t h i n the  (vonLoesecke 1950) and were steady  throughout r i p e n i n g i n a l l groups. Acidity: fruits  Peak a c i d i t y o c c u r r e d  a l t h o u g h l e v e l s were v a r i a b l e among groups.  decreased from 5.0 - 5.4 i n green f r u i t s fully  i n fully ripe  r i p e f r u i t s , then i n c r e a s e d  T i t r a b l e a c i d i t y increased decreased with continued  ripening.  to 4.85 - 6.0  and 4.0 - 5.5 m.equiv/lOOg  (heavily spotted) f r u i t s .  a c i d s are used as r e s p i r a t o r y  r i p e n i n g but  Values ranged from  3.3 - 5.0 m.equiv/lOOg i n green f r u i t s  in over-ripe  to 4.2 - 4.8 i n  w i t h advanced r i p e n i n g .  with i n i t i a l  m.equiv/lOOg i n f u l l y r i p e f r u i t s  This  suggests  This  that  substrates.  Maximum t i t r a b l e a c i d i t y d i d riot g e n e r a l l y w i t h minimum pH.  pH  coincide  i s p r o b a b l y due to d i f f e r e n c e s i n  b u f f e r i n g c a p a c i t y o f the o r g a n i c " a c i d s  p r e s e n t at d i f f e r e n t  stages of r i p e n e s s . Alcohol  insoluble solids:  decrease i n AIS d u r i n g  ripening.  There was a steady  Green f r u i t s  contained  41 .  FIGURE  9.  Changes i n m o i s t u r e during ripening.  content  o f banana  pulp  20 - 25% w h i l e i n o v e r - r i p e f r u i t s l e s s than 5%.  The  the l e v e l was  r a t e of decrease was  generally  f a s t e r and more  u n i f o r m i n groups 4, 5 and 6 ( F i g u r e 10).  In a d d i t i o n these  groups tended to have l e s s AIS than the o t h e r s . Changes i n AIS d u r i n g r i p e n i n g r e p r e s e n t s t r a n s f o r m a t i o n of s t a r c h and s t r u c t u r a l m a t e r i a l s such as c e l l u l o s e , h e m i c e l l u l o s e and p e c t i c substances and are c l o s e l y r e l a t e d to r h e o l o g i c a l Sugars:  properties.  T o t a l sugar i n c r e a s e d d u r i n g r i p e n i n g  i n a l l groups ( F i g u r e 11). have s l i g h t l y  Groups 4, 5 and 6 appeared to  l a r g e amounts of sugar i n o v e r - r i p e  fruits.  With advanced r i p e n i n g , the sugar c o n t e n t appeared  to reach  a plateau. Reducing sugars i n c r e a s e d s t e a d i l y d u r i n g r i p e n i n g ( F i g u r e 12).  The  r a t e of i n c r e a s e as w e l l as the  amount i n o v e r - r i p e f r u i t was  g r e a t e s t i n groups 4, 5 and  Reducing sugars d i d not decrease i n o v e r - r i p e indicating  final 6.  fruits,  t h a t n o n - r e d u c i n g sugars are p r o b a b l y u t i l i z e d  in r e s p i r a t i o n before reducing sugars. In t h i s study n o n - r e d u c i n g sugars c o n s t i t u t e a l a r g e r p e r c e n t a g e of t o t a l s u g a r .  T h i s i s i n agreement w i t h  c o m p o s i t i o n a l data g i v e n by U n i t e d F r u i t S a l e s Corp.  (1964).  In g e n e r a l r e d u c i n g sugars accounted f o r about 25% of t o t a l sugar c o n t e n t up to f u l l Starch : to those of AIS  ripeness.  Changes i n s t a r c h were g e n e r a l l y  ( F i g u r e s 10 and 13).  parallel  Starch content v a r i e d  43 .  FIGURE  10.  Changes i n AIS c o n t e n t during ripening.  o f banana  pulp  44 .  FIGURE  11.  Changes i n t o t a l s u g a r c o n t e n t pulp during ripening . i  o f banana  0  2  4  6  8  10  12  14  T i m e , days FIGURE  12.  