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Effects of sub-optimal ripening temperatures on tomato fruit quality as determined by objective measurement Koskitalo, Leslie Norman 1970

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EFFECTS OF SUB-OPTIMAL RIPENING TEMPERATURES ON TOMATO FRUIT QUALITY AS DETERMINED BY OBJECTIVE MEASUREMENT BY LESLIE NORMAN KOSKITALO B.Sc, University of Manitoba, 1963 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY i n the Department of Plant Science x We accept t h i s t h esis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA June 1970 i i 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 requirements f o r an advanced degree at the University of B r i t i s h Columbia, I agree that the Library s h a l l make i t f r e e l y available f o r reference and study. I further agree that permission f o r extensive copying of t h i s t h esis f o r scholarly purposes may be granted by the Head of my Department or by h i s representatives. I t i s understood that copying or publication of t h i s t h esis f o r f i n a n c i a l gain s h a l l not be allowed without my written permission. Department of Plant Science, The University of B r i t i s h Columbia Vancouver 8, Canada Date i i i ABSTRACT Controlled environment experiments were conducted to study the influence of four night/day temperature regimes; 1-7.8/25.6, 7.2/18.3, 4.4/15.6 and 2.8/13.9°C on the q u a l i t y of tomato f r u i t s , Lycopersicon  esculentum M i l l . c v . Ea r l y Red Chief, measured object i v e l y at three harvest dates. Temperature ef f e c t s on vegetative and reproductive growth and f r u i t cracking were also examined. In addition, the s t a b i l i t y of carotenoid pigments of macerated and cubed f r u i t stored at -20° f o r 0, 10, 20 and 40 days was studied. Low a i r temperatures decreased plant growth, caused chlorosis of vegetative growth, and reduced the frequency of f r u i t cracking but had l i t t l e e f f e c t on f r u i t weight. Flower formation continued at a l l temperatures with the exception of the 2.8/13.9 environment while f r u i t set occurred only at the two highest thermal regimes. F r u i t s harvested at 17.8/25.6 were considerably lower i n t o t a l s o l i d s , reducing sugars and t i t r a t a b l e a c i d i t i e s and had sub s t a n t i a l l y higher pH values than f r u i t exposed to 7.2/18.3, 4.4/15.6 and 2.8/13.9. Temperature had l i t t l e or no e f f e c t on f r u i t r e f r a c t i v e indices and t o t a l pectic substances. The f a i l u r e of t o t a l p ectic substances to r e f l e c t the apparent firmness differences between treatments indicates that t o t a l p ectic substances are not a sa t i s f a c t o r y index of t h i s q u a l i t y parameter. Surface and i n t e r n a l lightness and yellowness declined with i v increasing temperatures and l a t e r harvests, while redness values i n -creased. F r u i t harvested at 17.8/25.6 attained a f u l l red coloration i n 7 days, while those exposed to 7.2/18.3 required about 14 days to reach a comparable l e v e l of colour development. F r u i t exposed to 2.8/13.9 were of i n f e r i o r colour as evidenced by high L and b^ values and low a^ values. The high degree of association between lightness and yellowness values under a l l treatment conditions suggests that surface colour and, to a l e s s e r extent, i n t e r n a l colour can be adequately s p e c i f i e d i n terms of . a constant and two, rather than three, variables. The high o v e r a l l c o r r e l a t i o n c o e f f i c i e n t obtained between sur-face and i n t e r n a l Lb/a r a t i o s immediately indicated the p o s s i b i l i t y o f u t i l i z i n g surface Lb/a r a t i o s to predict i n t e r n a l colour. Temperature and harvest dates influenced the r e l a t i o n s h i p between i n t e r n a l and surface