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The effect of post-harvest treatment on the rate of weight loss from tomatoes during storage Risch, Eric 1977

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EFFECT OF POST-HARVEST TREATMENT ON THE RATE OF WEIGHT LOSS FROM TOMATOES DURING STORAGE  by ERIC RISCH B.Sc.  U n i v e r s i t y of Guelph, 1974  A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE  REQUIREMENTS FOR THE DEGREE OF MASTER OF APPLIED SCIENCE  i n THE FACULTY OF GRADUATE STUDIES i n t h e Department of Bio-Resource  Engineering  We accept t h i s t h e s i s as  conforming  to the r e q u i r e d standard  THE  UNIVERSITY OF BRITISH COLUMBIA August, 1977  ©  Eric Risch, 1977  In p r e s e n t i n g  t h i s t h e s i s i n p a r t i a l f u l f i l m e n t of the requirement f o r  advanced degree at the U n i v e r s i t y of B r i t i s h Columbia, I agree t h a t L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e  and  study.  an  the  I further  agree t h a t p e r m i s s i o n f o r e x t e n s i v e copying of t h i s t h e s i s f o r  scholarly  purposes may  representa-  tives.  be  g r a n t e d by  the Head of my  I t . i s understood t h a t copying or p u b l i c a t i o n of t h i s t h e s i s f o r  f i n a n c i a l gain  s h a l l not be  allowed without my  Department of Bio-Resource E n g i n e e r i n g  The  Department or by h i s  U n i v e r s i t y of B r i t i s h Columbia  Vancouver 8,  Canada.  Date September 6th. ,  1977  written  permission.  ii. ABSTRACT  The m o i s t u r e  l o s s and  changes i n c o l o u r and  s t o r a g e were i n v e s t i g a t e d u s i n g a 4x4x5 f a c t o r i a l  The  first  before c o o l i n g .  f i r m n e s s of tomatoes i n experiment.  f a c t o r s e l e c t e d i n v o l v e d f o u r d e l a y times a f t e r A f t e r h a r v e s t , the tomatoes were l e f t  for 0 hours,  10 h o u r s ,  20 hours and  cooled.  The  second f a c t o r i n v o l v e d f o u r p r e - s t o r a g e  moisture  loss  a t room temperature  30 h o u r s , r e s p e c t i v e l y , b e f o r e b e i n g treatments  to reduce  : (a) wrapping the i n d i v i d u a l tomatoes i n p o l y m e r i c  (b) waxing the c a l y x or stem ends o n l y , w i t h a f r u i t wax, to the whole s u r f a c e s of i n d i v i d u a l f r u i t s , and The  harvest,  film,  (c) a p p l y i n g  (d) c o n t r o l , w i t h no  treatment.  t h i r d f a c t o r c o n s i s t e d of f i v e c o n t r o l l e d temperature and h u m i d i t y  environments c)10°C and  : a) 10°C  60% r h ;  and  90%  d)15°C and  r h ( r e l a t i v e h u m i d i t y ) ; b)  15°C  50%  rh.  r h ; and e)18°C and  40%  and  wax  storage  88%  rh;  An a n a l y s i s of v a r i a n c e of the r e s u l t s showed t h a t i n d i v i d u a l l y wrapp i n g tomatoes i n p o l y m e r i c d u r i n g the steady found  t o be  state.  f i l m r e s u l t e d i n the lowest r a t e s of weight, l o s s A l s o the r a t e of weight l o s s from a tomato  i n f l u e n c e d by the s t o r a g e c o n d i t i o n (combination  temperature and h u m i d i t y ) , and storage  chamber.  was  e f f e c t of  the a i r f l o w c h a r a c t e r i s t i c s i n s i d e  the  iii.  TABLE OF CONTENTS PAGE TITLE PAGE ABSTRACT  i i  TABLE OF CONTENTS  i i i  LIST OF FIGURES AND PLATES  y  LIST OF TABLES  vi  NOMENCLATURE  viii  ACKNOWLEDGEMENTS  xi  INTRODUCTION  1  LITERATURE REVIEW  -  2  Cooling  2  Treatments To Reduce Water Loss Waxing of produce Packaging i n p o l y m e r i c f i l m s  4 4 4  Storage Refrigerated storage Controlled-atmosphere Hypobaric s t o r a g e  5 5 6 6  Colour And Firmness Tomato c o l o u r Tomato f i r m n e s s MATERIALS  storage  Changes  AND METHODS  7 8 8 10  E x p e r i m e n t a l Design  10  Equipment D e s c r i p t i o n  10  E x p e r i m e n t a l Procedure Pre-storage t e s t s Development of c o l o u r standards Firmness s c a l e M o i s t u r e content and d e n s i t y d e t e r m i n a t i o n T e s t method Post-storage tests I n v e s t i g a t i o n of e f f e c t of p r e s s u r e on tomatoes S a t u r a t i o n vapour p r e s s u r e d e t e r m i n a t i o n  16 16 16 16 18 18 21 21 22  THEORETICAL MODEL USED FOR ANALYSIS OF WATER LOSS  23  iv.  TABLE OF  CONTENTS (CONT'D) PAGE  RESULTS, ANALYSES OF DATA AND R e s u l t s of Pre-Storage  DISCUSSION  29  Tests  29  Data A n a l y s e s and D i s c u s s i o n P r e l i m i n a r y analyses G e n e r a l models f o r a n a l y s e s of d a t a A n a l y s i s of v a r i a n c e of weight l o s s R e g r e s s i o n a n a l y s i s of weight l o s s R e g r e s s i o n a n a l y s e s of c o l o u r and f i r m n e s s changes Colour change Firmness change R e s u l t s and d i s c u s s i o n of a n a l y s i s of v a r i a n c e of weight l o s s R e s u l t s and d i s c u s s i o n of r e g r e s s i o n a n a l y s i s of weight l o s s R e s u l t s and d i s c u s s i o n of r e g r e s s i o n a n a l y s e s of c o l o u r and f i r m n e s s changes Co l o u r ochang euwi thit'ime i J I FirmhessaGhangenwdithitajne^and£Lwithicblour.r>ur  R e s u l t s and  D i s c u s s i o n of P o s t - S t o r a g e  Tests  29 29 34 34 34 35 35 37 37 44 59 59 60  61  CONCLUSIONS  63  RECOMMENDATIONS  65  LITERATURE CITED  66  APPENDIX A  68  APPENDIX B  71  APPENDIX C  88  APPENDIX D  92  F e d e r a l and  I n d u s t r y Grading  Standards f o r Greenhouse Tomatoes  93  L I S T OF FIGURES AND PLATES  FIGURE  PAGE  1  Schematic of a i r c o n d i t i o n i n g system employing r e c i r c u l a t i o n of excess a i r  13  2  Schematic of a i r c o n d i t i o n i n g system s e r v i n g two c h a m b e r s  15  3  Turbulent d i f f u s i o n boundary  4  P l o t of cummulative w e i g h t l o s s vs time  5  P l o t of t o t a l weight l o s s per s u r f a c e a r e a (during steady state) vs i n i t i a l weight  33  6  Change  36  7  P l o t of r a t e of w e i g h t l o s s per a r e a v s vapour p r e s s u r e d e f i c i t s ( b e f o r e c o r r e c t i o n f o r e f f e c t of R e y n o l d ' s number)  51  8  P l o t of r a t e of w e i g h t l o s s per a r e a vs vapour p r e s s u r e d e f i c i t s ( w i t h c o r r e c t i o n f o r e f f e c t of R e y n o l d \ s number)  55  P l o t o f mean c o l o u r c o e f f i c i e n t (b ) d u e t o pre-storage treatment vs storage condition  85  1  Tomato c o l o u r g r a d i n g  17  2  Electron Micrographs surface layers  B]1  l a y e r on a f l a t  surface  per surface area  of c o l o u r w i t h t i m e  25 30  PLATE  standard o f t o m a t o s k i n s u r f a c e and s u b -  62  vi.  LIST OF TABLES TABLE  P  A  G  E  1  Summary of e x p e r i m e n t a l d e s i g n w i t h C-T-S codes  11  2  Labelling  20  3  R e l a t i o n s h i p between i n i t i a l weight of tomato and t o t a l weight l o s s d u r i n g 12 days of storage (data from run I I )  32  4  Summary of r e s u l t s of a n a l y s i s of v a r i a n c e of weight l o s s  38  5  The e f f e c t of c o o l i n g , treatment weight l o s s  40  6  Average r a t e s of water l o s s through s u r f a c e s of tomatoes u n t r e a t e d and w i t h s u r f a c e treatments  46  7  Reynold's numbers and c o n v e c t i v e heat t r a n s f e r c o e f f i c i e n t s f o r the v a r i o u s tomato storage chambers  47  8  Average tomato s u r f a c e temperatures arid vapour p r e s s u r e d e f i c i t s between tomatoes and s t o r a g e environment  50  9  Average r a t e s of water l o s s through s u r f a c e s of tomatoes u n t r e a t e d and w i t h s u r f a c e treatments (with c o r r e c t i o n f o r e f f e c t of Reynold's number of a i r f l o w i n s t o r a g e chambers)  53  10  Vapour p r e s s u r e d e f i c i t s and average r a t e s of water l o s s through tomato " m u l t i p l e b a r r i e r s " (with c o r r e c t i o n f o r e f f e c t of Reynold's number of a i r f l o w (run I I ) )  54  11  Vapour p r e s s u r e d e f i c i t s and average r a t e s of water l o s s through tomato " m u l t i p l e b a r r i e r s " (with c o r r e c t i o n f o r e f f e c t of Reynold's number of a i r f l o w (run I I I ) )  55  codes f o r e x p e r i m e n t a l tomatoes  and s t o r a g e on  vii.  LIST OF TABLES (CONT'D)  APPENDICES A, B AND C  TABLE  PAGE  A.l  Two-factor i n t e r a c t i o n e f f e c t s on weight l o s s  (run I I )  69  A. 2  Two-factor i n t e r a c t i o n e f f e c t s on weight l o s s  (run I I I )  70  B. l  Summary o f r e s u l t s s o f weight l o s s r e g r e s s i o n  analysis(run  I I ) 72  B.2  Summary of r e s u l t s of weight l o s s r e g r e s s i o n  analysis(run  I I I ) 76  B.3  Summary of c o l o u r change r e g r e s s i o n  (run I I I )  80  B.4  I n t e r a c t i o n e f f e c t of Treatment and Storage on the r a t e of c o l o u r change  83  B.5  Main e f f e c t s of Storage and Treatment on r a t e of c o l o u r change  84  B. 6  Summary of r e s u l t s of tomato f i r m n e s s changes w i t h time (regression analysis)  86  C. l  Resinite  91  f i l m WVTR d e t e r m i n a t i o n  analysis  viii.  NCMENCLATURE Units  Description Surface  a r e of tomato  m  Simple r e g r e s s i o n constant  (colour)  Simple r e g r e s s i o n constant  (Firmness)  Simple r e g r e s s i o n (weight l o s s )  coefficient  kg/(m .day)  Simple r e g r e s s i o n (colour)  coefficient  (day  l  )  Simple r e g r e s s i o n (Firmness)  coefficient  (day  l  )  Simple r e g r e s s i o n (weight l o s s )  constant  kg/m  Diameter of tomato  m  Mass d i f f u s i v i t y or d i f f u s i o n  constant  m /h 2  Water vapour p r e s s u r e  gradient  kPa/m  Factor f o r converting weight i n t o area  dimension of  m  C o n v e c t i v e heat t r a n s f e r  coefficient  W/(m .°C) 2  Subscript representing i n t e r f a c e i n t h e o r e t i c a l model f o r mass t r a n s f e r Mass t r a n s f e r c o e f f i c i e n t f o r water mov.ementefeacross*tomato s k i n r + •.bouhd ar y - l a y e r s  kg/(m  .day.kPa)  Mass t r a n s f e r c o e f f i c i e n t f o r water movement acr-ossaboundary^layer - alone  kg/(m  .day.kPa)  Mass t r a n s f e r c o e f f i c i e n t f o r water movement a c r o s s p l a s t i c f i l m  kg/(m  .day.kPa)  Mass t r a n s f e r c o e f f i c i e n t f o r water movement a c r o s s tomato s k i n  kg/(m  .day.kPa)  Mass t r a n s f e r c o e f f i c i e n t f o r water movement a c r o s s " m u l t i p l e - b a r r i e r "  kg/(m  .day.kPa)  f  ;  2  Mass t r a n s f e r c o e f f i c i e n t f o r water movement a c r o s s wax  kg/(m  .day.kPa)  coating 2  o  Thermal c o n d u c t i v i t y of heat and mass t r a n s f e r medium ( a i r )  W.m/(m . C)  L a t e n t heat of v a p o r i z a t i o n  kJ/kg  Mass t r a n s f e r per u n i t  kg/day.m  2  of  surface  t i m e , per u n i t  area kPa  P a r t i a l vapour p r e s s u r e of water i n a i r stream Saturation  vapour p r e s s u r e at temp. T  kPa  E q u i l i b r i u m vapour p r e s s u r e of tomatoes (measured)  kPa  D r i v i n g f o r c e (vapour p r e s s u r e d e f i c i t ) f o r mass t r a n s f e r  kPa  3 Universal  gas  constant  Temperatur.erafctsuBfiace  m of  "multiple  .kPa/(kg.mole,  b a r r i e r " ' °K  Air v e l o c i t y  m/min  No. of r e p l i c a t e s v a r i a n c e model)  (analysis  of  Time  days 2*  Weight l o s s per steady s t a t e  area during  kg/m  E s t i m a t e d mean m o i s t u r e l o s s f o r (tomatoes (cummulative)) Estimated colour tomatoes t r e a t e d  kg  code f o r 5 as a u n i t  E s t i m a t e d f i r m n e s s code f o r 5 tomatoes t r e a t e d as a u n i t  D e l a y c o o l i n g f a c t o r , used i n a n a l y s i s of v a r i a n c e model; i = l t o  4  P r e - s t o r a g e treatment f a c t o r used i n a n a l y s i s of v a r i a n c e model; j = 1 -to* Storage c o n d i t i o n f a c t o r ; a n a l y s i s of v a r i a n c e model k = ltt"cH~5  Symbol  Description  ^ N / ? ^  =  2-way i n t e r a c t i o n  effects  (o(|S>V)ijk  =  3-way i n t e r a c t i o n  effect  =  Independent random normal d e v i a t e s , w i t h mean z e r o  •  and v a r i a n c e ,  ^  a  ^  y^^-i^  -'  1  =  =  D e n s i t y of a i r  =  D e n s i t y of tomato  =  Absolute  viscosity  True p o p u l a t i o n mean weight l o s s per a r e a  Kinematic  viscosity  xi. ACKNOWLEDGEMENTS  I wish t o express my a p p r e c i a t i o n t o P r o f e s s o r E.L. Watson, of the Department of Bio-Resource E n g i n e e r i n g ,  U n i v e r s i t y of B r i t i s h Columbia, under  whose s u p e r v i s i o n t h i s study was undertaken, f o r h i s v a l u a b l e t i c i s m during  the r e s e a r c h ,  advice  and c r i -  and f o r h i s guidance i n the w r i t i n g of t h i s  report.  I am a l s o g r a t e f u l t o the other members of my graduate committee: Dr.  R, N. B u l l e y ;  Dr. P. J o l l i f f e Dr. M. Tung for  t h e i r keen i n t e r e s t i n my r e s e a r c h and f o r the review of t h i s I am e s p e c i a l l y indebted  t o Dr. G.W.  report.  Eaton (of the Department of P l a n t  S c i e n c e , U.B.C.), Dr. Kozak (of the F a c u l t y of F o r e s t r y , U.B.C.) and t o Mrs.  Kathleen  Hejjas  (of the F a c u l t y of F o r e s t r y , t e c h n i c i a n ) , f o r t h e i r  assist-  ance i n the s t a t i s t i c a l a n a l y s i s and computer programming of the d a t a . I thank Mr. J . Pehlke^ E l e c t r o n i c T e c h n i c i a n Engineering,  of the Dept. of Bio-Resource  f o r h i s a s s i s t a n c e i n u n d e r s t a n d i n g the e l e c t r o n i c aspects  of the  temperature c o n t r o l l e r on the Aninco A i r e u n i t s used i n . the r e s e a r c h , and t o Mrs.  Pam G i l l ,  of the Dept. of Food S c i e n c e , U . B . C , f o r h e r a s s i s t a n c e i n the  E l e c t r o n Microscopy  tests.  I am g r a t e f u l , t o o , t o Mr. Ben Abdallah  f o r h i s help f r e e l y given,  from  time t o t i m e , by way of d i s c u s s i o n and c r i t i c i s m . The monetary support  of the N a t i o n a l Research C o u n c i l of Canada through  p r o j e c t f i n a n c i n g , and the supply Western Green-house Co-operative  of experimental  material  (tomatoes) by the  of Burnaby,'B.C. a r e g r a t e f u l l y  acknowledged.  1. INTRODUCTION  A considerable s i o l o g y and s t o r a g e tomatoes  It  amount of work has been done on the p o s t - h a r v e s t  c h a r a c t e r i s t i c s of both f i e l d - g r o w n  and greenhouse  (8,9,17,22,23,27).  i s known t h a t t h e r i p e n i n g  c o l o u r towards i n c r e a s i n g r e d n e s s ) , storage  phy-  contribute to decreasing  ( u s u a l l y accompanied by changes i n and m o i s t u r e l o s s from tomatoes d u r i n g  firmness  The s k i n of the tomato f r u i t  (17/).  can be regarded as having  film properties.  T h i s assumption can thus l e a d t o e s t i m a t i o n of an e q u i v a l e n t water vapour transmission  r a t e or "apparent" p e r m e a b i l i t y  a v a i l a b l e concerning  of the s k i n .  L i t t l e data are  t h e f i l m p r o p e r t i e s of the tomato s k i n .  T h i s r e p o r t d e a l s w i t h t h e i n v e s t i g a t i o n of t h e e f f e c t s of  post-harvest  treatment on t h e r e l a t i o n of water l o s s t o t h e overa-111 q u a l i t y of greenhouse tomatoes h e l d  i n storage  f o r up t o n i n e t e e n  days.  The o v e r a l l  tomato, as judged by a consumer, i s a p s y c h o - p h y s i c a l (determined by t o u c h ) ,  q u a l i t y of a  c o n j u g a t e of  firmness  and c o l o u r ( j u d g e d i y i s u a l l y ) .  The r e p o r t a l s o i n v e s t i g a t e s the water vapour t r a n s m i s s i o n of t h e tomato s k i n d u r i n g  the steady s t a t e p e r i o d of weight l o s s .  properties The steady  s t a t e r a t e of weight l o s s i s reached a f t e r a p p r o x i m a t e l y 48 hours i n s t o r a g e .  2. LITERATURE REVIEW  Cooling It i s g e n e r a l l y agreed t h a t the mechanisms of s p o i l a g e i n h o r t i c u l t u r a l produce can be  e f f e c t i v e l y slowed by  low  been observed t h a t prompt c o o l i n g and to suppress u n d e s i r a b l e storage  temperatures  (3,31)*.  stage and  sugars d u r i n g  found t h a t i f tomatoes are p i c k e d  i f p r e - c o o l i n g and  three weeks or  (80%)  proper c o l d s t o r a g e  i n the  temperatures are  of the product would be  (b) f o r c e d - a i r c o o l i n g , (c) h y d r o - c o o l i n g ,  c o o l i n g , (e) vacuum c o o l i n g , and  ( f ) c o n t a c t - or  Room c o o l i n g i s the s i m p l e s t , cooling.  "turning"** employed,  longer.  (a) room c o o l i n g  and  Since  for highly perishable Forced-air  q u i t e "slow, and  pre-cooling.  of produce to c o l d a i r i n  thus may  included  i n the  not be s a t i s f a c t o r y  products.  cooling involves maintaining  a i r between, around and  These  (d) h y d r a i r -  o f t e n the cheapest means of  optimum a i r c i r c u l a t i o n i s not  room c o o l i n g tends to be  (3,20).  body-icing.  I t i n v o l v e s exposing the packed c o n t a i n e r s  a r e f r i g e r a t e d space.  