Changes i n r e d u c i n g s u g a r pulp during r i p e n i n g .  content  o f banana  46 .  from 17 - 22% i n green f r u i t s to l e s s than 2% i n r i p e f r u i t s . Histochemical  properties  F i g u r e 14 shows t h a t t a n n i n s are p r i m a r i l y w i t h the c a r p e l l a r y margins. t i o n through one present  A l o n g i t u d i n a l sec-  of the margins r e v e a l s t h a t l a t e x c e l l s  i n l a r g e numbers.  B a r n e l l and  r i p e n i n g t h e r e was  (polyphenols)  i n the pulp  are  B a r n e l l (1945) a l s o found  t h a t banana f r u i t t a n n i n s occur m a i n l y During  associated  in latex c e l l s .  a d e c l i n e i n the l e v e l of ( F i g u r e 14).  tannins  G o l d s t e i n and  Swain  (1963) have s t a t e d t h a t l o s s of a s t r i n g e n c y i n r i p e bananas r e s u l t s from a decrease i n " a c t i v e " t a n n i n s due  to p o l y -  merization. S t a r c h d i s a p p e a r a n c e began i n the p l a c e n t a l r e g i o n at c o l o r index index  3 and p r o g r e s s e d  7, s t a r c h was  towards the p e e l .  At c o l o r  c o n f i n e d l a r g e l y to the c e l l s at  the  p e r i p h e r y of the pulp w i t h some s t a r c h - l a d e n c e l l s s c a t t e r e d at random throughout the pulp t i s s u e s .  Starch granules  the c e n t r a l p a r t of p a r t of r i p e f r u i t s  appeared to decrease  i n s i z e , however the p e r s i s t e n c e of s t a r c h at the made i t d i f f i c u l t  in  periphery  to observe whether a s i m i l a i * t r e n d  occurred. Pulp t i s s u e from green f r u i t  ( c o l o r index  2) d i d  not g i v e a p o s i t i v e r e a c t i o n w i t h hydroxy 1 amine r e a g e n t . the onset of y e l l o w i n g  ( c o l o r index  At  3) an i n t e n s e red c o l o r ,  i n d i c a t i v e of e s t e r i f i e d p e c t i n s , was  obtained with  the  48. •  FIGURE 14.  S e c t i o n s o f banana pulp t i s s u e showing tannin d i s t r i b u t i o n . A = c o l o r index 2; B = c o l o r index 4; C = c o l o r index 6.5.  reagent. cided As  with  at  first  the  ripening  and in  The  decrease  progressed  color  vascular  index  factor  McComb  are  characterized  tion  to  and  esterified  in starch the  red  at  color  7 esterified  in pectic  i n the  and  soluble  of  1954;  textural qualities  Pilnik by  an  insoluble  and  Voragen  increase  pectins.  In  study  esterified  color  index  amounts  at  observations  It i s apparent  insoluble  pectic  these  substances  This wall  i n pulp  that  the well  softens  cell  study  At thickening  only  wall  i n pulp  of  color the  3 than  as  cells  the  depolymeriza-  of  green by  Thus  in  bananas.  Reeve  soluble  explain  fruit  1970).  were p r e s e n t  reported  ratio  of  esterified  i n hard  that  to  adequately  the  texture.  during  its rigidity., tissue  ripening lose  index cell  were  changes  properties  loses  that  These  Voragen in  a  (McCready  proportion  pectins  does not  revealed  but  and  i n banana  tissue  defined, such  that  substances  Histological  and  in intensity  fruits  1970).  a decrease  i n peaches  (1959).  of  region.  