colour r a t i o s as evidenced by the decrease i n c o r r e l a t i o n c o e f f i c i e n t s with higher temperatures and l a t e r harvests. The e f f e c t of decreasing temperatures on tomato colour was found to be l a r g e l y a function of temperature effects on lycopene syn-t h e s i s . Colour values showed marked changes as t o t a l carotene concen-t r a t i o n s increased up to about 55 ug/g fresh weight. Continued increases above t h i s l e v e l were not accompanied by p a r a l l e l changes i n surface or i n t e r n a l colour. Temperatures and harvest dates affected a l l pigment concen- • t r a t i o n s with the exception of T-carotene and, f o r the most part, /3-carotene. V The temperature regimes ranked i n order of decreasing f r u i t q u a l i t y were as follows: 7.2/18.3; 17.8/25.6; 4.4/15.6; 2.8/13.9. Although of sa t i s f a c t o r y c o l o r a t i o n , f r u i t s harvested at 17.8/25.6 were rated below the 7;2/18.3 f r u i t f o r reasons of lower dry matter, sugar and acid contents. Storage duration had l i t t l e e f f e c t on carotenoid concentrations of cubed samples. In macerated samples, phytoene, phytofluene and f-carotene concentrations decreased with storage time. When fresh samples were analysed, a l l pigment concentrations with the exception of lycopene were found to be much lower i n macerated than i n cubed samples. v i TABLE OF CONTENTS Page INTRODUCTION 1 LITERATURE REVIEW 3 Tomato Quality 3 Tomato Colour 3 Tomato Colour Measurement 4 Subjective Methods 4 Objective Methods 5 Assessment of Measuring Methods and Data Reduction 7 Carotenoids 9 Spectral Properties 10 Carotenoids of Tomato F r u i t s 10 Spe c i f i c a t i o n of Tomato Colour Based on Pigment Studies 11 Firmness 12 Firmness Measurements 13 Pectic Substances 14 Relationship of Pectic Substances to Kinesthetic Properties of Plant Materials 15 Changes i n Pectic Substances with Ripening 17 Other Constituents of Tomato Quality 19 Flavour 20 Temperature 21 Effect of Temperature on Colour and Pigment Concentrations during Ripening 21 v i i Page Ef f e c t o f Temperature on Firmness and P e c t i c Constituents 26 Temperature E f f e c t s on Other Components of Quality 27 Low Temperature Injury 29 MATERIALS AND METHODS 30 Plant Growth 30 Establishment of Temperature Programmes 32 Experimental Design 36 A n a l y t i c a l Sequence 36 Carotenoid S t a b i l i t y Study 43 RESULTS 44 E f f e c t o f Controlled Environment on Vegetative Growth 44 E f f e c t o f Controlled Environment on Reproductive Growth 47 E f f e c t s of Ripening Temperatures on some Chemical Characteristics of Tomato F r u i t s 47 Dry Matter 55 Refractive Index 55 pH 56 T i t r a t a b l e A c i d i t y 56 P e c t i c Substances 57 E f f e c t of Ripening Temperatures on F r u i t Colour 57 External Colour 57 Internal Colour 63 Relationships between Colour Variables 66 Ef f e c t of Temperature on Carotenoid Development During Ripening 73 v i i i Page Carotenoid S t a b i l i t y Study 80 DISCUSSION 85 Temperature Effects on Vegetative Growth 85 Temperature Effects on F r u i t i n g 86 F r u i t Cracking 87 Effect of Ripening Temperatures on Chemical Characteristics of Tomato F r u i t s 88 Effect of Temperature on Surface Colour 94 Internal Colour and the Relationship to Surface Colour 98 Association between Tristimulus Colour Coordinates of Tomato F r u i t s 100 Effect of Temperatures and Harvests on F r u i t Carotenoids .102 Relationship of Carotenoids to Tomato Colour 105 Effect of Sample Condition and Storage Duration on Carotenoid Pigments 106 SUMMARY AND CONCLUSIONS 108 BIBLIOGRAPHY 113 ix LIST OF TABLES Page Table 1. Data Used in Quantitative ^termination of Pigments 42 Table 2. Effect of Temperature on the Frequency of Fruit Cracking at Three Harvest Dates 48 Table 3. Effect of Temperature on Fruit Weight at Three Harvest Dates 49 Table 4. Specification