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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 the Department of Bio-Resource Engineering We accept t h i s t hesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA August, 1977 © Eric Risch, 1977 In presenting t h i s thesis i n p a r t i a l f u l f i l m e n t of the requirement for an 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 that the Library s h a l l make i t f r e e l y a v ailable for reference and study. I further agree that permission for extensive copying of t h i s thesis for scholarly purposes may be granted by the Head of my Department or by h i s representa-t i v e s . I t . i s understood that copying or p u b l i c a t i o n of t h i s thesis for f i n a n c i a l gain s h a l l not be allowed without my written permission. Department of Bio-Resource Engineering The 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 i i . ABSTRACT The moisture l o s s and changes i n colour and firmness of tomatoes i n storage were investigated using a 4x4x5 f a c t o r i a l experiment. The f i r s t f a c t o r selected involved four delay times a f t e r harvest, before c o o l i n g . A f t e r harvest, the tomatoes were l e f t at room temperature for 0 hours, 10 hours, 20 hours and 30 hours, r e s p e c t i v e l y , before being cooled. The second f a c t o r involved four pre-storage treatments to reduce moisture l o s s : (a) wrapping the i n d i v i d u a l tomatoes i n polymeric f i l m , (b) waxing the calyx or stem ends only, with a f r u i t wax, (c) applying wax to the whole surfaces of i n d i v i d u a l f r u i t s , and (d) c o n t r o l , with no treatment. The t h i r d f a c t o r consisted of f i v e c o n t r o l l e d temperature and humidity storage environments : a) 10°C and 90% rh ( r e l a t i v e humidity); b) 15°C and 88% rh; c)10°C and 60% rh; d)15°C and 50% rh; and e)18°C and 40% rh. An a n a l y s i s of variance of the r e s u l t s showed that i n d i v i d u a l l y wrap-ping tomatoes i n polymeric f i l m resulted i n the lowest rates of weight, loss during the steady state. Also the r a t e of weight loss from a tomato was found to be influenced by the storage condition (combination e f f e c t of temperature and humidity), and the a i r flow c h a r a c t e r i s t i c s i n s i d e the storage chamber. i i i . TABLE OF CONTENTS PAGE TITLE PAGE ABSTRACT i i TABLE OF CONTENTS i i i LIST OF FIGURES AND PLATES y LIST OF TABLES v i NOMENCLATURE v i i i ACKNOWLEDGEMENTS x i INTRODUCTION 1 LITERATURE REVIEW - 2 Cooling 2 Treatments To Reduce Water Loss 4 Waxing of produce 4 Packaging i n polymeric f i l m s 4 Storage 5 Refrigerated storage 5 Controlled-atmosphere storage 6 Hypobaric storage 6 Colour And Firmness Changes 7 Tomato colour 8 Tomato firmness 8 MATERIALS AND METHODS 10 Experimental Design 10 Equipment Description 10 Experimental Procedure 16 Pre-storage t e s t s 16 Development of colour standards 16 Firmness scale 16 Moisture content and density determination 18 Test method 18 Post-storage tests 21 Investigation of e f f e c t of pressure on tomatoes 21 Saturation vapour pressure determination 22 THEORETICAL MODEL USED FOR ANALYSIS OF WATER LOSS 23 i v . TABLE OF CONTENTS (CONT'D) PAGE RESULTS, ANALYSES OF DATA AND DISCUSSION 29 Results of Pre-Storage Tests 29 Data Analyses and Discussion 29 Preliminary analyses 29 General models for analyses of data 34 Analysis of variance of weight loss 34 Regression analysis of weight loss 34 Regression analyses of colour and firmness changes 35 Colour change 35 Firmness change 37 Results and discussion of analysis of variance of weight loss 37 Results and discussion of regression analysis of weight loss 44 Results and discussion of regression analyses of colour and 59 firmness changes Co lour ochang euwi thit'ime i J I - 59 FirmhessaGhangenwdithitajne^and£Lwithicblour.r>ur 60 Results and Discussion of Post-Storage Tests 61 CONCLUSIONS 63 RECOMMENDATIONS 65 LITERATURE CITED 66 APPENDIX A 68 APPENDIX B 71 APPENDIX C 88 APPENDIX D 92 Federal and Industry Grading Standards for Greenhouse Tomatoes 93 L IST OF FIGURES AND PLATES FIGURE PAGE 1 S c h e m a t i c o f a i r c o n d i t i o n i n g s y s t em e m p l o y i n g 13 r e c i r c u l a t i o n o f e x c e s s a i r 2 S c h e m a t i c o f a i r c o n d i t i o n i n g s y s tem s e r v i n g 15 two chambers 3 T u r b u l e n t d i f f u s i o n bounda ry l a y e r on a f l a t s u r f a c e 25 4 P l o t o f c ummu l a t i v e w e i g h t l o s s p e r s u r f a c e a r e a 30 v s t i m e 5 P l o t o f t o t a l w e i g h t l o s s p e r s u r f a c e a r e a ( d u r i n g 33 s t e a d y s t a t e ) v s i n i t i a l w e i g h t 6 Change o f c o l o u r w i t h t i m e 36 7 P l o t o f r a t e o f w e i g h t l o s s pe r a r e a v s v a p o u r 51 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 o f R e y n o l d ' s number) 8 P l o t o f r a t e o f w e i g h t l o s s pe r a r e a v s v a p o u r 55 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 o f R e y n o l d \ s number) B]1 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 ) due t o 85 p r e - s t o r a g e t r e a t m e n t v s s t o r a g e c o n d i t i o n PLATE 1 Tomato c o l o u r g r a d i n g s t a n d a r d 17 2 E l e c t r o n M i c r o g r a p h s o f tomato s k i n s u r f a c e and s u b - 62 s u r f a c e l a y e r s v i . LIST OF TABLES TABLE P A G E 1 Summary of experimental design with C-T-S codes 11 2 La b e l l i n g codes for experimental tomatoes 20 3 Relationship between i n i t i a l weight of tomato and 32 t o t a l weight loss during 12 days of storage (data from run II) 4 Summary of r e s u l t s of analysis of variance of weight loss 38 5 The e f f e c t of cooling, treatment and storage on 40 weight loss 6 Average rates of water loss through surfaces of tomatoes 46 untreated and with surface treatments 7 Reynold's numbers and convective heat transfer coef- 47 f i c i e n t s f o r the various tomato storage chambers 8 Average tomato surface temperatures arid vapour pressure 50 d e f i c i t s between tomatoes and storage environment 9 Average rates of water loss through surfaces of tomatoes 53 untreated and with surface treatments (with correction for e f f e c t of Reynold's number of a i r flow i n storage chambers) 10 Vapour pressure d e f i c i t s and average rates of water loss 54 through tomato "multiple b a r r i e r s " (with correction for e f f e c t of Reynold's number of a i r flow (run II)) 11 Vapour pressure d e f i c i t s and average rates of water loss 55 through tomato "multiple b a r r i e r s " (with correction f o r e f f e c t of Reynold's number of a i r flow (run III)) v i i . 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 loss (run II) 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 loss (run III) 70 B. l Summary of re s u l t s s o f weight l o s s regression analysis(run II) 72 B.2 Summary of r e s u l t s of weight loss regression analysis(run III) 76 B.3 Summary of colour change regression analysis (run III) 80 B.4 Interaction e f f e c t of Treatment and Storage on the rate 83 of colour change B.5 Main e f f e c t s of Storage and Treatment on rate of colour 84 change B. 6 Summary of r e s u l t s of tomato firmness changes with time 86 (regression analysis) C. l Resinite f i l m WVTR determination 91 v i i i . NCMENCLATURE Description Units Surface are of tomato Simple regression constant (colour) m Simple regression constant (Firmness) Simple regression c o e f f i c i e n t (weight loss) Simple regression c o e f f i c i e n t (colour) Simple regression c o e f f i c i e n t (Firmness) Simple regression constant (weight loss) Diameter of tomato Mass d i f f u s i v i t y or d i f f u s i o n constant kg/(m .day) (day l ) (day l ) kg/m m m2/h Water vapour pressure gradient Factor f o r converting dimension of weight into area Convective heat transfer c o e f f i c i e n t kPa/m m W/(m 2.°C) Subscript representing interface i n t h e o r e t i c a l model for mass transf e r Mass tr a n s f e r c o e f f i c i e n t for water mov.ementefeacross*tomato skinr+ •.bouhdfar;y -layers Mass transf e r c o e f f i c i e n t f o r water movement acr-ossaboundary^layer - alone Mass transf e r c o e f f i c i e n t for water movement across p l a s t i c f i l m Mass transfer c o e f f i c i e n t f o r water movement across tomato skin Mass transfer c o e f f i c i e n t f o r water movement across " m u l t i p l e - b a r r i e r " kg/(m .day.kPa) kg/(m .day.kPa) kg/(m .day.kPa) kg/(m .day.kPa) kg/(m .day.kPa) 2 Mass transfer c o e f f i c i e n t f o r water kg/(m .day.kPa) movement across wax coating 2 o Thermal conductivity of heat and W.m/(m . C) mass transf e r medium (a i r ) Latent heat of vaporization kJ/kg 2 Mass transf e r per unit time, per unit kg/day.m of surface area P a r t i a l vapour pressure of water i n a i r stream kPa Saturation vapour pressure at temp. T kPa Equilibrium vapour pressure of kPa tomatoes (measured) Driving force (vapour pressure d e f i c i t ) kPa f o r mass transfer 3 Universal gas constant m .kPa/(kg.mole, Temperatur . e r a f c t s u B f i a c e of "multiple 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 (analysis of variance model) Time days 2* Weight l o s s per area during kg/m steady state Estimated mean moisture loss f o r kg (tomatoes (cummulative)) Estimated colour code f o r 5 tomatoes treated as a unit Estimated firmness code for 5 tomatoes treated as a unit Delay cooling f a c t o r , used i n analysis of variance model; i = l to 4 Pre-storage treatment factor used i n analysis of variance model; j = 1 -to* Storage condition f a c t o r ; analysis of variance model k = ltt"cH~5 Symbol Description ^ N / ? ^ = 2-way i n t e r a c t i o n e f f e c t s (o(|S>V)ijk = 3-way in t e r a c t i o n e f f e c t = Independent random normal • deviates, with mean zero and variance, ^ a = Density of a i r ^ = Density of tomato = Absolute v i s c o s i t y y ^ ^ - i ^ = True population mean weight 1-' loss per area Kinematic v i s c o s i t y x i . ACKNOWLEDGEMENTS I wish to express my appreciation to Professor E.L. Watson, of the Department of Bio-Resource Engineering, U n i v e r s i t y of B r i t i s h Columbia, under whose supervision t h i s study was undertaken, for h i s valuable advice and c r i -t i c i s m during the research, and for h i s guidance i n the writing of t h i s report. I am also g r a t e f u l to the other members of my graduate committee: Dr. R,;N. Bulley 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 research and for the review of t h i s report. I am e s p e c i a l l y indebted to Dr. G.W. Eaton (of the Department of Plant Science, U.B.C.), Dr. Kozak (of the Faculty of Forestry, U.B.C.) and to Mrs. Kathleen Hejjas (of the Faculty of Forestry, technician), for t h e i r a s s i s t -ance i n the s t a t i s t i c a l analysis and computer programming of the data. I thank Mr. J . Pehlke^ E l e c t r o n i c Technician of the Dept. of Bio-Resource Engineering, for h i s assistance i n understanding 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 Aire units used in. the research, and to Mrs. Pam G i l l , of the Dept. of Food Science, U.B.C, for her assistance i n the Electron Microscopy t e s t s . I am g r a t e f u l , too, to Mr. Ben Abdallah f o r h i s help f r e e l y given, from time to time, by way of discussion and c r i t i c i s m . The monetary support of the National Research Council of Canada through project financing, and the supply of experimental material (tomatoes) by the Western Green-house Co-operative of Burnaby,'B.C. are g r a t e f u l l y acknowledged. 1. INTRODUCTION A considerable amount of work has been done on the post-harvest phy-siology and storage c h a r a c t e r i s t i c s of both field-grown and greenhouse tomatoes (8,9,17,22,23,27). It i s known that the ripening (usually accompanied by changes i n colour towards increasing redness), and moisture loss from tomatoes during storage contribute to decreasing firmness (17/). The skin of the tomato f r u i t can be regarded as having f i l m properties. This assumption can thus lead to estimation of an equivalent water vapour transmission rate or "apparent" permeability of the skin. L i t t l e data are a v a i l a b l e concerning the f i l m properties of the tomato skin. This report deals with the i n v e s t i g a t i o n of the e f f e c t s of post-harvest treatment on the r e l a t i o n of water los s to the overa-111 q u a l i t y of greenhouse tomatoes held i n storage f o r up to nineteen days. The overall q u a l i t y of a tomato, as judged by a consumer, i s a psycho-physical conjugate of firmness (determined by touch), and colour ( j u d g e d i y i s u a l l y ) . The report also investigates the water vapour transmission properties of the tomato skin during the steady state period of weight l o s s . The steady state rate of weight l o s s i s reached a f t e r approximately 48 hours i n storage. LITERATURE REVIEW 2. Cooling It i s generally agreed that the mechanisms of spoilage 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 storage temperatures (3,31)*. It has been observed that prompt cooling and e f f e c t i v e temperature management tends to suppress undesirable softening, loss of moisture and sugars during the storage period. Wang and Wang (30) found that i f tomatoes are picked i n the "turning"** stage and i f pre-cooling and proper cold storage temperatures are employed, up to eighty percent (80%) of the product would be i n salable condition a f t e r three weeks or longer. Several methods have been employed to achieve pre-cooling (3,20). These are: (a) room cooling (b) forced-air cooling, (c) hydro-cooling, (d) hydrair-cooling, (e) vacuum co o l i n g , and (f) contact- or body-icing. Room cooling i s the simplest, and often the cheapest means of pre-cooling. cooling. It involves exposing the packed containers of produce to cold a i r i n a r e f r i g e r a t e d space. Since optimum a i r c i r c u l a t i o n i s not included i n the design, room cooling tends to be quite "slow, and thus may not be s a t i s f a c t o r y for highly perishable products. Forced-air cooling involves maintaining suitable a i r v e l o c i t i e s of cold a i r between, around and through packed containers stacked i n a r e l a t i v e l y smaller space compared to that required for room cooling. Cooling by t h i s 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 rather than over the container. Tomatoes and apples have been e f f e c t i v e l y cooled t h i s way (7,30). Numbers i n parentheses r e f e r to appended references. See Appendix D for d e f i n i t i o n s fof terms used i n tomato c l a s s i f i c a t i o n . 