considered  f r a c t i o n s r e s u l t i n g from  de-esterification (Pilnik  this  are  of  i n the  with  role  coin-  were p r e s e n t  constituents  is associated  Similar  placental  decreased  pectins  softening  larger  the  pectins  tissue.  Changes major  appearance  6.5  wall  at  Figure  color  index  progresses  their to  ripening  the  15A  the  cell  shows  2 is  rigid  cell  wall  c h a r a c t e r i s t i c shapes.  7.0  there  (Figure  15C).  was In  an  apparent  contrast  to  FIGURE 15.  Photomicrographs during ripening A = c o l o r index C = c o l o r index  of banana pulp t i s s u e at 16 ± 1°C (X 320) . 2; B = c o l o r index 4; 7.  51 . l o s s of r i g i d i t y , ally.  c e l l wall thickening  T h i s phenomenon has  banana t i s s u e , but  has  stages of r i p e n e s s  by  can  with  the  Reeve (1959).  Cell wall  hydration  occurs at advanced r i p e n i n g  but  sections  the  c e l l s and  hydration  may  have been  i f t h i s i s so,  a sudden s t r u c t u r a l  there modification  c e l l w a l l to such t h i c k e n i n g .  advanced r i p e n i n g p u l p t i s s u e d i s i n t e g r a t e s and  early  Workman 1964).  that w a l l thickening  sample p r e p a r a t i o n ,  during  fractures  i n the  At handling  from such t i s s u e ^.show c e l l u l a r d e b r i s multiple  in  i n banana pulp i s  c l i m a c t e r i c (Bauer and  which p r e d i s p o s e s the  reported  been observed i n peaches at  It i s possible induced by  o c c u r gradu-  not been p r e v i o u s l y  r e s u l t in thickening,but  associated  d i d not  within  c e l l wall  (Figure  15C) . E f f e c t of R i p e n i n g Temperature E x a m i n a t i o n of changes d u r i n g  ripening  showed  that  r a t e s of change i n groups r e c e i v i n g s i m i l a r temperature t r e a t m e n t s tended to be necessarily  at the  ments began. of r i p e n e s s , properties  s i m i l a r , however the groups were  same stage of r i p e n e s s  Since peel  when the  experi-  c o l o r i s the most w i d e l y used i n d e x  changes i n p h y s i c a l , r h e o l o g i c a l and  were s t u d i e d  chemical  as a f u n c t i o n of c o l o r i n d e x .  method would enable comparison of these p r o p e r t i e s s t a g e s of r i p e n e s s ripening  based on p e e l  color.  The  was  studied  by  comparing changes i n the  This  at s i m i l a r  effect  temperature on p h y s i c a l , r h e o l o g i c a l and  properties  not  of  chemical pooled  data o f low and h i g h temperature groups as a f u n c t i o n o f color index. Physical  properties  • D u r i n g low temperature  (16 ± 1°C) r i p e n i n g p u l p -  to-peel r a t i o increased l i n e a r l y . (25 ± 1°C) r e s u l t e d i n s l i g h t l y  High  temperature  lower v a l u e s which d i d not  i n c r e a s e s t e a d i l y throughout r i p e n i n g ( F i g u r e 1 6 ) . The r a t e o f c o l o r change i n h i g h temperature groups was r o u g h l y t w i c e t h a t i n low temperature  groups.  Change i n c o l o r i n d e x p e r day was 0.76, 1.18 and 0.89 f o r low temperature groups and 1.81-., 1.44 and 2.00 f o r h i g h temperature groups. ripe f r u i t s  ( F i g u r e 6) was a s s o c i a t e d w i t h the l a c k o f  development o f f u l l fruits  P e r s i s t e n c e o f a c h l o r o p h y l l peak i n  yellow i n high temperature-ripened  and r e s u l t e d i n h i g h e r IVR v a l u e s .  