smaller  the  i n salable condition after  S e v e r a l methods have been employed to a c h i e v e p r e - c o o l i n g  design,  has  e f f e c t i v e temperature management tends  s o f t e n i n g , l o s s of m o i s t u r e and  Wang (30)  to e i g h t y percent  are:  It  period. Wang and  up  storage  s u i t a b l e a i r v e l o c i t i e s of c o l d  through packed c o n t a i n e r s  space compared to t h a t r e q u i r e d  stacked  f o r room c o o l i n g .  in a relatively C o o l i n g by  this  means i s . f a s t e r and more e f f e c t i v e than room'cooling because the a i r passes over the product r a t h e r e f f e c t i v e l y cooled  than over the c o n t a i n e r .  t h i s way  a p p l e s have been  (7,30).  Numbers i n parentheses r e f e r t o appended See  Tomatoes and  references.  Appendix D f o r d e f i n i t i o n s f o f terms used i n tomato c l a s s i f i c a t i o n .  3.  H y d r o - c o o l i n g i s more r a p i d than f o r c e d - a i r c o o l i n g , and by  circulating  between the  c h i l l e d water around the  c o o l i n g medium and  the  produce.  The  i s achieved  good thermal  contact  product r e s u l t s i n a r a p i d r a t e of  However, f o r some p r o d u c t s , the wetness a f t e r c o o l i n g may  cooling.  cause mold or  fungal  growth. Hydrair-cooling cooling  and  i s an attempt to combine the  h y d r o - c o o l i n g by  spraying  fine droplets  advantages of  forced-air  of c h i l l e d water over  around the produce which i s u s u a l l y p l a c e d  on a moving conveyor b e l t .  and  peaches.  Webb (3) have used t h i s method to c o o l For  l e a f y products with r e l a t i v e l y  large surface  Bennett  area-to-volume  ratios,  vacuum c o o l i n g p r o v i d e s a v e r y e f f e c t i v e means of c o o l i n g .  At reduced  s s u r e s , water b o i l s or e v a p o r a t e s at reduced temperatures.  Vacuum c o o l i n g  thus an rates  e v a p o r a t i v e c o o l i n g , and  of c o o l i n g  injury.  The  damaged by water or i c e .  t a i n e r , -i--The-melting of the the  uniform  experience  s h o u l d a l s o be made from m a t e r i a l  Cr.ushedticeais  that  mmxeddwithothe pr-oduce i n . the  i c e removes the  sensible  and  is  (20).  i s n o r m a l l y used f o r p r o d u c t s which do not containers  pre-  of the most r a p i d and  a mass of produce, even i n c o n t a i n e r s  Contact i c i n g chilling  i t p r o v i d e s one  and  i s not con-  r e s p i r a t i o n heat  from  produce. Wang and  teristics against  Wang (30)  of farm produce i n deep bed.  cooling  f a s t e r than the  cooling  The  cooling rates  predicted  much reduced e v a p o r a t i o n  rates  surface  They e x p l a i n e d  the  of the product d u r i n g  the  v e g e t a b l e s w i t h waxy s u r f a c e s  (7,30) and  cooling  charac-  some unaccountably  from the model.  e v a p o r a t i o n from the  F r u i t s and  cooling  determined e x p e r i m e n t a l l y were much  c o o l i n g r a t e s as p r e d i c t e d  as caused by  process.  Checking the  r a t e s determined e x p e r i m e n t a l l y r e v e a l e d  large discrepancies.  difference  have developed a model to , p r e d i c t the  thus t h e r e should be  normally experience  little  or no  difference  4. between the p r e d i c t e d and a c t u a l c o o l i n g r a t e s . Wang and Wang (30) confirmed t h i s Fockens  The r e s u l t s of the work of  postulation.  and M e f f e r t (7) found t h a t the amount of water l o s t from  horti-  c u l t u r a l p r o d u c t s d u r i n g p r e - c o o l i n g v a r i e s i n v e r s e l y w i t h the d i f f u s i o n a l r e s i s t a n c e of the s k i n of the p r o d u c t .  Thus p r o d u c t s w i t h low  diffusional  r e s i s t a n c e l o s e r e l a t i v e l y l a r g e amounts of water d u r i n g p r e - c o o l i n g , and versa.  They a l s o found t h a t when the a i r v e l o c i t y was  vice  i n c r e a s e d , the amount  of water l o s s from p r o d u c t s d e c r e a s e d .  Treatments  To Reduce Water Loss  Waxing of  produce  I t has been found t h a t waxing reduces m o i s t u r e l o s s from seme f r u i t s such as apples (11,19,26). t h e i r appearance sometimes s h e l l a c  (11).  Cold emulsions  on tomatoes.  c o n t a i n i n g carnauba wax,  are b e i n g used on apples and pears packed  and the U n i t e d S t a t e s ( 5 ) . wax  A l s o , waxing f r e s h f r u i t s and v e g e t a b l e s enhances paraffins  and  i n Western-Canada  Not much work has been done on the a p p l i c a t i o n of  For some apple v a r i e t i e s i t has been found t h a t the i n t e r n a l  l e v e l s of carbon d i o x i d e gas and e t h y l e n e r e a c h h i g h e r l e v e l s when waxed and stored  (19).  Packaging  i n polymeric f i l m s  P o l y m e r i c f i l m s have been w i d e l y used (10,12,28).  i n packaging f r e s h  produce  The primary aims i n u s i n g these packaging m a t e r i a l s a r e :  (a)  t o prevent or minimize m o i s t u r e  loss,  (b)  t o p r o t e c t a g a i n s t m e c h a n i c a l damage, and  (c)  to p r o v i d e b e t t e r  appearance.  C e r t a i n f i l m s can extend the s h e l f - l i f e of the product by m o d i f y i n g the gaseous c o m p o s i t i o n of the atmosphere around  the p r o d u c t , and c r e a t i n g a m i n i a -  ture "controlled-atmosphere  s t o r a g e " (28) .  S e l e c t i o n o f the p o l y m e r i c  film  i s based on i t s water vapour t r a n s m i s s i o n p r o p e r t i e s ( i n c l u d i n g a n t i - f o g g i n g ) , and  i t s e f f e c t i v e n e s s as a b a r r i e r to gaseous d i f f u s i o n .  Storage A f t e r produce has been p r e - c o o l e d and p r o p e r l y prepared d e c i s i o n remains t o be made c o n c e r n i n g  f o r storage, a  the type of storage f a c i l i t y  t o employ.  For s t o r a g e of f r e s h produce, t h r e e main types of s t o r a g e have been t r i e d . These a r e : (a) R e f r i g e r a t e d s t o r a g e , (c) Hypobaric  (b) C o n t r o l l e d atmosphere s t o r a g e , and  storage.  ( > Re f-r i g era! t e d s t or ag e a  l  ;c  T h i s i n v o l v e s the d i r e c t c o n t r o l of temperature combined w i t h an i n d i r e c t c o n t r o l of h u m i d i t y . have been t r i e d  of temperature and h u m i d i t y  f o r the c o l d s t o r a g e of tomatoes (5,9,17,22,23).  e r a t u r e most c i t e d and  S e v e r a l combinations  The temp-  i n the l i t e r a t u r e i s 10°C (50°F) f o r " f i r m - r i p e " tomatoes  12.8 - 15.6°C (55 - 60°F) f o r "mature-green" tomatoes (5,9),  temperatures  a r e r e q u i r e d t o prevent  chilling  These h i g h e r  i n j u r y t o the green  fruit.  "Mature-green" and " t u r n i n g " tomatoes r i p e n s l o w l y when h e l d a t temperat u r e s between 10 - 12.8°C (50 - 5 5 ° F ) . attendant  The r a t e of c o l o u r change w i t h some  s o f t e n i n g i n c r e a s e s as t h e , s t o r a g e temperatures  are increased to  about 21.1°C (70°F) ( 5 ) . Above 21.1°C, e x c e s s i v e l y r a p i d r i p e n i n g and r a p i d t e x t u r a l break down w i t h some o f f - f l a v o u r may occur ( 5 ) . ]  Very h i g h h u m i d i t i e s i n the s t o r a g e space may be advantageous i n r e -  ducing moisture  l o s s from tomatoes.  However, the environmental  should be c o n t r o l l e d so t h a t condensation does n o t o c c u r .  conditions  on t h e s u r f a c e of the s t o r e d produce  Working w i t h B r u s s e l s s p r o u t s , c e l e r y , Chinese  cabbage and  l e e k s at 0 - 1°C  (32 - 34°F) , van den Berg and Lentz  at v e r y h i g h h u m i d i t i e s , 98%  - 100%,  In t h i s p a r t i c u l a r  that storage  r e s u l t e d i n g e n e r a l l y reduced  l o s s , accompanied by a c r i s p e r , greener ties.  (4) found  product  moisture  than s t o r a g e at lower  t e s t , even s u r f a c e c o n d e n s a t i o n ,  humidi-  r e s u l t i n g from the  v e r y h i g h h u m i d i t i e s d i d not a p p r e c i a b l y i n c r e a s e decay, and a c t u a l l y f u r t h e r reduced  weight  loss.  C o n t r o l l e d - atmosphere s t o r a g e In a c o n t r o l l e d - a t m o s p h e r e  (CA)  s t o r a g e , the gaseous composition  of the  s t o r a g e chamber environment as w e l l as the temperature are c o n t r o l l e d .  The  a d j u s t e d l e v e l s of oxygen arid carbon d i o x i d e are o p t i m i z e d f o r each product be s t o r e d .  Parsons e t a l . (23), found  l e v e l s as low as 3% and  t h a t tomatoes kept  t h a t carbon d i ripe-  d i b x i d e - f r e e atmosphere.  storage  The p i o n e e r i n g work of T o l l e of a new  They found  r e s u l t e d i n the tomatoes being more a c i d a f t e r  n i n g than those h e l d i n carbon Hypobaric  i n s t o r a g e a t oxygen  zero carbon d i o x i d e r e s u l t e d i n s i g n i f i c a n t l y b e t t e r  p o s t - s t o r a g e c o n d i t i o n than those s t o r e d i n a i r . oxide l e v e l s of 3 - 5 %  concept  (27) and  p r e s s u r e s i n c o n j u n c t i o n w i t h low temperatures  of the p r i n c i p l e s of c o n t r o l l e d - a t m o s p h e r e termed Hypobaric  o t h e r s have l e d to the development  i n the storage of f r e s h f r u i t s and v e g e t a b l e s which u t i l i z e s  sub-normal atmospheric  Storage, and  a i d of vacuum pumps.  The  storage.  and some  T h i s system of s t o r a g e i s  the sub-normal p r e s s u r e s are o b t a i n e d w i t h  system i s s t i l l  i n the developmental  stage,  the  but i t  h o l d s g r e a t promise f o r the f u t u r e . As i n the case of a l l f r u i t and v e g e t a b l e for e f f e c t i v e hypobaric should be  to  high.  s t o r a g e , a key  s t o r a g e i s t h a t the i n i t i a l  requirement  q u a l i t y of the produce  T e s t s conducted  by T o l l e on the h y p o b a r i c s t o r a g e of tomatoes gave some  h i g h l y promising r e s u l t s .  He found  t h a t the tomatoes r e t a i n e d t h e i r  c o l o u r l o n g e s t a t the lowest p r e s s u r e , one-quarter  (h)  green  atmosphere, and t h a t  a f t e r s t o r a g e , a l l l o t s e v e n t u a l l y r i p e n e d t o equal r e d c o l o u r , w i t h e q u a l l y s a t i s f a c t o r y f l a v o u r when f u l l y There a r e s t i l l enjoy wide-spread (a)  ripe.  some problems t o be s o l v e d b e f o r e t h i s new concept can  use i n the i n d u s t r y .  The r e s p i r a t i o n requirements  Key among these a r e : under h y p o b a r i c p r e s s u r e s are unknown.  Most r e s p i r a t i o n d a t a have been o b t a i n e d a t normal  atmospheric  pressures. (b)  The o p t i m a l s t o r a g e h u m i d i t i e s a r e n o t y e t known.  (c)  The e f f e c t s of the d i f f e r e n t i a l r e l e a s e of v o l a t i l e s from produce i n t e r i o r s ' on'^their f l a v o u r s are unknown.  (d)  The e f f e c t s of h y p o b a r i c p r e s s u r e s on the development o f pathogens, and on the b i o c h e m i s t r y of the produce i t s e l f tively  (e)  are r e l a -  unexplored.  P o t e n t i a l c e l l u l a r damage i n the event  of too r a p i d attainment o r  r e l e a s e of h y p o b a r i c p r e s s u r e s a r e a l s o n o t known.  Colour And Firmness  Changes  Tomatoes i n s t o r a g e tend t o undergo two major changes d u r i n g r i p e n i n g : (a)  Colour change towards i n c r e a s i n g redness lycopene  (b)  s y n t h e s i s and c h l o r o p h y l l  S o f t e n i n g of the f r u i t substances sols. due  c h a r a c t e r i z e d by marked  degradation.  caused by depolymerizati.on of p e c t i c  r e s u l t i n g i n a decrease  i n the v i s c o s i t y of the  M o i s t u r e l o s s a l s o c o n t r i b u t e s t o s o f t e n i n g of the f r u i t s  t o l o s s of t u r g i d i t y i n the c e l l s .  8.  Tomato c o l o u r Colour i n foods i s g e n e r a l l y a v e r y d i f f i c u l t luate  q u a l i t y f a c t o r t o eva-  o b j e c t i v e l y , p a r t i c u l a r l y i n view of the f a c t t h a t the development of  measuring methods has p r e s e n t e d unique  problems w i t h each product ( 2 5 ) .  S u b j e c t i v e l y , tomato c o l o u r has been assessed by d i r e c t v i s u a l  ins-  p e c t i o n , and a l s o w i t h the a i d o f r e f e r e n c e guides i n c l u d i n g s t a n d a r d c o l o u r p l a t e s , t h r e e d i m e n s i o n a l models, c o l o u r hand books and c o l o u r d i c t i o n a r i e s (6,18,25) . The  accuracy of s u b j e c t i v e e v a l u a t i o n i s dependent upon s e v e r a l f a c t o r s ,  the p r i n c i p a l ones b e i n g  (13,18):  (a)  N o r m a l i t y of observer  vision  (b)  Observer  (c)  Colour u n i f o r m i t y of sample  (d)  Surface g l o s s  (e)  S i z e and shape of product  (f)  Internal c e l l structure  (g)  Sample environment i n c l u d i n g q u a l i t y and d i r e c t i o n o f i l l u m i n a t i o n .  fatigue  There have been t h r e e major t e c h n i q u e s f o r o b j e c t i v e d e t e r m i n a t i o n of tomato c o l o u r , v i s : (a)  Chemical  a n a l y s i s method  (b)  Photo-electric tristimulus colorimetry  (c)  Transmittance  or r e f l e c t a n c e s p e c t r o photometric method.  The r e f l e c t a n c e technique has been u t i l i z e d by von Beckmann e t a l . (2) to  develop  a tomato c o l o u r g r a d e r .  Tomato f i r m n e s s Work on measuring the f i r m n e s s of tomatoes dates back some f o u r decades, however, t h e r e . i s no known n o n - d e s t r u c t i v e t e s t f o r t h i s o p e r a t i o n .  9. Researchers  have developed p r e s s u r e  testers  to a i d i n measuring  o f f r u i t s and t h e c o r r e l a t i o n o f f r u i t f i r m n e s s and Webb of  (13)  define firmness  to maturity  as t h e f o r c e n e c e s s a r y  a tomato f r u i t i n c l u d i n g the s k i n or p e e l .  the  (8,13,14).  to rupture the  Using  firmness  a cross-head  Hood  surface  speed  of  10 cm/min o n a m o d e l TM-M I n s t r o n t e s t e r , t h e y p e r f o r m e d e x t e n s i v e t e s t s tomato f i r m n e s s .  These  are however, d e s t r u c t i v e i n n a t u r e , i n t h a t a f t e r  s i n g l e d e t e r m i n a t i o n of f i r m n e s s , also  t h e e x p e r i m e n t a l f r u i t c o u l d n o t be  r e p r e s e n t a t i v e of the whole  of  tomato. device that simulates  t o m a t o e s b y h a n d was d e v e l o p e d b y K a t t a n  (14).  f i r m - o - m e t e r w h i c h d e t e r m i n e s f i r m n e s s by t h e c o n s t r i c t i o n of given force.  The p r i n c i p l e o f o p e r a t i o n o f  of a u n i f o r m p r e s s u r e fruit  i s measured  time  This  is  the a  the e x e r t i o n  The d e f o r m a t i o n o f  (30 s e c o n d s )  The f i r m e s t t o m a t o r e a d s  the  the f r u i t by  the firm-o-meter i s  the f r u i t by a c h a i n .  a f t e r a p e r i o d of  d u a t e d f r o m 0 t o 10. scale.  around  inch  r i s e t o t h e q u e s t i o n of w h i c h spot would be most  The m o s t p r a c t i c a l f i r m n e s s m e a s u r i n g "squeezing"  each  re-used;  ( a n d more i m p o r t a n t l y ) , o n l y an a r e a on t h e f r u i t s u r f a c e o n e - q u a r t e r  i n d i a m e t e r was t e s t e d , g i v i n g  the  on  on a n i n v e r s e  the  scale  0 and t h e s o f t e s t r e a d s  gra-  10 on  10. MATERIALS  AND  METHODS  Experimental Design.  A 4x4x5 f a c t o r i a l experiment was (a) d e l a y ( i . e .  used t o i n v e s t i g a t e the e f f e c t s of  between h a r v e s t and c o o l i n g ) ,  p r e p a r a t i o n f o r s t o r a g e ) , and d i t y ) , on the s t o r a g e l i f e f o l l o w e d by measuring ness and c o l o u r of  (b) p r e - s t o r a g e treatment ( i n  (c) s t o r a g e c o n d i t i o n (temperature and humi-  of green house tomatoes.  Storage l i f e  was  the r a t e of m o i s t u r e l o s s and the changes i n f i r m -  tomatoes when s t o r e d under c o n t r o l l e d temperature  and  humidity.  In many cases tomatoes do not go i n t o c o n t r o l l e d s t o r a g e after harvesting.  D e l a y s may  be as long as twenty-four hours.  d e l a y e d c o o l i n g were s e l e c t e d f o r the experiment.  immediately Four l e v e l s of  There were a l s o 4 k i n d s of  a f t e r - c o o l treatment and 5 combinations of temperature  and h u m i d i t y used.  See  T a b l e 1 f o r summary of e x p e r i m e n t a l d e s i g n .  Equipment D e s c r i p t i o n .  To p r o v i d e the s t o r a g e c o n d i t i o n s , a Conviron C o n t r o l l e d c a b i n e t , model E8M,  and two  Aminco A i r e u n i t s ,  Environment  models 4-5580 and 4-5460A  were u t i l i z e d .  The Conviron chamber was (50 F) and 90% r e l a t i v e  The  programmed t o d e l i v e r c o n d i t i o n e d a i r at  humidity.  10°C  This constituted storage condition n o . l .  Aminco A i r e unit-; model 4-5580 w i t h a manufacturer's  list  capacity  3 of 6mm  28.32  m /miri  (1000  c.f.m.) was  a t t a c h e d t o a chamber c o n s t r u c t e d from  (%-inch) plywood w i t h 1 0 . 2 c m ( 4 - i h ) styrofoam i n s u l a t i o n .  dimensions were 1 m x 1 m  nc  The  (39 i n . x 39 i n . ) h o r i z o n t a l a r e a , by 1.57  inside m(62 i n . ) •  11. TABLE 1. SUMMARY OF EXPERIMENTAL DESIGN WITH C-T-S CODING  FACTOR  A.  LEVELS  COOLING  1. 