3. Hydro-cooling i s more rapid than forced-air cooling, and i s achieved by c i r c u l a t i n g c h i l l e d water around the produce. The good thermal contact between the cooling medium and the product r e s u l t s i n a rapid rate of cooling. However, for some products, the wetness af t e r cooling may cause mold or fungal growth. Hydrair-cooling i s an attempt to combine the advantages of forced-air cooling and hydro-cooling by spraying f i n e droplets of c h i l l e d water over and around the produce which i s usually placed on a moving conveyor b e l t . Bennett and Webb (3) have used t h i s method to cool peaches. For l e a f y products with r e l a t i v e l y large surface area-to-volume r a t i o s , vacuum cooling provides a very e f f e c t i v e means of cooling. At reduced pre-ssures , water b o i l s or evaporates at reduced temperatures. Vacuum cooling i s thus an evaporative cooling, and i t provides one of the most rapid and uniform rates of cooling a mass of produce, even i n containers (20). Contact i c i n g i s normally used for products which do not experience c h i l l i n g i n j u r y . The containers should also be made from material that i s not damaged by water or i c e . Cr.ushedticeais mmxeddwithothe pr-oduce i n . the con-taine r , -i--The-melting of the i c e removes the sensible and r e s p i r a t i o n heat from the produce. Wang and Wang (30) have developed a model to ,predict the cooling charac-t e r i s t i c s of farm produce i n deep bed. Checking the predicted cooling rates against cooling rates determined experimentally revealed some unaccountably large discrepancies. The cooling rates determined experimentally were much fas t e r than the cooling rates as predicted from the model. They explained the d i f f e r e n c e as caused by evaporation from the surface of the product during the cooling process. F r u i t s and vegetables with waxy surfaces normally experience much reduced evaporation (7,30) and thus there should be l i t t l e or no d i f f e r e n c e 4. between the predicted and actual cooling rates. The r e s u l t s of the work of Wang and Wang (30) confirmed t h i s postulation. Fockens and Meffert (7) found that the amount of water l o s t from h o r t i -c u l t u r a l products during pre-cooling v a r i e s inversely with the d i f f u s i o n a l resistance of the skin of the product. Thus products with low d i f f u s i o n a l resistance lose r e l a t i v e l y large amounts of water during pre-cooling, and v i c e versa. They also found that when the a i r v e l o c i t y was increased, the amount of water l o s s from products decreased. Treatments To Reduce Water Loss Waxing of produce It has been found that waxing reduces moisture loss from seme f r u i t s such as apples (11,19,26). Also, waxing fresh f r u i t s and vegetables enhances t h e i r appearance (11). Cold emulsions containing carnauba wax, p a r a f f i n s and sometimes shellac are being used on apples and pears packed i n Western-Canada and the United States (5). Not much work has been done on the a p p l i c a t i o n of wax on tomatoes. For some apple v a r i e t i e s i t has been found that the i n t e r n a l l e v e l s of carbon dioxide gas and ethylene reach higher l e v e l s when waxed and stored (19). Packaging i n polymeric films Polymeric films have been widely used i n packaging fresh produce (10,12,28). The primary aims i n using these packaging materials are: (a) to prevent or minimize moisture l o s s , (b) to protect against mechanical damage, and (c) to provide better appearance. Certain films can extend the s h e l f - l i f e of the product by modifying the gaseous composition of the atmosphere around the product, and creating a minia-ture "controlled-atmosphere storage" (28) . Selection of the polymeric f i l m i s based on i t s water vapour transmission properties (including anti-fogging), and i t s effectiveness as a b a r r i e r to gaseous d i f f u s i o n . Storage After produce has been pre-cooled and properly prepared f o r storage, a decision remains to be made concerning the type of storage f a c i l i t y to employ. For storage of fresh produce, three main types of storage have been t r i e d . These are: (a) Refrigerated storage, (b) Controlled atmosphere storage, and (c) Hypobaric storage. ( a > Re f-r i g era! t eld;cs t or ag e This involves the d i r e c t c o n t r o l of temperature combined with an i n -d i r e c t control of humidity. Several combinations of temperature and humidity have been t r i e d f o r the cold storage of tomatoes (5,9,17,22,23). The temp-erature most c i t e d i n the l i t e r a t u r e i s 10°C (50°F) for "f i r m - r i p e " tomatoes and 12.8 - 15.6°C (55 - 60°F) for "mature-green" tomatoes (5,9), These higher temperatures are required to prevent c h i l l i n g i n j u r y to the green f r u i t . "Mature-green" and "turning" tomatoes ripen slowly when held at tempera-tures between 10 - 12.8°C (50 - 55°F). The rate of colour change with some attendant softening increases as the,storage temperatures are increased to about 21.1°C (70°F) (5). Above 21.1°C, excessively rapid ripening and rapid t e x t u r a l break down with some o f f - f l a v o u r may occur (5). ] Very high humidities i n the storage space may be advantageous i n r e -ducing moisture loss from tomatoes. However, the environmental conditions should be co n t r o l l e d so that condensation on the surface of the stored produce does not occur. Working with Brussels sprouts, c e l e r y , Chinese cabbage and leeks at 0 - 1°C (32 - 34°F) , van den Berg and Lentz (4) found that storage at very high humidities, 98% - 100%, resulted i n generally reduced moisture l o s s , accompanied by a c r i s p e r , greener product than storage at lower humidi-t i e s . In t h i s p a r t i c u l a r t e s t , even surface condensation, r e s u l t i n g from the very high humidities did not appreciably increase decay, and a c t u a l l y further reduced weight l o s s . Controlled- atmosphere storage In a controlled-atmosphere (CA) storage, the gaseous composition of the storage chamber environment as well as the temperature are c o n t r o l l e d . The adjusted l e v e l s of oxygen arid carbon dioxide are optimized for each product to be stored. Parsons et a l . (23), found that tomatoes kept i n storage at oxygen l e v e l s as low as 3% and zero carbon dioxide resulted i n s i g n i f i c a n t l y better post-storage condition than those stored i n a i r . They found that carbon d i -oxide l e v e l s of 3 - 5 % resulted i n the tomatoes being more acid a f t e r r i p e -ning than those held i n carbon dibxide-free atmosphere. Hypobaric storage The pioneering work of T o l l e (27) and others have led to the development of a new concept i n the storage of fresh f r u i t s and vegetables which u t i l i z e s sub-normal atmospheric pressures i n conjunction with low temperatures and some of the p r i n c i p l e s of controlled-atmosphere storage. This system of storage i s termed Hypobaric Storage, and the sub-normal pressures are obtained with the aid of vacuum pumps. The system i s s t i l l i n the developmental stage, but i t holds great promise for the future. As i n the case of a l l f r u i t and vegetable storage, a key requirement for e f f e c t i v e hypobaric storage i s that the i n i t i a l q u a l i t y of the produce should be high. Tests conducted by T o l l e on the hypobaric storage of tomatoes gave some highly promising r e s u l t s . He found that the tomatoes retained t h e i r green colour longest at the lowest pressure, one-quarter (h) atmosphere, and that af t e r storage, a l l l o t s eventually ripened to equal red colour, with equally s a t i s f a c t o r y flavour when f u l l y r i p e . There are s t i l l some problems to be solved before t h i s new concept can enjoy wide-spread use i n the industry. Key among these are: (a) The r e s p i r a t i o n requirements under hypobaric pressures are unknown. Most r e s p i r a t i o n data have been obtained at normal atmospheric pressures. (b) The optimal storage humidities are not yet known. (c) The e f f e c t s of the d i f f e r e n t i a l release of v o l a t i l e s from produce i n t e r i o r s ' on'^their flavours are unknown. (d) The e f f e c t s of hypobaric pressures on the development of path-ogens, and on the biochemistry of the produce i t s e l f are r e l a -t i v e l y unexplored. (e) P o t e n t i a l c e l l u l a r damage i n the event of too rapid attainment or release of hypobaric pressures are also not known. Colour And Firmness Changes Tomatoes i n storage tend to undergo two major changes during ripening: (a) Colour change towards increasing redness characterized by marked lycopene synthesis and chlo r o p h y l l degradation. (b) Softening of the f r u i t caused by depolymerizati.on of pec t i c substances 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 so l s . Moisture loss also contributes to softening of the f r u i t s due to loss of t u r g i d i t y i n the c e l l s . 8. Tomato colour Colour i n foods i s generally a very d i f f i c u l t q u a l i t y factor to eva-luate 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 fac t that the development of measuring methods has presented unique problems with each product (25). Subjectively, tomato colour has been assessed by d i r e c t v i s u a l i n s -pection, and also with the aid of reference guides including standard colour plat e s , three dimensional models, colour hand books and colour d i c t i o n a r i e s (6,18,25) . The accuracy of subjective evaluation i s dependent upon several f a c t o r s , the p r i n c i p a l ones being (13,18): (a) Normality of observer v i s i o n (b) Observer fatigue (c) Colour uniformity of sample (d) Surface gloss (e) Size and shape of product (f) Internal c e l l structure (g) Sample environment including q u a l i t y and d i r e c t i o n of i l l u m i n a t i o n . There have been three major techniques f o r objective determination of tomato colour, v i s : (a) Chemical analysis method (b) Photo-electric t r i s t i m u l u s colorimetry (c) Transmittance or reflectance spectro photometric method. The reflectance technique has been u t i l i z e d by von Beckmann et a l . (2) to develop a tomato colour grader. Tomato firmness Work on measuring the firmness of tomatoes dates back some four decades, however, there.is no known non-destructive test for t h i s operation. 9. R e s e a r c h e r s have d e v e l o p e d p r e s s u r e t e s t e r s t o a i d i n m e a s u r i n g t h e f i r m n e s s 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 t o m a t u r i t y ( 8 , 1 3 , 1 4 ) . Hood and Webb (13) d e f i n e f i r m n e s s as t h e f o r c e n e c e s s a r y t o r u p t u r e t h e s u r f a c e o f a tomato f r u i t i n c l u d i n g t h e s k i n o r p e e l . U s i n g a c r o s s - h e a d speed o f 10 cm/min on 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 on tomato f i r m n e s s . These a r e howeve r , 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 each s i n g l e d e t e r m i n a t i o n o f f i r m n e s s , 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 - u s e d ; a l s o (and 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 c h i n d i a m e t e r was t e s t e d , g i v i n g r i s e t o t h e q u e s t i o n o f w h i c h s p o t wou ld be most r e p r e s e n t a t i v e o f t h e w h o l e t o m a t o . The most 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 d e v i c e t h a t s i m u l a t e s t h e " s q u e e z i n g " o f t omatoes by hand was d e v e l o p e d by K a t t a n ( 1 4 ) . T h i s i s t h e 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 o f t h e f r u i t b y a g i v e n f o r c e . The p r i n c i p l e o f o p e r a t i o n o f t h e f i r m - o - m e t e r i s t h e e x e r t i o n o f a u n i f o r m p r e s s u r e a round t h e f r u i t b y a c h a i n . The d e f o r m a t i o n o f t h e f r u i t i s measured a f t e r a p e r i o d o f t i m e (30 s econd s ) on an i n v e r s e s c a l e g r a -d u a t e d f r o m 0 t o 10. The f i r m e s t tomato r e a d s 0 and t h e s o f t e s t r e a d s 10 on t h e s c a l e . MATERIALS AND METHODS 10. Experimental Design. A 4x4x5 f a c t o r i a l experiment was used to investigate the e f f e c t s of (a) delay ( i . e . between harvest and cooling), (b) pre-storage treatment (in preparation f o r storage), and (c) storage condition (temperature and humi-di t y ) , on the storage l i f e of green house tomatoes. Storage l i f e was followed by measuring the rate of moisture loss and the changes i n f i r m -ness and colour of tomatoes when stored under co n t r o l l e d temperature and humidity. In many cases tomatoes do not go into controlled storage immediately af t e r harvesting. Delays may be as long as twenty-four hours. Four l e v e l s of delayed cooling were selected f o r the experiment. There were also 4 kinds of a f t e r - c o o l treatment and 5 combinations of temperature and humidity used. See Table 1 for summary of experimental design. Equipment Description. To provide the storage conditions, a Conviron Controlled Environment cabinet, model E8M, and two Aminco Aire u n i t s , models 4-5580 and 4-5460A were u t i l i z e d . The Conviron chamber was programmed to d e l i v e r conditioned a i r at 10°C (50 F) and 90% r e l a t ive humidity. This constituted storage condition n o . l . The Aminco Aire unit-; model 4-5580 with a manufacturer's l i s t capacity 3 of 28.32 m /miri (1000 c.f.m.) was attached to a chamber constructed from 6mm (%-inch) plywood with 10.2cm(4-i n ch) styrofoam i n s u l a t i o n . The inside dimensions were 1 m x 1 m (39 i n . x 39 in.) h o r i z o n t a l area, by 1.57 m(62 i n . ) • TABLE 1. SUMMARY OF EXPERIMENTAL DESIGN WITH C-T-S CODING (*) 11. FACTOR LEVELS A. COOLING 1. 