of Controlled Environment Temperature Replicates 50 Table 5. F Values and the Significances of Main Effects and Interactions on Chemical Characteristics of Tomato Fruits 51 Table 6. Effect of Temperature on Chemical Characteristics of Tomato Fruits at Three Harvest Dates 52 Table 7. Analysis of Variance for L e Colour Values to Indicate the Complete Partition of Variation in the Split Plot Analysis 60 Table 8. F Values and the Significances of Main Effects and Interactions on Fruit Colour 61 Table 9. Effect of Temperature on Surface Colour 62 Table 10. Effect of Temperature on Internal Colour 64 Table 11. Correlation Coefficients for External and for Internal Colour Variables 67 Table 12. Correlation Coefficients for Surface and Internal Colour Measurements at Four Temperatures 70 Table 13. Correlation Coefficients for Surface and Internal Lb/a Indices 71 Table 14. Analysis of Variance for Carotenoid Temperature-Harvest Date Study 74 Table 15. F Values and the Significances of Main Effects on Pigment Concentrations 75 X Page -Table 16. Temperature and Harvest Effects on Pigment Concentrations 76 Table 17. F Values and the Significances of Main Effects and Interactions f o r Pigment Losses During Storage at -20°C 82 Table 18. Effect of Sample Condition and Storage Duration on Carotenoid Concentrations 84 x i •LIST OF FIGURES Page Fig. 1. Greenhouse Grown Plant Immediately P r i o r to Placement i n a Growth Cabinet 31 Fig . 2. Average Daily Temperature Curve 33 Fig . 3. Temperature Programmes Used i n Growth Chamber Experiments 34 Fig . 4. Growth Chamber Temperature Programmer i n Operation f o r the 17.8/25.6 Regime 35 Fig . 5. Sequence of Analysis 37 Fig . 6. Typical Absorption Spectrum of a Carotenoid Extract P r i o r to Chromatography 41 Fig . 7a. Plant Responses to Controlled Environment Treatments of 40 Days Duration. Temperatures: 17.8/25.6 l e f t , and 7.2/18.3 r i g h t . 45 Fi g . 7b. Plant Responses to Controlled Environment Treatments of 40 Days Duration. Temperatures: 4.4/15.6 l e f t , and 2.8/13.9 r i g h t . ' 46 Fig . 8a. Influence of Temperature and Harvest Dates on Dry Matter, Refractive Index and Reducing Sugars of Tomato F r u i t s 53 Fi g . 8b. Influence of Temperature and Harvest Dates on pH and T i t r a t a b l e A c i d i t y of Tomato F r u i t s 54 Fig . 9. Temperature-Maturity Tomato Colour Gradients. Above: Side View. Below: Blossom End View. 58 Fi g . 10. Influence of Temperature on Internal Colour Ratios 65 Fig . l l a - c . Relationships Between Surface L, a. and b T Values 68 X l l Page Fig . 12a-c. Relationships Between Internal L, a, and b. Values L L 69 Fig. 13a. Influence of Temperature at Three Harvest Dates on Carotenoid Pigments. Top: Phytoene. Centre: Phytofluene. Bottom: a-Carotene. 77 Fi g . 13b. Influence of Temperature at Three Harvest Dates on Carotenoid Pigments. Top: /3-Carotene. Centre: f-Carotene. Bottom: 7-Carotene. 78 Fi g . 13c. Influence of Temperature at Three Harvest Dates on Carotenoid Pigments. Top: Neurosporene. Bottom: Lycopene. 79 x i i i ACKNOWLEDGEMENTS I wish to express my sincere appreciation to Dr. Douglas P. Ormrod, formerly Professor, Department of Plant Science, University of British Columbia and presently Professor and Chairman, Department of Horticultural Science, University of Guelph, Ontario, under whose supervision this study was conducted, for his valuble advice and criticism during the research and for his guidance in the preparation of this manuscript. I am also thankful to the members of my graduate committee: Dr. V.C. Brink, Department of Plant Science Dr. C.A. Hornby, Department of Plant Science Dr. J.F. Richards, Department of Food Science Prof. E.L. Watson, Department of Agricultural Engineering Dr. G.H.N. Towers, Department of Botany for their encouragement and continued interest in my research and for the review of this thesis. I am especially indebted