20 - Hour Delay  ( i . e . Delay between h a r v e s t and c o o l i n g )  2. 10 - Hour Delay 3.  0 - Hour Delay  4. 30 - Hour Delay  B.  (*)  TREATMENT  1. U n t r e a t e d  ( i . e . Pre-storage Treatment)  ( i . e . Immediate C o o l i n g ) (**)  (**)  2. Wrap i n P o l y m e r i c F i l m 3. Calyx-End  Only Waxed  4. Whole S k i n Waxed.  C.  STORAGE CONDITION  ( i . e . Temp. and humidity)  *  1. 10°C  (+0.5°C) : 90% r h  (+2%  rh )  2. 15°C  (+0.5°C) : 88%  (+2%  )  3. 10°C  (+0.5°C) : 60%  (+2%  • )  4. 15°C  (+0.'5°C) : 50%  (+2%  ' .)  5. 18°C  (+1.0°C) : 40% (**)  ( Ave,, of range 30% - 60%)  e.g. A C-T-S combination of 3 2 4 r e p r e s e n t s tomatoes which were immediately  c o o l e d a f t e r h a r v e s t ; i n d i v i d u a l l y wrapped i n  plastic  f i l m ; and s t o r e d a t 15°C and 50% r h . These r e p r e s e n t v a r i o u s l e v e l s of t h e t h r e e f a c t o r s c o n s i d e r e d as c o n t r o l o r check on the o t h e r  levels.  12. high.  Two  removable h o r i z o n t a l s h e l v e s made from n y l o n mesh, and 0.31  (12 i n . ) apart were p l a c e d i n the chamber. (59 F) and 88% r h was 0.15  x 0.18  m  The c o n d i t i o n e d a i r a t  m  15°C  f e d i n t o the chamber through a r e c t a n g u l a r a i r d u c t ,  (6 x 7 i n ) i n s i d e dimensions, connected near the bottom  r i g h t - s i d e w a l l of the chamber.  The c o n t r o l l e d environment  c o n s t i t u t e d s t o r a g e c o n d i t i o n no.2 a i r , a d i f f u s e r made from 3 mm  of the  i n t h i s chamber  To o b t a i n a u n i f o r m upward movement of the  (^/s  in)  plywood w i t h 5  mm  ( / 16 i n ) h o l e s on p l a c e d h o r i z o n t a l l y between the a i r i n l e t and the 3  25 mm  (1-in) centres  was  3 bottom  shelf.  (246 cfm ).o'f a i r was circulated  gate type f l o w - d i v i d e r , about 7 m  U s i n g an aluminium  passed through the.chamber, and the remainder was  (see F i g u r e 1 f o r schematic diagram).  ( F l o w t r o n i c model 55B1)  and a p r o p e l l e r - t y p e v e l o m e t e r , the b u l k upward a i r  C o n d i t i o n e d a i r at 10°C  was  re-  U s i n g an a i r v e l o c i t y meter  f l o w was measured t o be 6 . 4 + 0 . 5 m/min (21.1 +1.5  u n i t was  /min  ft./min).  (50°F) and 60% r h from the second  d i v i d e d i n t o two streams by a f l o w - d i v i d e r .  One  Aminco A i r e  of the a i r streams  r e - h e a t e d w i t h a t h e r m o s t a t i c a l l y c o n t r o l l e d space h e a t e r t o 15°C  (59°F) ,  w i t h a r e l a t i v e h u m i d i t y of 5 0 + 2 % .  The a i r streams were then passed  two f l e x i b l e c i r c u l a r a i r ducts 0.15m  (6 i n ) i n diameter and connected near  the bottoms of the s i d e w a l l s of two (h  identicallGhambe^samade'from  in)hplywpodoandn515mmi^(2 (dn)/astyrof oam  of the chambers were 0.81 removable  x 0.89  m  insulation.  (32 x 35 i n ) by 1.09  The i n s i d e m  h o r i z o n t a l s h e l v e s made from w i r e mesh, and 0.31  were p l a c e d i n each chamber.  To e f f e c t  13 mm  through  _  dimensions  (43 i n ) h i g h . m  Two  (12 i n ) a p a r t  a uniform upward movement of the  c o n d i t i o n e d a i r , a d i f f u s e r c o n s t r u c t e d as f o r the chamber a t t a c h e d to the f i r s t Aminco A i r e u n i t , d e s c r i b e d above, was air  i n l e t and the bottom  p l a c e d h o r i z o n t a l l y between the  s h e l f i n each chamber.  a i r a t 10°C and 60% r h and t h a t w i t h a i r a t 15°C s t o r a g e c o n d i t i o n s 3 and 4 r e s p e c t i v e l y .  The chamber w i t h c o n d i t i o n e d (59°F) and 50% r h c o n s t i t u t e d  Measurement of the a i r v e l o c i t i e s  13. FIGURE 1.  SCHEMATIC OF AIR CONDITIONING SYSTEM EMPLOYING RECIRCULATION OF EXCESS AIR  LEGEND  3 A :  Aminco A i r e u n i t  (28.32mc/min')ain)  B :  Flow-divider  C :  Conditioned-air to controlled  D :  By-pass f o r unused a i r (back t o Aninco A i r e u n i t )  E  :  C o n t r o l l e d environment  F  :  M i x t u r e of a i r streams C and D  environment chamber  chamber, storage no. 2  14. through the two chambers a t t a c h e d t o the Aminco A i r e u n i t model 4^-5460A gave 3.1 + 0.5 m/min ( 10.2 +.1.5 f t . / m i n ) and 3.1 + 0.5 m/min (10.1 + 1.5 f t . / m i n ) for  s t o r a g e c o n d i t i o n s 3 and 4, r e s p e c t i v e l y .  T h i s was l e s s than t h e average  v e l o c i t y of 5.9 m/min (19.4 f t . / m i n ) as suggested by  the manufacturer's  list  3 c a p a c i t y of 8.5 m /min (300 cfm) f o r the u n i t .  (See F i g u r e 2 f o r schematic  diagram of u n i t ) . To s i m u l a t e s t o r a g e a t room temperature and h u m i d i t y , a s t o r a g e was set  up i n an a i r - c o n d i t i o n e d room w i t h temperature s e t a t 18 + 1°C (64 + 2 ° F ) .  The r e l a t i v e  h u m i d i t y i n t h i s room was i n f l u e n c e d by the o u t s i d e  conditions  and v a r i e d between 30% and 60%, g i v i n g a b u l k average h u m i d i t y of 40% d u r i n g the  test period.  T h i s environment  c o n s t i t u t e d the s t o r a g e c o n d i t i o n no.5.  The temperature i n s i d e each chamber was monitored by a YSI t e l e thermometer model 47 and t h e r e l a t i v e h u m i d i t y by a Phys-Chemical Corp. Humeter h u m i d i t y sensor model 47-1072-9000.  Research  The YSI tele-thermometer  was s t a n d a r d i z e d a g a i n s t a copper-constantan thermocouple; and the Humeter was checked a g a i n s t a dew p o i n t hygrometer model 880.  Both Humeter and dew p o i n t  hygrometer were s t a n d a r d i z e d a g a i n s t a s a t u r a t e d copper s u l p h a t e s o l u t i o n a t 20°C  ( r h = 97.2%).  To check chamber c o n d i t i o n s b e f o r e the s t o r a g e t e s t s were  begun, the temperature and h u m i d i t y i n each chamber were monitored f o r s e v e r a l days and r e c o r d e d w i t h a R i k e n d e n s h i r e c o r d i n g p o t e n t i o m e t e r , model SP-H6V. As an a d d i t i o n a l check on the u n i f o r m i t y of temperature and h u m i d i t y w i t h i n the chambers, STgrhygrorithermpgraphsr^model 134882/46/1 were p l a c e d i n the chambers at  c e r t a i n times. A p r e - c o o l e r was c o n s t r u c t e d from a t a b l e f a n w i t h f o u r b l a d e s of 0 . 4 m  (18 i n ) diameter. plastic  conduit attached to a perforated shipping container f u l l  During a t r i a l the  T h i s was used t o blow 4.4°C (40°F) a i r through a c i r c u l a r  tomatoes  of  tomatoes.  r u n , i t r e q u i r e d two hours t o reduce the average temperature of  from 20°C  (68°F) t o 13.9°C  (57°F) .  SCHEMATIC OF AIR CONDITIONING SYSTEM SERVING TWO CHAMBERS.  C  B  T>  •  1 LEGEND 3 A::  Aminco Aire u n i t (8. 5Cmc^min?)iin)  B :  Flow-divider  C :  Conditioned-air t o chamber  D :  Conditioned a i r incorporating reheatt  H :  Space heater & Thermostat  E^:  Controlled environment chamber, storage no. 3  E :  Controlled environment chamber, storage no. 4  0  16.  Experimental  Procedure  Pre-storage  tests  Development of c o l o u r  standards  Ten tomatoes, two each of c o l o u r c l a s s i f y i n g  them a s : a) mature  green;  b) t u r n i n g ; c) s e m i - r i p e ; d) f i r m - r i p e ; and e) t a b l e - r i p e , were s e l e c t e d f o r the development of a s c a l e , l i n e a r i n the amount of redness.  On a s c a l e of  1 to 5, the f o l l o w i n g d e s i g n a t i o n s were employed: the g r e e n e s t mature tomatoes were g i v e n a c o l o u r code 1 the t u r n i n g tomatoes were assigned c o l o u r code 2 the s e m i - r i p e tomatoes were a s s i g n e d c o l o u r code 3 the f i r m - r i p e tomatoes were a s s i g n e d c o l o u r code 4 the t a b l e - r i p e tomatoes were a s s i g n e d c o l o u r code 5  Colour p i c t u r e s were taken of each grade of tomato, and a r e shown on Plate  1.  Firmness s c a l e  In o r d e r t o keep the number of tomatoes used to a r e a l i s t i c v a l u e , and t o permit f o l l o w i n g changes i n f i r m n e s s index w i t h time, the e x p e r i m e n t a l design required a non-destructive firmness t e s t . t e s t e r c o u l d not be used.  I n s t e a d , a f i r m n e s s s c a l e , as judged  tomato i n the hand, was developed Department of Bio-Resource  Thus a c o n v e n t i o n a l p r e s s u r e  w i t h the h e l p of a p a n e l of 5 judges  E n g i n e e r i n g at U.B.C.  was e v a l u a t e d as :  t o have the same f i r m n e s s ) .  i n the  Each judge i n t u r n was  to p l a c e 240 tomatoes i n 5 groups of v a r y i n g f i r m n e s s . group were judged  by h o l d i n g the  asked  (The tomatoes i n each  On a s c a l e of 0 t o 4,  firmness  0 r e p r e s e n t s the s o f t e s t tomato (unacceptable or u n s a l a b l e  i n the market p l a c e ) , and 4 r e p r e s e n t s the f i r m e s t tomato (as i n a t y p i c a l  17.  Colour Code 3  Colour Code 4  Colour Code 5  18. mature g r e e n - t o - t u r n i n g tomato).  Intermediate e v a l u a t i o n s of 1, 2 and 3  r e p r e s e n t t r e n d s of i n c r e a s i n g f i r m n e s s .  In over e i g h t y p e r c e n t of the  tomatoes thus graded the j u d g e s ' e v a l u a t i o n s agreed w i t h those of the author.  Moisture.content and.density determination  The m o i s t u r e content of a randomly s e l e c t e d sample of 5 tomatoes was determined by f r e e z e - d r y i n g to constant-weight  ( a f t e r 3-4  days).  The d e n s i t y was determined by weighing each of a random sample of 5 tomatoes i n a i r , and then re-weighing them w h i l e t o t a l l y submerged at 4°C (39.2°F).  i n water  The d i f f e r e n c e i n weights between t h a t i n a i r and i n water  gave the volume of a tomato, and d i v i d i n g  the weight i n a i r by the volume  gave the d e n s i t y of the tomato.  T e s t method  Three experiments were done i n the p e r i o d between August and November 1976, w i t h each r u n i n v o l v i n g 400rtbmajoesi.tomatoes.  In the f i r s t r u n , 400 greenhouse tomatoes ( c v . Vendor) were hand-picked from the Gipaanda Greenhouse i n S u r r e y , B.C.  (8060 146 S t . ) . The f r u i t s were  at stages of r i p e n i n g r a n g i n g from "mature-green" to " f i r m - r i p e " .  T h i s group  of 400 tomatoes was d i v i d e d randomly i n t o f o u r subgroups of 100 tomatoes each. The tomatoes i n one subgroup were l a b e l l e d 201-300, and were p l a c e d immediately i n the p r e - c o o l e r at 4.4°C  (40°F) and c o o l e d from a f i e l d  (68°F) to 13.9°C (57°F) i n 2 h.  temperature of 20°C  ( A c t u a l l y t h e r e was a d e l a y of 2 t o 4 h  between h a r v e s t and placement i n the pre-cooler.'.. 'TMsswas the_time i t took to b r i n g the e x p e r i m e n t a l m a t e r i a l from the farmftotithe l a b o r a t o r y ) .. T h i s c o n s t i t u t e d c o o l i n g procedure 3. A f t e r c o o l i n g , the 100 tomatoes i n t h i s subgroup were f u r t h e r  subdivided  19. i n t o f o u r l o t s of 25 f r u i t s each.  The f i r s t  l o t (nos. 201  f u r t h e r treatment; the 25 f r u i t s i n the second i n d i v i d u a l l y wrapped i n 0.55  l o t (nos. 226  m i l . polyvinyl chloride film  the 25 f r u i t s i n the t h i r d l o t (nos. 251  - 225)  received  no  - 250) were  (PVC - R e s i n i t e ) ;  - 275) had t h e i r c a l y x ends o n l y  waxed w i t h APL-LUSTER, o b t a i n e d from A g r i c u l t u r a l Chemicals - Pennwalt Corporation.  The wax  covered a c i r c u l a r a r e a about  The f o u r t h l o t (nos. 276 emulsion. All  - 300) had  After application  (+ 0.01  (by b r u s h i n g on), the wax  g) on a M e t t l e r  wax  d r i e d i n 2 t o 3 min.  - 300) were then  individually  Balance.  Each l o t of 25 tomatoes was each, and each s u b l o t was  i n diameter.  t h e i r whole s u r f a c e s coated w i t h the  the tomatoes i n t h i s subgroup (nos. 201  weighed  1 i n (2.5 cm)  f u r t h e r d i v i d e d i n t o 5 s u b l o t s of 5 tomatoes  p l a c e d i n one of the 5 s t o r a g e c o n d i t i o n s d e s c r i b e d  earlier.  The remaining t h r e e subgroups  (each c o n s i s t i n g of 100  tomatoes) were  h e l d f o r 10, 20 and 30 h o u r s , r e s p e c t i v e l y , and then t r e a t e d e x a c t l y as the first  subgroup.  See T a b l e s 1 and 2 f o r a summary of a l l c o o l i n g - t r e a t m e n t -  s t o r a g e (C-T-S) regimes.  A f t e r 48 h i n s t o r a g e , the 400 time, and weighed. on d i f f e r e n t about  The s h e l v e s were then r e p l a c e d i n t h e i r o r i g i n a l  shelf l e v e l s .  3 h and was  The r o u t i n e of weighing  repeated every 48-hour p e r i o d s .  f o l l o w e d i n the removal  The  tomatoes were removed one s h e l f at a  of the f r u i t  400  tomatoes r e q u i r e d  No p a r t i c u l a r order  was  from the v a r i o u s chambers.  second run of the experiment was  performed  i n September, 1976.  t h i s r u n a l s o , the 400  tomatoes i n v o l v e d were hand-picked  Greenhouse i n Surrey.  I t was  The  chambers  run e x a c t l y as the  t h i r d r u n of the experiment was  from the  Gipaanda  first.  performed  i n November,  1976.  In  20.  TABLE 2.  LABELLING CODES FOR EXPERIMENTAL  STORAGE CONDITION  TOMATOES  20-HOUR DELAY  10-HOUR DELAY  (COOLING NO.l)  (COOLING  PRE-STORAGE TREATMENT 1  2  NO.2)  PRE-STORAGE TREATMENT  (*)  3  4  1  2  (*)  3  4  1. 10°C:90%  1-5.  26-30.  51-55  76-80  101-105 126-130 151-155 176-180  2. 15°C:88%  6-10  31-35  56-60  81-85  106-110 131-135 156-160 181-185  3. 10°C:60%  11-15  36-40  61-65  86-90  111-115 136-140 161-165 186-190  4. 15°C:50%  16-20  41-45  66-70  91-95  116-120 141-145 166-170 191-195  5. 18°C:40%  21-25  46-50  71-75  96-100  121-125 146-150 171-175 196-200  0-DELAY :  (COOLING  STORAGE CONDITION - -  (IMMEDIATE)  (COOLING  NO.3)  PRE-STORAGE TREATMENT 1  2  39-HOUR DELAY  PRE-STORAGE TREATMENT  (*)  3  NO.4)  1  4  2  (*)  3  4  1. 10°C:90% 201-205 226-230 251-255 276-280  301-305 326-330 351-355 376-380  2. 15°C:88% 206-210 231-235 256-260 281-285  306-310 331-335 356-360 381-385  3. 10°C:60% 211-215 236-240 261-265 286-290  311-315 336-340 361-365 386-390  4. 15°C:50% 216-220 241-245 266-270 291-295  316-320 341-345 366-370 391-395  5. 18°C:40% 221-225 246-250 271-275 296-300  321-325 346-350 371-375 396-400  Pre-Storage  Treatment 1 = U n t r e a t e d  Tomatoes;  2 = Tomatoes wrapped i n p l a s t i c ; 3 = Tomatoes w i t h c a l y x ends o n l y waxed; 4 = Tomatoes w i t h whole s k i n s u r f a c e waxed.  21.  The  400  B.C.  tomatoes (cv. Vendor) r e q u i r e d were p i c k e d from Seto Farms, Surrey,  (17453 8th. Ave.).  treatments, one and  and  two.  In t h i s r u n , the c o o l i n g procedures,  pre-storage  the storage c o n d i t i o n s employed, were s i m i l a r to those i n runs  In a d d i t i o n , as each tomato was  48 h i n s t o r a g e , a c o l o u r code (1 to 5) was  weighed and reweighed a f t e r each  a s s i g n e d by v i s u a l comparison w i t h  the c o l o u r photographs taken d u r i n g the p r e - s t o r a g e r a t i n g was  the  tests.  A l s o , a firmness  a s s i g n e d by a p p l y i n g g e n t l e f i n g e r p r e s s u r e to each tomato as  previously described. removal of f r u i t  Post-storage  As b e f o r e , no p a r t i c u l a r o r d e r was  f o l l o w e d i n the  ofrom the v a r i o u s chambers f o r reweighing,  etc.  t e s t s on tomatoes  I n v e s t i g a t i o n of e f f e c t of P r e s s u r e on tomatoes  To i n v e s t i g a t e the e f f e c t of a p p l i e d p r e s s u r e on the tomatoes a p p l i e d d u r i n g p e r i o d i c weighing decided  to,perform  surface c e l l u l a r  and e v a l u a t i o n of the f i r m n e s s  e l e c t r o n microscopy  the s k i n s were not touched  t e s t s on the tomato s u r f a c e and  v e r y c a r e f u l l y p i c k e d and handled  or brushed.  of the c a r e f u l l y hand-picked  Aa2.2 7 kge(5 l b t ) , weight was H  Another c a r e f u l l y p i c k e d tomato was  s e c t i o n s of s u r f a c e t i s s u e , a few  temperature.  l o s s tomato from the weight  e l e c t r o n microscopy  c e l l l a y e r s deep.  g l u t a r a l d e h y d e i n 0.07  The  t i s s u e was  placed  tomatoes.  examinations  For these t e s t s ,  tomato t i s s u e were e x c i s e d from the f r u i t near the s u r f a c e and  f i x e d w i t h 2.5%  so t h a t  g i v e n a "low p r e s s u r e r u b " w i t h the hand.  l o s s tomato and a low m o i s t u r e  t e s t s were a l s o i n c l u d e d i n scanning  of  sub-  tomatoes f o r 5 seconds to s i m u l a t e extreme  rough h a n d l i n g d u r i n g s u c c e s s i v e weighings of the e x p e r i m e n t a l  A high moisture  index) , i t was  layers.  A sample of s i x tomatoes was  on one  (pressure  loss  of c r o s s samples  immediately  M phosphate b u f f e r f o r 4 h at room  f u r t h e r f i x e d w i t h osmium t e x t r o x i d e (OsO.) i n  0.07  M phosphate b u f f e r f o r one hour at room temperature,  for  10 min  and  100%  a t each stage of an e t h a n o l s e r i e s  (twice)).  The e t h a n o l was  (50%, 70%,  then  dehydrated  80%,90% (twice)  then r e p l a c e d u s i n g 10 min  w i t h a s e r i e s of amyl a c e t a t e s o l u t i o n s  (25%, 50%,  f o l l o w e d by c r i t i c a l  specimens were cemented on SEM  point drying.  