20 - Hour Delay ( i . e . Delay between har- 2. 10 - Hour Delay vest and cooling) 3. 0 - Hour Delay ( i . e . Immediate Cooling) 4. 30 - Hour Delay (**) B. TREATMENT 1. Untreated (**) ( i . e . Pre-storage 2. Wrap i n Polymeric Film Treatment) 3. Calyx-End Only Waxed 4. Whole Skin Waxed. C. STORAGE CONDITION 1. 10°C (+0.5°C) : 90% rh (+2% rh ) ( i . e . Temp. and 2. 15°C (+0.5°C) : 88% (+2% ) humidity) 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 represents tomatoes which were immediately cooled a f t e r harvest; 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 ; and stored at 15°C and 50% rh. These represent various l e v e l s of the three factors considered as con t r o l or check on the other l e v e l s . 12. high. Two removable h o r i z o n t a l shelves made from nylon mesh, and 0.31 m (12 in.) apart were placed i n the chamber. The conditioned a i r at 15°C (59 F) and 88% rh was fed into the chamber through a rectangular a i r duct, 0.15 x 0.18 m (6 x 7 in) ins i d e dimensions, connected near the bottom of the r i g h t - s i d e wall of the chamber. The controlled environment i n t h i s chamber constituted storage condition no.2 To obtain a uniform upward movement of the a i r , a d i f f u s e r made from 3 mm ( ^ / s i n ) plywood with 5 mm ( 3/ 16 in) holes on 25 mm (1-in) centres was placed 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 bottom s h e l f . Using an aluminium gate type flow-divider, about 7 m /min (246 cfm ).o'f a i r was passed through the.chamber, and the remainder was r e -c i r c u l a t e d (see Figure 1 for schematic diagram). Using an a i r v e l o c i t y meter (Flowtronic model 55B1) and a propeller-type velometer, the bulk upward a i r flow was measured to be 6.4+0.5 m/min (21.1 +1.5 ft./min). Conditioned a i r at 10°C (50°F) and 60% rh from the second Aminco Aire unit was divided into two streams by a flow-divider. One of the a i r streams was re-heated with a thermostatically controlled space heater to 15°C (59°F) , with a r e l a t i v e humidity of 5 0 + 2 % . The a i r streams were then passed through two f l e x i b l e c i r c u l a r a i r ducts 0.15m (6 in) i n diameter and connected near the bottoms of the side walls of two identicallGhambe^samade'from 13 mm _ (h in)hplywpodoandn515mmi^(2 (dn)/astyrof oam i n s u l a t i o n . The ins i d e dimensions of the chambers were 0.81 x 0.89 m (32 x 35 in) by 1.09 m (43 in) high. Two removable h o r i z o n t a l shelves made from wire mesh, and 0.31 m (12 in) apart were placed i n each chamber. To e f f e c t a uniform upward movement of the conditioned a i r , a d i f f u s e r constructed as for the chamber attached to the f i r s t Aminco Aire u n i t , described above, was placed h o r i z o n t a l l y between the a i r i n l e t and the bottom shelf i n each chamber. The chamber with conditioned a i r at 10°C and 60% rh and that with a i r at 15°C (59°F) and 50% rh constituted storage conditions 3 and 4 re s p e c t i v e l y . 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 Aire unit (28.32mc/min')ain) B : Flow-divider C : Conditioned-air to controlled environment chamber D : By-pass for unused a i r (back to Aninco Aire unit) E : Controlled environment chamber, storage no. 2 F : Mixture of a i r streams C and D 14. through the two chambers attached to the Aminco Aire unit model 4^-5460A gave 3.1 + 0.5 m/min ( 10.2 +.1.5 ft./min) and 3.1 + 0.5 m/min (10.1 + 1.5 ft./min) for storage conditions 3 and 4, res p e c t i v e l y . This was less than the average v e l o c i t y of 5.9 m/min (19.4 ft./min) as suggested by the manufacturer's l i s t 3 capacity of 8.5 m /min (300 cfm) for the u n i t . (See Figure 2 for schematic diagram of u n i t ) . To simulate storage at room temperature and humidity, a storage was set up i n an air-conditioned room with temperature set at 18 + 1°C (64 + 2°F). The r e l a t i v e humidity i n t h i s room was influenced by the outside conditions and varied between 30% and 60%, giving a bulk average humidity of 40% during the test period. This environment constituted the storage condition no.5. The temperature inside each chamber was monitored by a YSI t e l e -thermometer model 47 and the r e l a t i v e humidity by a Phys-Chemical Research Corp. Humeter humidity sensor model 47-1072-9000. The YSI tele-thermometer was standardized against a copper-constantan thermocouple; and the Humeter was checked against a dew point hygrometer model 880. Both Humeter and dew point hygrometer were standardized against a saturated copper sulphate s o l u t i o n at 20°C (rh = 97.2%). To check chamber conditions before the storage tests were begun, the temperature and humidity i n each chamber were monitored for several days and recorded with a Rikendenshi recording potentiometer, model SP-H6V. As an ad d i t i o n a l check on the uniformity of temperature and humidity within the chambers, STgrhygrorithermpgraphsr^model 134882/46/1 were placed i n the chambers at c e r t a i n times. A pre-cooler was constructed from a table fan with four blades of 0 . 4m (18 in) diameter. This was used to blow 4.4°C (40°F) a i r through a c i r c u l a r p l a s t i c conduit attached to a perforated shipping container f u l l of tomatoes. During a t r i a l run, i t required two hours to reduce the average temperature of the tomatoes from 20°C (68°F) to 13.9°C (57°F) . SCHEMATIC OF AIR CONDITIONING SYSTEM SERVING TWO CHAMBERS. C B T> • 1 LEGEND 3 A:: Aminco Aire unit (8. 5Cmc^min?)iin) B : Flow-divider C : Conditioned-air to chamber D : Conditioned a i r incorporating reheat t H : Space heater & Thermostat E^: Controlled environment chamber, storage no. 3 E 0: Controlled environment chamber, storage no. 4 16. Experimental Procedure Pre-storage tests Development of colour standards Ten tomatoes, two each of colour c l a s s i f y i n g them as: a) mature green; b) turning; c) semi-ripe; d) f i r m - r i p e ; and e) t a b l e - r i p e , were selected f or the development of a scale, l i n e a r i n the amount of redness. On a scale of 1 to 5, the following designations were employed: the greenest mature tomatoes were given a colour code 1 the turning tomatoes were assigned colour code 2 the semi-ripe tomatoes were assigned colour code 3 the firm-ripe tomatoes were assigned colour code 4 the t a b l e - r i p e tomatoes were assigned colour code 5 Colour pictures were taken of each grade of tomato, and are shown on Plate 1. Firmness scale In order to keep the number of tomatoes used to a r e a l i s t i c value, and to permit following changes i n firmness index with time, the experimental design required a non-destructive firmness t e s t . Thus a conventional pressure tester could not be used. Instead, a firmness scale, as judged by holding the tomato i n the hand, was developed with the help of a panel of 5 judges i n the Department of Bio-Resource Engineering at U.B.C. Each judge i n turn was asked to place 240 tomatoes i n 5 groups of varying firmness. (The tomatoes i n each group were judged to have the same firmness). On a scale of 0 to 4, firmness was evaluated as : 0 represents the s o f t e s t tomato (unacceptable or unsalable i n the market pl a c e ) , and 4 represents the firmest tomato (as i n a t y p i c a l 17. Colour Code 3 Colour Code 4 Colour Code 5 18. mature green-to-turning tomato). Intermediate evaluations of 1, 2 and 3 represent trends of increasing firmness. In over eighty percent of the tomatoes thus graded the judges' evaluations agreed with those of the author. Moisture.content and.density determination The moisture content of a randomly selected sample of 5 tomatoes was determined by freeze-drying to constant-weight (after 3-4 days). The density was determined by weighing each of a random sample of 5 tomatoes i n a i r , and then re-weighing them while t o t a l l y submerged i n water at 4°C (39.2°F). The difference i n weights between that 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 density of the tomato. Test method Three experiments were done i n the period between August and November 1976, with each run involving 400rtbmajoesi.tomatoes. In the f i r s t run, 400 greenhouse tomatoes (cv. Vendor) were hand-picked from the Gipaanda Greenhouse i n Surrey, B.C. (8060 146 S t . ) . The f r u i t s were at stages of ripening ranging from "mature-green" to "firm-ripe". This group of 400 tomatoes was divided randomly into four subgroups of 100 tomatoes each. The tomatoes i n one subgroup were l a b e l l e d 201-300, and were placed immediately i n the pre-cooler at 4.4°C (40°F) and cooled from a f i e l d temperature of 20°C (68°F) to 13.9°C (57°F) i n 2 h. (Actually there was a delay of 2 to 4 h between harvest and placement i n the pre-cooler.'.. 'TMsswas the_time i t took to bring the experimental material from the farmftotithe laboratory) .. This constituted cooling procedure 3. After cooling, the 100 tomatoes i n t h i s subgroup were further subdivided 19. into four l o t s of 25 f r u i t s each. The f i r s t l o t (nos. 201 - 225) received no further treatment; the 25 f r u i t s i n the second l o t (nos. 226 - 250) were i n d i v i d u a l l y wrapped i n 0.55 m i l . p o l y v i n y l chloride f i l m (PVC - R e s i n i t e ) ; the 25 f r u i t s i n the t h i r d l o t (nos. 251 - 275) had t h e i r calyx ends only waxed with APL-LUSTER, obtained 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 area about 1 i n (2.5 cm) i n diameter. The fourth l o t (nos. 276 - 300) had t h e i r whole surfaces coated with the wax emulsion. After a p p l i c a t i o n (by brushing on), the wax dried i n 2 to 3 min. A l l the tomatoes i n t h i s subgroup (nos. 201 - 300) were then i n d i v i d u a l l y weighed (+ 0.01 g) on a Mettler Balance. Each l o t of 25 tomatoes was further divided into 5 sublots of 5 tomatoes each, and each sublot was placed i n one of the 5 storage conditions described e a r l i e r . The remaining three subgroups (each consisting of 100 tomatoes) were held for 10, 20 and 30 hours, r e s p e c t i v e l y , and then treated exactly as the f i r s t subgroup. See Tables 1 and 2 for a summary of a l l cooling-treatment-storage (C-T-S) regimes. After 48 h i n storage, the 400 tomatoes were removed one shelf at a time, and weighed. The shelves were then replaced i n t h e i r o r i g i n a l chambers on d i f f e r e n t shelf l e v e l s . The routine of weighing 400 tomatoes required about 3 h and was repeated every 48-hour periods. No p a r t i c u l a r order was followed i n the removal of the f r u i t from the various chambers. The second run of the experiment was performed i n September, 1976. In t h i s run also, the 400 tomatoes involved were hand-picked from the Gipaanda Greenhouse i n Surrey. It was run exactly as the f i r s t . The t h i r d run of the experiment was performed i n November, 1976. 20. TABLE 2. LABELLING CODES FOR EXPERIMENTAL TOMATOES 20-HOUR DELAY (COOLING NO.l) 10-HOUR DELAY (COOLING NO.2) STORAGE CONDITION PRE-STORAGE TREATMENT (*) PRE-STORAGE TREATMENT (*) 1 2 3 4 1 2 3 4 1. 10°C:90% 2. 15°C:88% 3. 10°C:60% 4. 15°C:50% 5. 18°C:40% 1-5. 26-30. 51-55 76-80 6-10 31-35 56-60 81-85 11-15 36-40 61-65 86-90 16-20 41-45 66-70 91-95 21-25 46-50 71-75 96-100 101-105 126-130 151-155 176-180 106-110 131-135 156-160 181-185 111-115 136-140 161-165 186-190 116-120 141-145 166-170 191-195 121-125 146-150 171-175 196-200 :  0-DELAY (IMMEDIATE) (COOLING NO.3) 39-HOUR DELAY (COOLING NO.4) STORAGE CONDITION - -PRE-STORAGE TREATMENT (*) PRE-STORAGE TREATMENT (*) 1 2 3 4 1 2 3 4 1. 10°C:90% 2. 15°C:88% 3. 10°C:60% 4. 15°C:50% 5. 18°C:40% 201-205 226-230 251-255 276-280 206-210 231-235 256-260 281-285 211-215 236-240 261-265 286-290 216-220 241-245 266-270 291-295 221-225 246-250 271-275 296-300 301-305 326-330 351-355 376-380 306-310 331-335 356-360 381-385 311-315 336-340 361-365 386-390 316-320 341-345 366-370 391-395 321-325 346-350 371-375 396-400 Pre-Storage Treatment 1 = Untreated Tomatoes; 2 = Tomatoes wrapped i n p l a s t i c ; 3 = Tomatoes with calyx ends only waxed; 4 = Tomatoes with whole skin surface waxed. 