It i s possible  t h a t c h l o r o p h y l l r e t e n t i o n may be an i n i t i a l "boiling"--  a commercial  sign of  c o n d i t i o n which i s e x p e r i e n c e d  d u r i n g r i p e n i n g above 30°C ( W i l k i n s o n 1970).  Intense  s p o t t i n g and c o n s i d e r a b l e r o t t i n g o f the p e e l at advanced r i p e n i n g i n h i g h temperature groups was p r o b a b l y due to f u n g a l growth  (Hall  1967).  Rheological  properties  F r u i t s r i p e n e d at low temperature were much f i r m e r than those r i p e n e d at h i g h t e m p e r a t u r e .  Linear l i m i t of  r i p e f r u i t t i s s u e i n both temperature groups were not a p p r e c i a b l y d i f f e r e n t , however d e f o r m a t i o n due to 1 kg  1  2  3  4 Color  FIGURE  16.  5.  6  7  index  E f f e c t o f r i p e n i n g t e m p e r a t u r e on pulp-topeel r a t i o of bananas. Vertical bars represent ± one standard deviation.  8  54 .  f o r c e showed very d i f f e r e n t p a t t e r n s i n the two t r e a t m e n t s ( F i g u r e 17). ripe f r u i t s  T h i s v a r i a b l e remained more o r l e s s c o n s t a n t i n (beyond c o l o r i n d e x 4) at low temperature but  i n c r e a s e d l i n e a r l y w i t h h i g h temperature  ripening.  The e f f e c t s of r i p e n i n g temperature on f l o w b e h a v i o r was r e f l e c t e d i n a l l power-law p a r a m e t e r s .  Consistency  c o e f f i c i e n t and y i e l d s t r e s s were g e n e r a l l y lower w h i l e f l o w b e h a v i o r i n d e x was h i g h e r i n h i g h temperature Chemical  groups.  properties  High temperature r e s u l t e d i n i n c r e a s e d m o i s t u r e content i n pulp t i s s u e . to-peel - ratios  T h i s was i n c o n t r a s t to lower p u l p -  ( F i g u r e 16).  A p p a r e n t l y weight i n c r e a s e s due  to m o i s t u r e are n u l l i f i e d by i n c r e a s e d s t r u c t u r a l breakdown and  hydrolysis. A c i d i t y was not a f f e c t e d by temperature t r e a t m e n t .  There was c o n s i d e r a b l e o v e r l a p p i n g o f pH and t i t r a b l e  acidity  i n both t r e a t m e n t s . Alcohol insoluble solids  (AIS) and s t a r c h were  a f f e c t e d i n a s i m i l a r p a t t e r n by t e m p e r a t u r e . t u r e r e s u l t e d i n lower l e v e l s of both v a r i a b l e s ripening;  High temperathroughout  w h i l e the AIS c o n t e n t o f o v e r - r i p e f r u i t s  remained  c o n s t a n t i n low temperature groups, i t c o n t i n u e d t o d e c l i n e i n h i g h temperature groups.  Starch content of o v e r - r i p e  f r u i t s i n both t r e a t m e n t s d e c r e a s e d s l i g h t l y on c o n t i n u e d ripen ing.  55 .  1-2  1  2  3  4 C o l o r  FIGURE  17.  5  6  7  8  i n d e x  E f f e c t o f r i p e n i n g t e m p e r a t u r e on d e f o r m a t i o n o f b a n a n a p u l p t i s s u e ujider 1 kg f o r c e . V e r t i c a l b a r s r e p r e s e n t ± one s t a n d a r d deviation.  56 .  