and coated w i t h approximately examination.  200  The  100%  ( t w i c e ) ) and  $ of a g o l d / p a l l a d i u m mixture b e f o r e  The m a g n i f i c a t i o n s used were up to 400  S a t u r a t i o n vapour p r e s s u r e d e t e r m i n a t i o n  The  75% and  treatments  stubs SEM  times.  i  s a t u r a t i o n vapour p r e s s u r e of 4 tomatoes, one from each of the f o u r  p r e - s t o r a g e t r e a t m e n t s , was Each tomato was  determined  p l a c e d i n a s e a l e d b o t t l e and l e f t  brium w i t h the a i r i n the b o t t l e .  p o i n t sensor of the hygrometer and  f o r 24 h to reach  equili-  c i r c u l a t e d by a s m a l l pump to the  then back to the b o t t l e .  Knowing the temperature  e q u i l i b r i u m r e l a t i v e h u m i d i t y was  p o i n t hygrometer.  At the end of the 24 h p e r i o d , a sample of  the e q u i l i b r i u m a i r i n the b o t t l e was  c l o s e d system.  w i t h the a i d of a dew  and  the  dew  dew  Thus t h i s was  p o i n t of the a i r , the  read from a p s y c h r o m e t r i c c h a r t .  a  23. THEORETICAL MODEL UTILIZED FOR  In  a tomato  ANALYSIS OF MOISTURE LOSS  of average shape, t h e r e i s a good c o r r e l a t i o n between the 2  "major d i a m e t e r " and the weight of the tomato  (2) (r  = 0.9675).  I t has been  assumed ( i n t h i s p r o j e c t ) t h a t the average tomato has a s p h e r i c i t y of c l o s e to  one.  Thus we  can express the s u r f a c e a r e a of the tomato i n terms of i t s  diameter, a s :  7C D  A = We  1  2  can a l s o express the weight i n terms of the diameter a s : W = £ (> D  Thus t a k i n g the  2  /3^  d  2  3  r o o t s of each s i d e of equn. 2, and m u l t i p l y i n g through  by a f a c t o r , f , y i e l d s :  f. If  W  2/3  TT  =  e )  f.(f  2/3  -D  9  3  f i s s e l e c t e d such t h a t :  TT  2  f . (-JT ^ ) 2  then,  f.W  /3  /3 = 7TD  -ir =71= 2  =  3a  constant  area  4  Tomatoes have a l a r g e m o i s t u r e content (93% m . c , thus d e c i d e d t o c o n s i d e r as a p h y s i c a l model, porous s k i n . a) the  I t was  a wet m a t e r i a l covered by a  F u r t h e r assumptions made were:  Below the porous s k i n a r e s p h e r i c a l c e l l s f i l l e d w i t h water, w i t h  i n t e r c e l l u l a r spaces f i l l e d b)  wet b a s i s ) .  w i t h vapour.  The water .yapour p r e s s u r e i n the i n t e r c e l l u l a r  g r a d u a l l y through the t h i c k n e s s of the s k i n and boundary - i n t e r c e l l u l a r vapour p r e s s u r e = 0.98 temperature)  just  spaces decreases l a y e r from 98% ( i . e .  xr-vap'our p r e s s u r e of pure water at same  i n s i d e of the s k i n , to..the v a l u e p  of the s t o r a g e  24. chamber a i r . c)  Transport  of m o i s t u r e  through  the s k i n occurs i n the form of vapour  ( 7 ) , w i t h energy f o r e v a p o r a t i o n b e i n g s u p p l i e d by c o n v e c t i v e heat  transfer  from the s t o r a g e chamber a i r . d)  The v e l o c i t y and vapour p r e s s u r e p r o f i l e s of the boundary l a y e r a r e  s i m i l a r t o those on a f l a t  surface.  slow moving l a y e r o f f l u i d next  See F i g . 3. Thus t h e r e i s a r e l a t i v e l y  t o t h e s u r f a c e which i s i n laminar  flow.  Between t h i s laminar s u b l a y e r and t h e main body of the t u r b u l e n t stream  there  i s a t r a n s i t i o n r e g i o n i n which t h e f l u i d may be a l t e r n a t e l y i n laminar  flow  and  i n turbulent flow.  W i t h i n the laminar occurs.  T h i s flow regime i s r e f e r r e d t o as the b u f f e r l a y e r .  s u b l a y e r , i t i s assumed t h a t o n l y m o l e c u l a r  The r a t e of m o l e c u l a r  diffusion  d i f f u s i o n from the wetted s u r f a c e through the  laminar s u b l a y e r i s g i v e n by F i c k ' s law a s : D i f f u s i o n Rate  =  - (D / R T . ) Cdp /dy)•s l s 1 v  D  v  5  J  i s the mass d i f f u s i v i t y or c o e f f i c i e n t of d i f f u s i o n and i s r e l a t e d  temperature and p r e s s u r e . are important  In the b u f f e r l a y e r both m o l e c u l a r  c o n t r i b u t o r s t o the mass t r a n s f e r p r o c e s s .  r e g i o n , eddy d i f f u s i o n predominates-"-  The and  r  ^  .  0  the  and eddy d i f f u s i o n  In .the t u r b u l e n t ......  system of s t o r a g e i n v o l v i n g the c i r c u l a t i o n of c o n d i t i o n e d a i r over  around tomatoes arranged  simultaneous  heat  i n a s i n g l e l a y e r on s h e l v e s can be regarded  and mass t r a n s f e r o p e r a t i o n .  s u p p l i e d by the a i r . same temperature,  as a  The tomatoes l o s e m o i s t u r e by  e v a p o r a t i o n from t h e s u r f a c e s , w i t h the l a t e n t heat  surface.  £  of v a p o r i z a t i o n being  Thus i f the a i r and tomato s u r f a c e a r e i n i t i a l l y  v a p o r i z a t i o n w i l l tend t o lower  a t the  the. temperature of the tomato  25.  FIGURE  3:  TURBULENT DIFFUSION BOUNDARY LAYER ON A FLAT SURFACE (1)  LEGEND L.S.L.  Laminar Sublayer  Br.L.  Buffer Layer  By.L.  Boundary Layer  T.R.  Turbulent Region  V a  Bulk v e l o c i t y i n a i r stream  T  Temperature of a i r  (average)  3.  p  Vapour pressure of water i n a i r stream 3.  p *  Saturation vapour pressure(with E . R . H . = 98%)  26. T h i s w i l l e s t a b l i s h a temperature  g r a d i e n t and heat w i l l be t r a n s f e r r e d t o t h e  tomato s u r f a c e from t h e a i r . The tomato s u r f a c e w i l l d e c r e a s e i n temperature u n t i l a p o i n t i s reached where the heat t r a n s f e r r e d t o the tomato j u s t b a l a n c e s the heat removed i n e v a p o r a t i o n . The use of a w i r e and n y l o n mesh f o r the c o n s t r u c t i o n of s h e l v e s f o r the tomatoes (see s e c t i o n on equipment d e s c r i p t i o n ) r e s u l t s i n a g r e a t e r degree of  t u r b u l e n c e i n t h e a i r f l o w than would n o r m a l l y be expected from t h e v o l u -  m e t r i c f l o w r a t e s alone (16). by c o n v e c t i o n .  Thus t h e heat and mass t r a n s f e r p r o c e s s o c c u r s  The c o n v e c t i v e heat and mass t r a n s f e r c o e f f i c i e n t s a r e  r e l a t e d through t h e f o l l o w i n g two e q u a t i o n s g i v e n by K r e i t h  and (For  ( i 6 ) Chapter 13:  m /A s  = h MT - T )/E c a wb  6a  m /A s  ==K.i (p * - p ) s a  6b  7  d e f i n i t i o n of terms used i n e q u a t i o n s 6a and 6b, see t a b l e on nomencla-  ture) . The c o n v e c t i v e heat t r a n s f e r c o e f f i c i e n t , h , depends on t h e v e l o c i t y (V),  density  ( ^ ) , viscosity  ( / O and t h e r m a l c o n d u c t i v i t y  (k^) of t h e f l u i d  medium and a l s o on some c h a r a c t e r i s t i c dimension, D, of the heat t r a n s f e r s u r face. ber  F o r a s p h e r i c a l body, and w i t h a i r f l o w r a t e s g i v i n g a Reynold's num-  (Re = VD ^ /y-t) between 25 and 100 000, t h e heat t r a n s f e r c o e f f i c i e n t i s  g i v e n by K r e i t h  (16) chapter 9 a s :  hv. = 0.37 ( R e ) c  0 , 6  k,/D t  7  Thus s o l v i n g e q u a t i o n 7 f o r h^. and s u b s t i t u t i n g :  found, knowing t h e r a t e of weight  l o s s per a r e a .  a r e a i s c a l c u l a t e d from d i r e c t measurements).  i n t o e q u a t i o n 6a, T ^  can be  (The r a t e of weight  l o s s per  27.  The function and  mass t r a n s f e r c o e f f i c i e n t as determined from e q u a t i o n 6b i s a  of the mass d i f f u s i v i t y  (D^),  the v e l o c i t y ( V ) , d e n s i t y  ( ^  ) ,  v i s c o s i t y (f* ) of t h e f l u i d , and a l s o , of some c h a r a c t e r i s t i c dimension,  D, of t h e mass t r a n s f e r s u r f a c e .  I t i s assumed t h a t w i t h i n  v a r i a t i o n of 10 C°,the v i s c o s i t y and d e n s i t y (e.g.  a t 10°C \/* =  kg/(m.h ) , ^  0.064 kg/(m.h ) ,  = 1.25 kg/m ) .  a i r , the mass t r a n s f e r  a temperature  of a i r do not v a r y  = 1.29 kg/m  3  ; a t 20°C  appreciably :yu=» 0.066  Thus f o r a g i v e n temperature and p r e s s u r e of  c o e f f i c i e n t f o r m o i s t u r e l o s s from tomatoes, as c a l c u -  l a t e d by e q u a t i o n 6b depends o n l y on the a i r v e l o c i t y .  The degree of t u r b u -  l e n c e i n t h e a i r : f l o w may a l s o a f f e c t the mass t r a n s f e r  coefficient.  Knowing  the wet b u l b temperature, T ^ , from e q u a t i o n 6a, the water vapour p r e s s u r e at the  tomato s u r f a c e ,  p '*, can be c a l c u l a t e d s  from steam t a b l e s ; and the mass  t r a n s f e r c o e f f i c i e n t , K, can be c a l c u l a t e d by d i r e c t s u b s t i t u t i o n  into  e q u a t i o n 6b. The  mass t r a n s f e r  c o e f f i c i e n t , K, can a l s o be expressed i n d i m e n s i o n l e s s  form as t h e Sherwood number, which i s r e l a t e d t o t h e Reynold number and t o t h e Schmidt number by the f o l l o w i n g  Sh  =  where :  e q u a t i o n (31).:^  0.023 ( R e ) ' 0  8 3  (Sc) ' 0  8  6 7  Sherwood number,  Sh  =  Reynold  number,  Re  =  Schmidt  number,  Sc  =  KRTD/D v ^ VDA^  a g i v e n heat and mass t r a n s f e r medium (e.g.  and  p r e s s u r e , t h e Schmidt number i s c o n s t a n t .  9  9b '9c  /*/^D^  For  9a  a i r ) at a given  temperature  T h e r e f o r e , from equations;. 8 and  (a,b,c): K  oC  (Re)  0 , 8 3  10,  28.  When a tomato i s wrapped i n p l a s t i c f i l m or i s brushed w i t h a wax c o a t i n g , the m u l t i p l e b a r r i e r  ( t o m o i s t u r e l o s s ) made up of the tomato  the p l a s t i c f i l m and the wax c o a t i n g can be r e g a r d e d as a sum of in series. K  _ 1  t  conductances  Thus the f o l l o w i n g r e l a t i o n h o l d s : = K" sk  1  +  KT by  1  +  ¥.'} pi  +  K wc _  1  skin,  11 i X  29. RESULTS, ANALYSES OF DATA AND  Results  DISCUSSION.  of P r e - S t o r a g e T e s t s :  The m o i s t u r e content to constant  The centimetre  weight was  l o s s and  + 0.5%  (1010  kilogram  per  Engineering,  gram per  cubic  i n v o l v e d , the o r i g i n a l data on weight  firmness  have been compiled i n a  separate  i n the G e n e r a l O f f i c e of the Department of Bio-Resource  U.B.C. Vancouver, Canada.  Preliminary  The  1.0.1  cubic metre). •  t o the mass of i n f o r m a t i o n  filed  found to be  Discussion:  changes i n c o l o u r and  volume and  freeze-drying  (wet b a s i s ) .  d e n s i t y of the tomatoes was  Data Analyses and  Due  93.0  of the tomatoes, as determined by  analyses  cummulative weight l o s s e s per u n i t of s u r f a c e a r e a were p l o t t e d  a g a i n s t time f o r seven s e t s of r e s u l t s 35 i n d i v i d u a l tomatoes).  s e l e c t e d at random ( i . e . p l o t s f o r  F i g u r e 4 shows the p l o t f o r one  An i n s p e c t i o n of the p l o t s showed t h a t i n each case,  s e t of  t h e r e was  results.  a relatively  l a r g e weight l o s s per a r e a between the s t a r t of the experiment, and of the f i r s t c o u l d be  period  ( i . e . between 0 and  2 days).  not from  analysed  in this report.  Between the second and  p e r i o d , d u r i n g which  This t r a n s i e n t process  time.  Between the e i g h t h and  is  e i g h t h weighings ( i . e .  2 to 14 days) , the .cummulative -weight l o s s per u n i t of s u r f a c e a r e a  l i n e a r with  end  T h i s l a r g e weight l o s s  a t t r i b u t e d to the t r a n s i e n t n a t u r e of the f i r s t  the heat and mass t r a n s f e r are not y e t s t a b i l i z e d .  the  was  t e n t h w e i g h i n g s , the r a t e of weight  30. FIGURE 4  PLOT OF CUMMULATIVE WEIGHT LOSS PER SURFACE AREA ^ O J M E ^ ^  LEGEND Tomato # 206  +  207 o  208 209 210  0.80  o k  o  0.60 1  u  SS  Q) Pu O-  o l—l 4-1  0.40  rS  60  o  '—s •a; •a)CN '§  >  •H 4-1 cd  4-  60  0.20 X o  0.10 CJ  0T00: 2  4  6  8  10  Time (days)  12  14  16  18  l o s s per s u r f a c e  a r e a was seen t o decrease s l i g h t l y .  t i o n t o be analysed was thus s e l e c t e d eight  The steady s t a t e  t o occur between p e r i o d  ( i . e . from 2 t o 14 days, f o r a t o t a l of 12 d a y s ) .  condi-  two and p e r i o d  There were seen t o be  wide v a r i a t i o n s between the r a t e s of m o i s t u r e l o s s from i n d i v i d u a l tomatoes w i t h the same C-T-S combination. offered.  No e x p l a n a t i o n  f o r t h i s v a r i a t i o n can be  I t i s p r o b a b l y r e l a t e d t o b i o l o g i c a l v a r i a b i l i t y between the  tomatoes and a l s o t o d i f f e r e n c e s . i n m a t u r i t y experiment.  of the tomatoes used i n the  I t i s noted t h a t tomatoes e n t e r i n g  storage at apparently  the same  stage of r i p e n i n g were found t o r i p e n a t d i f f e r e n t r a t e s .  To determine the e f f e c t of the i n i t i a l weight its in  r a t e of weight l o s s , 10 u n t r e a t e d  ( o r s i z e ) . o f a tomato on  tomatoes ( i . e . non-waxed and n o t wrapped  p l a s t i c f i l m ) were s e l e c t e d a t random from one experiment, and the t o t a l  change i n weight p e r u n i t area d u r i n g against  the i n i t i a l w e i g h t s .  the steady s t a t e p e r i o d were p l o t t e d  (See T a b l e 3, and F i g u r e  d e t e r m i n a t i o n beteweensweigh'tsloss per u n i t of s u r f a c e  5 ) . The c o e f f i c i e n t of area and i n i t i a l  weight  was found t o be 0.15, thus i n d i c a t i n g t h a t the i n i t i a l weight of a tomato d i d not  a f f e c t i t s r a t e of weight l o s s .  variance  I t was thus d e c i d e d t h a t an a n a l y s i s of  t e s t o f the mean weight l o s s e s per a r e a d u r i n g  e f f e c t i v e l y r e v e a l any d i f f e r e n c e s between the v a r i o u s  For functioning  the two s u c c e s s f u l runs (during  the f i r s t  the steady s t a t e would C-T-S combinations.  r u n t h e r e was a mal-  of one of the a i r c o n d i t i o n i n g u n i t s l e a d i n g  t o the l o s s of 40  p e r c e n t of the tomatoes), a f o r t r a n computer program was w r i t t e n the t o t a l weight l o s s p e r u n i t s u r f a c e (i.e.  during  the steady s t a t e p e r i o d  area during  to c a l c u l a t e  storage periods  of weight l o s s ) .  Missing  two t o e i g h t  d a t a (due t o  some tomatoes having developed Rhizopus and P e n i c i l l i u m r o t b e f o r e the e i g h t weighing) were generated on the b a s i s of the e a r l i e r weighings, and on the f u r t h e r assumption of l i n e a r i t y of weight l o s s per area w i t h time.  (About  32. TABLE 3  RELATIONSHIP BETWEEN INITIAL WEIGHT OF TOMATO AND TOTAL WEIGHT LOSS DURING 12 DAYS OF STORAGE  Tomato No.  (DATA FROM RUN I I )  I n i t i a l Weight (  k  8  )  T o t a l Weight Loss p e r Area During 12 Days •  (kg/m ) 2  2  0.1086  0.20  6  0.1510  0.24  101  0.1473  0.21  107  0.1349  0.21:  124  0.1129  0.38  201  0.1801  0.15  205  0.1201  0.36  218  0.1545  0.40  307  0.1152  0.17  316  0.1656  0.37  (  33.  FIGURE  5  PLOT  OF T O T A L  WEIGHT  <vs^  LOSS  INITIAL  P E R SURFACE  A R E A ''(-DTJRM^  J  WEIGHT.  LEGEND  •TomatoSriumbers appear beside points CTr" ^= 0 . 1 5 2  4-) rt 0.40  'rt  CD  218  EL  016  124  .5  2C;5  O 0.30  rt cu  CD o 14-1 CN 3  c/i  60  107  2  0.20  101  307  <D P.  201  cn cn O  60 •rl  0.10  rt •u o  H  0.00 0 .08  0.10  0.12  0.14  I n i t i a l Weight of Tomato (kg)  0.16  0.18  34. 5 p e r c e n t of the tomatoes used i n the experiments developed the s p o i l a g e d e s c r i b e d above, g i v i n g r i s e to m i s s i n g d a t a ) .  An a n a l y s i s of v a r i a n c e of the  mean weight l o s s e s was done u s i n g MFAV, a m u l t i p l e f a c t o r a n a l y s i s of v a r i a n c e program-from  the U.B.C. computing  system.  G e n e r a l models f o r a n a l y s e s of d a t a A n a l y s i s of v a r i a n c e of weight  loss  The t o t a l steady s t a t e weight l o s s e s per u n i t of s u r f a c e a r e a were analysed u s i n g the f o l l o w i n g s t a t i s t i c a l model: 4x4x5 f a c t o r i a l  ijkv  / ijk  • 1  i  kk  i j ij  -t- i k  6.., ^ k  v  jk  '  ijk  ' x  IK.  +  h-  experiment:  , ijkv  12  (See t a b l e on nomenclature f o r d e f i n i t i o n s of terms used i n e q u a t i o n 1 2 ) .  R e g r e s s i o n a n a l y s i s of weight  loss  T r e a t i n g the f i v e tomatoes i n each group as a u n i t , the f o l l o w i n g model was u t i l i z e d  ( i . e . each C-T-S combination)  i n a simple r e g r e s s i o n  analysis  of the cummulative weight l o s s per u n i t of s u r f a c e a r e a , w i t h time i n s t o r a g e : Y = b  o  + b. XtC  In e q u a t i o n 13, b  13  1  Q  i s the i n t e r c e p t on the y - a x i s , and g i v e s the " t h e o r e t i c a l "  v a l u e of the weight l o s s p e r u n i t of s u r f a c e a r e a a t the s t a r t of the e x p e r i ment.  S i n c e we a r e a n a l y s i n g o n l y the "steady s t a t e " weight l o s s , the i n t e r -  cept can be n e g l e c t e d and b  Q  drops out of the e q u a t i o n which thus becomes:  Y = b X  13a  (See t a b l e on nomenclature f o r d e f i n i t i o n s of terms used i n e q u a t i o n s 13 and 13a). The U.B.C. computer  program TRIP was employed  i n the r e g r e s s i o n a n a l y s i s of  weight l o s s p e r s u r f a c e a r e a , v e r s u s time f o r each s e t of r e s u l t s .  