to Dr. G.W. Eaton and Mr. W.R. Coshow for their assistance in the statistical analysis and computer programming of the data. The technical assistance of Mrs. E. Gates, Mrs. E. Searl, Miss C. Beech, and Mr. R. Charles and the help with laboratory equipment by Mr. I. Derics, technician, is greatly appreciated. I thank Mr. F. Eady for his help given from time to time, and Miss J. Burnell-Jones and Mrs. P. Ward for their typing of this thesis. xiv The -monetary support o f the Canada Department o f A g r i c u l t u r e and N a t i o n a l Research C o u n c i l o f Canada through p r o j e c t f i n a n c i n g and through post-graduate s c h o l a r s h i p s i s g r a t e f u l l y acknowledged. 1 INTRODUCTION The tomato (Lycopersicon esculentum M i l l . ) i s a warm climate species of sub-tropical o r i g i n , grown extensively i n the United States ( C a l i f o r n i a , F l o r i d a , Texas, Indiana, Maryland, New Jersey), Mexico, Spain, Netherlands and A u s t r a l i a . Cool temperatures represent one of the dominant factors l i m i t i n g the d i s t r i b u t i o n of the crop i n Canada, and consequently production i s l a r g e l y confined to areas i n southern Ontario, notably the counties of Essex and Kent. Tomatoes destined f o r fresh market consumption are harvested at stages of maturity ranging from mature green to f i r m red, while those destined f o r processing are usually harvested at a f u l l red condition. Low temperatures during the harvest period not only influence the y i e l d , but also the q u a l i t y of the f r u i t . Prolonged exposure of vine-ripening f r u i t to temperatures below about 10°C r e s u l t s i n c h i l l i n g i n j u r y and hence f r u i t of i n f e r i o r or unacceptable q u a l i t y . Many studies have been ca r r i e d out to assess the ef f e c t s of ripening temperatures on f r u i t q u a l i t y constituents; however, a wide number have not considered the diurnal character of the temperature factor. In most instances, detached f r u i t have been used to study the influence of ripening temperatures on physical and chemical components. The use of the l a t t e r experiments as a basis of prediction of f r u i t q u a l i t y under glasshouse or f i e l d conditions may be invalidated to some degree by vi r t u e of the fact that continuing translocation between the vine and f r u i t during the ripening process has been eliminated as an 2 i n t r i n s i c factor. Colour i s one of the most important and complex at t r i b u t e s of f r u i t q u a l i t y and hence considerable attention has been directed towards i t s characterization and measurement. Although colour grading of tomatoes i s based, almost without exception, on v i s u a l a p p r a i s a l , emphasis i n recent years has been placed on objective measurement by photoelectric t r i s t i m u l u s colorimetry. The i n t e r - r e l a t i o n s h i p s of the tri-coordinate colour values during the ripening of tomato f r u i t s has received only l i m i t e d investigation. A knowledge of the re l a t i o n s h i p between these values under a wide range of environmental conditions i s imperative i n the derivation of meaningful colour indices. The chemical analysis of f r u i t tissues during maturation affords the opportunity of studying changes i n chemical constituents and t h e i r possible r e l a t i o n s h i p s ; i n many cases, a n a l y t i c a l data can be u t i l i z e d as indices of q u a l i t y . For example, carotenoid analysis of tomatoes not only permits i d e n t i f i c a t i o n and q u a n t i f i c a t i o n of pigments, but also indicates the p a r t i c u l a r pigments relevant to colour and permits an approximate evaluation of colour q u a l i t y . .Quality improvement through se l e c t i v e breeding and improved c u l t u r a l practices requires a comprehension of the physical and chemical p o t e n t i a l i t i e s of the plant material against a background of s p e c i f i c environments. The primary objectives of the present study were to determine the effects of sub-optimal a i r temperatures at three s p e c i f i c harvest dates on tomato f r u i t q u a l i t y as indicated by colour, pigments, pH, t i t r a t a b l e a c i d i t y , sugars, r e f r a c t i v e index, t o t a l pectic substances and dry matter. 