T o t a l sugar c o n t e n t o f banana p u l p was i n c r e a s e d by h i g h t e m p e r a t u r e , a l t h o u g h t h e r e was more v a r i a t i o n i n h i g h t e m p e r a t u r e groups ( F i g u r e 1 8 ) . The 16°C t r e a t m e n t was c h a r a c t e r i z e d by a more or l e s s c o n s t a n t l e v e l o f r e d u c i n g s u g a r s i n r i p e f r u i t s , w h i l e the 25°C temperature i n a l i n e a r i n c r e a s e i n t h e s e sugars throughout  resulted  ripening.  T h i s accounted f o r the o v e r a l l i n c r e a s e i n sugar c o n t e n t o f h i g h temperature In  groups.  t h i s s t u d y the r i p e n i n g t r e a t m e n t was a p p l i e d  d u r i n g the e n t i r e e x p e r i m e n t a l p e r i o d . c o n d i t i o n s the f r u i t  Under  commercial  i s c o n s i d e r e d r i p e at c o l o r i n d e x 4,  thus the e f f e c t o f r i p e n i n g temperature s h o u l d be c o n s i d e r e d up to t h a t stage o f r i p e n e s s .  Subsequent changes are  g e n e r a l l y r e f e r r e d t o as s t o r a g e changes and are t r e a t e d separately.  F u r t h e r m o r e , s i n c e the study was l i m i t e d to two  temperature t r e a t m e n t s , i t i s not p o s s i b l e to d i s c u s s the  fully  e f f e c t s o f temperature on r i p e n i n g b e h a v i o r . The  r e s u l t s s u p p o r t the o b s e r v a t i o n s o f Sanchez  N i e v a ejt aj_. (1969) and D a l a i ejt aj_. (1969) t h a t bananas r i p e n e d at h i g h temperature are more s u s c e p t i b l e t o mechanical injury.  R e d u c t i o n o f s h e l f l i f e by h i g h temperature  F r u i t S a l e s Corp.  1964) i s a l s o i l l u s t r a t e d by the r a t e s o f  r i p e n i n g i n h i g h temperature groups.  The l a c k o f complete  yellowing i n high temperature-ripened f r u i t the  initial  (United  i s probably  symptom o f a p h y s i o l o g i c a l d i s o r d e r .  Haard and  57 .  25  1  2  3  4 Color  FIGURE 18.  5  6  7  index  E f f e c t o f r i p e n i n g t e m p e r a t u r e on t o t a l sugar c o n t e n t of banana p u l p t i s s u e . V e r t i c a l b a r s r e p r e s e n t ± one s t a n d a r d deviation.  8  Hultin  (1969) r e p o r t e d  t h a t a s i m i l a r e f f e c t on y e l l o w i n g  was brought about by low r e l a t i v e h u m i d i t y . Relationships  Among  Properties  I t has been demonstrated elsewhere i n t h i s that r i p e n i n g i s accompanied by s e v e r a l r i p e n i n g temperatures e x e r t properties  o f bananas.  study  changes and t h a t  a considerable  e f f e c t on the  The r e l a t i o n s h i p s among r e p r e s e n -  t a t i v e parameters o f p h y s i c a l , r h e o l o g i c a l and c h e m i c a l properties  were s t u d i e d by p o o l i n g  data from the three  groups i n each temperature t r e a t m e n t and c a l c u l a t i n g s i m p l e correlations.  This would i n d i c a t e whether r e l a t i o n s h i p s  between d i f f e r e n t v a r i a b l e s are the same at temperatures.  In a d d i t i o n , i t would be p o s s i b l e  the v a l u e o f p e e l  c o l o r as an i n d e x o f r i p e n e s s  different ripening  ripening t o assess  under  conditions.  Simple c o r r e l a t i o n s among s e l e c t e d during  both  variables  r i p e n i n g at 16 ± 1°C and 25 ± 1°C are shown i n T a b l e s  3 and 4 r e s p e c t i v e l y .  In g e n e r a l ,  the c o r r e l a t i o n s were  h i g h l y s i g n i f i c a n t (P < 0.01) d u r i n g  both t r e a t m e n t s .  