2 1 . The 400 tomatoes (cv. Vendor) required were picked from Seto Farms, Surrey, B.C. (17453 8th. Ave.). In t h i s run, the cooling procedures, the pre-storage treatments, and the storage conditions employed, were s i m i l a r to those i n runs one and two. In addition, as each tomato was weighed and reweighed a f t e r each 48 h i n storage, a colour code (1 to 5) was assigned by v i s u a l comparison with the colour photographs taken during the pre-storage t e s t s . Also, a firmness r a t i n g was assigned by applying gentle finger pressure to each tomato as previously described. As before, no p a r t i c u l a r order was followed i n the removal of f r u i t ofrom the various chambers for reweighing, etc. Post-storage tests on tomatoes Investigation of e f f e c t of Pressure on tomatoes To investigate the e f f e c t of applied pressure on the tomatoes (pressure applied during periodic weighing and evaluation of the firmness index) , i t was decided to,perform electron microscopy tests on the tomato surface and sub-surface c e l l u l a r l a y e r s . A sample of s i x tomatoes was very c a r e f u l l y picked and handled so that the skins were not touched or brushed. Aa2.2H7 kge(5 l b t ) , weight was placed on one of the c a r e f u l l y hand-picked tomatoes for 5 seconds to simulate extreme rough handling during successive weighings of the experimental tomatoes. Another c a r e f u l l y picked tomato was given a "low pressure rub" with the hand. A high moisture loss tomato and a low moisture loss tomato from the weight loss t e s t s were also included i n scanning electron microscopy examinations of cross-sections of surface t i s s u e , a few c e l l layers deep. For these t e s t s , samples of tomato tissue were excised from the f r u i t near the surface and immediately f i x e d with 2.5% glutaraldehyde i n 0.07 M phosphate buffer f o r 4 h at room temperature. The ti s s u e was further fixed with osmium textroxide (OsO.) i n 0.07 M phosphate buffer for one hour at room temperature, then dehydrated for 10 min at each stage of an ethanol series (50%, 70%, 80%,90% (twice) and 100% (twice)). The ethanol was then replaced using 10 min treatments with a s e r i e s of amyl acetate solutions (25%, 50%, 75% and 100% (twice)) and followed by c r i t i c a l point drying. The specimens were cemented on SEM stubs and coated with approximately 200 $ of a gold/palladium mixture before SEM examination. The magnifications used were up to 400 times. Saturation vapour pressure determination i The saturation vapour pressure of 4 tomatoes, one from each of the four pre-storage treatments, was determined with the aid of a dew point hygrometer. Each tomato was placed i n a sealed b o t t l e and l e f t for 24 h to reach e q u i l i -brium with the a i r i n the b o t t l e . At the end of the 24 h period, a sample of the equilibrium a i r i n the b o t t l e was c i r c u l a t e d by a small pump to the dew point sensor of the hygrometer and then back to the b o t t l e . Thus t h i s was a closed system. Knowing the temperature and the dew point of the a i r , the equilibrium r e l a t i v e humidity was read from a psychrometric chart. THEORETICAL MODEL UTILIZED FOR ANALYSIS OF MOISTURE LOSS 23. In a tomato of average shape, there i s a good c o r r e l a t i o n between the 2 "major diameter" and the weight of the tomato (2) (r = 0.9675). It has been assumed (in t h i s project) that the average tomato has a s p h e r i c i t y of close to one. Thus we can express the surface area of the tomato i n terms of i t s diameter, as: A = 7C D 2 1 We can also express the weight i n terms of the diameter as: W = £ (> D 3 2 Thus taking the 2 / 3 ^ d roots of each side of equn. 2, and multiplying through by a f a c t o r , f , y i e l d s : 2/3 TT 2/3 9 f. W = f . ( f e ) -D 3 If f i s selected such that: TT 2 / 3 - i r f. (-JT ^ ) = 7 1 = constant 3 a 2 / 3 2 then, f.W = 7TD = area 4 Tomatoes have a large moisture content (93% m.c, wet b a s i s ) . It was thus decided to consider as a phy s i c a l model, a wet material covered by a porous skin. Further assumptions made were: a) Below the porous skin are s p h e r i c a l c e l l s f i l l e d with water, with the i n t e r c e l l u l a r spaces f i l l e d with vapour. b) The water .yapour pressure i n the i n t e r c e l l u l a r spaces decreases gradually through the thickness of the skin and boundary layer from 98% ( i . e . -i n t e r c e l l u l a r vapour pressure = 0.98 xr-vap'our pressure of pure water at same temperature) j u s t i n s i d e of the skin , to..the value p of the storage 24. chamber a i r . c) Transport of moisture through the skin occurs i n the form of vapour ( 7 ) , with energy for evaporation being supplied by convective heat transfer from the storage chamber a i r . d) The v e l o c i t y and vapour pressure p r o f i l e s of the boundary layer are si m i l a r to those on a f l a t surface. See F i g . 3. Thus there i s a r e l a t i v e l y slow moving layer of f l u i d next to the surface which i s i n laminar flow. Between t h i s laminar sublayer and the main body of the turbulent stream there i s a t r a n s i t i o n region i n which the 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. This flow regime i s ref e r r e d to as the buffer layer. Within the laminar sublayer, i t i s assumed that only molecular d i f f u s i o n occurs. The rate of molecular d i f f u s i o n from the wetted surface through the laminar sublayer i s given by Fick's law as: D i f f u s i o n Rate = - (D /R T. ) Cdp /dy)- 5 v • s l r s J 1 D 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 related £ 0 the v temperature and pressure. In the buffer layer both molecular and eddy d i f f u s i o n are important contributors to the mass transfer process. In .the turbulent region, eddy d i f f u s i o n predominates-"- ^ . ...... The system of storage involving the c i r c u l a t i o n of conditioned a i r over and around tomatoes arranged i n a si n g l e layer on shelves can be regarded as a simultaneous heat and mass transfer operation. The tomatoes lose moisture by evaporation from the surfaces, with the latent heat of vaporization being supplied by the a i r . Thus i f the a i r and tomato surface are i n i t i a l l y at the same temperature, vaporization w i l l tend to lower the. temperature of the tomato surface. 25. FIGURE 3: TURBULENT DIFFUSION BOUNDARY LAYER ON A FLAT SURFACE (1) LEGEND L . S . L . Laminar Sublayer B r . L . Buffer Layer By .L . Boundary Layer T.R. Turbulent Region V Bulk ve loc i t y i n a i r stream a 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. This w i l l e s t a b l i s h a temperature gradient and heat w i l l be transferred to the tomato surface from the a i r . The tomato surface w i l l decrease i n temperature u n t i l a point i s reached where the heat transferred to the tomato j u s t balances the heat removed i n evaporation. The use of a wire and nylon mesh f o r the construction of shelves f o r the tomatoes (see section on equipment description) r e s u l t s i n a greater degree of turbulence i n the a i r flow than would normally be expected from the v o l u -metric flow rates alone (16). Thus the heat and mass transfer process occurs by convection. The convective heat and mass transfer c o e f f i c i e n t s are related through the following two equations given by Kre i t h (i6) Chapter 13: m /A = h MT - T )/E 6a s c a wb and m /A ==K.i7(p * - p ) 6b s s a (For d e f i n i t i o n of terms used i n equations 6a and 6b, see table on nomencla-ture) . The convective heat transfer c o e f f i c i e n t , h, depends on the v e l o c i t y (V), density ( ^ ) , v i s c o s i t y ( / O and thermal conductivity (k^) of the f l u i d medium and also on some c h a r a c t e r i s t i c dimension, D, of the heat transfer sur-face. For a sp h e r i c a l body, and with a i r flow rates giving a Reynold's num-ber (Re = VD ^  /y-t) between 25 and 100 000, the heat t r a n s f e r c o e f f i c i e n t i s given by Kre i t h (16) chapter 9 as: hv. = 0.37 ( R e ) 0 , 6 k,/D 7 c t Thus solving equation 7 f o r h^. and : s u b s t i t u t i n g into equation 6a, T ^ can be found, knowing the rate of weight loss per area. (The rate of weight los s per area i s calculated from d i r e c t measurements). 27. The mass transfer c o e f f i c i e n t as determined from equation 6b i s a function 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), density ( ^ ) , and v i s c o s i t y (f* ) of the f l u i d , and also, of some c h a r a c t e r i s t i c dimension, D, of the mass transfer surface. It i s assumed that within a temperature v a r i a t i o n of 10 C°,the v i s c o s i t y and density of a i r do not vary appreciably (e.g. at 10°C \/* = 0.064 kg/(m.h ), = 1.29 kg/m3 ; at 20°C :yu=» 0.066 kg/(m.h ), ^ = 1.25 kg/m ). Thus f or a given temperature and pressure of a i r , the mass transfer c o e f f i c i e n t f o r moisture loss from tomatoes, as ca l c u -lated by equation 6b depends only on the a i r v e l o c i t y . The degree of turbu-lence i n the a i r : f l o w may also a f f e c t the mass transfer c o e f f i c i e n t . Knowing the wet bulb temperature, T ^ , from equation 6a, the water vapour pressure at the tomato surface, p '*, can be calculated from steam tables; and the mass s t r a n s f e r c o e f f i c i e n t , K, can be calculated by d i r e c t s u b s t i t u t i o n i n t o equation 6b. The mass transfer c o e f f i c i e n t , K, can also be expressed i n dimensionless form as the Sherwood number, which i s re l a t e d to the Reynold number and to the Schmidt number by the following equation (31).:^ Sh = 0.023 ( R e ) 0 ' 8 3 ( S c ) 0 ' 6 7 8 where : Sherwood number, Sh = KRTD/D 9a v Reynold number, Re = ^ VDA^ 9b Schmidt number, Sc = /*/^D^ '9c For a given heat and mass transfer medium (e.g. a i r ) at a given temperature and pressure, the Schmidt number i s constant. Therefore, from equations;. 8 and 9 (a,b,c): K oC ( R e ) 0 , 8 3 10, 2 8 . 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 ( to mois ture l o s s ) made up of the tomato s k i n , the p l a s t i c f i l m and the wax coa t ing can be regarded as a sum of conductances i n s e r i e s . Thus the f o l l o w i n g r e l a t i o n ho lds : K _ 1 = K " 1 + K T 1 + ¥ . '} + K _ 1 11 t sk by p i wc i X 29. RESULTS, ANALYSES OF DATA AND DISCUSSION. Results of Pre-Storage Tests: The moisture content of the tomatoes, as determined by freeze-drying to constant weight was 93.0 + 0.5% (wet b a s i s ) . The density of the tomatoes was found to be 1.0.1 gram per cubic centimetre (1010 kilogram per cubic metre). • Data Analyses and Discussion: Due to the mass of information involved, the o r i g i n a l data on weight loss and changes i n colour and firmness have been compiled i n a separate volume and f i l e d i n the General O f f i c e of the Department of Bio-Resource Engineering, U.B.C. Vancouver, Canada. Preliminary analyses The cummulative weight losses per unit of surface area were plotted against time for seven sets of r e s u l t s selected at random ( i . e . plots for 35 i n d i v i d u a l tomatoes). Figure 4 shows the plot for one set of r e s u l t s . An inspection of the plots showed that i n each case, there was a r e l a t i v e l y large weight loss per area between the s t a r t of the experiment, and the end of the f i r s t period ( i . e . between 0 and 2 days). This large weight loss could be a t t r i b u t e d to the transient nature of the f i r s t period, during which the heat and mass transfer are not yet s t a b i l i z e d . This transient process i s not analysed i n t h i s report. Between the second and eighth weighings ( i . e . from 2 to 14 days) , the .cummulative -weight los s per unit of surface area was l i n e a r with time. Between the eighth and tenth weighings, the rate of weight 30. FIGURE 4 PLOT OF CUMMULATIVE WEIGHT LOSS PER SURFACE AREA ^ O J M E ^ ^ k 1 u Q) Pu O-SS o l—l 4-1 rS 60 •a; '—s •a) '§ CN 60 > • H 4-1 cd CJ 0.80 0.60 0.40 0.20 0.10 0T00: + o LEGEND Tomato # 206 207 208 209 210 o o o 4-X o 2 4 6 8 10 12 14 16 18 Time (days) l o s s per surface area was seen to decrease s l i g h t l y . The steady state condi-t i o n to be analysed was thus selected to occur between period two and period eight ( i . e . from 2 to 14 days, f o r a t o t a l of 12 days). There were seen to be wide v a r i a t i o n s between the rates of moisture loss from i n d i v i d u a l tomatoes with the same C-T-S combination. No explanation for t h i s v a r i a t i o n can be offered. It i s probably related to 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 also to d i f f e r e n c e s . i n maturity of the tomatoes used i n the experiment. It i s noted that tomatoes entering storage at apparently the same stage of ripening were found to ripen at d i f f e r e n t rates. To determine the e f f e c t of the i n i t i a l weight (or siz e ) . o f a tomato on i t s rate of weight l o s s , 10 untreated tomatoes ( i . e . non-waxed and not wrapped i n p l a s t i c film) were selected at random from one experiment, and the t o t a l change i n weight per unit area during the steady state period were plotted against the i n i t i a l weights. (See Table 3, and Figure 5). The c o e f f i c i e n t of determination beteweensweigh'tsloss per unit of surface area and i n i t i a l weight was found to be 0.15, thus i n d i c a t i n g that the i n i t i a l weight of a tomato did not a f f e c t i t s rate of weight l o s s . It was thus decided that an analysis of variance test of the mean weight losses per area during the steady state would e f f e c t i v e l y reveal any differences between the various C-T-S combinations. For the two successful runs (during the f i r s t run there was a mal-functioning of one of the a i r conditioning units leading to the loss of 40 percent of the tomatoes), a fo r t r a n computer program was written to calculate the t o t a l weight loss per unit surface area during storage periods two to eight ( i . e . during the steady state period of weight l o s s ) . Missing data (due to some tomatoes having developed Rhizopus and P e n i c i l l i u m r o t before the eight weighing) were generated on the basis of the e a r l i e r weighings, and on the further assumption of l i n e a r i t y of weight loss per area with time. (About 32. TABLE 3 RELATIONSHIP BETWEEN INITIAL WEIGHT OF TOMATO AND TOTAL WEIGHT LOSS DURING 12 DAYS OF STORAGE (DATA FROM RUN II) Tomato No. I n i t i a l Weight Total Weight Loss per Area During 12 Days ( k 8 ) • (kg/m2) 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 ( 3 3 . F I G U R E 5 P L O T OF T O T A L W E I G H T L O S S P E R S U R F A C E A R E A ' '(-DTJRM^ J <vs^ I N I T I A L W E I G H T . L E G E N D •TomatoSriumbers appear beside points CTr" 2 ^= 0 . 