3 LITERATURE REVIEW Tomato Quality Food q u a l i t y has been defined as "the composite of those c h a r a c t e r i s t i c s that d i f f e r e n t i a t e i n d i v i d u a l units of a product and have significance i n determining the degree of a c c e p t a b i l i t y of that unit to the user" (Kramer, 1965). Attributes of q u a l i t y have been measured by sensory, chemical and instrumental means. For purposes of standardization and uniformity i n q u a l i t y evaluation, emphasis has been placed on the development and u t i l i z a t i o n of objective methods f o r the measurement of various q u a l i t y a t t r i b u t e s (Kramer, 1951, 1966; Nauman, 1965; Mackinney et a l . , 1966). Of the c h a r a c t e r i s t i c s contributing to the q u a l i t y of tomatoes and tomato products, colour, texture, and flavour have been considered as major c r i t e r i a of product acceptance. Objective measurements to determine the q u a l i t y of tomatoes have included: colour, pigments, firmness, pectic substances, pH, t o t a l a c i d i t y , sugars, soluble s o l i d s , t o t a l s o l i d s and ascorbic acid. (Underwood, 1950; Forshey and Alban, ^S 1*; Kattan et a l . , 1957; Yamaguchi et a l . , 1960). Tomato Colour Colour has not only been found to constitute an important com-ponent and measure of f r u i t q u a l i t y , but also i s recognized as contributing s i g n i f i c a n t l y to the grade of raw and processed tomato products. Colour has been found to serve as the most r e l i a b l e index of tomato maturity. McCollum (1956) pointed out that age, s i z e and appearance 4 before i n c i p i e n t c o l o r a t i o n , were not accurate measures of maturity. He concluded that although carotenoid production varied i n r e l a t i o n to other ripening changes, colour served as the best i n d i c a t o r of ripeness. He therefore suggested the breaker stage as a good base l i n e i n sampling f o r ripeness. The breaker stage may be defined as that point at which the green f r u i t f i r s t shows v i s u a l evidence of yellow to orange pigmentation. Coloration usually i n i t i a t e s at the s t y l a r region. Tomato Colour Measurement Colour i s regarded as one of the most d i f f i c u l t q u a l i t y factors to evaluate, p a r t i c u l a r l y i n view of the fact that the development of measur-ing methods has presented i n d i v i d u a l problems with each food product (Robinson et al.,1952). Desrosier (1954) concluded that tomato colour q u a l i t y was most accurately estimated by evaluation of the extracted j u i c e rather than by surface or cross-sectional examination. Yeatman and Sidwell (1958) found that the resultant colour of a blend of several tomatoes was biased i n the d i r e c t i o n of the redder f r u i t and hence concluded that i n d i v i d u a l f r u i t s were best f o r colour determination. Subjective Methods Tomato colour has been subjectively assessed by d i r e c t v i s u a l inspection, or more commonly, with the assistance of reference guides including standard colour plates, three-dimensional models, colour handbooks and colour d i c t i o n a r i e s . For example, t h e ' p r a c t i c a l l y uniform good red colour" of Canada Fancy grade canned tomatoes i s defined as "a colour t y p i c a l of red or reddish v a r i e t i e s i n which not le s s than 95 per cent of the surface areas of the tomatoes are as red as "Tomato