When  data from both t r e a t m e n t s were p o o l e d (Table 5) c o r r e l a t i o n c o e f f i c i e n t s were g e n e r a l l y obtained  intermediate  f r o the s e p a r a t e t r e a t m e n t s .  between p u l p - t o - p e e l  between those However, c o r r e l a t i o n s  r a t i o and o t h e r v a r i a b l e s  decreased  when the d a t a were p o o l e d .  There i s l i t t l e  i n d i c a t i o n that  r i p e n i n g temperature e x e r t s  a major i n f l u e n c e on the  TABLE 3.  SIMPLE CORRELATIONS AMONG SELECTED PHYSICAL, RHEOLOGICAL AND CHEMICAL PROPERTIES OF BANANAS RIPENED AT 16 ± 1°C. (n = 110).  Color index Pulp/peel IVR  Pulp/ peel  IVR  L i n e a r Maxi- Deforlimit mum mation force  m*  Total sugar  Reducing sugar  AIS  Starch  0.810 -0.754 -0.672  Linear limit  -0.452 -0.311  0.606  force  -0.474 -0.332  0.628  Deformation m*  0.645 0.532 -0.716 -0.645 -0.654 'f> -0.670 -0.540 0.704 0.709 0.715 -0.531  Maximum 0.996  Total sugar  0.881  0.746 -0.904 -0,587 -0.607  0.781 -0.702  0.94*7  0.814 -0.814 -0.516 -0.535  0.729 -0.696  Reducing sugar  0.959  AIS  -0.903 -0.751  0.896  0.597  0.617 -0.781  0.670 -0.994 -0.999  Starch  -0.896 -0.744  0.904  0.632  0.632 -0.778  0.719 -0.993 -0.943  Moisture  0.952  0.791 -0.798 -0.533 -0.552  Power-law c o n s i s t e n c y  coefficient  0.734 -0.634  0.921  0.999  0.966 -0.949 -0.940  TABLE 4.  SIMPLE CORRELATIONS AMONG SELECTED PHYSICAL, RHEOLOGICAL AND CHEMICAL PROPERTIES OF BANANAS RIPENED AT 25 + 1°C. (n = 8 5 ) .  Color index  Pulp/peel IVR Linear limit Maxi mum force De format i o n m* Total sugar Reducing sugar AIS Starch Mois t u r e  Pulp/ peel  IVR  L i n e a r Maxi- Deforlimit mum mation force  m*  Total sugar  Reducing sugar  AIS  Starch  0.661 •0.734 -0.629 •0.427 -0.483  0.645  •0.432 •0.520  0. 630  0.982  0. 726  0. 690 -0.583 -0.464 -0. 4 7/7 -0.885 -0.702 0. 703 0.413 0.427 -0.680 0.761  0.538 .0.814 -0.549 -0.510  0 .934  0. 674  •0.816 •0.599 •0.826 •0 .599 0. 805  0.477  Power-law c o n s i s t e n c y  0.818 0 . 867 0. 849 0.694  0.492 -0.760  •0.521 •0.507 0.725 -0.905 0.838 0.583 0.551 •0.609 0.802 -0.933 -0.927 0.533 0.503 •0.604 0.811 -0.919 -0.925 0.981 0.503 0.473 0.716 -0.795 0.683 0.884 -0.828 -0.829  coefficient. o  TABLE 5.  SIMPLE CORRELATIONS AMONG SELECTED PHYSICAL, RHEOLOGICAL AND CHEMICAL PROPERTIES OF RIPENING BANANAS. (Pooled d a t a , n = 195).  Color index  Pulp/ peel  IVR  Pulp/peel IVR  -0.613 -0.613  Linear limit  -0.380 -0.212  0.556  Maxi mum force  -0.402 -0.230  0.579  Deformation m*  L i n e a r Maxi- Deforlimit mum mation f o rce  m*  Reducing sugar  AIS  Starch  0.718  0.598  0.996  0.356 -0.583 -0.505  -0.640 -0.420  0.677  0.710  •0.566 , ?  0.719 -0.566  Total sugar  0.820  0.570 -0.866 -0.544 -0.566  0.681 -0.709  Reducing sugar  0.909  0.625 -0.785 -0.457 -0.481  0 . 757 •0.702  AIS  0.853 -0.597  0.877  0.555  •0.853 -0.594  0.878  0.564  S tarch Moi s t u r e  Total sugar  0.873  0.578  0.711  0.713  0.905 •0.936 -0.936  0.587 •0 . 706 0 . 