1 5 4-) rt ' r t CD .5 O rt cu CD o 14-1 CN 3 c/i <D P. cn cn O 60 •rl rt •u o H 60 0 . 4 0 EL 0 . 3 0 0 . 2 0 0 . 1 0 0 . 0 0 2 1 8 0 1 6 1 2 4 2C;5 2 1 0 7 1 0 1 3 0 7 2 0 1 0 . 0 8 0 . 1 0 0 . 1 2 0 . 1 4 0 . 1 6 0 . 1 8 I n i t i a l Weight of Tomato (kg) 34. 5 percent of the tomatoes used i n the experiments developed the spoilage described above, giving r i s e to missing data). An analysis of variance of the mean weight losses was done using MFAV, a multiple factor analysis of variance program-from the U.B.C. computing system. General models for analyses of data Analysis of variance of weight loss The t o t a l steady state weight losses per unit of surface area were analysed using the following s t a t i s t i c a l model: 4x4x5 f a c t o r i a l experiment: i j k v / i j k i • 1 kk i j i j -t- i k h- jk ' i j k IK. ' x + 6 . . , ^ k v , 12 i j k v (See table on nomenclature for d e f i n i t i o n s of terms used i n equation 12). Regression analysis of weight loss Treating the f i v e tomatoes i n each group ( i . e . each C-T-S combination) as a u n i t , the following model was u t i l i z e d i n a simple regression analysis of the cummulative weight loss per unit of surface area, with time i n storage: Y = b + b. XtC 13 o 1 In equation 13, b Q i s the intercept on the y-axis, and gives the " t h e o r e t i c a l " value of the weight loss per unit of surface area at the s t a r t of the experi-ment. Since we are analysing only the "steady s t a t e " weight l o s s , the i n t e r -cept can be neglected and b Q drops out of the equation which thus becomes: Y = b X 13a (See table on nomenclature for d e f i n i t i o n s of terms used i n equations 13 and 13a). The U.B.C. computer program TRIP was employed i n the regression analysis of weight loss per surface area, versus time for each set of r e s u l t s . The 35 regression c o e f f i c i e n t , b, has units of kilogram per square metre, per day (kh/(m 2.d)). Regression analysis of colour and firmness changes  Colour change An i n i t i a l inspection of the colour change data obtained from the study showed that i n over 70 percent of a l l the tomatoes, the maximum of 5 on the colour scale was reached a f t e r only 5 readings ( i . e . 10 days). After 6 readings, the number of tomatoes with the maximum colour r a t i n g was over 85%. It was thus decided to perform a regression analysis of colour change with time, u t i l i z i n g only the f i r s t 5 readings. A preliminary analysis, treating the 5 tomatoes i n each cooling-treatment-storage combination as a single unit ( i . e . taking the average periodic colour reading)yyielded a l i n e a r r e l a t i o n s h i p 2 between colour and time, with an r of 0.93, (See Eigure 6). Using the U.B.C. computer program TRIP (computation i s by method of lea s t squares), a simple regression of colour on time was generated for each C-T-S combination for the f i r s t f i v e readings. The model used for the colour regression with time i s given by: Y c " ac + b c x 1 4 (See table on nomenclature for explanation of terms used i n eq. 14) FIGURE 6 CHANGE OF COLOUR WITH TIME (RUN III) 36. Ji L 2 ii Time (days) Plot f o r tomatoes with C-T-S code: 211 Y = 1.75 + 0.29 X ( r 2 = 0.93) c 37. "" firmness change As i n the case of colour change, the f i v e tomatoes i n each C-T-S combination were treated as a single unit by deriving an average firmness code f o r each period. The average firmness change was analysed according to the model: YF = *F + V 15 (See table on nomenclature f o r explanation of terms used i n eq.-15) The U.B.C. computer program TRIP was used i n the simple regression analysis of firmness with time, f o r a l l the data. To investigate the c o r r e l a t i o n between the firmness and the colour of the tomatoes, the f i r s t f i v e p e r i o d i c colour and firmness codes were analysed. Results and discussion of analysis of variance of weight loss Table 4 gives a summary of the weight loss analysis of variance r e s u l t s . The notations II and III represent the 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 calculated which gives an i n d i c a t i o n of i t s r e l a t i v e contribution, 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 (rate of weight l o s s ) . The analysis of variance showed that the cooling procedure ( i . e . delay a f t e r harvest before cooling) employed did not s i g n i f i c a n t l y a f f e c t the steady state rate of weight loss from the 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 Degrees of Sum of squares (II) Sum of squares (III) v a r i a t i o n freedom (percent of t o t a l (percent of t o t a l sum of squares) sum of squares) Cooling (C) Treatment (T) Storage (S) 3 3 4 0.79 29.01 (**) 30.21 (**) 0.05 42.01 (**) 32.18 (**) C x T C x S T x S 9 12 12 0.64 1.03 2.31 (*) 00/39 0.58 5.66 (**) C x T x S Error 36 320 2.50 33.51 2.53 16.59 Tot a l (***) 399 100.00 = 8.01 100.00 = 105.06 Highly s i g n i f i c a n t (P<0.01) S i g n i f i c a n t (P<0.05) To obtain the mean square deviation due to any source of v a r i a t i o n divide:the percent sum-of squares by the degrees of freedom, then M u x . x t - x y j * — " . stun, ui squares J V tors • • , • . ; • ' . multiply„the intermediate value by the t o t a l ( i . e . 8.01 or 105.06) and divide by 100. e.g. For run I I , Cooling f a c t o r : Mean square = (f(0779/3<) x^8 i00") /100. =•.0.021 39. Range Test on t h i s factor showed no differences (P>0.05) among the four l e v e l s . The e f f e c t of the pre-storage treatment on the steady state rate of weight loss from the tomatoes was found to be highly s i g n i f i c a n t (P<0.01). The tomatoes wrapped i n polymeric f i l m gave the lowest weight l o s s , followed, i n reverse order of magnitude of weight l o s s , by those tomatoes whose surfaces 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 untreated tomatoes experienced, as expected, the highest rates of steady state weight l o s s . Table 5 shows the r e s u l t s of a Duncan's M u l t i p l e Range Test performed on the e f f e c t of the pre-storage treatment f a c t o r , and also the mean weight los s per area f o r the duration of the steady state period. Of the f i v e combinations of temperature and humidity used for storage, condition h'o.l (10°C and 90% ,-ch,)hum ) resulted i n s i g n i f i c a n t l y (P<0.01) lower rate of weight loss (and thus the best storage) than any of the other four. The m u l t i p l e range t e s t could not detect any s i g n i f i c a n t d i f f e r e n c e between the e f f e c t of storage at 15°C and 88% rh and 10°C and 60% rh However, these, as a group, were found to r e s u l t i n s i g n i f i c a n t l y (P<.0.01) lower weight los s than the remaining two storage conditions (15°C and 50% rh and 18°C and 40% rh ). For the r e s u l t s of run I I , the Duncan's M u l t i p l e Range Test could not detect any s i g n i f i c a n t d i f f e r e n c e between storage condi-tions r.c„4 and r>.3«5. In run I I I , storage condition no.4 (15°C and 50% rh" ) was found to y i e l d s i g n i f i c a n t l y (P< 0.01) lower weight loss per unit of sur-face area than storage at 18°C and 40% rhh. None of the 2-f actor i n t e r a c t i o n s involving cooling had any signii-f i c a n t e f f e c t on the rate of weight loss per unit of surface area of tomato. The 2-way i n t e r a c t i o n of the treatment and storage factors was found to be 40. TABLE 5 THE EFFECT OF COOLING, TREATMENT AND STORAGE ON WEIGHT LOSS (a) Cooling Factor Mean t o t a l weight loss/area (*) (kg An2) Time Delay Run II Run III 1. 20-hour delay 0.22 (a) 0.70 (b) 2. 10-hour delay 0.24 (a) 0.71 (b) 3. "0"-edlay 0.24 (a) 0.72 (b) 4. 30-hour delay 0.21 (a) 0.73 (b) * Average of 100 measurements (b) Pre-Storage Treatment Mean t o t a l weight loss/area (*) (kg/m2) Treatment Run II Run III 1. Untreated 0.32 (d) 1.10 (h) 2. Wrapped i n p l a s t i c f i l m 0.12 (a) 0.25 (e) 3. Calyx end waxed 0.27 (c) 0.95 (g) 4. Whole surface waxed 0.19 (b) 0.55 (f) Average of 100 measurements. Responses followed by d i f f e r e n t l e t t e r s are 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 (CONT'D) (c) Storage Condition Mean t o t a l weight loss/area * (kg/m2) Temperature: Humidity Run II Run III 1. 10°C 90% rh 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 followed by d i f f e r e n t l e t t e r s are 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) 42. s i g n i f i c a n t (P<0.05 for run I I , and P<0.01 for run III) i n i t s e f f e c t on the rate of weight l o s s . The i n t e r p r e t a t i o n of the s i g n i f i c a n c e of the 2-factor i n t e r a c t i o n i s that the differences between the responses ( i . e . rate of weight loss) to one f a c t o r , vary with the l e v e l of the second f a c t o r , where responses are measured over a l l l e v e l s of the second f a c t o r . In other words, the rate of weight loss from a tomato i n a p a r t i c u l a r storage environ-ment depends on the type of pre-storage treatment i t was subjected to. The 3-factor i n t e r a c t i o n involving the cooling, treatment, and the storage environment was not found to be s i g n i f i c a n t i n i t s e f f e c t on the rate of weight l o s s . Tables A . l and A.2 give the summary for the mean weight losses per uni t of surface area f o r a l l the fa c t o r s and t h e i r i n t e r a c t i o n s , and also the r e s u l t s of the Duncan's Mult i p l e Range Tests. Comparing the figures f o r runs II and I I I , i t i s seen that run I I I r e s u l t e d i n cons i s t e n t l y higher (<"*-3 times) weight losses for a l l the f a c t o r s . The reason for t h i s i s not f u l l y understood. It i s suggested that the tomatoes, even though they are of the same v a r i e t y , may have had some inherent v a r i a b i l i t y due to the fac t that they sere obtained from two d i f f e r e n t farmers at two d i f f e r e n t times. Comparison of the r e s u l t s of mean weight losses f o r runs II and III also show that i n some instances (e.g. the 2-factor i n t e r a c t i o n between the pre-storage treatment and the storage 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 to the f a c t o r s . Also, the multiple range te s t s did not give f u l l y consistent r e s u l t s i n a l l cases. Some of these inconsistencies may have arisen from lack of s u f f i c i e n t data. I t should :c. be pointed out that 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 to mean a v e r d i c t of "not proven". T o r e m e d y t h ± s ^ m o r e t e g t s ^ have to be performed with possible modifications. Nevertheless, on the whole, the trends of the e f f e c t s of the various 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 consistent between the two runs. On the question of whether or not the rate of moisture loss from a tomato occurs at d i f f e r e n t i a l rates across the various regions on the ski n , the r e s u l t s of the analysis of variance show some quite i n t e r e s t i n g trends. In the second run, "untreated" ( i . e . "unwaxed", non " p l a s t i c wrapped") toma-2 toes had a mean steady state moisture loss per surface area of 0.32 kg/m under a l l conditions. T o t a l l y waxing the tomatoes cut t h i s down to 2 2 0.19 kg/m , i . e . a drop of 0.13 kg/m . Waxing the calyx-ends only, resulted 2 i n a drop of 0.05 ( i . e . from 0.32 to 0.27) kg/m . Thus i t can be deduced that the calyx end accounts for 0.05/0.13 of the change i n moisture loss ( i . e . over 38 per cent) a t t r i b u t a b l e to waxing of the tomato. In other words, the calyx-end accounts for over 38 per cent of the moisture loss per surface area. Since the wax i n the calyx region covers l e s s than 10 per cent of the t o t a l surface, i t follows that there i s a disproportionately large rate of moisture loss through the skin i n the calyx end. A s i m i l a r analysis of the r e s u l t s of the t h i r d run showed the calyx region accounting f o r over 27 per cent ( i . e . 0.15/0.55) of the change i n moisture los s between "treated" and "untreated" tomatoes. 44. Results and discussion of regression analysis of weight loss The r e l a t i o n s h i p between the weight los s per unit of surface area, and time of storage (during steady state period) as determined by regression analysis i s summarized i n tables B.l and B.2 (Appendix B). Comparing : m /A = K(p * - p ) 6b S S 3 -and Y = bX; 13a i t i s evident that b = m /A = K(p * - p ) 13b s s r a Thus, knowing b from the.regression analysis r e s u l t s , the mass transf e r c o e f f i c i e n t of the tomato skin plus i t s covering of wax layer or p l a s t i c f i l m (as the case may be), plus the boundary layer, can be calculated from know-ledge of the water vapour pressure d e f i c i t between the inner surface of the "m u l t i p l e - b a r r i e r " and the a i r i n the storage chamber.. Since the d i f f u s i o n a l resistance of a tomato i s a function of i t s pre-storage treatment ( i . e . treatment to reduce water l o s s ) , the mass transfer 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 " are determined by handling the tomatoes i n each treatment separately. As was shown from the r e s u l t s of the analysis of variance of the mean rates of weight los s per area, the four cooling pro-cedures do not a f f e c t the steady state rate of water l o s s . Thus for each storage condition, the four values obtained f o r the regression c o e f f i c i e n t , b ( i . e . rate of weight los s per surface area), can be averaged to represent the rate of weight los s per area of a l l tomatoes with a p a r t i c u l a r treatment and stored at a p a r t i c u l a r temperature and humidity. As an example, f or the Run I I , the 20 untreated tomatoes i n storage condition no. 1 (10 UC, 90% rh ) have an average rate of weight los s per unit of surface area of 45. 