The  35 r e g r e s s i o n c o e f f i c i e n t , b , has u n i t s of k i l o g r a m p e r square metre, p e r day (kh/(m .d)). 2  R e g r e s s i o n a n a l y s i s of c o l o u r and f i r m n e s s changes C o l o u r change An i n i t i a l i n s p e c t i o n of the c o l o u r change d a t a o b t a i n e d from the study showed t h a t i n over 70 p e r c e n t o f a l l the tomatoes, the maximum of 5 on the c o l o u r s c a l e was reached  a f t e r only 5 readings  ( i . e . 10 d a y s ) .  r e a d i n g s , the number of tomatoes w i t h the maximum c o l o u r  After 6  r a t i n g was over 85%.  I t was thus d e c i d e d t o perform  a r e g r e s s i o n a n a l y s i s of c o l o u r change w i t h  time, u t i l i z i n g  5 readings.  o n l y the f i r s t  A preliminary analysis,  the 5 tomatoes i n each c o o l i n g - t r e a t m e n t - s t o r a g e combination (i.e.  t a k i n g the average  treating  as a s i n g l e  periodic colour reading)yyielded a l i n e a r  unit  relationship  2 between c o l o u r and time, w i t h an r of 0.93, (See E i g u r e 6 ) . U s i n g the U.B.C. computer program TRIP (computation  i s by method of  l e a s t s q u a r e s ) , a simple r e g r e s s i o n of c o l o u r on time was generated C-T-S  combination  f o r the f i r s t  f i v e readings.  The model used  f o r each  f o r the c o l o u r  r e g r e s s i o n w i t h time i s g i v e n by: Y  c " c a  +  b  c  x  (See t a b l e on nomenclature f o r e x p l a n a t i o n of terms used  1 4  i n eq. 14)  36.  FIGURE 6  CHANGE OF COLOUR WITH TIME (RUN I I I )  Ji 2  L ii  Time (days)  P l o t f o r tomatoes w i t h C-T-S code: 211 Y  c  = 1.75 + 0.29 X  ( r = 0.93) 2  37.  "" f i r m n e s s change  As  i n the case of c o l o u r  combination were t r e a t e d code f o r each  The  as a s i n g l e u n i t by d e r i v i n g an average f i r m n e s s  period.  average f i r m n e s s change was analysed a c c o r d i n g t o t h e model: Y F  (See  change, t h e f i v e tomatoes i n each C-T-S  =*+V  15  F  t a b l e on nomenclature f o r e x p l a n a t i o n  The  of terms used i n eq.-15)  U.B.C. computer program TRIP was used i n t h e simple  regression  a n a l y s i s of f i r m n e s s w i t h time, f o r a l l t h e d a t a .  To  i n v e s t i g a t e t h e c o r r e l a t i o n between the f i r m n e s s and the c o l o u r  of t h e tomatoes, t h e f i r s t  f i v e p e r i o d i c colour  and f i r m n e s s codes were  analysed.  Results  and d i s c u s s i o n  Table 4 gives results.  The n o t a t i o n s  of a n a l y s i s o f v a r i a n c e  of weight  loss  a summary of the weight l o s s a n a l y s i s of v a r i a n c e I I and I I I r e p r e s e n t t h e second and t h i r d  experi-  mental runs, r e s p e c t i v e l y .  For each source of v a r i a t i o n , a f i g u r e has  been c a l c u l a t e d which g i v e s  an i n d i c a t i o n of i t s r e l a t i v e c o n t r i b u t i o n , or  the  s i g n i f i c a n c e of i t s e f f e c t on the response ( r a t e of weight  The  a n a l y s i s of v a r i a n c e  showed t h a t t h e c o o l i n g  delay a f t e r harvest before cooling) the  loss).  procedure ( i . e .  employed d i d not s i g n i f i c a n t l y a f f e c t  steady s t a t e r a t e of weight l o s s from t h e tomatoes.  A Duncan's M u l t i p l e  38.  TABLE 4  SUMMARY OF RESULTS OF ANALYSIS OF VARIANCE OF WEIGHT LOSS  Source of variation  Degrees of freedom  Sum of squares ( I I ) (percent of t o t a l sum of squares)  Sum of squares ( I I I ) (percent of t o t a l sum of squares)  C o o l i n g (C)  3  0.79  Treatment  3  29.01  (**)  42.01  (**)  Storage (S)  4  30.21  (**)  32.18  (**)  C x T  9  0.64  00/39  C x S  12  1.03  0.58  T x S  12  2.31  C x T x S  36  2.50  2.53  320  33.51  16.59  (T)  Error  Total  (***)  399  0.05  (*)  100.00 = 8.01  Highly s i g n i f i c a n t  (P<0.01)  Significant  (P<0.05)  5.66  (**)  100.00 = 105.06  To o b t a i n the mean square d e v i a t i o n due t o any source of v a r i a t i o n d i v i d e : t h e p e r c e n t sum-of squares by the degrees of freedom, then M u x . x t - x y j * — " . stun, ui squares J V t o r s •• • , • . ; • ' . multiply„the i n t e r m e d i a t e v a l u e by the t o t a l ( i . e . 8.01 or 105.06) and d i v i d e by 100. e.g. F o r run I I , C o o l i n g  factor:  Mean square = (f(0779/3<) x^8 i00") /100. =•.0.021  39.  Range T e s t on t h i s f a c t o r  showed no d i f f e r e n c e s  (P>0.05)  among the f o u r  levels.  The e f f e c t weight The  of the p r e - s t o r a g e treatment on the steady s t a t e r a t e of  l o s s from the tomatoes was  found t o be h i g h l y s i g n i f i c a n t  tomatoes wrapped i n p o l y m e r i c f i l m gave the lowest weight  f o l l o w e d , i n r e v e r s e order of magnitude of weight  (P<0.01).  loss,  l o s s , by those tomatoes  whose s u r f a c e s were t o t a l l y waxed, then the d i f f e r e n t i a l l y waxed tomatoes. The u n t r e a t e d tomatoes e x p e r i e n c e d , as expected, the h i g h e s t r a t e s of s t e a d y s t a t e weight  loss.  T e s t performed  T a b l e 5 shows the r e s u l t s of a Duncan's M u l t i p l e Range  on t h e e f f e c t of t h e p r e - s t o r a g e treatment f a c t o r , and  t h e mean weight  l o s s per a r e a f o r the d u r a t i o n of the steady s t a t e  Of t h e f i v e combinations c o n d i t i o n h'o.l (10°C  and 90%  lower r a t e of weight  loss  four.  of temperature  ,-ch,)hum ) r e s u l t e d  and  in significantly  of s t o r a g e a t 15°C and 88%  l o s s than the remaining two  18°C and 40%  rh ).  (P<0.01)  (and thus the b e s t s t o r a g e ) than any of the o t h e r  rh  However, t h e s e , as a group, were found t o r e s u l t lower weight  period.  and h u m i d i t y used f o r s t o r a g e ,  The m u l t i p l e range t e s t c o u l d n o t d e t e c t any  between the e f f e c t  also  significant and  difference  10°C and 60% r h  in significantly  s t o r a g e c o n d i t i o n s (15°C  (P<.0.01) and 50% r h  For the r e s u l t s of r u n I I , the Duncan's M u l t i p l e  Range T e s t c o u l d not d e t e c t any s i g n i f i c a n t d i f f e r e n c e between s t o r a g e c o n d i t i o n s r.c„4 and r>.3«5. was  found t o y i e l d  In run I I I , s t o r a g e c o n d i t i o n no.4  significantly  f a c e a r e a than s t o r a g e a t 18°C  (P< 0.01)  and  lower weight  (15°C  and 50% r h "  l o s s per u n i t of s u r -  40% r h h .  None of the 2-f a c t o r i n t e r a c t i o n s i n v o l v i n g c o o l i n g had ficant  effect  on the r a t e of weight  )  any  signii-  l o s s per u n i t of s u r f a c e a r e a of tomato.  The 2-way i n t e r a c t i o n of the treatment and  s t o r a g e f a c t o r s was  found t o be  40. TABLE 5  (a)  THE EFFECT OF COOLING, TREATMENT AND  STORAGE ON WEIGHT LOSS  Cooling Factor Mean t o t a l weight l o s s / a r e a  (*)  (kg An ) 2  Time  Delay  Run I I  Run I I I  1.  20-hour d e l a y  0.22  (a)  0.70  (b)  2.  10-hour d e l a y  0.24  (a)  0.71  (b)  3.  "0"-edlay  0.24  (a)  0.72  (b)  4.  30-hour d e l a y  0.21  (a)  0.73 (b)  * Average of 100 measurements  (b) Pre-Storage  Treatment Mean t o t a l weight l o s s / a r e a (kg/m ) 2  Treatment  1.  Untreated  2.  Wrapped  3. 4.  Run I I  Run I I I  0.32  (d)  1.10  (h)  0.12  (a)  0.25  (e)  Calyx end waxed  0.27 (c)  0.95  (g)  Whole s u r f a c e waxed  0.19  0.55 ( f )  in plastic  film  (b)  Average of 100 measurements. Responses f o l l o w e d by d i f f e r e n t l e t t e r s a r e s i g n i f i c a n t l y d i f f e r e n t (P<0.01)  (*)  TABLE 5  (c)  (CONT'D)  Storage C o n d i t i o n Mean t o t a l weight l o s s / a r e a  *  (kg/m ) 2  Temperature: Humidity  Run  II  Run  III  1.  10°C  90% r h  0.12 (a)  0.39 (d)  2.  15°C  88%  0.18 (b)  0.54 (e)  3.  10°C  60%  0.19 (b)  0.55 (e)  4.  15°C  50%  0.31 (c)  0.89 ( f )  5.  18°C  50%  0.32 (c)  1.19 (g)  Average of 80 measurements. Responses f o l l o w e d by d i f f e r e n t l e t t e r s a r e s i g n i f i c a n t l y different  (P<0.01)  42. significant the r a t e  (P<0.05 f o r run I I , and P<0.01 f o r r u n I I I ) i n i t s e f f e c t on  of weight l o s s .  The i n t e r p r e t a t i o n  2-factor i n t e r a c t i o n i s that  of t h e s i g n i f i c a n c e  the d i f f e r e n c e s  of the  between t h e responses ( i . e . r a t e  of weight l o s s ) t o one f a c t o r , v a r y w i t h t h e l e v e l of t h e second  factor,  where responses a r e measured over a l l l e v e l s of t h e second f a c t o r . words, t h e r a t e  In other  of weight l o s s from a tomato i n a p a r t i c u l a r s t o r a g e e n v i r o n -  ment depends on the type of p r e - s t o r a g e treatment i t was s u b j e c t e d t o .  The  3-factor interaction involving  the cooling,  treatment, and the  s t o r a g e environment was n o t found t o be s i g n i f i c a n t i n i t s e f f e c t on t h e r a t e of weight  loss.  T a b l e s A . l and A.2 g i v e the summary f o r t h e mean weight l o s s e s per unit the  of s u r f a c e area f o r a l l the f a c t o r s r e s u l t s of t h e Duncan's M u l t i p l e  and t h e i r i n t e r a c t i o n s , and a l s o  Range T e s t s .  Comparing t h e f i g u r e s f o r  runs I I and I I I , i t i s seen t h a t r u n I I I r e s u l t e d (<"*-3 times) weight l o s s e s f u l l y understood. the  f o r a l l the f a c t o r s .  I t i s suggested t h a t  i n consistently  higher  The reason f o r t h i s i s n o t  the tomatoes, even though they a r e of  same v a r i e t y , may have had some i n h e r e n t v a r i a b i l i t y due t o the f a c t  they s e r e o b t a i n e d from two d i f f e r e n t farmers a t two d i f f e r e n t  Comparison of t h e r e s u l t s of mean weight l o s s e s a l s o show t h a t  i n some i n s t a n c e s  (e.g.  that  times.  f o r runs I I and I I I  the 2 - f a c t o r i n t e r a c t i o n between the  p r e - s t o r a g e treatment and t h e s t o r a g e environment), d i f f e r e n t l e v e l s of s i g n i ficance  are ascribed  t o the f a c t o r s .  Also,  give f u l l y consistent  r e s u l t s i n a l l cases.  have a r i s e n  of s u f f i c i e n t d a t a .  from l a c k  the m u l t i p l e  range t e s t s d i d n o t  Some of these i n c o n s i s t e n c i e s I t should  :c.  may  be p o i n t e d out t h a t  i n a s t a t i s t i c a l t e s t of s i g n i f i c a n c e , a r e s u l t of "not s i g n i f i c a n t " should be understood t o mean a v e r d i c t o f "not proven".  T  o  r  e  m  e  d  y  t h ± s  ^  m  o  r  e  t  e  g  t  s  ^  have t o be performed  with possible m o d i f i c a t i o n s .  N e v e r t h e l e s s , on the whole,  t h e t r e n d s of t h e e f f e c t s of the v a r i o u s f a c t o r s and t h e i r i n t e r a c t i o n s were c o n s i s t e n t between the two  runs.  On the q u e s t i o n of whether or not the r a t e of m o i s t u r e  l o s s from  tomato o c c u r s at d i f f e r e n t i a l r a t e s a c r o s s the v a r i o u s r e g i o n s on the  a  skin,  t h e r e s u l t s of t h e a n a l y s i s of v a r i a n c e show some q u i t e i n t e r e s t i n g t r e n d s . In the second  r u n , " u n t r e a t e d " ( i . e . "unwaxed", non  t o e s had a mean steady s t a t e m o i s t u r e under a l l c o n d i t i o n s . 0.19  kg/m  2  " p l a s t i c wrapped") toma-  l o s s p e r s u r f a c e a r e a of 0.32  kg/m  2  T o t a l l y waxing the tomatoes cut t h i s down t o  , i . e . a drop of 0.13  kg/m  2  .  Waxing the calyx-ends o n l y , r e s u l t e d 2  i n a drop  of 0.05  ( i . e . from 0.32  t o 0.27)  kg/m  .  Thus i t can be deduced  t h a t the c a l y x end accounts f o r 0.05/0.13 of the change i n m o i s t u r e ( i . e . over 38 per cent) a t t r i b u t a b l e t o waxing of the tomato. the c a l y x - e n d area.  accounts f o r over 38 per cent of the m o i s t u r e  S i n c e t h e wax  loss  In other words,  l o s s per s u r f a c e  i n the c a l y x r e g i o n c o v e r s l e s s than 10 per cent of the  t o t a l s u r f a c e , i t f o l l o w s t h a t t h e r e i s a d i s p r o p o r t i o n a t e l y l a r g e r a t e of moisture  l o s s through  the s k i n i n the c a l y x  end.  A s i m i l a r a n a l y s i s of the r e s u l t s of the t h i r d run showed the c a l y x r e g i o n a c c o u n t i n g f o r over 27 per cent moisture  l o s s between " t r e a t e d " and  ( i . e . 0.15/0.55) of the change i n  " u n t r e a t e d " tomatoes.  44.  Results  The and  and d i s c u s s i o n of r e g r e s s i o n a n a l y s i s of weight l o s s  r e l a t i o n s h i p between the weight l o s s p e r u n i t of s u r f a c e  time of s t o r a g e  (during  steady s t a t e p e r i o d )  a n a l y s i s i s summarized i n t a b l e s B . l and B.2 Comparing  :  as determined by r e g r e s s i o n  (Appendix B ) .  m /A = K(p * - p ) S  S  3  area,  6b  -  and  Y = bX; it  i s evident  13a  t h a t b = m /A = K(p * - p ) s s a  13b  r  Thus, knowing b from t h e . r e g r e s s i o n  a n a l y s i s r e s u l t s , t h e mass t r a n s f e r  c o e f f i c i e n t of t h e tomato s k i n p l u s i t s c o v e r i n g  of wax l a y e r or p l a s t i c  film  (as the case may b e ) , p l u s t h e boundary l a y e r , can be c a l c u l a t e d from knowledge of t h e water vapour p r e s s u r e  d e f i c i t between t h e i n n e r s u r f a c e  " m u l t i p l e - b a r r i e r " and t h e a i r i n t h e storage  Since pre-storage  of the  chamber..  the d i f f u s i o n a l r e s i s t a n c e of a tomato i s a f u n c t i o n of i t s treatment  ( i . e . treatment t o reduce water l o s s ) , t h e mass t r a n s f e r  c o e f f i c i e n t s of t h e " m u l t i p l e - b a r r i e r s " a r e determined by h a n d l i n g i n each treatment s e p a r a t e l y .  t h e tomatoes  As was shown from t h e r e s u l t s of the a n a l y s i s  of v a r i a n c e of t h e mean r a t e s of weight l o s s p e r a r e a , the f o u r c o o l i n g cedures do not a f f e c t t h e steady s t a t e r a t e of water l o s s . storage  c o n d i t i o n , the four values  obtained  Thus f o r each  f o r the regression  coefficient,  b ( i . e . r a t e of weight l o s s per s u r f a c e a r e a ) , can be averaged the r a t e of weight l o s s p e r area and  t o represent  of a l l tomatoes w i t h a p a r t i c u l a r treatment  s t o r e d a t a p a r t i c u l a r temperature and h u m i d i t y .  Run I I , t h e 20 u n t r e a t e d  pro-  tomatoes i n storage  As an example, f o r t h e  c o n d i t i o n no. 1 ( 1 0 C , 90% r h  have an average r a t e of weight l o s s p e r u n i t of s u r f a c e area of  U  )  45.  0.015  kg/(m  2  .d)  (S.D. = 0.001).  T h i s i s the average  of the r e g r e s s i o n l i n e s c o r r e s p o n d i n g as shown i n T a b l e B . l . and  Similar  to C-T-S  codes 111, 211,  c a l c u l a t i o n s were performed  the r e s u l t s are summarized i n T a b l e  It i s r e c a l l e d  of the f o u r s l o p e s , b, and  411,  f o r a l l the samples  6.  (See s e c t i o n on t h e o r e t i c a l model) t h a t  storage undergo simultaneous  311  heat and mass t r a n s f e r .  tomatoes i n  Both the c o n v e c t i v e heat  and mass t r a n s f e r c o e f f i c i e n t s are f u n c t i o n s of the Reynold's number of airflow.  From the d e s i g n of t h i s experiment  number of a i r f l o w and  and  the d a t a o b t a i n e d , the Reynold's  the c o n v e c t i v e heat t r a n s f e r  mined b e f o r e the mass t r a n s f e r c o e f f i c i e n t can be  c o e f f i c i e n t must be d e t e r -  calculated.  Sample c a l c u l a t i o n of Reynold's number (Re) and Heat T r a n s f e r C o e f f i c i e n t .  In the f i r s t i s 0.12  ;  •  (h )  C__  s t o r a g e chamber (10°C, 90% r h ) , the b u l k v e l o c i t y of a i r f l o w  + 0.03  m/s.  An average  tomato diameter  d e c i d e d upon f o r the present c a l c u l a t i o n s .  "V  = 0.0143 x 10~  Re = V.D/y k  f  of 0.08  m  (3 i n ) have been  The k i n e m a t i c v i s c o s i t y ,  m /s  3  2  = (0.12 x 0.08)/0.0143 x 10"  = 0.0249 W.m/(m .°C)  3  =  670  f o r a i r at lOoC.  0 6 From e q u a t i o n 7 : h  c  = 0.37  (Re)  = 0.37  x  = 5.7 Similar  '  k /D f  (670) * 0  6  x 0.0249/0.08  W/(m .°C). 2  c a l c u l a t i o n s f o r the other storage c o n d i t i o n s are r e p o r t e d i n T a b l e  S i n c e s t o r a g e 5 (18°C, 40% rh) d i d not have any d i r e c t e d  a i r movement  (See  s e c t i o n on equipment d e s c r i p t i o n ) , the a i r v e l o c i t y c o u l d not be measured  7.  TABLE 6  Storage  AVERAGE RATES OF WATER.JLOSS THROUGH SURF/ACES^ OF TOMATOES UNTREATED AND WITH SURFACE TREATMENTS (  Condition  Average r a t e of water l o s s per a r e a c a l c u l a t e d from t a b l e s B . l and B.2 22 (kg/i(m :.day))* ;  U n t r e a t e d Tomatoes. Samples Wrapped i n plastic film.  Samples w i t h c a l y x ends waxed.  Samples w i t h whole s u r f a c e waxed.  Run I I  Run I I I  Run I I  Run I I I  Run I I  Run I I I  Run I I  Run I I I  1. 