727 •0.933 -0.933 0.561 -0.749 -0.474 -0.496 0.740 -0.648 0.850 0.939  Power-law c o n s i s t e n c y  coefficient  0 .994 0.911 -0.906  62  r e l a t i o n s h i p between s e l e c t e d coefficients  v a r i a b l e s , although  tended to be h i g h e r  at  the  correlation  lower  temperature (Table 3 ) . Variations 82.6%  i n c o l o r . i n d e x account f o r 63.7 and  o f the v a r i a t i o n i n m o i s t u r e  and r e d u c i n g  r e s p e c t i v e l y , when a l l the d a t a were p o o l e d . ing temperatures,  Index o f V a r i a n c e  sugar  At both  Reflectance  ripen-  (IVR) was  c l o s e l y r e l a t e d to c o l o r index with c o r r e l a t i o n c o e f f i c i e n t s of -0.754 and -0.734 f o r low and high temperature  respec-  tively.  color  T h i s v a r i a b l e , on the a v e r a g e , s u r p a s s e d  in correlations with rheological Correlations  properties.  among r h e o l o g i c a l  and c h e m i c a l  p r o p e r t i e s were on the average h i g h e r d u r i n g r i p e n i n g temperature.  index  at low  An e x c e p t i o n to t h i s t r e n d was found i n the  r e l a t i o n s h i p between r e d u c i n g sugars  and c o n s i s t e n c y  c o e f f i c i e n t where the c o r r e l a t i o n c o e f f i c i e n t s were -0.905 and  -0.696 d u r i n g high and low t e m p e r a t u r e s  Some r h e o l o g i c a l p r o p e r t i e s , tency  respectively.  such as d e f o r m a t i o n  and c o n s i s -  c o e f f i c i e n t s , were c l o s e l y r e l a t e d t o c h e m i c a l  properties. Correlations very h i g h d u r i n g both with a l l variables  among chemical treatments.  except  c o n s t i t u e n t s were  Moisture  correlated  pulp-to-peel r a t i o during  well  ripening  at h i g h t e m p e r a t u r e .  This i s probably  due t o the h i g h  degree o f v a r i a b i l i t y  i n pulp-to-peel r a t i o during t h i s  63.  t r e atment. In rheological index  if  indicates  to be  that  Among  a good  the  their  the  time  the  total  index  fruits  fruit  rheological had  usefulness and  as  equipment  of  may  be  indices  but  effect and  of  deforma-  ripening  with  index  quality of  does not  It i s  deformation  correlation  overall  internal  a good  1966)  and  with  careful consideration  ripeness.  size  needed  the b e s t  to e s t i m a t e  parameters,  the b e s t  correlation  moisture  given  (Simmonds  of stage  was  sugar,  i s used  low  demonstrated  i t s h o u l d be  e x t e n t by  coefficient but  index  Pulp-to-peel ratio  i n green  a large  Yet  on  e x t e r n a l appearance  maturity  color  quality.  temperature  of bananas.  to  of i t s r e l a t i v e l y  properties,  of.fruit  ripening tion  spite  appear  influenced  temperature. and  consistency  chemical p r o p e r t i e s  o f r i p e n e s s are  for determination.  limited  by  CONCLUSIONS  The roughly  r i p e n i n g r a t e o f bananas at 25 ± 1°C was  t w i c e t h a t at 16 ± 1 ° C .  High  temperature-ripened  f r u i t s were c h a r a c t e r i z e d by c h l o r o p h y l l r e t e n t i o n which prevented  the development o f f u l l y e l l o w c o l o r .  p e e l r a t i o i n c r e a s e d d u r i n g r i p e n i n g i n both but was somewhat lower  i nfruits  Pulp-to-  treatments  r i p e n e d at the  higher  temperature. Deformation due to 1 kg f o r c e i n c r e a s e d d u r i n g r i p e n i n g a t high  linearly  t e m p e r a t u r e , w h i l e i t remained  f a i r l y s t a b l e beyond c o l o r index 6 d u r i n g r i p e n i n g at low temperature. consistency at high  Maximum f o r c e and l i n e a r l i m i t  c o e f f i c i e n t were g e n e r a l l y lower d u r i n g r i p e n i n g  temperature. T o t a l sugar and m o i s t u r e  were h i g h e r i n f r u i t s sugars i n c r e a s e d  content  o f pulp t i s s u e  r i p e n e d at high t e m p e r a t u r e .  