Red" (Plate 3, 1-12) and not more than 5 per cent of the surface areas may be as yellow as or possess less red 5 than Plate 4, F-12 as i l l u s t r a t e d i n Maerz and Paul 1s Dictionary of Colour" (Canada Department of Agriculture, 1966). Spinning disc colorimeters employing Munsell notations have been used extensively f o r tomato colour measurement (MacGillivray, 1928, 1931a, 1931b, 1937, 1948; M i t c h e l l , 1935; Nickerson, 1946; Kramer and Smith, 1946; Robinson et a l . , 1952; Gould, 1953). The "good colour" and "reasonably good colour" of Canada Fancy and Canada Choice tomato j u i c e and concentrated tomato ju i c e are spe c i f i e d i n terms of Munsell colour discs (Canada Department of Agriculture 1966). Although the use of spinning disc colorimeters constitutes an improvement over the aforementioned procedures, the f i n a l judgement remains subjective and hence, f o r example, Kramer et a l . (1959) reported that evaluations of the same samples by d i f f e r e n t laboratories resulted i n a va r i a t i o n of as much as two colour grade points. Carasco (1937) indicated preference f o r the Lovibond Tintometer i n the colour grading of canned and dried tomatoes but t h i s instrument does not appear to be used extensively f o r tomato colour measurements. The accuracy of subjective evaluations may be regarded as being dependent upon such factors as normality of observer v i s i o n , observer fatigue, colour uniformity of the sample, surface gloss, s i z e and shape of the f r u i t , product wetness, i n t e r n a l c e l l structure, p a r t i c l e d i s t r i b u t i o n and 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 . (MacGillivray, 1931a; Hunter, 1942; Smith and Huggins, 1952; Mavis and Gould, 1954; Wegener et a l . , 1957; Mackinney and L i t t l e , 1962). Objective Methods Objective .techniques f o r tomato colour determination have i n -cluded chemical a n a l y s i s , reflectance spectrophotometry, and photoelectric 6 .tristimulus colorimetry. The l a t t e r represents a most rapid and convenient .means of measurement. .The Hunter Color and Color Difference Meter (C.D.M.) (Hunter, 1948, 1958) has perhaps been the most widely applied instrument i n tomato colour measurement. The Hunter C.D.M. was designed as a photoelectric t r i s t i m u l u s colorimeter that incorporated source f i l t e r photo-cell combinations approximating the Commission Internationale de l'Eclairage ( C L E . ) x, y, z", standard observer functions and computer c i r c u i t r y , thereby permitting psy-c h o l o g i c a l l y s i g n i f i c a n t colour estimation without elaborate c a l c u l a t i o n (Hunter, 1942, 1958; Hunter Assoc. Lab. Inc., 1966). In other words, the Hunter instrument measures colour p h y s i c a l l y and d i r e c t l y translates the stimulus i n terms of three v i s u a l l y meaningful scales, data from which can be used f o r c a l c u l a t i n g values which correlate w e l l with the hue, saturation and lightness of v i s u a l perception. The Hunter L scale measures lig h t n e s s , the a^ scale redness when p o s i t i v e , gray when zero and greenness when negative, and the b^ scale yellowness when p o s i t i v e , gray when zero and blueness when negative. Hunter (1958) presented the following equations f o r the conversion of Hunter C.D.M. values i n t o C L E . values: L = lOOY^ a L = 175Y~^ (1.02X-Y) b L = 70Y - J s (Y-0.847Z) The C L E . system was designed to provide f o r the mathematical expression of colour data i n terms of the absolute (X,Y,Z) or f r a c t i o n a l (x,y,z) amounts of the red, green and blue primaries necessary f o r the imaginary standard observer to ef f e c t a match with a given sample (Davis and Gould, 1955; Clydesdale, 1969). 