10°C:90%r.h.  0.015  0.043  0.005  0.006  0.012  0.043  0.008  0.024  2. 15°C:88%  0.024  0.063  0.007' .  0.011,  0.019  0.056  0.013  0.042  3. 10°C:60%  0.024  0.070  0.008  0.013 ,  0.023  0.056  0.012  0.034  4. 15°C:50%  0.036  0.114  0.015  0.027  0.027  0.093  0.023  0.051  5. 18°C:40%  0.029  0.124  0.016 .  0.044 ,  0.030  0.116  0.023  0.068  Average of 20 tomatoes w i t h s i m i l a r treatment  and s t o r a g e  combination.  TABLE  7  REYNOLD'S NUMBERS AND CONVECTIVE HEAT TRANSFER  COEFFICIENTS FOR THE VARIOUS TOMATO  STORAGE  CHAMBERS a Storage Condition  Air  Velocity  inside  stor-  age chamber V (m/s)  Characteristic  Kinematic  Thermal Con-  Reynold's  Convective  dimension of  viscosity  d u c t i v i t y of  number  heat  air,  Re = V.D/y  coefficient  heat  transfer  surface,  D  v = (m /s) 2  (W.m/(m .°C))  transfer  h=0.37(Re)°' k /D  2  6  f  (W/(m .°C)) 2  x 10  3  1.10°C:90% rh„  0.12+0.03  0.08  0.0143  0.0249  670  5.7  2.15°C:88%  0.11+0.01  0.08  0.0148  0.0253  . . 595  5.2  3.10°C:60%  0.05+ 0.01  0.08  0.0143  0.0249  •  280  3.4  4.15°C:50%  0.05+ 0.01  0.08  0.0148  0.0253  270  3.4  48. by the a v a i l a b l e means.  Thus s t o r a g e c o n d i t i o n no.5 was dropped from f u r t h e r  analysis.  Knowing the average r a t e s of weight l o s s per u n i t of s u r f a c e a r e a , m /A, and the average c o n v e c t i v e heat t r a n s f e r c o e f f i c i e n t s , h (Tables 6 s c and 7, r e s p e c t i v e l y ) , the average tomato  s u r f a c e temperatures i n the v a r i o u s  s t o r a g e chambers can be c a l c u l a t e d from e q u a t i o n 6a. t i c a l model).  (see s e c t i o n on t h e o r e -  The vapour p r e s s u r e d e f i c i t s between the tomatoes and the  s t o r a g e environments can be determined a f t e r the s u r f a c e temperatures are established.  Sample C a l c u l a t i o n of Tomato S u r f a c e Temperature  For s t o r a g e n o . l and d u r i n g Run m /A g  h  T  = 0.015  II :  kg/(irm .dd}.; = 2  6  =5.72 W / ( m . ° C ) 2  c  6.25  x 10~  2 5  x  1 0  ~  kg/(m .h)  4  2  (from t a b l e  7)  (from steam  tables)  >  k  = 10°C  a  L = 2477.7 kJ/kg Thus from  and Vapour P r e s s u r e D e f i c i t  : m /A = h ,(T - T , )/L s c a wb  =  4 2  m  5  u -h  72-JL_ * _.2 o„ m-."C  f  1  0  ° C  T w b  T  kg x  2477.7 k j  3  -6  J W.h  T h e r e f o r e T , = 9.9°C wb As assumed i n the t h e o r e t i c a l model and v e r i f i e d  from d i r e c t d e t e r m i n a t i o n  ( p o s t - s t o r a g e t e s t ) , the water vapour p r e s s u r e at the tomato 0.98  x vapour p r e s s u r e of pure water at the same temperature.  surface i s  49. The saturation vapour pressure of water at 10°C = 1.228 kPa The saturation vapour pressure of water at 9.9°C = 1.221 kPa Therefore, the vapour, pressure at the tomato surface = 0.98 x 1.221 = 1.196 kPa The water vapour pressure i n the conditioned a i r at 10°C and 90% r . h . = 0.90 x 1.228 = 1.105 kPa. Therefore, the vapour pressure d e f i c i t between the i t omato and i t s environment = 1.19.6 - 1.105 = 0.091 kPa S i m i l a r c a l c u l a t i o n s for the surface temperatures and vapour pressure d e f i c i t s i n the other storage environments are reported i n table 8.  As reported  e a r l i e r (see section on Results and d i s c u s s i o n of weight loss analysis of variance) , the tomatoes used i n Run I I I underwent c o n s i s t e n t l y higher rates of weight l o s s ( ^ 3 times those for Run I I ) .  This resulted i n the tomato  surface temperatures i n Run I I I being c o n s i s t e n t l y lower than the c o r r e s ponding values i n Run I I .  The vapour pressure d e f i c i t s were also lower i n  Run I I I than i n Run I I . P l o t t i n g the average rates of weight l o s s per area for each storage c o n d i t i o n against the vapour pressure d e f i c i t on rectangular  co-ordinates  should give a slope which i s the equivalent of the mass transfer of the tomato " m u l t i p l e - b a r r i e r " .  coefficient  The p h y s i c a l model u t i l i z e d i n f e r s that  there should be a zero intercept on the v e r t i c a l a x i s , so that when there i s no vapour pressure d e f i c i t , there w i l l be no water l o s s ( i . e . no mass transfer). In the a c t u a l p l o t s (see Eig*nr.e» 11) , i t was found that for any p r e storage treatmentj there could not be a s i n g l e slope that would s a t i s f a c t o r i l y  TABLE 8  AVERAGE TOMATO SURFACE TEMPERATURES AND VAPOUR PRESSURE DEFICITS BETWEEN TOMATOES AND STORAGE ENVIRONMENT  Run IIStorage C o n d i t i o n  Tomato S u r f a c e Temperature, T ,  wb  Run I I I Vapour  Pressure  Deficit  Tomato Surface Temperature, T , WD  Vapour  Pressure  Deficit  °C  kPa  9.9  0.091  9.8  0.084  2. 15°C:88%  14.9  0.162  14.7  0.143  3. 10°C:60%  9.8  0.452  9.4  0.425  4. 15°C:50%  14.7  0.805  14.1  0.749  1. 10°C:90% r . h .  °C  kPa  51.  PLOT OF RATE OF WEIGHT LOSS PER AREA vs' VAPOUR PRESSURE DEFICITS (BEFORE CORRECTION  FOR EFFECT OF REYNOLD'S NUMBER)  LEGEND  RUN II m Untreated  0.12  A  Wrapped in plastic film  o  Calyx end waxed Whole skin waxed  R U N III • Untreated  0.10  +  Wrapped i n plastic film  o  Calyx'end waxed  x Whole skin waxed 0.08  0.06  0.04  + 0.02  o  •  • a D  0.00  JL  0.0  0..V2  0.4  0.6  Vapour p r e s s u r e d e f i c i t ,  (kPa )  0.8  52.  p r e d i c t t h e r a t e of weight l o s s per a r e a f o r a l l t h e storage c o n d i t i o n s .  As  d e s c r i b e d e a r l i e r , t h e mass t r a n s f e r c o e f f i c i e n t , K, i s a f u n c t i o n of the Reynold's number, i . e .  c<- ( R e )  K  also,  m /A  =  10  0 , 8 3  K (ps  - p )  S  3.  i . e . m /A «c K s Therefore,  ™ / S  A  °^  (Re) ' 0  8 3  S e l e c t i n g t h e Reynold's number of a i r f l o w i n s i d e one storage chamber as a b a s i s f o r comparison, f h e r a t e s of weight l o s s per s u r f a c e a r e a i n t h e other chambers can be a d j u s t e d t o account f o r t h e e f f e c t  of a i r f l o w r a t e s .  The  Reynold's number i n t h e s t o r a g e c o n d i t i o n n o . l (10°C, 90% r.h.) has been used as a b a s i s f o r comparison i n t h i s r e p o r t . Sample C a l c u l a t i o n of a d j u s t e d r a t e s of weight l o s s per s u r f a c e a r e a : The Reynold's number i n s t o r a g e c o n d i t i o n 1  =  671.33  The Reynold's number i n s t o r a g e c o n d i t i o n 2  =  594.59.  ( t a b l e 7)  T h e r e f o r e ^ t h e s a d ' j u s t e d r r a t e of weight l o s s p e r a r e a of tomatoes  s t o r e d at  15°C and 88% r e l . hum. i s g i v e n , f o r Run I I r e s u l t s ,  by  :  (m/A) = (m/A) x s adjusted s old (m /A) ,. _ . = 0.024 x s adjusted = 0.027  (671.33/594.59)°'  (671.33/594.59)  83  0,83  kg/(m .day). 2  S i m i l a r c a l c u l a t i o n s f o r the complete s e t of d a t a a r e r e p o r t e d i n t a b l e 9.  T a b l e s 10 and 11 g i v e the a d j u s t e d r a t e s of weight l o s s per are w i t h the c o r r e s p o n d i n g vapour p r e s s u r e d e f i c i t s .  F i g u r e 8 shows the p l o t s of the  TABLE  9  AVERAGE RATES OF WATER LOSS THROUGH SURFACES^OF TOMATOES.«UNTREATED AND WITH SURFACE TREATMENTS (WITH CORRECTION FOR EFFECT OF REYNOLD'S NUMBER OF AIR FLOW IN STORAGE CHAMBERS)  Storage  C o n d i t i o n, r  Average r a t e of water l o s s p e r a r e a w i t h c o r r e c t i o n f o r e f f e c t Reynold's 2 number of a i r f l o w i n s i d e s t o r a g e chamber (kg/(m . d a y ) ) * Untreated Tomatoes. Samples Wrapped i n plastic  film.  Samples w i t h c a l y x ends waxed.  Run I I I  Run I I  Run I I I  0.005  0.006  0.012  0.070  0.008  0.012  0.050  0.145  0.015  0.077  0.243  0.032  Run I I  Run I I I  1. 10°C:90% r . h .  0.015  0.043  2. 15°C:88%  0.027  3. 10°C:60% 4. 15°C:50%  Run I I  Samples w i t h whole s u r f a c e waxed. Run I I  Run I I I  0.043  0.008  0.024  0.021  0.062  0.014  0.046  0.028  0.048  0.116  0.025  0.070  0.058  0.057  0.198  0.049  0.109  Average of 20 tomatoes w i t h s i m i l a r treatment  and s t o r a g e  combination.  i  TABLE 10. VAPOUR PRESSURE DEFICITS AND AVERAGE RATES OF WATER LOSS THROUGH TOMATO MULTIPLE. BARRIERS" ( WITH CORRECTION FOR EFFECT OF REYNOLD'S NUMBER OF AIR FLOW  Vapour P r e s s u r e  Average r a t e of water l o s s per a r e a w i t h c o r r e c t i o n f o r e f f e c t number of a i r f l o w  Deficit (kPa)  (RUN I I ) )  U n t r e a t e d Tomatoes.  i n s i d e s t o r a g e chamber  Samples Wrapped i n plastic  film.  of Reynold's  (kg/(m .day))  Samples w i t h c a l y x ends waxed.  Samples w i t h whole s u r f a c e waxed.  1.  0.091  0.015  0.005  0.012  0.008  2.  0.162  0.027  0.008  0.021  0.014  3.  0.452  0.050  0.015  0.048  0.025  4.  0.805  0.077  0.032  0.057  0.049  0.115  0.040  0.094  0.060  (0.97)  (0.99)  (0.89)  (0.95)  (kg/(m .day.kPa)) 2  Numbers i n parentheses g i v e t h e c o r r e l a t i o n c o e f f i c i e n t between t h e r a t e s of weight l o s s / a r e a and  t h e vapour p r e s s u r e d e f i c i t s between the tomato " m u l t i p l e b a r r i e r " and t h e tomato environment  VAPOUR PRESSURE DEFICITS AND AVERAGE RATES OF WATER LOSS THROUGH TOMATOr'.'MULTIPLE BARRIER"  TABLE 11.  (vWITH CORRECTION FOR EFFECT OF REYNOLD'S NUMBER OF AIR FLOW (RUN I I I ) )  Vapour  Pressure  Deficit (kPa)  Average r a t e of water l o s s per area w i t h c o r r e c t i o n f o r e f f e c t of Reynold's 2 number of a i r f l o w i n s i d e storage chamber (kg/m .day)) Untreated  Tomatoes.  Samples Wrapped i n  Samples w i t h c a l y x  Samples w i t h whole  plastic  ends waxed.  s u r f a c e waxed.  film.  1.  0.084  0.043  0.006  0.043  0.024  2.  0.143  0.070  0.012  0.062  0.046  3.  0.425  0.145  0.028  0.116  0.070  4.  0.749  0.243  0.058  0.198  0.109  0.333  0.075  0.281  0.175  (0.99)  (0.98)  (0.98)  (0.92)  K (kg/(m .day.kPa)) 2  Numbers i n parentheses  g i v e the c o r r e l a t i o n c o e f f i c i e n t between the r a t e s of weight l o s s / a r e a  and the vapour p r e s s u r e d e f i c i t s between the tomato " m u l t i p l e b a r r i e r '  1 a  n  d the tomato environment.  56. FIGURE 8. PLOT OF RATE OF WEIGHT LOSS PER AREA^s^VAPCUR PRESSURE DEFICITS (WITH CORRECTION FOR EFFECT OF REYNOLD'S NUMBER)  LEGEND RUN I I  m Untreated A Wrapped i n p l a s t i c  0.24  film  D Calyx^end waxed tk Whole skin waxed RUN I I I  •  0.20  Untreated  + Wrapped i n p l a s t i c  film  O  o Calyx-oTend waxed X cd T3  Whole skin waxed  0.16  0.12  0.0§  + @  0.04  • A  A  a +A  0.00 0.0  0.2  0.4  Vapour pressure d e f i c i t ,  0.6 (kPa)  0.8  57. a d j u s t e d r a t e s of weight l o s s p e r a r e a , a g a i n s t the vapour p r e s s u r e corresponding  t o T a b l e s 10 and 11.  deficits,  The s l o p e s of the p l o t s a r e l i s t e d  as the  mass t r a n s f e r c o e f f i c i e n t s of the " m u l t i p l e - b a r r i e r s " i n T a b l e s 10 and 11.  The p e r m e a b i l i t y of r e s i n i t e i s g i v e n as (23) measurements made a t 100°F (37.8°C), 3-hu  (i.e.  0.55 m i l .  = 90%).  over 25g"/(m . d . m i l ) ,  and change i n r e l a t i v e h u m i d i t y  of 90%  The r e s i n i t e used i n t h e experiments was measured t o be  The iifeer.atune v a l u e of t h e p e r m e a b i l i t y of r e s i n i t e thus  converts  ?2 t o 0.0077 ikg-'Adn „.cdycB6')a) . concerning  No upper bound or range i s g i v e n i n t h e l i t e r a t u r e  t h e water vapour p e r m e a b i l i t y of r e s i n i t e .  I t was thus d e c i d e d t o  determine e x p e r i m e n t a l l y , t h e water vapour t r a n s m i s s i o n p r o p e r t i e s of t h e resinite.  (See Appendix C f o r d e s c r i p t i o n of t h i s d e t e r m i n a t i o n ) .  average, t h e water p e r m e a b i l i t y of t h e f i l m was found kPa).  t o be - 0.060 kg'/(m ..d.  Since t h e water vapour p e r m e a b i l i t y of t h e r e s i n i t e f i l m was determined  in " s t i l l obtained  a i r " ( i . e . i n s i d e a d e s i c c a t o r ) , we can o n l y c o n s i d e r t h e v a l u e as an approximate one.  For r u n I I r e s u l t s  : t h e mass t r a n s f e r c o e f f i c i e n t f o r water l o s s from  the "bare" tomato s k i n ( p l u s boundary l a y e r ) was found kPa);  On t h e  t o be . 0* 115 kg/(m .d.  when wrapped i n t h e p l a s t i c f i l m , t h e mass t r a n s f e r c o e f f i c i e n t f o r t h e 2  resulting equation  " m u l t i p l e - b a r r i e r " was 0.040 kg/(m .dskEa^a) (Table 10). Thus from 11 (See s e c t i o n on T h e o r e t i c a l M o d e l ) , we have : -1 K ;, sk  +  -1 K_ by  =  K  -1 t  = 0.040  Therefore, K  g k  +  =  -1  -1 K , pi -  0.060"  1  =  8.333  0.120 kg/ (m .4 ,kPa»).Pa). 2  The d e v i a t i o n of t h e v a l u e of t h e mass t r a n s f e r c o e f f i c i e n t  of t h e tomato s k i n  58. p l u s boundary l a y e r as " e x t r a c t e d " from the mass t r a n s f e r c o e f f i c i e n t f o r the " m u l t i p l e - b a r r i e r " , c o n s i s t i n g o f : tomato s k i n p l u s boundary l a y e r p l u s p l a s r tic film  i s given  by:  D e v i a t i o n = (0.120 - 0.115)/0.120 A similar  =  4.17  per  cent.  set of c a l c u l a t i o n s w i t h the d a t a f o r run I I I gave the f o l l o w i n g :  K  f o r t h e "bare" tomato s k i n + boundary l a y e r = '0.333 kg/(m  2  .d.kPa)  2 K  for  Therefore,  plastic-wrapped  from e q u a t i o n 11 : K" + K" = 0.075" sk by 1  and  1  K  +  g k  The n e g a t i v e v a l u e film  tomato  increases  ^  1  = '0.075 kg/(m  - 0.06"!  ..d .kPa)  = - 3.333  = - 0.300 kg/(m ..4r.kPfc})a; . 2  i m p l i e s t h a t , packaging the tomatoes i n the p l a s t i c  the r a t e of weight l o s s .  resinite  P h y s i c a l l y , t h i s i s an u n l i k e l y . , .  phenomenon. A number of f a c t o r s c o u l d have c o n t r i b u t e d t o the above  observation  among them are : a) the method of d e t e r m i n a t i o n  of the p e r m e a b i l i t y of the r e s i n i t e  film  c o u l d o n l y g i v e an approximate v a l u e , b) the a i r f l o w c h a r a c t e r i s t i c s i n the s t o r a g e chambers a r e not f u l l y understood and It one  (the experiment was  c o n t r o l of the f l o w  i s pointed  not  s p e c i f i c a l l y designed  t o permit measurement  characteristics).  out t h a t the system under i n v e s t i g a t i o n i s a complex b i o l o g i c a l  and not a l l the c o n t r o l l i n g v a r i a b l e s are f u l l y known and  understood.  x  59. R e s u l t s and d i s c u s s i o n of r e g r e s s i o n a n a l y s e s of c o l o u r and f i r m n e s s changes Colour change w i t h The  time  r e s u l t s of the a n a l y s i s of c o l o u r change w i t h time a r e g i v e n i n  T a b l e B.3 i n the.appendix An i n i t i a l However, r e c a l l i n g  B.  i n s p e c t i o n of t a b l e B.3 shows no d i s c e r n i b l e t r e n d s . t h a t i n the weight l o s s a n a l y s i s of v a r i a n c e , o n l y the  p r e - s t o r a g e treatments  and d i f f e r e n t s t o r a g e c o n d i t i o n s were shown t o be  significantly different  i n t h e i r e f f e c t s on weight l o s s , and a p p l y i n g t h i s  knowledge i n t h e i n t e r p r e t a t i o n of the c o l o u r r e g r e s s i o n r e s u l t s ,  trends  become e v i d e n t . T a b l e B.4 was c o n s t r u c t e d from T a b l e B.3 by t a k i n g averages r e g r e s s i o n c o e f f i c i e n t s of the p r e - s t o r a g e treatment f o r a l l c o o l i n g regimes. treatment  no.2 (wrapping  and s t o r a g e  of the combinations  F o r example, under s t o r a g e n o . l (10°C, 90% r h ) and i n p l a s t i c f i l m ) , the f i g u r e 0.53 r e p r e s e n t s the mean  c o l o u r r e g r e s s i o n c o e f f i c i e n t , b , f o r a l l 20 tomatoes w i t h C-T-S codes 121, c 221,  321,and 421.  The range of b  £  v a l u e s i s from 0.48 t o 0.56 w i t h a standard  d e v i a t i o n of 0.03. F i g u r e B . l shows a p l o t of the mean c o l o u r c o e f f i c i e n t s f o r the v a r i o u s p r e - s t o r a g e treatments Y-axis.  on the Y - a x i s , a g a i n s t the storage c o n d i t i o n on the  ( p o i n t s are j o i n e d by s t r a i g h t l i n e s t o i n d i c a t e o v e r - a l l t r e n d s ) .  T a b l e B . 5 . i shows the mean c o l o u r c o e f f i c i e n t s f o r a l l tomatoes maintained a t a p a r t i c u l a r storage c o n d i t i o n .  A Duncan's M u l t i p l e Range t e s t and  the t - t e s t o n l y showed a s i g n i f i c a n t d i f f e r e n c e  (P  0.05) between the s t o r a g e  c o n d i t i o n s 1 (10°C, 90% r h ) and 3 (10°C, 60% r h ) on one hand, and the o t h e r t h r e e s t o r a g e s c o n d i t i o n s on the other hand.  The r e s u l t s a r e thus  i n c o n c l u s i v e ^ but -theitreridssare"-quite i n t e r e s t i n g * ; " -It -would appear t h a t the  60. tomatoes s t o r e d a t t h e lowest temperature  (10°C) underwent the slowest r a t e  of c o l o u r change, whereas those s t o r e d at the h i g h e r temperatures the f a s t e s t . A tentative  underwent  T h i s o b s e r v a t i o n c o n f i r m s the f i n d i n g s of Pharr and K a t t a n o b s e r v a t i o n may  thus be made t h a t low temperature  (26)  and h i g h humi-  d i t y i n the s t o r a g e chamber tends t o slow down the p r o c e s s of c o l o u r change.  