linearly  beyond c o l o r index  Reducing  throughout r i p e n i n g at high  temperature w h i l e at low temperature they constant  as w e l l as  6.  remained  essentially  S t a r c h and AIS l e v e l s were  somewhat h i g h e r i n low t e m p e r a t u r e - r i p e n e d  fruits.  This  i n d i c a t e s t h a t s t a r c h h y d r o l y s i s was enhanced by h i g h temperature  treatment.  R i p e n i n g was c h a r a c t e r i z e d by a g r a d u a l rigidity  loss of  as w e l l as an apparent t h i c k e n i n g o f the c e l l w a l l  65 .  i n the pulp o f o v e r - r i p e f r u i t s .  Tannins  decreased but d i d  not c o m p l e t e l y d i s a p p e a r d u r i n g r i p e n i n g .  E s t e r i f i e d pectins  were p r e s e n t i n the l a r g e s t amount at c o l o r i n d e x 3 and decreased d u r i n g r i p e n i n g .  Starch granule  disappearance  began i n the c e n t r a l r e g i o n o f the p u l p t i s s u e and p r o g r e s s e d towards the p e e l as r i p e n i n g c o n t i n u e d . P e e l c o l o r was e v a l u a t e d by c o l o r i n d e x and IVR was the best i n d e x o f stage o f r i p e n e s s i n f r u i t s  r i p e n e d at  both low and h i g h t e m p e r a t u r e .  However, i n view o f the  e f f e c t s o f r i p e n i n g temperature  on some c h e m i c a l and r h e o l o g i c a l  p r o p e r t i e s , the r e l a t i o n s between these p r o p e r t i e s and c o l o r i n d e x would be i n f l u e n c e d by r i p e n i n g This suggested  t h a t r i p e n i n g temperature  q u a l i t y o f the r i p e f r u i t ,  as w e l l  temperature.  may a f f e c t e a t i n g  as the a c c u r a c y o f p e e l  c o l o r as an index o f r i p e n e s s . C o r r e l a t i o n s among r h e o l o g i c a l p r o p e r t i e s were h i g h l y s i g n i f i c a n t  and c h e m i c a l  although  correlations  among the c h e m i c a l v a r i a b l e s were h i g h e r than those among the r h e o l o g i c a l v a r i a b l e s .  Variations i n tissue strength  (maximum f o r c e ) c o u l d be e x p l a i n e d l a r g e l y by v a r i a t i o n s i n s t a r c h and AIS w h i l e v a r i a t i o n s i n s o f t e n i n g ( d e f o r m a t i o n ) c o u l d be accounted reducing sugars.  f o r m a i n l y by v a r i a t i o n s i n t o t a l and In g e n e r a l , r i p e n i n g temperatures  appear to i n f l u e n c e g r e a t l y the c o r r e l a t i o n among the d i f f e r e n t p r o p e r t i e s examined.  d i d not  coefficients  66.  LITERATURE CITED A r t h u r , H.B., Houck, J.P. and B e c k f o r d , G.L. 1968. T r o p i c a l A g r i b u s i n e s s S t r u c t u r e s and Adjustments - Bananas. Graduate School o f B u s i n e s s A d m i n i s t r a t i o n , H a r v a r d U n i v e r s i t y , Boston. Assoc. O f f i c . A g r i c . Chem. 1965. O f f i c i a l methods 10th ed., Washington, D.C.  of.analysis,  B a r n e l l , H.R. 1941. 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