2 0.015 kg/(m .d) (S.D. = 0.001). This i s the average of the four slopes, b, of the regression l i n e s corresponding to C-T-S codes 111, 211, 311 and 411, as shown i n Table B . l . Similar c a l c u l a t i o n s were performed for a l l the samples and the r e s u l t s are summarized i n Table 6. It i s r e c a l l e d (See section on t h e o r e t i c a l model) that tomatoes i n storage undergo simultaneous heat and mass transfer. Both the convective heat and mass transfe r c o e f f i c i e n t s are functions of the Reynold's number of air-flow. From the design of t h i s experiment and the data obtained, the Reynold's number of a i r flow and the convective heat transfer c o e f f i c i e n t must be deter-mined before the mass transfer c o e f f i c i e n t can be calculated. Sample c a l c u l a t i o n of Reynold's number (Re) and Heat Transfer C o e f f i c i e n t (h ) . ; • C__ In the f i r s t storage chamber (10°C, 90% r h ) , the bulk v e l o c i t y of a i r flow i s 0.12 + 0.03 m/s. An average tomato diameter of 0.08 m (3 in) have been decided upon f o r the present c a l c u l a t i o n s . The kinematic v i s c o s i t y , "V = 0.0143 x 10~ 3 m2/s Re = V.D/y = (0.12 x 0.08)/0.0143 x 10" 3 = 670 k f = 0.0249 W.m/(m .°C) for a i r at lOoC. 0 6 From equation 7 : h c = 0.37 (Re) ' k f/D = 0.37 x (670) 0* 6 x 0.0249/0.08 = 5.7 W/(m 2.°C). Similar c a l c u l a t i o n s f or the other storage conditions are reported i n Table 7. Since storage 5 (18°C, 40% rh) did not have any directed a i r movement (See section 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 could not be measured TABLE 6 AVERAGE RATES OF WATER.JLOSS THROUGH SURF/ACES (^OF TOMATOES UNTREATED AND WITH SURFACE TREATMENTS Storage Condition Average rate of water loss per area calculated from tables B.l and B.2 22 (kg/i(m ;:.day))* Untreated Tomatoes. Samples p l a s t i c Wrapped i n f i l m . Samples with calyx-ends waxed. Samples with whole surface waxed. Run II Run III Run II Run III Run II Run I I I Run II 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 with s i m i l a r treatment and storage combination. TABLE 7 REYNOLD'S NUMBERS AND CONVECTIVE HEAT TRANSFER COEFFICIENTS FOR THE VARIOUS TOMATO STORAGE CHAMBERS a Storage Condition Air V e l o c i t y inside s t o r -age chamber V (m/s) Cha r a c t e r i s t i c dimension of heat transfer surface, D Kinematic v i s c o s i t y v = (m2/s) x 10 3 Thermal Con-d u c t i v i t y of a i r , (W.m/(m 2.°C)) Reynold's number Re = V.D/y Convective heat t r a n s f e r c o e f f i c i e n t h=0.37(Re)°' 6k f/D (W/(m 2.°C)) 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 storage condition no.5 was dropped from further analysis. Knowing the average rates of weight loss per unit of surface area, m /A, and the average convective heat transfer 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 surface temperatures i n the various storage chambers can be calculated from equation 6a. (see section on theore-t i c a l model). The vapour pressure d e f i c i t s between the tomatoes and the storage environments can be determined after the surface temperatures are established. Sample C a l c u l a t i o n of Tomato Surface Temperature and Vapour Pressure D e f i c i t For storage no.l and during Run II : mg/A = 0.015 kg/(irm2.dd}.; = 6 - 2 5 x 1 0 ~ 4 kg/(m2.h) h =5.72 W/(m 2.°C) (from table 7) c T = 10°C a L = 2477.7 kJ/kg (from steam tables) Thus from : m /A = h ,(T - T , )/L s c a wb 6.25 x 10~ 4 = 5 72 - J L _ f 1 0 ° C - T w b > kg k J 2 u * _.2 o„ T x 3-6 W.h m -h m-."C 2477.7 k j Therefore 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 determination (post-storage t e s t ) , the water vapour pressure at the tomato surface i s 0.98 x vapour pressure of pure water at the same temperature. 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 Similar ca lcula t ions 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 discussion of weight loss analysis of variance) , the tomatoes used i n Run I I I underwent consis tent ly higher rates of weight loss (^3 times those for Run I I ) . This resulted i n the tomato surface temperatures i n Run I I I being consis tent ly lower than the corres-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 lo t t i ng the average rates of weight loss per area for each storage condi t ion 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 coeff ic ient of the tomato "mul t ip le -bar r ie r" . The physical model u t i l i z e d infers that there should be a zero intercept on the v e r t i c a l ax 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 loss ( i . e . no mass t ransfer ) . In the ac tual p lo ts (see Eig*nr.e» 11) , i t was found that for any pre-storage treatmentj there could not be a single 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 Storage Condition Run II-Tomato Surface Temperature, T , wb °C Vapour Pressure D e f i c i t kPa Run Tomato Surface Temperature, T , WD °C III Vapour Pressure D e f i c i t kPa 1. 10°C:90% r.h. 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 51. PLOT OF RATE OF WEIGHT LOSS PER AREA vs' VAPOUR PRESSURE DEFICITS (BEFORE CORRECTION FOR EFFECT OF REYNOLD'S NUMBER) LEGEND 0.12 0.10 0.08 0.06 0.04 0.02 0.00 0.0 RUN II m Untreated A Wrapped in plastic film o Calyx end waxed Whole skin waxed R U N III • Untreated + Wrapped in plastic film o Calyx'end waxed x Whole skin waxed a D • • JL + o 0..V2 0.4 0.6 Vapour pressure d e f i c i t , (kPa ) 0.8 52. predict the rate of weight loss per area f o r a l l the storage conditions. As described e a r l i e r , the mass transfer c o e f f i c i e n t , K, i s a function of the Reynold's number, i . e . K c<- ( R e ) 0 , 8 3 10 als o , m /A = K (ps - p ) S 3. i . e . m /A «c K s Therefore, ™ S / A °^ ( R e ) 0 ' 8 3 Selecting the Reynold's number of a i r flow inside one storage chamber as a basis f o r comparison, fhe rates of weight loss per surface area i n the other chambers can be adjusted to account f o r the e f f e c t of a i r flow rates. The Reynold's number i n the storage condition no.l (10°C, 90% r.h.) has been used as a basis f o r comparison i n t h i s report. Sample Ca l c u l a t i o n of adjusted rates of weight loss per surface area: The Reynold's number i n storage condition 1 = 671.33 (table 7) The Reynold's number i n storage condition 2 = 594.59. Therefore^thesad'justedrrate of weight loss per area of tomatoes stored at 15°C and 88% r e l . hum. i s given, f o r Run II r e s u l t s , by : (m/A) = (m/A) x (671.33/594.59)°' 8 3 s adjusted s old (m /A) ,. _ . = 0.024 x (671.33/594.59) 0 , 8 3 s adjusted = 0.027 kg/(m 2.day). Similar c a l c u l a t i o n s f o r the complete set of data are reported i n table 9. Tables 10 and 11 give the adjusted rates of weight loss per are with the corresponding vapour pressure d e f i c i t s . Figure 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 Condition r, Average rate of water loss per area with correction f o r e f f e c t Reynold's 2 number of a i r flow in s i d e storage chamber (kg/(m .day))* Untreated Tomatoes. Samples Wrapped i n p l a s t i c f i l m . Samples with calyx-ends waxed. Samples with whole surface waxed. Run II Run III Run II Run III Run II Run III Run II 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% 0.027 0.070 0.008 0.012 0.021 0.062 0.014 0.046 3. 10°C:60% 0.050 0.145 0.015 0.028 0.048 0.116 0.025 0.070 4. 15°C:50% 0.077 0.243 0.032 0.058 0.057 0.198 0.049 0.109 Average of 20 tomatoes with s i m i l a r treatment and storage 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 (RUN I I ) ) Vapour Pressure Average rate of water loss per area with c o r r e c t i o n f o r e f f e c t of Reynold's D e f i c i t number of a i r flow inside storage chamber (kg/(m .day)) (kPa) Untreated Tomatoes. Samples Wrapped in Samples with calyx Samples with whole p l a s t i c f i l m . ends waxed. surface 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 (kg/(m 2.day.kPa)) 0.115 0.040 0.094 0.060 (0.97) (0.99) (0.89) (0.95) Numbers i n parentheses give 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 rates of weight loss/area and the vapour pressure d e f i c i t s between the tomato "multiple b a r r i e r " and the tomato environment TABLE 11. VAPOUR PRESSURE DEFICITS AND AVERAGE RATES OF WATER LOSS THROUGH TOMATOr'.'MULTIPLE BARRIER" (vWITH CORRECTION FOR EFFECT OF REYNOLD'S NUMBER OF AIR FLOW (RUN III)) Vapour Pressure D e f i c i t Average rate of water loss per area with 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 flow inside storage chamber (kg/m .day)) (kPa) Untreated Tomatoes. Samples Wrapped i n Samples with calyx Samples with whole p l a s t i c f i l m . ends waxed. surface waxed. 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 K (kg/(m 2.day.kPa)) 0.333 0.075 0.281 0.175 (0.99) (0.98) (0.98) (0.92) Numbers i n parentheses give 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 rates of weight loss/area and the vapour pressure d e f i c i t s between the tomato "multiple barrier' 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) cd T3 0.24 0.20 0.16 0.12 0.0§ 0 . 0 4 LEGEND RUN I I m Untreated A Wrapped i n p l a s t i c f i l m D Calyx^end waxed tk Whole skin waxed RUN I I I • Untreated + Wrapped i n p l a s t i c f i l m o Calyx-oTend waxed X Whole skin waxed 0.00 @ O a + A + • A A 0.0 0.2 0.4 0.6 0.8 Vapour pressure d e f i c i t , (kPa) 57. adjusted rates of weight l o s s per area, against the vapour pressure d e f i c i t s , corresponding to Tables 10 and 11. The slopes of the plo t s are l i s t e d as the mass transfer 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 Tables 10 and 11. The permeability of r e s i n i t e i s given as (23) over 25g"/(m .d.mil), measurements made at 100°F (37.8°C), and change i n r e l a t i v e humidity of 90% ( i . e . 3-hu = 90%). The r e s i n i t e used i n the experiments was measured to be 0.55 m i l . The iifeer.atune value of the permeability of r e s i n i t e thus converts ?2 to 0.0077 ikg-'Adn „.cdycB6')a) . No upper bound or range i s given i n the l i t e r a t u r e concerning the water vapour permeability of r e s i n i t e . It was thus decided to determine experimentally, the water vapour transmission properties of the r e s i n i t e . (See Appendix C for d e s c r i p t i o n of t h i s determination). On the average, the water permeability of the f i l m was found to be - 0.060 kg'/(m ..d. kPa). Since the water vapour permeability of the r e s i n i t e f i l m was determined i n " s t i l l a i r " ( i . e . inside a d e s i c c a t o r ) , we can only consider the value obtained as an approximate one. For run I I r e s u l t s : the mass tr a n s f e r c o e f f i c i e n t f o r water loss from the "bare" tomato skin (plus boundary layer) was found to be . 0* 115 kg/(m .d. kPa); when wrapped i n the p l a s t i c f i l m , the mass transf e r c o e f f i c i e n t for the 2 re s u l t i n g " 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 equation 11 (See section on T h e o r e t i c a l Model), we have : -1 -1 -1 -1 K ;, + K_ = K - K , sk by t p i = 0.040 - 1 - 0.060"1 = 8.333 Therefore, K g k + = 0.120 kg/ (m2.4 ,kPa»).Pa). The deviation of the value of the mass transfer c o e f f i c i e n t of the tomato skin 58. plus boundary layer as "extracted" from the mass transfer c o e f f i c i e n t f or the " m u l t i p l e - b a r r i e r " , consisting of: tomato skin plus boundary layer plus p l a s r t i c f i l m i s given by: Deviation = (0.120 - 0.115)/0.120 = 4.17 per cent. A s i m i l a r set of c a l c u l a t i o n s with the data for run III gave the following : 2 K for the "bare" tomato skin + boundary layer = '0.333 kg/(m .d.kPa) 2 K for plastic-wrapped tomato = '0.075 kg/(m ..d .kPa) Therefore, from equation 11 : K"1 + K"1 = 0.075"1 - 0.06"! = - 3.333 sk by and K g k + ^ = - 0.300 kg/(m 2 ..4r.kPfc})a; . The negative value implies that, packaging the tomatoes i n the p l a s t i c r e s i n i t e f i l m increases the rate of weight l o s s . 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 could have contributed to the above observation x among them are : a) the method of determination of the permeability of the r e s i n i t e f i l m could only give an approximate value, b) the a i r flow c h a r a c t e r i s t i c s i n the storage chambers are not f u l l y under-stood (the experiment was not s p e c i f i c a l l y designed to permit measurement and c o n t r o l of the flow c h a r a c t e r i s t i c s ) . It i s pointed out that 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 one 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. 59. Results and discussion of regression analyses of colour and firmness changes Colour change with time The r e s u l t s of the analysis of colour change with time are given i n Table B.3 i n the.appendix B. An i n i t i a l inspection of table B.3 shows no d i s c e r n i b l e trends. However, r e c a l l i n g that i n the weight loss analysis of variance, only the pre-storage treatments and d i f f e r e n t storage conditions were shown to be s i g n i f i c a n t l y d i f f e r e n t i n t h e i r e f f e c t s on weight l o s s , and applying t h i s knowledge i n the i n t e r p r e t a t i o n of the colour regression r e s u l t s , trends become evident. Table B.4 was constructed from Table B.3 by taking averages of the regression c o e f f i c i e n t s of the pre-storage treatment and storage combinations f o r a l l cooling regimes. For example, under storage no.l (10°C, 90% rh) and treatment no.2 (wrapping i n p l a s t i c f i l m ) , the figu r e 0.53 represents the mean colour regression c o e f f i c i e n t , b , for a l l 20 tomatoes with C-T-S codes 121, c 221, 321,and 421. The range of b £ values i s from 0.48 to 0.56 with a standard deviation of 0.03. Figure B.l shows a plo t of the mean colour c o e f f i c i e n t s f o r the various pre-storage treatments on the Y-axis, against the storage condition on the Y-axis. (points are joined by str a i g h t l i n e s to indicate o v e r - a l l trends). Table B.5.i shows the mean colour c o e f f i c i e n t s f o r a l l tomatoes main-tained at a p a r t i c u l a r storage condition. A Duncan's M u l t i p l e Range te s t and the t - t e s t only showed a s i g n i f i c a n t difference (P 0.05) between the storage conditions 1 (10°C, 90% rh) and 3 (10°C, 60% rh) on one hand, and the other three storages conditions on the other hand. The r e s u l t s are thus i n c o n c l u s i v e ^ but -theitreridssare"-quite interesting*; " -It -would appear that the 60. tomatoes stored at the lowest temperature (10°C) underwent the slowest rate of colour change, whereas those stored at the higher temperatures underwent the f a s t e s t . This observation confirms the findings of Pharr and Kattan (26) A ten t a t i v e observation may thus be made that low temperature and high humi-d i t y i n the storage chamber tends to slow down the process of colour change. Table B . 