T a b l e B . 5 . i i shows the mean c o l o u r c o e f f i c i e n t s f o r a l l tomatoes w i t h i d e n t i c a l p r e - s t o r a g e treatment.  The Duncan's and s t u d e n t ' s t - t e s t once a g a i n  f a i l e d to yield conclusive results. form o f p r e - s t o r a g e treatment  N e v e r t h e l e s s , the t r e n d s suggest  ( i . e . p l a s t i c film-wrapping  t h a t any  or waxing, e t c ) tends  t o slow down the p r o c e s s of c o l o u r change d u r i n g r i p e n i n g . .  F  iimnaEirmnessechangeiwithatdmeiahdCwlthrcolour  A summary of the r e s u l t s of the r e g r e s s i o n of f i r m n e s s w i t h time and w i t h c o l o u r i s g i v e n i n t a b l e B.6  (appendix B ) .  The tomatoes t h a t were e i t h e r i n d i v i d u a l l y wrapped i n p l a s t i c f i l m , or whose whole s u r f a c e were waxed g e n e r a l l y m a i n t a i n e d '4.4 throughout Bio-Resource  t h e experiment.  t h e i r f i r m n e s s r a t i n g of  (See o r i g i n a l d a t a i n G e n e r a l O f f i c e of  E n g i n e e r i n g , U.B.C.). Thus s i n c e the c o l o u r was changing  without  any c o r r e s p o n d i n g change i n f i r m n e s s , the c o r r e l a t i o n c o e f f i c i e n t s between c o l o u r and f i r m n e s s f o r the tomatoes w i t h these two treatments  are z e r o .  The r e g r e s s i o n of f i r m n e s s w i t h time f o r the tomatoes wrapped i n p l a s t i c or t o t a l l y waxed was a l s o found  t o be z e r o .  film  T a b l e B.6 was c o n s t r u c t e d minus  the r e s u l t s f o r tomatoes wrapped i n p l a s t i c f i l m or tomatoes whose e n t i r e s u r faces  were waxed.  With t h e e x c e p t i o n of t h e tomatoes s t o r e d i n s t o r a g e c o n d i t i o n no. 2 ( 1 5 C , 88% y  roK' ) t h e r e was found t o be a g e n e r a l l y h i g h c o r r e l a t i o n  (negative  61.  c o r r e l a t i o n ) between the r a t e of c o l o u r change and that of f i r m n e s s change (r  2  0.9).  R e s u l t s and D i s c u s s i o n of P o s t - S t o r a g e T e s t s  P l a t e 2 shows e l e c t r o n micrographs the e f f e c t s of p r e s s u r e on tomatoes. by " s q u e e z i n g " t o determine test  taken d u r i n g the i n v e s t i g a t i o n of  They showed no d i s c e r n i b l e damage caused  the f i r m n e s s r a t i n g of the tomatoes d u r i n g the  period.  The average e q u i l i b r i u m r e l a t i v e h u m i d i t y of the tomatoes was be 98  percent  (range: 96%  - 99%).  found to  T h i s confirmed the assumption made i n the  development of the model (see s e c t i o n on T h e o r e t i c a l Model).  At the end of each e x p e r i m e n t a l r u n , 5 people were asked fruit  to determine  i f o f f - f l a v o u r had developed  to t a s t e the  i n any of the v a r i o u s t r e a t -  ments, and a l s o to i n d i c a t e any p r e f e r e n c e s .  The t o t a l l y waxed and p l a s t i c - w r a p p e d tomatoes were g e n e r a l l y judged  to  t a s t e s l i g h t l y more a c i d i c , and were thus more p r e f e r a b l e to the u n t r e a t e d tomatoes.  The a c i d i c t a s t e of the " t r e a t e d " tomatoes might  carbon d i o x i d e ( C ^ ) waxed tomatoes and  be due  l e v e l s as r e p o r t e d by Parsons, e t a l . (23).  to h i g h e r The  partially  the u n t r e a t e d tomatoes were q u i t e a c c e p t a b l e , too, and  r e c o g n i z a b l e o f f - f l a v o u r i n any of the treatments was  noted.  no  62.  PLATE 2 ELECTRON MICROGRAPHS OF TOMATO SKIN SURFACE AND SUB-SURFACE LAYER  Magnification = 1600 X  3. Hand-picked tomato with "high contact" (2.27 kg weight for 5 s ) . Magnification = 150 X  4. High moisture loss tomato Magnification - 140 X  5. Low moisture loss tomato Magnification = 140 X  CONCLUSIONS  From t h e t e s t s conducted on  greenhouse tomatoes, t h e f o l l o w i n g  g e n e r a l c o n c l u s i o n s can be drawn: 1.  There i s no s i g n i f i c a n t d i f f e r e n c e between the steady  s t a t e r a t e s of  weight l o s s per u n i t of s u r f a c e area as a r e s u l t of the time d e l a y harvest, before cooling.  after  The p e r i o d s of d e l a y s t u d i e d were as g r e a t as  30 hours.  2a.  Wrapping i n d i v i d u a l tomatoes i n p l a s t i c polymeric  s t o r a g e , r e d u c e s t h e steady area t o about o n e - t h i r d  2b.  (resinite)  before  s t a t e r a t e of weight l o s s p e r u n i t of s u r f a c e  (^/3) the r a t e f o r unwrapped and u n t r e a t e d  tomatoes.  A p p l i c a t i o n of wax emulsion as a c o a t i n g over the whole s u r f a c e of a  tomato b e f o r e s t o r a g e reduces the steady of s u r f a c e a r e a t o about one-half r  film  (h)  s t a t e r a t e of weight l o s s per u n i t  of what would otherwise  r e s u l t i n the  'barey®t"omatoesO •  3.  The r a t e of water l o s s from t h e stem end (calyx- end) of the tomato f r u i t  during  storage  i s disproportionately large.  In t h e t e s t s conducted, water  l o s s from the stem end c o n t r i b u t e d t o over 27 percent.t of t h e t o t a l l o s s , y e t t h i s r e g i o n c o n s t i t u t e s only about 10 percent.t of t h e t o t a l s u r f a c e  4.  As expected, s t o r a g e a t t h e low temperatures (10°C) and h i g h  (90%, 80% rrh.)hugiyegislower.w/-ratesc3of)f steady s u r f a c e area of tomato than storage at the higher and  lower h u m i d i t i e s  5.  The p r e - s t o r a g e  area.  humidities  ssfeafee .weight... l o s s  per  temperatures (15°C, 18°C)  (60%, 50%, 4 0 % ) .  treatment of wrapping i n d i v i d u a l tomatoes i n p l a s t i c or  a p p l y i n g wax over t h e s u r f a c e s of t h e tomatoes tends  t o slow down the r a t e  of c o l o u r change d u r i n g r i p e n i n g , and a l s o t h e r a t e of t e x t u r a l breakdown ( r a t e at which t h e f i r m n e s s d e c r e a s e s ) .  The a l t e r e d atmosphere(i.e.  higher  l e v e l of carbon d i o x i d e ) (23.,28) c r e a t e d may have p l a y e d a p a r t i n t h e above changes noted.  T h i s c o u l d a l s o have l e d t o t h e tomatoes wrapped i n t h e  p l a s t i c f i l m b e i n g s l i g h t l y more p r e f e r e d t o t h e u n t r e a t e d tomatoes by t h e members of t h e t a s t e p a n e l .  T h i s agrees w i t h Parsons et a l . r e p o r t ( 2 3 ) on  the i n f l u e n c e of carbon d i o x i d e . 6.  For a group of tomatoes w i t h a s i m i l a r p r e - h a r v e s t h i s t o r y , t h e mass  transfer coefficient f i l m or waxfceoating and  and h u m i d i t y  of t h e tomato s k i n p l u s boundary l a y e r , p l u s p l a s t i c (as t h e case may be) i s independent of t h e temperature  of t h e s t o r a g e environment.  T h i s independence i s shown  by the l i n e a r r e l a t i o n s h i p between t h e r a t e s of water l o s s and t h e vapour p r e s s u r e d e f i c i t between t h e tomato s u r f a c e and t h e s t o r a g e environment.  t  65.  RECOMMENDATIONS AND PROPOSALS FOR FUTURE WORK IN THIS AREA.  From t h e e x p e r i e n c e g a i n e d . i n t h i s r e s e a r c h , t h e author would suggest 1.  that :  There should be a s i m p l e r e x p e r i m e n t a l d e s i g n w i t h fewer t r e a t m e n t s , but  i n v o l v i n g more tomatoes i n each treatment.  T h i s would a i d i n t h e a n a l y s e s  and  i n t e r p r e t a t i o n of t h e d a t a  2.  A n o n - d e s t r u c t i v e but o b j e c t i v e method of measuring c o l o u r and f i r m n e s s  needs t o be developed.  generated.  T h i s would a i d i n t h e understanding  of t h e exact  c o r r e l a t i o n between t h e weight l o s s and c o l o u r and f i r m n e s s changes d u r i n g storage.  3.  The tomatoes should a l l be p i c k e d at t h e same stage of r i p e n e s s ; and  more e x p e r i e n c e d hands should be employed t o h e l p i n t h e i n i t i a l t i o n f o r storage  prepara-  ( i . e . w e i g h i n g , p r e - c o o l i n g , r e a d i n g c o l o u r and f i r m n e s s  s c a l e , waxing, e t c ) .  4.  The s o l u b l e s o l i d s content and r e s p i r a t i o n r a t e i n a tomato should be  monitored d u r i n g t h e t e s t p e r i o d .  T h i s would a i d i n t h e i n t e r p r e p a t i o n of  the weight l o s s .  5.  The s t o r a g e chambers  should be designed  c h a r a c t e r i s t i c s i n s i d e t h e chambers  f o r c l o s e study of the a i r - f l o w  ( e s p e c i a l l y t h e boundary l a y e r s should  be w e l l d e f i n e d and c o n t r o l l e d ) , s i n c e the'sea f a c t o r s may i n f l u e n c e t h e r a t e of water l o s s through t h e tomato  "multiple-barrier".surface.  66.  LITERATURE CITED  1.  ASHRAE Handbook of fundamentals.  1967.  pp.65 - 78.  2.  von Beckmann, J.W. 1976. g r a d e r f o r tomatoes.  3.  Bennet, A.H. and J.N. Webb. 1976. Western F r u i t Frower.. May 1976  4.  van den Berg, L. and C P . L e n t z . 1974. High humidity s t o r a g e of some vegetables. Can I n s t . Food S c i . T e c h n o l . J . Vol.7 No.4.  5.  Commercial Storage of F r u i t s and V e g e t a b l e s . P u b l i c a t i o n No.1532, 1974.  6.  D e s r o s i e r , N.W. 1954. 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L u t z , J.M. 1944. M a t u r i t y and h a n d l i n g of green-wrap tomatoes i n Mississippi. U.S.D.A. C i r c . 695.  1968. C o r r e l a t i o n s of c e r t a i n ASAE Paper No. 68 - 120.  N.Y.  State  physical  2d Ed. I n t e r n a t i o n a l  67.  17.  M c C o l l o c h , L.P. and J.N. Yeatman. Colour changes and c h i l l i n g i n j u r y of p i n k tomatoes h e l d at v a r i o u s temperatures. U.S.D.A. Marketing Research Report No.735.  18.  McKinney, G. and A.C. L i t t l e , 1962. Co. Westport, Conn.  19.  Meherink, M. and S.W. P o r r i t t , 1972. The e f f e c t s of waxing on r e s p i r a t i o n , e t h y l e n e p r o d u c t i o n and o t h e r p h y s i c a l and c h e m i c a l changes i n s e l e c t e d apple c u l t i v a r s . Can. J . P l a n t S c i . 52:257-259.  20.  M i t c h e l l , F.G., R.- G u i l l o u and R.A. Parsons. 1972. Commercial c o o l i n g of f r u i t s and v e g e t a b l e s . U n i v e r s i t y of C a l i f . Manual 43.  21.  Modern Packaging  22.  P a n t a s t i c o , ER.B. 1975. P o s t - h a r v e s t p h y s i o l o g y , h a n d l i n g and u t i l i z a t i o n of t r o p i c a l and s u b - t r o p i c a l f r u i t s and v e g e t a b l e s . A v i . P u b l i s h i n g Co. Westport, Conn.  23.  Parsons, C.S., R.E. Anderson and R.W. Penney. 1970. Storage of maturegreen tomatoes i n c o n t r o l l e d atmosphere. J . Amer. Soc. H o r t . S c i . 95(6) :791-794  24.  P h a r r , D.M. and A.A. K a t t a n . 1971. E f f e c t s of a i r f l o w r a t e , s t o r a g e temperature, and h a r v e s t m a t u r i t y on r e s p i r a t i o n and r i p e n i n g of tomato f r u i t s . Plant Physiol. 48,53-55.  25.  Robinson, W.B. 1952. A study of methods f o r the measurement of tomato j u i c e c o l o u r . Food T e c h n o l . 6:269-275.  26.  Smock, R.M. 1960. Some a d d i t i o n a l e f f e c t s of waxing a p p l e s . Soc. H o r t . S c i . 37:448-452.  27.  T o l l e , W.E. 1972. Hypobaric s t o r a g e of f r e s h produce. F r u i t and V e g e t a b l e Assn. Yearbook, 1972.  28.  Tomkins, R.G. 1962. The c o n d i t i o n s produced i n f i l m packages by f r e s h f r u i t s and v e g e t a b l e s and e f f e c t s of these c o n d i t i o n s on s t o r a g e l i f e . A p p l . B a c t e r i o l . 25:290-307.  29.  T r e y b a l , R.E. 1955. Mass T r a n s f e r O p e r a t i o n s . I n c . , N.Y.  30.  Wang, J-K and P-Y Wang. 1967. A computational technique f o r deep-bed f o r c e d - a i r p r e - c o o l i n g of tomatoes. ASAE paper No.67-819.  31.  Watsoni E.L. 1960. Prompt h a n d l i n g p l u s proper c o o l i n g f o r b e t t e r quality. Can. Food Ind. June 1960.  C o l o u r of f o o d s .  Avi. Publishing  Encyclopaedia.»1971. P.146.  P r o c . Amer.  United Fresh  McGraw-Hill  Book Co.  68.  APPENDIX•  A  69.  TABLE  A . l TWO-FACTGR INTERACTION EFFECTS ON.WEIGHT LOSS. (RUN I I )  (a)  COOLING  X  TREATMENT  Untreated  Plastic-film wrapped  C*)  Calyx end waxed  Whole s k i n waxed  o .11  0 .26  0,.19  0,.36  0,.12  0 .29  0..20  0-hour d e l a y  0..33  0,.13  0 .28  0..20  30-hour d e l a y  0,.29  0,.12  0 .25  0..17  20-hour d e l a y  0,.31  10-hour d e l a y  *  ;  Mean of 25 r e a d i n g s  (b)  COOLING  X  :u  (kvg/m ) 2  STORAGE  St.l (*)  St.2  St.3  St.4  St.5  0,.18  0..18  0..29  0..32  20-hour-delay  0,  10-hour d e l a y  0..11  0,.19  0..20  0..32  0..37  0-hour d e l a y  0..13  0..21  0..21  0..33  0..30  30-hour d e l a y  0..13  0..16  0..17  0.,29  0..30  Mean of 20 r e a d i n g s  (c)  TREATMENT  (kig/m )  STORAGE  Sf.1  St.2  St.3  St.4  St. 5  Untreated  0 .18 <*>  0,.29  0,.26  0,.44  0 .44  Plastic wrapped  0,.06  0,.08  0,.09  0,.18  0 .19  Calyx end waxed  0,.14  0,.21  0..27  0..33  0 .38  Whole s k i n waxed  0,.10  0.,15  0,.14  0..28  0 .28  film  Mean of 20 r e a d i n g s  (Kg/m )  70.  TABLE A. 2 (a)  TWO-FACTOR INTERACTION EFFECTS  ON WEIGHT LOSS (RUN I I I )  ' COOLING X-TREATMENT  Untreated  20-hour  Plastic-film wrapped  (*)  Calyx end waxed  Whole s k i n waxed'  0.26  0.94  0.56  1.08  0.25  1.00  0.50  delay  1.02  10-hour d e l a y  v  ;  0-hour  delay  1.12  0.25  0.96  0.57  30-hour  delay  1.16  0.26  0.91  0.57  * (b)  Mean of 25 r e a d i n g s  COOING C 3CsTO#AGE-^  ORAG7i:  , 2 fteg/m ) 9  CONDITION  X  ...  i  *  ,  St.l (*)  #  St.2  St. 3  St. 4  St. 5  0.49  0.61  0.88  0.13  20-hour d e l a y  0.37  10-hour d e l a y  0.39  0.57  0.55  0.84  0.18  delay  0.41  0.61  0.50  0.90  1.18  30-hour d e l a y  0.38  0.49  0.54  0.95  1.27  0-hour  v  ;  «->  * (c)  Mean of 20 r e a d i n g s  -TllATMENT^X S T O R S G E ^ G ^  (kg/'m ) 2  CONDITION  Untreated  St.l  St. 2  St. 3  St.4  St.5  Untreated  0.58  0.79  0.90  1.43  1.77  Plastic film wrapped  0.08  0.14  0.16  0.33  0.56  Calyx-end waxed  0.58  0.71  0.71  1.19  1.57  Whole s k i n waxed  0.31  0.52  0.44  0.63  0.86  Mean o f 20 r e a d i n g s  (%/mi ) 2  71.  APPENDIX  B  72,  TABLE  C-T-S code  #1  SUMMARY OF RESULTS OF WEIGHT LOSS REGRESSION A N A L Y S I S (RUN  Regression coef (b) k g / ( m . d a y ) •  FPr.ob (b)  Std. error (b)  r  2  111  0.015  0.0000  0.53 x  10"  4  0.9984  112  0.025  0.0000  0.11 x  10"  3  0.9977  113  0.023  0.0000  0.29 x  10"  4  0.9998  114  0.030  0.0000  0.13 x  10"  3  0.9976  115  0.025  0.0000  0.52 x  10~  3  0.9500  121  0.0036  0.0000  0.20 x 1 0 ~  4  0.9961  122  0.0072  0.0000  0.19 x 1 0 ~  4  0.9991  123  0.0066  0.0000  0.33 x  10~  4  0.9969  124  0.0130  0.0000  0.20 x 1 0 ~  4  0.9997  125  0.0175  0.0000  0.21 x 1 0 ~  4  0.9998  131  0.012  0.0000  0.37 x 1 0 ~  4  0.9988  132  0.013  0.0000  0.68 x  10~  4  0.9969  133  0.018  0.0000  0.24 x 1 0 ~  4  0.9998  134  0.029  0.0000  0.13 x 1 0 ~  4  0.9976  135  0.032  0.0000  0.75 x 1 0 ~  4  0.9993  141  0.00 8  0.0000  0.35 x  10~  4  0.9974  142  0.013  0.0000  0.83 x  10~  4  0.9947  143  0.013  0.0000  0.29 x 1 0 ~  4  0.9994  144  0.023  0.0000  0.13 x  10"  3  0.9962  145  0.023  0.0000  0.44 x  10~  4  0.9995  II)  73.  T a b l e i-l G-T-S code  continued. R e g r e s s i o n coef.,b 2 ' kg/-(m .day)  FProb . (b)  Std. e r r o r (b)  . .2 r  211  0.015  0.0000  0.86 x 1 0 ~  4  0.9961  212  0.025  0.0000  0.12 x 1 0 ~  3  0.9973  213  0.024  0.0000  0.27 x 1 0 ~  4  0.9998  214  0.042  0.0000  0.21 x 1 0 ~  3  0.9970  215  0.040  0.0001  0.57 x 1 0 ~  3  0.9756  221  0.0040  0.0001  0.50 x 1 0 "  4  0.9802  222  0.0063  0.0000  0.24 x 1 0 ~  4  0.9989  223  0.0082  0.0000  0.35 x I O  - 4  0.9962  224  0.0133  0.0000  0.21 x 1 0 ~  4  0.9997  225  0/0170  0.0000  0.39 x 1 0 ~  4  0.9993  231  0.009i  0.0000  0.60 x 1 0 ~  4  0.9944  232  0.019  0.0000  0.62 x 1 0 ~  4  0.9986  233  0.024  0.0000  0.40 x I O  - 4  0.9997  234  0.029  0.0000  0.71 x 1 0 ~  4  0.9993  235  0.035  0.0000  0.22 x 1 0 ~  3  0.9954  241  0.008  0.0000  0.55 x 1 0 "  4  0.9941  242  0.013  0.0000  0.66 x 1 0 ~  4  0.9970  243  0.011  0.0000  0.26 x I O  - 4  0.9993  244  0.020  0.0000  0.54 x 1 0 ~  4  0.9991  245  0.023  0.0000  0.10 x 1 0 ~  3  0.9976  74.  TABLE £ . 