7 Although Hunter values do not d i r e c t l y constitute measures of .the physiological colour a t t r i b u t e s , Younkin (1950a, 1950b) and Davis and Gould (1955) developed methods f o r converting Hunter measurements of tomato purees into Munsell renotation terminology. The Munsell system was produced f o r the s p e c i f i c a t i o n of colour i n terms of three v i s u a l l y uniform scales namely, hue, value and chroma. How-ever, an examination of the Munsell colours confirmed i r r e g u l a r i t i e s i n spacing and hence revised notations referred to 'as Munsell renotations were derived (Newhall, 1940; Newhall et a l . , 1943; Nimeroff, 1968). Assessment of Measuring Methods and Data Reduction Evaluations of methods of colour measurement have been based on the degree of association with complementary colour scoring by experienced observers. In discussing the r e l a t i o n s h i p of v i s u a l estimates and measured values, Hunter (1942) summarized factors which could i n t e r f e r e with the c o r r e l a t i o n . Kramer (1952) stated that a co r r e l a t i o n c o e f f i c i e n t of .90 between a measurement method and observer s p e c i f i c a t i o n constituted excellent agreement, while a co r r e l a t i o n c o e f f i c i e n t of<(.80 was in d i c a t i v e of an unsatisfactory method. In terms of tomato colour measurement, the performance of the Hunter C.D.M. was rated superior to subjective procedures, chemical methods, reflectance spectrophotometry and the use of the Photovolt Reflection Meter, the Agtron and the Purdue Colour-Ratio Meter, f o r reasons of speed, accuracy and precision (Kramer, 1950; Robinson et a l . , 1952; Desrosier, 1954). Younkin (1950) found that the C.D.M. could detect differences i n puree colours that were not v i s u a l l y apparent. 8 Data reduction has taken the form of u t i l i z a t i o n of the one or more measured variables f o r the computation of single value colour indices through the use of multiple regression equations, charts or nomographs (Kramer, 1951). Numerous colour indices have been proposed f o r the s p e c i f i c a t i o n of raw or processed tomato colour. MacGillivray (1931a) formulated a colour index based on the Munsell System. His colour r a t i n g formula was: (13.00 - Chroma Number) + Hue. Kramer (1950) derived a regression equation where colour score = 12.6 + .553a - 1.478b. Robinson et a l . (1952) found that Hunter a^/b^ r a t i o s were "a convenient and accurate method of expressing the colour of tomato j u i c e within the brightness and chromaticity ranges normally encountered". Halsey and Jamison (1958) observed a high c o r r e l a t i o n between v i s u a l scoring of tomato colour and a/b r a t i o s . In contrast, Mavis and Gould (1954) reported that the Lb/a expression gave superior correlations with subjective (U.S.D.A.) colour evaluations of tomato pulp. Yeatman and Sidwell (1958) confirmed Younkin's (1954) opinion that a/b values did not f u l l y characterize tomato j u i c e colour. Younkin (1954) pointed out that since the concentrations and types of pigments varied with v a r i e t y , environment and stage of maturity, each colour a t t r i b u t e could a f f e c t the appearance thus necessitating incorporation of a l l three dimensions of colour i n the c a l c u l a t i o n of indices. In concurrence with Younkin's views, Yeatman et a l . (1960) derived a formula f o r computing raw tomato jui c e colour which was capable of d i s -tinguishing differences between the samples obtained from f r u i t ripened under a wide range of conditions. The formula 9 TP , n , 2000 cos 6 Tomato Colour = j- a. where cos 6 = (Hunter notations), 4 was found to provide the best r e l a t i o n s h i p ( r = .95) between v i s u a l colour scores and instrumental evaluations. Based on t h i s function, Hunter and Yeatman (1961) developed the Direct-Reading Tomato Colorimeter. In the measurement of processed tomato jui c e colour, i t was found that the Lb/a r a