5 . i i shows the mean colour c o e f f i c i e n t s for a l l tomatoes with i d e n t i c a l pre-storage treatment. The Duncan's and student's t - t e s t once again f a i l e d to y i e l d conclusive r e s u l t s . Nevertheless, the trends suggest that any form of pre-storage treatment ( i . e . p l a s t i c film-wrapping or waxing, etc) tends to slow down the process of colour change during ripening. . F iimnaEirmnessechangeiwithatdmeiahdCwlthrcolour A summary of the r e s u l t s of the regression of firmness with time and with colour i s given i n table B.6 (appendix B). The tomatoes that were either 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 surface were waxed generally maintained t h e i r firmness r a t i n g of '4.4 throughout the experiment. (See o r i g i n a l data i n General O f f i c e of Bio-Resource Engineering, U.B.C.). Thus since the colour was changing without any corresponding change i n firmness, 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 colour and firmness f or the tomatoes with these two treatments are zero. The regression of firmness with time f or the tomatoes wrapped i n p l a s t i c f i l m or t o t a l l y waxed was also found to be zero. Table B.6 was constructed 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 sur-faces were waxed. With the exception of the tomatoes stored i n storage condition no. 2 (15 yC, 88% roK' ) there was found to be a generally high c o r r e l a t i o n (negative 61 . correlation) between the rate of colour change and that of firmness change ( r 2 0.9). Results and Discussion of Post-Storage Tests Plate 2 shows electron micrographs taken during the i n v e s t i g a t i o n of the e f f e c t s of pressure on tomatoes. They showed no d i s c e r n i b l e damage caused by "squeezing" to determine the firmness rating of the tomatoes during the test period. The average equilibrium r e l a t i v e humidity of the tomatoes was found to be 98 percent (range: 96% - 99%). This confirmed the assumption made i n the development of the model (see section on T h e o r e t i c a l Model). At the end of each experimental run, 5 people were asked to taste the f r u i t to determine i f o f f - f l a v o u r had developed i n any of the various t r e a t -ments, and also to ind i c a t e any preferences. The t o t a l l y waxed and plastic-wrapped tomatoes were generally judged to taste s l i g h t l y more a c i d i c , and were thus more preferable to the untreated tomatoes. The a c i d i c taste of the "treated" tomatoes might be due to higher carbon dioxide ( C ^ ) l e v e l s as reported by Parsons, et a l . (23). The p a r t i a l l y waxed tomatoes and the untreated tomatoes were quite acceptable, too, and no recognizable o f f - f l a v o u r i n any of the treatments was noted. 62. PLATE 2 ELECTRON MICROGRAPHS OF TOMATO SKIN SURFACE AND SUB-SURFACE LAYERS 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 5. Low moisture loss tomato Magnification - 140 X Magnification = 140 X CONCLUSIONS From the tes t s conducted on greenhouse tomatoes, the following general conclusions 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 state rates of weight l o s s per unit of surface area as a r e s u l t of the time delay a f t e r harvest, before cooling. The periods of delay studied were as great 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 f i l m ( r e s i n i t e ) before storage, reduces the steady state r a t e of weight l o s s per unit of surface area to about one-third (^/3) the rate f o r unwrapped and untreated tomatoes. 2b. A p p l i c a t i o n of wax emulsion as a coating over the whole surface of a tomato before storage reduces the steady state rate of weight loss per unit of surface area to about one-half (h) of what would otherwise r e s u l t i n the r'barey®t"omatoesO • 3. The rate of water l o s s from the stem end (calyx- end) of the tomato f r u i t during storage i s disproportionately large. In the tes t s conducted, water loss from the stem end contributed to over 27 percent.t of the t o t a l l o s s , yet t h i s region constitutes only about 10 percent.t of the t o t a l surface area. 4. As expected, storage at the low temperatures (10°C) and high humidities (90%, 80% rrh.)hugiyegislower .w /-ratesc3of)f steady ssfeafee .weight... loss per surface area of tomato than storage at the higher temperatures (15°C, 18°C) and lower humidities (60%, 50%, 40%). 5. The pre-storage treatment of wrapping i n d i v i d u a l tomatoes i n p l a s t i c or applying wax over the surfaces of the tomatoes tends to slow down the rate of colour change during ripening, and also the rate of t e x t u r a l breakdown (rate at which the firmness decreases). The altered atmosphere(i.e. higher l e v e l of carbon dioxide) (23.,28) created may have played a part i n the above changes noted. This could also have led to the tomatoes wrapped i n the p l a s t i c f i l m being s l i g h t l y more prefered to the untreated tomatoes by the members of the taste panel. This agrees with Parsons et a l . report(23) on the influence of carbon dioxide. 6. For a group of tomatoes with a sim i l a r pre-harvest h i s t o r y , the mass transfer c o e f f i c i e n t of the tomato skin plus boundary lay e r , plus p l a s t i c f i l m or waxfceoating (as the case may be) i s independent of the temperature and and humidity of the storage environment. This 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 the rates of water loss and the vapour pressure d e f i c i t between the tomato surface and the storage environment. t 65. RECOMMENDATIONS AND PROPOSALS FOR FUTURE WORK IN THIS AREA. From the experience gained.in t h i s research, the author would suggest that : 1. There should be a simpler experimental design with fewer treatments, but involving more tomatoes i n each treatment. This would aid i n the analyses and i n t e r p r e t a t i o n of the data generated. 2. Anon-destructive but objective method of measuring colour and firmness needs to be developed. This would aid i n the understanding of the exact c o r r e l a t i o n between the weight l o s s and colour and firmness changes during storage. 3. The tomatoes should a l l be picked at the same stage of ripeness; and more experienced hands should be employed to help i n the i n i t i a l prepara-t i o n for storage ( i . e . weighing, pre-cooling, reading colour and firmness scale, waxing, e t c ) . 4. The soluble s o l i d s content and r e s p i r a t i o n rate i n a tomato should be monitored during the test period. This would aid i n the interprepation of the weight l o s s . 5. The storage chambers should be designed f o r close study 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 chambers ( e s p e c i a l l y the boundary layers should be w e l l defined and c o n t r o l l e d ) , since the'sea f a c t o r s may influence the rate of water l o s s through the tomato "multiple-barrier".surface. 66. LITERATURE CITED 1. ASHRAE Handbook of fundamentals. 1967. pp.65 - 78. 2. von Beckmann, J.W. 1976. Development of an e l e c t r o n i c s i z e and colour grader f o r tomatoes. Ph.D. Thesis, U.B.C. Dept. of Bio-Resource Eng. 3. Bennet, A.H. and J.N. Webb. 1976. Peach pre-cooling aims at p e r f e c t i o n . Western F r u i t Frower.. May 1976 p.13, 33. 4. van den Berg, L. and C P . Lentz. 1974. High humidity storage of some vegetables. Can Inst. Food S c i . Technol. J . Vol.7 No.4. 5. Commercial Storage of F r u i t s and Vegetables. Can. Dept. of Agric. Pu b l i c a t i o n No.1532, 1974. 6. Desrosier, N.W. 1954. Colour measurements with tomatoes. Colour i n foods symposium. Nat. Acad. S c i . Nat. Res. Council, Washington, D.C. 7. Fockens, F.H. and H.F. Th. Meffert, 1972. Biophysical properties of h o r t i c u l t u r a l products as r e l a t e d to loss of moisture during cooling down. J. S c i . Fd. Agric. 23:285-298. 8. Hamson, A.R. 1952. Measuring firmness of tomatoes i n a breeding program. Proc. Amer. Soc. Hort. S c i . 60:425-433. 9. Handbook on the storage of f r u i t s and vegetables. Can. Dept. of Agric. Pu b l i c a t i o n No.1260, 1967. 10. Hardenburg, R.E. 1947. Moisture losses of vegetables packaged i n trans-parent f i l m s and t h e i r e f f e c t s on s h e l f - l i f e . Proc. Amer. Soc. Hort. S c i . 53:426-430. 11. Hartman, J.D. and F.M. Isenberg, 1956. Waxing vegetables. N.Y. State Agric. Expn. Stn. Cornell Ext. Bui. 965 (4p). 12. Hening, Y.S. and S.G. G i l b e r t , 1975. Computer analysis of the v a r i a b l e s a f f e c t i n g r e s p i r a t i o n and equality of produce packaged i n polymeric f i l m s . J . Food S c i . V o l . 40:1033-1035. 13. Hood, C.E. and B.K. Webb. 1968. Correlations of c e r t a i n physical properties of tomatoes. ASAE Paper No. 68 - 120. 14. Kattan, A.A. 1957. Changes i n colour and firmness of detached tomatoes and the use of a new instrument ofor measuring firmness. Proc. Amer. Soc. Hort. S c i . 70:379-384. 15. K r e i t h , F. 1965. P r i n c i p l e s of Heat Transfer. 2d Ed. International Textbook Company. Scranton, Pennsylvania. 16. Lutz, J.M. 1944. Maturity and handling of green-wrap tomatoes i n M i s s i s s i p p i . U.S.D.A. C i r c . 695. 67. 17. McColloch, L.P. and J.N. Yeatman. Colour changes and c h i l l i n g i n j u r y of pink tomatoes held at various temperatures. U.S.D.A. Marketing Research Report No.735. 18. McKinney, G. and A.C. L i t t l e , 1962. Colour of foods. Avi. Publishing Co. Westport, Conn. 19. Meherink, M. and S.W. P o r r i t t , 1972. The ef f e c t s of waxing on r e s p i r a -t i o n , ethylene production and other physical and chemical changes i n selected apple c u l t i v a r s . Can. J . Plant 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 cooling of f r u i t s and vegetables. Un i v e r s i t y of C a l i f . Manual 43. 21. Modern Packaging Encyclopaedia.»1971. P.146. 22. Pantastico, ER.B. 1975. Post-harvest physiology, handling and u t i l i z a t i o n of t r o p i c a l and sub-tropical f r u i t s and vegetables. Avi. Publishing Co. Westport, Conn. 23. Parsons, C.S., R.E. Anderson and R.W. Penney. 1970. Storage of mature-green tomatoes i n controlled atmosphere. J . Amer. Soc. Hort. S c i . 95(6) :791-794 24. Pharr, D.M. and A.A. Kattan. 1971. Ef f e c t s of a i r flow rate, storage temperature, and harvest maturity on r e s p i r a t i o n and ripening of tomato f r u i t s . Plant P h y s i o l . 48,53-55. 25. Robinson, W.B. 1952. A study of methods f o r the measurement of tomato j u i c e colour. Food Technol. 6:269-275. 26. Smock, R.M. 1960. Some add i t i o n a l e f f e c t s of waxing apples. Proc. Amer. Soc. Hort. S c i . 37:448-452. 27. T o l l e , W.E. 1972. Hypobaric storage of fresh produce. United Fresh F r u i t and Vegetable Assn. Yearbook, 1972. 28. Tomkins, R.G. 1962. The conditions produced i n f i l m packages by fr e s h f r u i t s and vegetables and e f f e c t s of these conditions on storage l i f e . Appl. B a c t e r i o l . 25:290-307. 29. Treybal, R.E. 1955. Mass Transfer Operations. McGraw-Hill Book Co. Inc., N.Y. 30. Wang, J-K and P-Y Wang. 1967. A computational technique for deep-bed fo r c e d - a i r pre-cooling of tomatoes. ASAE paper No.67-819. 31. Watsoni E.L. 1960. Prompt handling plus proper cooling f or better q u a l i t y . Can. Food Ind. June 1960. 