1 (Cont'd)  2  C-T-S code  Regression ^oef. ,b kg/(m .day)  FProb (b)  Std. .error (b)  311  0.017  0.0000  0.15 x 10~  3  0.9902  312  0.026  0.0000  0.16 x 10~  3  0.9955  313  0.022  0.0000  0.ft9 x 10~  4  ' 0.9988  314  0.040  0.0000  0.20 x 10~  3  0.9968  315  0.024  0.0003  0.43 x 1 0 "  3  0.9591  321  0.0045  0.0000  0.25 x 10~  4  0.9962  322  0.0076  0.0000  0.20 x TO""  4  0.9991  323  0.0088  0.0000  0.14 x 10~  4  0.9997  324  0.0190  0.0000  0.23 x 1 0 "  4  0.9998  325  0.0134  0.0000  0.65 x 10~  4  0.9971  331  0.012  0.0000  0.10 x 10~  3  0.9917  332  0.023  0.0000  0.11 x T O  - 3  0.9973  333  0.027  0.0000  0.64 x 10~  4  0.9993  334  0.023  0.0000  0.45 x 10~  4  0.9995  335  0.027  - 0.0001  0.38 x 1 0 "  3  0.9759  341  6.010  0.0001  0.98 x 10~  4  0.9886  342  0.012  0.0000  0.52 x 16~  4  0.9978  343  0.012  0.0000  0.25 x 10~  4  0.9994  344  0.025  0.0000  0.97 x 10~  4  0.9982  345  0.025  0.0000  0.87 x 10~  4  0.9985  r  75. TABLE Q>-1 C-T-S code  (Cont'd) R e g r e s s i o n eoef.,b kg/(m  .day) -•"  EPr.ob, (b)  -Std. e r r o r  •r  2  (b)  411  0.014  0.0000  0.29  X  io"  4  0.9995  412  0.019  0.0000  0.67  X  io"  4  0.9984  413  0.026  0.0000  0.56  X  io"  4  0.9921  414  0.032  0.0000  0.17  X  io"  3  0.9966  415. '  0.028  0.0001  0.28  X  io"  3  0.9876  421  0.0067  0.0012  0.19  K  io"  3  0.9100  422  0.0061  0.0000  0.35  X  10 '  0.9958  423  0.0061  0.0000  0.37  X  io"  4  0.9954  424  0.0155  0.0000  0.12  X  io"  4  0.9999  425  0.0156  0.0000  0.16  X  io"  4  0.9999  431  0.014  0.0000  0.22  X  io"  4  0.9997  432  0.016  0.0000  0.79  X  io"  4  0.9969  433  0.021  0.0000  0.99  X  io"  4  0.9972  434  0.025  0.0000  0.13  X  io"  3  0.9967  435  0.027  0.0000  0.38  X  io"  4  0.9997  441  0.007  0.0000  0.15  X  io"  4  0.9994  442  0.012  0.0000  0.57  X  io  = 4  0.9970  443  0.012  0.0000  0.27  X  io"  4  0.9993  444  0.023  0.0000  0.91  X  io"  4  0.9980  445  0.020  0.0000  0.24  X  io"  4  0.9998  -L  TABLE G> .X SUMMARY OF RESULTS OF WEIGHT LOSS JREGRESSION ANALYSIS (RUN I I I ) C-T-S code  R e g r e s s i o n c o e f . ,,b 2 kg/(m .day)  FProb  Std. e r r o r  (b)" '.  (b)  r  2  -  -3  111  0.042  0.0000  0.30 x 10  112  0.058  0.0000  0.26 x l O "  3  0.9965  113  0.076  0.0000  0.46 x l O "  3  0.9936  114  0.102  0.0000  0.43 x l O "  3  0.9969  115  0.127  0.0000  0.71 x l O "  3  121  0.006  0.0000  0.38 x 10"  122  0.016  0.0000  0.58 x l O "  4  0.9977  123  0.013  0.0000  0.33 x l O "  4  0.9988  124  0.027  0.0000  0.50 x l O "  4  0.9994  125  0.043  0.0000  0.15 x l O "  3  0.9978  0.9909  0.9946  0.9931  4  7  131  0.033  0.0000  0.51 x l O "  132  0.054  0.0000  0.13 x 10  133  0.068  0.0000  0.27 x l O "  3  0.9974  134  0.093  0.0000  0.61 x l O "  3  0.9925  135  0.104  0.0000  0.12 x l O "  2  0.9778  141  0.025  0.0000  0.17 x l O "  3  0.9915  142  0.034  0.0000  0.71 x l O "  4  0.9992  143  0.037  0.0000  0.16 x l O "  3  0.9968  144  0.057  0.0000  0.27 x l O "  3  0.9960  145  0.071  0.0000  0.40 x l O "  3  0.9944  3  -3  0.9590 0.9990  77.  TABLE 8%  -C-T-S code  (Cont'd)  coef.,b  FProb  ' . kg/(m .day)  (b)  Regression  Std. e r r o r  r  2  (b)  211  0.045  0.0000  0.42  X  io"  3  0.9855  212  0.070  0.0000  0.29  X  io"  3  0.9970  213  0.071  0.0000  0.59  X  io"  3  0.9879  214  0.117  0.0000  0.51  X  io"  3  0.9967  215  0.105  0.0000  0.12  X  io"  2  0.9789  221  0.006  0.0000  0.82  X  io"  4  0.9712  222  0.009  0.0000  0.12  X  io"  4  0.9997  223  0.013  0.0000  0.39  X  io"  4  0.0083  224  0.026  0.0000  0.24  X  io"  4  0.9998  225  0.044  0.-000  0.15  X  io"  3  0.9979  231  0.043  0.0000  0.41  X  io"  3  0.9843  232  0.055  0.0000  0.21  X  io"  3  0.9974  233  0.056  0.0000  0.32  X  IO"  3  0.9942  234  0.088  0.0000  0.39  X  IO"  3  0.9966  235  0.130  0.0000  0.18  X  io"  2  0.9668  241  0.024  0.0000  0.23  X  io"  3  0.9836  242  0.047  0.0000  0.11  X  IO"  3  0.9991  243  0.027  0.0000  0.28  X  io"  3  0.9823  244  0.041  0.0000  0.16  X  io"  3  0.9972  245  0.058  0.0000  0.25  X  10  -3  0.9967  78.  TABLE  8-2-  C-T-S code  (Cont'd)  R e g r e s s i o n ^ c o e f . ,b kg/(m .day) 2  FF.rob (b)  2 r .  Std. e r r o r (b)  311  0.043  0.0000  0.54  X  io"  3  0.9737  312  0.069  0.0000  0.30  X  io"  3  0.9966  313  0.067  0.0000  0.40  X  io"  3  0.9937  314  0.110  0.0000  0.39  X  io"  3  0.9978  315  0.118  0.0000  0.19  X  io"  2  0.9550  321  0.006  0.0000  0.21  X  io'  4  0.9977  322  0.010  0.0000  0.63  X  io"  4  0.9929  323  0.014  0.0000  0.49  X  io"  4  0.9978  324  0.027  0.0000  0.33  X  io"  4  0.9997  325  0.044  0.0000  0.12  X  io"  3  0.9988  331  0.045  0.0000  0.36  X  io"  3  0.9893  332  0.060  0.0000  0.62  X  io"  3  0.9814  333  0.044  0.0000  0.22  X  io"  3  0.9956  334  0.105  0.0000  0.47  X  io"  3  0.9965  335  0.119  0.0000  0.63  X  l(f  3  0.9952  341  0.028  0.0000  0.19  X  io~  3  0.9916  342  0.053  0.0000  0.16  X  io"  3  0.9984  343  0.034  0.0000  0.14  X  io"  3  0.9969  344  0.045  0.0000  0.14  X  io"  3  0.9982  3S5  0.066  0.0000  0.24  X  lo"  3  0.9977  79.  TABLE  C-T-S code  6a  (Cont'd)  R e g r e s s i o n c o e f . ,b . . 2. kg/(m .day)  FProb (b) ' v  2 r.  Std; error (b) '  411  0.044  0.0000  0.35 x i o "  412  0.056  0.0000  0.19,x i o "  413  0.066  0.0000  0.25 x H f  414  0.127  0.0000  0.48 x i o " 3  0.9975  415  0.145  0.0000  0.19 x i o "  2  0.9722  421  0.006  0.0000  0.26 x i o "  4  0.9961  422  0.009  0.0000  0.65 x i o "  4  0.9916  423  0.013  0.0000  0.25 x i o "  4  0.9994  424  0.029  0.0000  0.36 x I O "  4  0.9997  425  0.048  0.0000  0.17 x i o "  3  0.9977  431  0.050  0.0000  0.32 x i o "  3  0.9929  432  0.053  0.0000  0.33 x i o "  3  0.9929  433  0.056  0.0000  0.23 x i o "  3  0.9972  434  0.086  0.0000  0.50 x i o "  3  0.9941  435  0.111  0.0000  0.51 x i o "  3  C.9963  441  0.019  0.0000  0.13 x 10  442  0.034  0.0000  0.17 x i o "  443  0.039  0.0000  0.16 x i o "  444  0.059  0.0000  0.26 x i o " 3  0.9965  445  0.075  0.0000  0.36 x i o "  0.9959  3  0.9890  3  0.9979 0.9976  3  -3  0.9921  3  0.9955  3  0.9969  3  TABLE B.3  C-T-S C  o  d  e  SUMMARY^OF  COLOUR CHANGE REGRESSION ANALYSIS (RUN I I I )  Const a  Coef.  C  b  C  FProb  r  2  (day" ) 1  111  1.34  0.31  0.00  0.981  112  0.98  0.43  0.00  0.969  113  1.30  0.35  0.01  0.914  114  1.20  0.40  0.01  0.941  115  1.40  0.45  0.01  0.938  121  1.52  028-  0.01  0.956  122  1.92  038  0.00  0.987  123  2.26  0 24  0.03  0.860  124  1.40  0.39-  0.01  0.939  125  1.24  0.32.  0.00  0.977  131  1.82  0.23  0.01  0.912  132  1.38  0.35:  0.01  0.920  133  1.10  0.27  0.02  0.898  134  1.40  036  0.00  0.976  135  1.94  025  0.01  0.936  141  1.80  0.26  0.00  0.983  142  0.40  O.35  0.00  0.989  143  1.36  0.32  0.02  0.905  144  1.40  0.38  0.01  0.930  145  1.42  0.38  0.01  0.946  211  1.75  0.29'  0.00  0.930  212  1.10  O.43  0.00  0.930  213  1.46  0.25  0.02  0.936  214  1.74  O.35  0.01  0.966  215  1.56  0.38  0.01  0.945  .  81.  TABLE B.3 (CONT'D) C-T-S Code  Const  Coef. b  FProb  2 r  (day ) -1  c  221  1.50  0.27  0.01  0.940  221  1.56  0.34  0.01  0.960  223  1.32  0.24  0.02  0.889  224  1.42  0.30  0.01  0.939  225  1.36  0.36  0.01  0.959  231  1.60  022  0.00  0.984  232  2.30  0.25;  " 0.01  0.947  233  1.20  0.26  0.02  0.879  234  1.40  0.34;  0.01  0.941  235  1.04  0.4:4.  0.01  0.934  241  1.52  0.-24  0.01  0.947  242  1.08  0.30  0.00  0.985  243  3.18  0.i>.9  0.02  0.880  244  2.32  0.;28  0.02  0.891  245  1.40  0.38  0.00  0.968  311  . 1.38  0.27  0.00  0.985  312  1.24  0.36  0.00  0.982  313  0.82  0.41  0.01  0.949  314  1.44  0.40  0.01  0.926  315  1.30  0.41-  0.01  0.940  321  1.40  0.24:  0.01  0.947  322  1.30  0 31-  0.01  0.935  323  1.42  0.27.  0.02  0.902  324  1.62  0.33  0.01  0.939  325  1.86  0.33  0.02  0.887  -.  .  TABLE B.3 (CONT'D) C-T-S Code  Const a C  Coef. .. -1, b (day )  FProb  -  2 r  c  331  1.10  O.33  0-00  0-997  332  1.18  0.37  0.00  0.992  333  2.26  0.25  0.02  0.898  334  2.20  0.32  0.02  0.889  335  2.34  0.29  0.01  0.943  341  2.18  0.21  0.00  0.984  342  2.22  0.25  0.02  0.903  343  2.26  0.23  0.01  0.931  344  2.10  0.61  0.00  0.973  345  1.98  0.8-3  0.01  0.949  411  1.98  0.21  0.00  0.984  412  1.76  0.36  0.01  0.931  413  1.96  0..28  0.01  0.925  414  2.36  0.30  0.02  0.893  415  2.30  0.31  0.02  0.883  421  1.22  0.27  0.01  0.949  422  0.96  0.39  0.00  0.988  423  1.06  0.61  0.00  0.969  424  0.90  0.43  0.00  0.977  425  1.78  0:35  0.01  0.948  431  2.32  0..16  0.01  0.941  432  2.14  0..25  0.01  0.936  433  1.84  0.24  0.01  0.911  434  1.56  0.34  0.00  0.980  435  1.78  0.27  0.01  0.960  441  1.86  0.21  0.02  0.896  442  1.70  0..32  0.00  0.972  443  1.50  0..25  0.02  0.893  444  1.54  0.37  0.00  0.972  445  1.24  0.140  0.00  0.971  ,  TABLE B.4  INTERACTION EFFECT OF TREATMENT AND STORAGE ON THE RATE OF COLOUR CHANGE  Treatment 1  2  3  4 r  Storage 1  0.27*  0.27  0.24  0.23  (0.01)  (0.07)  (0.02)  0.40  0.36  0.31  0.31  (0.04)  (0.03)  (0.06)  (0.04)  0.32  0.26  0.25  0.23  (0.07)  (0.03)  (0.01)  (0.09)  0.38  0.36  0.34  0.33  (0.05)  (0.09)  (0.01)  (0.09)  0.36  0.34  0.36  0.38  (0.05)  (0.02)  (0.08)  (0.03)  (0.04)**  2  3  4 •  5  Mean of 20 measurements. Numbers i n parentheses  r e f e r t o the s t a n d a r d e r r o r s of the means.  84.  TABLE B.5  MAIN EFFECTS OF STORAGE AND TREATMENT ON RATE OF COLOUR CHANGE  (ii) Storage -  1  Mean Colour Coef. (*)  PreStorage Treatment  0.25 (a)  1  (0.02)(**)  2  0.34 (b)  2  0.27 (a)  3  0.29 (a) (0.04)  0.35 (b)  4  (0.02)  5  0.32 (a) (0.05)  (0.04)  4  0.35 (a) (0.05)(**)  (0.04)  3  Mean Colour Coef.(***)  0.30 (a) (0.06)  0.35 (b) (0.02)  * ** ***  Mean of 80 measurements. Numbers i n parentheses r e f e r  t o t h e standard e r r o r s of t h e means.  Mean of 100 measurements. Responses f o l l o w e d by d i f f e r e n t different (P 0.05).  l e t t e r s are s i g n i f i c a n t l y  FIGURE B . l PLOT OF MEAN COLOUR COEFFICIENT (b ) DUE TO PRE-STORAGE c TREATMENT V s . STORAGE CONDITION  Storage C o n d i t i o n  86.  TABLE --C-T-S Code  B.6 SUMMARY OF RESULTS OF TOMATO FIRMNESS CHANGES WITH TIME (REGRESSION ANALYSIS) Const. Coef FProb a  F (day  111 112  2  r-  4.16  l  )  C o r r e l a t i o n Coef colour/firmness  4.08  -0. .0.6 -0. ,02  6.017 0.180  0.900 0.500  -0.909 -0.58  113  4.30  -o.aa-  0.008  114  4.54  0.024  -0.966 -0.891  115  4.46  -0.17 -0.9$  0.945 0.871  . 0.001  0.995  -0.974  131 132  4.36 4.08  0.780  -0.954  -o.oa  0.049 0.182  133 134  4.36 4.30  -0 .E2+-0.2.9}  0.027 0.060  0.503 0.862 0.751  -0.543 -0.960 -0.821  135  4.20  -0.E3S  0.017  0.899  -0.967  211 212 213  -0.0:9 -0.08.  0.061  0 752  -0.961 -0.527 -0.977  -0. us -0.2.8  0.183 0.034 0.068 0.003  0.502 0.843  214 215  4.30 4.32 4.46 4.60 4.72  0.753 0.972  -0.864 -0.940  231 232 233  4.10 4.18 4.20  -0.03 -0.05: -0X0.4!  0.755 0.783 0.754  -0.899 -0.832 -0.998  234 235  4.36 4.68  -o.m -0.30)  0.841 0.995  -0.911 -0.956  7  -0.1.0)  -0.BS"  0.063 0.053 0.066 0.032 0.001  ?  TABLE B.6  (CONT'D)  C o r r e l a t i o n Coef colour/firmness  311  4.06  -0.0Q  0.063  312  0.752  4.08  -0.856  -0.0/2  0.181  313  0.502  4.22  -0.781  -0.10!9  0.021  314  0.887  4.78  -0.35  -0.964  0.015  315  0.900  4.72  -0.889  -0..2(8  0.001  0.971  -0.943  331  4.06  -0.06  0.065  0.752  -0.862  332  4.08  -0.02  0.183  0.504  -0.672  333  4.10  -0.06  0.064  0.752  -0.930  334  4.52  -0..T.6  0.021  0.893  -0.818  335  4.56  -0.22  0.011  0.953  -0.975  4fl  4.26  -o.  0.074  412  0.723  4.16  -0.819  -0.04  0.188  413  4.26  0.504  -0.511  -0. IB  0.000  414  0.998  4.64  -0.22  -0.978  0.015  415  4.66  0.944  -0.31  -0.874  0.007  0.984  -0.927  431  4.10  -0.03  0.065  432  0.753  4.08  -0.913  -0.02  0.183  0.501  433  4.06  -0.660  -0 .QS>  0.026  434  0.898  4.46  -0.875  -0.135)  0.035  435  0.843  4.34  -0.912  -0.B5)  0.004  0.998  -0.963  L  m  88.  APPENDIX  C  89".  APPENDIX DETERMINATION OF THE MATERIAL AND  C PERMEABILITY OF RESINITE FILM  METHOD  A roll  of r e s i n i t e f i l m , Batch No.4577/46, Type AF-50 (manufactured  A p r i l 23rd 1974)  was  used i n the d e t e r m i n a t i o n  (*).  E i g h t r e c t a n g u l a r pouches were made by f o l d i n g over, r e c t a n g u l a r of the p l a s t i c f i l m , and h e a t - s e a l i n g along  two  sides.  samples  In each pouch was  a w i r e gauze of comparable dimensions (whose sharp edges had over t o prevent  :  placed  been doubly f o l d e d  p i n - h o l i n g of the p l a s t i c f i l m ) to keep the two  s i d e s of  the  pouch a p a r t . Dehydrated s i l i c a s p a t u l a , i n each pouch The  pouches and  g e l (blue c r y s t a l s ) was and  then p l a c e d , by means of a  the l a s t s i d e heat- s e a l e d .  contents were t h e n weighed on a M e t t l e r Balance and  v e r t i c a l l y on a r a c k i n s i d e a d e s i c c a t o r .  There was  d i s t i l l e d water i n the  bottom of the d e s i c c a t o r to c r e a t e s a t u r a t e d c o n d i t i o n s of 100%)  on the o u t s i d e s of the pouches, w h i l e  hung  (i.e. relative  the i n s i d e s were  humidity  initially  "bone d r y " . The  pouches and  t h e i r contents were  reweighed a f t e r every  24 h f o r 4  c o n s e c u t i v e . 24-hour p e r i o d s : The of the t e s t  dimensions  ( i . e . l e n g t h x width) of the pouches were taken at the  end  period.  The  t h i c k n e s s of the r e s i n i t e f i l m was  measured on a model 549  The  average temperature of the environment d u r i n g the t e s t was  micrometer. 22°C  (71.6°F). (.*)  T h i s was  the same r o l l  of f i l m used i n the wrapping of  the tomatoes ( P r e - s t o r a g e experiment.  treatment no.2)  d u r i n g the main  90.  RESULTS  AND CALCULATION OF  The s u c c e s s i v e of t a b l e C . l .  PERMEABILITIES  weights o f the pouches are g i v e n i n the f i r s t  The f i f t h  column of t a b l e CI  4 columns  g i v e s the s u r f a c e areas  of the  v a r i o u s pouches.  Sample C a l c u l a t i o n o f M o i s t u r e  P e r m e a b i l i t y of F i l m  The t h i c k n e s s o f the f i l m was measured t o be 0.55 m i l (+0.05 m i l ) . For pouch n o . l , change i n weight between day 1 and day 2 i s g i v e n a s : 14.2397  -  12.2441  =  1.9956 gar  Adjustment t o 24 h o u r s , g i v e s : wt. g a i n = 1.9956 x 2_4_ = 1.9158 g 25 The water vapour t r a n s m i s s i o n r a t e (WVTR) i s thus 1.9158 g. 0.0121 m .dz  = 158.3306 g. 0" j . m. d z  The s a t u r a t i o n vapour p r e s s u r e WVTR  =  a t 22°C  158.3306 gz. 2.d-. 2.66'kPaf  = x  m  2.66 kPa  1 kg 1000 g.,  =  0.060 kg m^.d-kPa.  S i m i l a r • c a l c u l a t i o n s y i e l d e d d a t a i n columns 6 , 7 , 8 of t a b l e £>• 1 which shows t r e n d of d e c r e a s i n g  p e r m e a b i l i t y between s u c c e s s i v e p e r i o d s .  expected s i n c e the h y d r a t i o n o f the s i l i c a g e l decreased  the vapour  d i f f e r e n c e between the i n s i d e s and o u t s i d e s of the pouches. column 6 ( i . e . the WVTR d u r i n g the f i r s t p e r m e a b i l i t y of the r e s i n i t e  T h i s was as pressure  Thus the v a l u e s i n  p e r i o d ) were-averaged t o g i v e the  f i l m , as. 0j.06pj kg/m  2 .d .;kPa.  Table C . l  Successive (g  1 4.00  Day  2 5.00  Day pm  Resinite  determination  weights  )  3 6.00  Day pm  f i l m WVTR  4 6.00  Day pm  pn  Area  WVTR B e t w e e n  of Pouch  periods  (m2)  i-»2 -  2-> 3 '  •3-* 4  seccessive  (Kg/m .day.kPa) 2  12.2441  14.2396  15.8786  16.9786  0.0121  0.0595  0.0489  0.0342  13.8567  16.2213  18.0081  19.2391  0.0143.  0.0597  0.0451  0.0324  12.7340  15.1298  16.8256  17.8891  0.0156  0.0605  0.0392  0.0256  14.6638  17.4659  19.5910  20.8147  0.0162  0.0624  0.0473  0.0284  11.9306  13.9723  15.5353  16.8851  0.0138  0.0534  0.0408  0.0368  12.2680  14.1013  15.3699  16.4701  •0.0113  0.0586  0.0405  0.0366  12.7356  14.9960  16.8168  17.9956  0.0145  0.0563  0.0453  0.0306  13.0012  15.6054  17.0054  17.9842  0.0138  0.0681  0.0366  0.0267  92.  APPENDIX D  APPENDIX D  FEDERAL* AND INDUSTRY** GRADING STANDARDS FOR GREENHOUSE TOMATOES F e d e r a l and I n d u s t r y Colour Grades  and Standards ***  Canada No.l Grade are,  i n a n y > i n d i v i d u a l package,  s t a t e s of development: r i p e " or " f i r m (a)  one of the f o l l o w i n g  "mature", " t u r n i n g " ,  "semi-  ripe",  ^mature" means, (i)  except f o r f i e l d  tomatoes grown i n B r i t i s h  Columbia  and Manitoba, t h a t the tomato shows a d e f i n i t e of  tinge  p i n k a t t h e blossom end, and i n t h e case of f i e l d  tomatoes grown i n B r i t i s h Columbia and Manitoba, t h a t the tomato i s f u l l y  developed, w e l l f i l l e d out,  g i v e s a f e e l i n g of s p r i n g i n e s s when p r e s s u r e i s a p p l i e d , i s b r i g h t waxy i n appearance, has seeds are  w e l l developed and seed c a v i t i e s of a  that  jelly-like  c o n s i s t e n c y , and (ii)  n o t more than 25% of t h e f i e l d  tomatoes by count a r e  t u r n i n g i n the case of tomatoes grown i n B r i t i s h Columbia  *  and Manitoba, and not more than 10% of the  Canada A g r i c u l t u r a l P r o d u c t s Standards A c t , 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 , Queen's P r i n t e r ,  Ottawa 1968, Catalogue  No. YX7/9-1955-27-1968. ** %  **  Courtesy Western Greenhouse C o - o p e r a t i v e , Burnaby, B.C. Greenhouse tomato grades and standards a r e t h e same as f i e l d tomato grades and s t a n d a r d s .  field of  tomatoes by count  a r e t u r n i n g i n the case  tomatoes grown o t h e r than i n B r i t i s h Columbia  and Manitoba;  " t u r n i n g " means (i)  t h a t the f i e l d  tomato shows from a t i n g e t o  25 p e r c e n t p i n k or r e d c o l o u r , and (ii)  n o t more than 10% of the f i e l d  tomatoes by count  are mature or s e m i - r i p e ; " s e m i - r i p e " means (i)  t h a t the f i e l d  tomato shows from 25 p e r c e n t t o  75 p e r c e n t p i n k or r e d c o l o u r , and (ii)  n o t more than 10 p e r c e n t of t h e f i e l d  tomatoes  by count a r e t u r n i n g or f i r m r i p e ; and  "firm (i)  r i p e " means t h a t the f i e l d  tomato shows from 75 p e r c e n t t o  100 p e r c e n t p i n k o r r e d c o l o u r , and (ii)  not more than 10 p e r c e n t of the f i e l d by count a r e s e m i - r i p e .  tomatoes  

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