6 8 . A P P E N D I X • A 69. TABLE A . l TWO-FACTGR INTERACTION EFFECTS ON.WEIGHT LOSS. (RUN II) (a) COOLING X TREATMENT Untreated P l a s t i c - f i l m Calyx end Whole skin :u wrapped waxed waxed 20-hour delay 0, C*) .31 ; o .11 0 .26 0, .19 10-hour delay 0, .36 0, .12 0 .29 0. .20 0-hour delay 0. .33 0, .13 0 .28 0. .20 30-hour delay 0, .29 0, .12 0 .25 0. .17 * Mean of 25 readings (kvg/m2) (b) COOLING X STORAGE S t . l St.2 St.3 St.4 St.5 20-hour-delay 0, (*) 0, .18 0. .18 0. .29 0. .32 10-hour delay 0. .11 0, .19 0. .20 0. .32 0. .37 0-hour delay 0. .13 0. .21 0. .21 0. .33 0. .30 30-hour delay 0. .13 0. .16 0. .17 0. ,29 0. .30 Mean of 20 readings (kig/m ) (c) TREATMENT STORAGE Sf.1 St.2 St.3 St.4 St. 5 Untreated 0 .18 <*> 0, .29 0, .26 0, .44 0 .44 P l a s t i c f i l m 0, .06 0, .08 0, .09 0, .18 0 .19 wrapped Calyx end waxed 0, .14 0, .21 0. .27 0. .33 0 .38 Whole skin waxed 0, .10 0. ,15 0, .14 0. .28 0 .28 Mean of 20 readings (Kg/m ) 70. TABLE A. 2 TWO-FACTOR INTERACTION EFFECTS ON WEIGHT LOSS (RUN III) (a) ' COOLING X-TREATMENT Untreated P l a s t i c - f i l m wrapped Calyx end waxed Whole skin waxed' 20-hour delay (*) 1.02v ; 0.26 0.94 0.56 10-hour delay 1.08 0.25 1.00 0.50 0-hour delay 1.12 0.25 0.96 0.57 30-hour delay 1.16 0.26 0.91 0.57 * Mean , 29 of 25 readings fteg/m ) (b) COOING CX3CsTO#AGE-^ORAG7i: CONDITION * i # ... , S t . l St.2 St. 3 St. 4 St. 5 20-hour delay (*) 0.37 v ; 0.49 0.61 0.88 0.13 10-hour delay 0.39 0.57 0.55 0.84 0.18 0-hour delay 0.41 0.61 0.50 0.90 1.18 30-hour delay 0.38 0.49 0.54 0.95 1.27 * Mean «-> of 20 readings (kg/'m2) (c) -TllATMENT^X STORSGE^G^ CONDITION Untreated S t . l St. 2 St. 3 St.4 St.5 Untreated 0.58 0.79 0.90 1.43 1.77 P l a s t i c f i l m 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 skin waxed 0.31 0.52 0.44 0.63 0.86 Mean of 20 readings (%/mi 2 ) 71. APPENDIX B 72 , TABLE # 1 SUMMARY OF RESULTS OF WEIGHT LOSS REGRESSION ANALYSIS (RUN I I ) C-T-S R e g r e s s i o n coe f FPr.ob S t d . e r r o r 2 r code (b) kg/(m .day) • (b) (b) 111 0.015 0.0000 0.53 x 1 0 " 4 0.9984 112 0.025 0.0000 0.11 x 1 0 " 3 0.9977 113 0 .023 0.0000 0.29 x 1 0 " 4 0.9998 114 0.030 0.0000 0.13 x 1 0 " 3 0.9976 115 0.025 0.0000 0.52 x 1 0 ~ 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 1 0 ~ 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 1 0 ~ 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 1 0 ~ 4 0.9974 142 0 .013 0.0000 0.83 x 1 0 ~ 4 0.9947 143 0 .013 0.0000 0.29 x 1 0 ~ 4 0.9994 144 0 .023 0.0000 0.13 x 1 0 " 3 0.9962 145 0 .023 0.0000 0.44 x 1 0 ~ 4 0.9995 73. Table i-l continued. G-T-S - Regression coef.,b - 2 ' kg/-(m .day) FProb Std. error . .2 r code . (b) (b) 211 0.015 0.0000 0.86 x 10~ 4 0.9961 212 0.025 0.0000 0.12 x 10~ 3 0.9973 213 0.024 0.0000 0.27 x 10~ 4 0.9998 214 0.042 0.0000 0.21 x 10~ 3 0.9970 215 0.040 0.0001 0.57 x 10~ 3 0.9756 221 0.0040 0.0001 0.50 x 10" 4 0.9802 222 0.0063 0.0000 0.24 x 10~ 4 0.9989 223 0.0082 0.0000 0.35 x I O - 4 0.9962 224 0.0133 0.0000 0.21 x 10~ 4 0.9997 225 0/0170 0.0000 0.39 x 10~ 4 0.9993 231 0.009i 0.0000 0.60 x 10~ 4 0.9944 232 0.019 0.0000 0.62 x 10~ 4 0.9986 233 0.024 0.0000 0.40 x I O - 4 0.9997 234 0.029 0.0000 0.71 x 10~ 4 0.9993 235 0.035 0.0000 0.22 x 10~ 3 0.9954 241 0.008 0.0000 0.55 x 10" 4 0.9941 242 0.013 0.0000 0.66 x 10~ 4 0.9970 243 0.011 0.0000 0.26 x I O - 4 0.9993 244 0.020 0.0000 0.54 x 10~ 4 0.9991 245 0.023 0.0000 0.10 x 10~ 3 0.9976 74. TABLE £ . 1 (Cont'd) C-T-S code Regression ^oef. ,b kg/(m .day) FProb (b) Std. .error (b) 2 r 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 10" 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 10" 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 10" 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 75. TABLE Q>-1 (Cont'd) C-T-S code Regression eoef.,b kg/(m .day) -•" EPr.ob, (b) -Std. error (b) 2 •r 411 0.014 0.0000 0.29 X i o " 4 0.9995 412 0.019 0.0000 0.67 X i o " 4 0.9984 413 0.026 0.0000 0.56 X i o " 4 0.9921 414 0.032 0.0000 0.17 X i o " 3 0.9966 415. ' 0.028 0.0001 0.28 X i o " 3 0.9876 421 0.0067 0.0012 0.19 K i o " 3 0.9100 422 0.0061 0.0000 0.35 X -L 10 ' 0.9958 423 0.0061 0.0000 0.37 X i o " 4 0.9954 424 0.0155 0.0000 0.12 X i o " 4 0.9999 425 0.0156 0.0000 0.16 X i o " 4 0.9999 431 0.014 0.0000 0.22 X i o " 4 0.9997 432 0.016 0.0000 0.79 X i o " 4 0.9969 433 0.021 0.0000 0.99 X i o " 4 0.9972 434 0.025 0.0000 0.13 X i o " 3 0.9967 435 0.027 0.0000 0.38 X i o " 4 0.9997 441 0.007 0.0000 0.15 X i o " 4 0.9994 442 0.012 0.0000 0.57 X i o = 4 0.9970 443 0.012 0.0000 0.27 X i o " 4 0.9993 444 0.023 0.0000 0.91 X i o " 4 0.9980 445 0.020 0.0000 0.24 X i o " 4 0.9998 TABLE G> .X SUMMARY OF RESULTS OF WEIGHT LOSS J REGRESSION ANALYSIS (RUN III) C-T-S Regression coef., ,b FProb Std. error 2 r code 2 kg/(m .day) (b)" '. (b) -111 0.042 0.0000 0.30 x -3 10 0.9909 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 0.9946 121 0.006 0.0000 0.38 x 10" 4 0.9931 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 7 131 0.033 0.0000 0.51 x l O " 3 0.9590 132 0.054 0.0000 0.13 x -3 10 0.9990 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 77. TABLE 8% (Cont'd) -C-T-S code Regression coef.,b ' . kg/(m .day) FProb (b) Std. error (b) 2 r 211 0.045 0.0000 0.42 X i o " 3 0.9855 212 0.070 0.0000 0.29 X i o " 3 0.9970 213 0.071 0.0000 0.59 X i o " 3 0.9879 214 0.117 0.0000 0.51 X i o " 3 0.9967 215 0.105 0.0000 0.12 X i o " 2 0.9789 221 0.006 0.0000 0.82 X i o " 4 0.9712 222 0.009 0.0000 0.12 X i o " 4 0.9997 223 0.013 0.0000 0.39 X i o " 4 0.0083 224 0.026 0.0000 0.24 X i o " 4 0.9998 225 0.044 0.-000 0.15 X i o " 3 0.9979 231 0.043 0.0000 0.41 X i o " 3 0.9843 232 0.055 0.0000 0.21 X i o " 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 i o " 2 0.9668 241 0.024 0.0000 0.23 X i o " 3 0.9836 242 0.047 0.0000 0.11 X IO" 3 0.9991 243 0.027 0.0000 0.28 X i o " 3 0.9823 244 0.041 0.0000 0.16 X i o " 3 0.9972 245 0.058 0.0000 0.25 X -3 10 0.9967 78. TABLE 8-2- (Cont'd) C-T-S Regression^coef. ,b FF.rob Std. error 2 r . code kg/(m 2.day) (b) (b) 311 0.043 0.0000 0.54 X i o " 3 0.9737 312 0.069 0.0000 0.30 X i o " 3 0.9966 313 0.067 0.0000 0.40 X i o " 3 0.9937 314 0.110 0.0000 0.39 X i o " 3 0.9978 315 0.118 0.0000 0.19 X i o " 2 0.9550 321 0.006 0.0000 0.21 X i o ' 4 0.9977 322 0.010 0.0000 0.63 X i o " 4 0.9929 323 0.014 0.0000 0.49 X i o " 4 0.9978 324 0.027 0.0000 0.33 X i o " 4 0.9997 325 0.044 0.0000 0.12 X i o " 3 0.9988 331 0.045 0.0000 0.36 X i o " 3 0.9893 332 0.060 0.0000 0.62 X i o " 3 0.9814 333 0.044 0.0000 0.22 X i o " 3 0.9956 334 0.105 0.0000 0.47 X i o " 3 0.9965 335 0.119 0.0000 0.63 X l ( f 3 0.9952 341 0.028 0.0000 0.19 X i o ~ 3 0.9916 342 0.053 0.0000 0.16 X i o " 3 0.9984 343 0.034 0.0000 0.14 X i o " 3 0.9969 344 0.045 0.0000 0.14 X i o " 3 0.9982 3S5 0.066 0.0000 0.24 X l o " 3 0.9977 79. TABLE 6 a (Cont'd) 2 C-T-S Regression coef. ,b . FProb Std; error r. code . 2 . (b) (b) kg/(m .day) v ' ' 411 0.044 0.0000 0.35 x i o " 3 0.9890 412 0.056 0.0000 0.19,x i o " 3 0.9979 413 0.066 0.0000 0.25 x H f 3 0.9976 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 IO" 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 -3 10 0.9921 442 0.034 0.0000 0.17 x i o " 3 0.9955 443 0.039 0.0000 0.16 x i o " 3 0.9969 444 0.059 0.0000 0.26 x i o " 3 0.9965 445 0.075 0.0000 0.36 x i o " 3 0.9959 2 r TABLE B.3 SUMMARY^OF COLOUR CHANGE REGRESSION ANALYSIS (RUN III) C-T-S Const Coef. FProb C o d e a C b C (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 TABLE B.3 (CONT'D) 81. C-T-S Const Coef. FProb r 2 Code b c (day - 1) 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 Const Coef. FProb - r 2 Code a .. -1, C b c (day )  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 (0.04)** (0.01) (0.07) (0.02) 2 0.40 0.36 0.31 0.31 (0.04) (0.03) (0.06) (0.04) 3 0.32 0.26 0.25 0.23 (0.07) (0.03) (0.01) (0.09) 4 0.38 0.36 0.34 0.33 • (0.05) (0.09) (0.01) (0.09) 5 0.36 0.34 0.36 0.38 (0.05) (0.02) (0.08) (0.03) Mean of 20 measurements. Numbers i n parentheses r e f e r to the standard errors of the means. 84. TABLE B.5 MAIN EFFECTS OF STORAGE AND TREATMENT ON RATE OF COLOUR CHANGE Storage - Mean Colour Coef. (*) 1 0.25 (a) (0.02)(**) 2 0.34 (b) (0.04) 3 0.27 (a) (0.04) 4 0.35 (b) (0.02) 5 0.35 (b) (0.02) ( i i ) Pre-Storage Treatment Mean Colour Coef.(***) 1 0.35 (a) (0.05)(**) 2 0.32 (a) (0.05) 3 0.29 (a) (0.04) 4 0.30 (a) (0.06) * Mean of 80 measurements. ** Numbers i n parentheses r e f e r to the standard errors of the means. *** Mean of 100 measurements. Responses followed by d i f f e r e n t l e t t e r s are s i g n i f i c a n t l y d i f f e r e n t (P 0.05). FIGURE B.l PLOT OF MEAN COLOUR COEFFICIENT (b ) DUE TO PRE-STORAGE c TREATMENT Vs. STORAGE CONDITION Storage Condition 86. TABLE B.6 SUMMARY OF RESULTS OF TOMATO FIRMNESS CHANGES WITH TIME (REGRESSION ANALYSIS) --C-T-S Code Const . a F Coef (day l ) FProb 2 r -C o r r e l a t i o n Coef c o l o u r / f i r m n e s s 111 4.16 -0. .0.6 6.017 0.900 -0.909 112 4.08 -0. ,02 0.180 0.500 -0.58 113 4.30 - o . a a - 0.008 0.945 -0.966 114 4.54 -0.177 0.024 0.871 -0.891 115 4.46 -0.9$ . 0.001 0.995 -0.974 131 4.36 -0.1.0) 0.049 0.780 -0.954 132 4.08 -o.oa 0.182 0.503 -0.543 133 4.36 -0 .E2+- 0.027 0.862 -0.960 134 4.30 -0.2.9} 0.060 0.751 -0.821 135 4.20 -0.E3S 0.017 0.899 -0.967 211 4.30 -0.0:9 0.061 0?752 -0.961 212 4.32 -0.08. 0.183 0.502 -0.527 213 4.46 -0.BS" 0.034 0.843 -0.977 214 4.60 -0. us 0.068 0.753 -0.864 215 4.72 -0.2.8 0.003 0.972 -0.940 231 4.10 -0.03 0.063 0.755 -0.899 232 4.18 -0.05: 0.053 0.783 -0.832 233 4.20 -0X0.4! 0.066 0.754 -0.998 234 4.36 -o.m 0.032 0.841 -0.911 235 4.68 -0.30) 0.001 0.995 -0.956 TABLE B.6 (CONT'D) C o r r e l a t i o n Coef c o l o u r / f i r m n e s s 311 4.06 -0.0Q 0.063 0.752 -0.856 312 4.08 -0.0/2 0.181 0.502 -0.781 313 4.22 -0.10!9 0.021 0.887 -0.964 314 4.78 -0.35 0.015 0.900 -0.889 315 4.72 -0..L2(8 0.001 0.971 -0.943 3 3 1 4 . 0 6 - 0 . 0 6 0 . 0 6 5 0 . 7 5 2 - 0 . 8 6 2 3 3 2 4 . 0 8 - 0 . 0 2 0 . 1 8 3 0 . 5 0 4 - 0 . 6 7 2 3 3 3 4 . 1 0 - 0 . 0 6 0 . 0 6 4 0 . 7 5 2 - 0 . 9 3 0 3 3 4 4 . 5 2 - 0 . . T . 6 0 . 0 2 1 0 . 8 9 3 - 0 . 8 1 8 3 3 5 4 . 5 6 - 0 . 2 2 0 . 0 1 1 0 . 9 5 3 - 0 . 9 7 5 4fl 4.26 -o. m 0.074 0.723 -0.819 412 4.16 -0.04 0.188 0.504 -0.511 413 4.26 -0. IB 0.000 0.998 -0.978 414 4.64 -0.22 0.015 0.944 -0.874 415 4.66 -0.31 0.007 0.984 -0.927 431 4.10 -0.03 0.065 0.753 -0.913 432 4.08 -0.02 0.183 0.501 -0.660 433 4.06 -0 .QS> 0.026 0.898 -0.875 434 4.46 -0.135) 0.035 0.843 -0.912 435 4.34 -0.B5) 0.004 0.998 -0.963 88. APPENDIX C 89". APPENDIX C DETERMINATION OF THE PERMEABILITY OF RESINITE FILM  MATERIAL AND METHOD A r o l l 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 determination (*). Eight rectangular pouches were made by f o l d i n g over, rectangular samples of the p l a s t i c f i l m , and heat-sealing along two sides. In each pouch was placed a wire gauze of comparable dimensions (whose sharp edges had been doubly folded over to prevent pin-holing of the p l a s t i c film) to keep the two sides of the pouch apart. Dehydrated s i l i c a g e l (blue c r y s t a l s ) was then placed, by means of a spatula, i n each pouch and the l a s t side heat- sealed. The pouches and contents were then weighed on a Mettler Balance and hung v e r t i c a l l y on a rack i n s i d e a desiccator. There was d i s t i l l e d water i n the bottom of the desiccator to create saturated conditions ( i . e . r e l a t i v e humidity of 100%) on the outsides of the pouches, while the insides were i n i t i a l l y "bone dry". The pouches and t h e i r contents were reweighed a f t e r every 24 h for 4 consecutive. 24-hour periods: The dimensions ( i . e . length x width) of the pouches were taken at the end of the test period. The thickness of the r e s i n i t e f i l m was measured on a model 549 micrometer. The average temperature of the environment during the test was 22°C (71.6°F). (.*) This was the same r o l l of f i l m used i n the wrapping of the tomatoes (Pre-storage treatment no.2) during the main experiment. 90. RESULTS AND CALCULATION OF PERMEABILITIES The successive weights of the pouches are given i n the f i r s t 4 columns of table C.l. The f i f t h column of table CI gives the surface areas of the various pouches. Sample C a l c u l a t i o n of Moisture Permeability of Film The thickness of the f i l m was measured to 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 given as: 14.2397 - 12.2441 = 1.9956 gar Adjustment to 24 hours, gives: wt. gain = 1.9956 x 2_4_ = 1.9158 g 25 The water vapour transmission rate (WVTR) i s thus 1.9158 g. = 158.3306 g. 0.0121 mz.d- 0" j . mz. d The saturation vapour pressure at 22°C = 2.66 kPa WVTR = 158.3306 gz. x 1 kg = 0.060 kg m2.d-. 2.66'kPaf 1000 g., m^.d-kPa. Si m i l a r • c a l c u l a t i o n s yielded data i n columns 6,7,8 of table £>• 1 which shows trend of decreasing permeability between successive periods. This was as expected since the hydration of the s i l i c a g e l decreased the vapour pressure d i f f e r e n c e between the insides and outsides of the pouches. Thus the values i n column 6 ( i . e . the WVTR during the f i r s t period) were-averaged to give the 2 permeability of the r e s i n i t e f i l m , as. 0j.06pj kg/m .d .;kPa. T a b l e C . l R e s i n i t e f i l m WVTR d e t e r m i n a t i o n S u c c e s s i v e w e i g h t s ( g ) D a y 1 D a y 2 D a y 3 D a y 4 A r e a WVTR B e t w e e n s e c c e s s i v e 4.00 pm 5.00 pm 6.00 pm 6.00 pn o f p e r i o d s ( K g / m 2 . d a y . k P a ) P o u c h (m2) i - » 2 - 2-> 3 ' •3-* 4 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 Federal and Industry Colour Grades and Standards *** Canada No.l Grade are, i n any>individual package, one of the following states of development: "mature", "turning", "semi-r i p e " or "firm r i p e " , (a) ^mature" means, (i) except for f i e l d tomatoes grown i n B r i t i s h Columbia and Manitoba, that the tomato shows a d e f i n i t e tinge of pink at the blossom end, and i n the case of f i e l d tomatoes grown i n B r i t i s h Columbia and Manitoba, that the tomato i s f u l l y developed, well f i l l e d out, gives a f e e l i n g of springiness when pressure i s applied, i s bright waxy i n appearance, has seeds that are w e ll developed and seed c a v i t i e s of a j e l l y - l i k e consistency, and ( i i ) not more than 25% of the f i e l d tomatoes by count are turning 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 Products Standards Act, F r u i t and Vegetable Regulations, Queen's P r i n t e r , Ottawa 1968, Catalogue No. YX7/9-1955-27-1968. ** Courtesy Western Greenhouse Co-operative, Burnaby, B.C. %** Greenhouse tomato grades and standards are the same as f i e l d tomato grades and standards. f i e l d tomatoes by count are turning i n the case of tomatoes grown other than i n B r i t i s h Columbia and Manitoba; "turning" means (i) that the f i e l d tomato shows from a tinge to 25 percent pink or red colour, and ( i i ) not more than 10% of the f i e l d tomatoes by count are mature or semi-ripe; "semi-ripe" means (i) that the f i e l d tomato shows from 25 percent to 75 percent pink or red colour, and ( i i ) not more than 10 percent of the f i e l d tomatoes by count are turning or firm r i p e ; and "firm r i p e " means (i ) that the f i e l d tomato shows from 75 percent to 100 percent pink or red colour, and ( i i ) not more than 10 percent of the f i e l d tomatoes by count are semi-ripe. 

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