t i o was s u b s t a n t i a l l y superior to the ^QQQ^cos 6 formula (Yeatman, 1969). Carotenoids The colour of ripening tomatoes has been found to be due largely to the presence of a complex carotenoid pigment system; the colour appearance are conditioned by the p a r t i c u l a r pigment types and concentrations; these i n turn are determined by genetic c o n s t i t u t i o n and environment. Carotenoids have been described as yellow to red fat-soluble polyenes (usually C^g compounds) composed of isoprene units arranged such that c e n t r a l methyl groups occupy 1:6 positions r e l a t i v e to each other while a l l other methyl side chains occupy 1:5 positions v i z : l-« *-5 CH, CH, CH, CH, I l I 3 I -C=CH-CH=CH-C=CH-CH=CH-CH=C-CH=CH-CH=C-l-< *~t> The series of conjugated C=C double bonds constitutes the chromophoric system of the carotenoids (Karrer, 1948; Goodwin, 1952, 1955; Commission of the 10 Nomenclature of B i o l o g i c a l Oiemistry, 1960). Spectral Properties The wavelength and i n t e n s i t i e s of the carotenoid absorption maxima (generally three) have been found to be a function of the number of con-jugated double bonds. The colour properties of carotenoids are dependent upon a chromophoric system of greater than four conjugated double bonds. Thus, f o r example, the 'colourless carotenoid' phytoene with three conjugated double bonds, shows no absorption maxima i n the v i s i b l e region of the spectrum, whereas lycopene ( i n hexane) with eleven conjugated bonds absorbs predominantly at 443, 472, and 504 m u (Weedon, 1965). In addition, solvent ef f e c t s and s t r u c t u r a l variations i n carotenoid molecules have been shown to profoundly influence the spectral properties. In t h i s connection, Karrer and Jucker (1950) have outlined a series of empirical relationships e x i s t i n g between carotenoid structure and spectra. Zechmeister (1962) has reviewed the ef f e c t of trans>cis isomerization on the absorption spectra of carotenoids. Zechmeister and Polgar (1943) Observed that i n the conversion o f the a l l - t r a n s i n t o a mixture of cis-trans isomers, colour i n t e n s i t y decreased. The spectral curves i n the v i s i b l e region were altered as follows: 1) the ex t i n c t i o n values and the degree of fi n e structure decreased; 2) the absorption maxima s h i f t e d towards shorter wavelengths. Carotenoids of Tomato F r u i t s Jensen (1967) has stated that approximately 180 carotenoids are known to occur n a t u r a l l y . Curl (1961) reported i s o l a t i n g 22 xanthophyll components from tomato f r u i t s of which the major proportion consisted of l u t e i n , v i o laxathin and neoxanthin. The carotenoids of tomatoes have been found 11 to consist predominantly of carotenes (Kuhn and Grundmann, 1932). Trombly and Porter (1953) l i s t e d 19 carotenes obtained from tomato extracts. The two polyenes (colourless carotenoids) phytoene and phytofluene are common to tomatoes (Porter and Zscheile, 1946a; Rabourn and Quackenbush, 1953; Tomes, 1963) McCollum (1955) showed that the colour of red tomatoes was dependent upon the t o t a l carotenoids as w e l l as the r a t i o of the dominant pigments, lycopene and /3-carotene. McCollum noted that although /3-carotene represented only two to ten percent of the t o t a l carotenoids, i t exerted a pronounced e f f e c t on colour. figment d i s t r i b u t i o n studies indicated that the concentration of t o t a l carotenoids was highest i n the outer pericarp while /3-carotene quantities were greatest i n the l o c u l a r region (McCollum 1955). Polar differences have been studied by E l l i s and Hamner (1943) and McCollum (1955) who found that although coloration was usually i n i t i a t e d i n the a p i c a l end, carotene content was greatest i n the proximinal region of the r i p e f r u i t . To compensate f o r polar and morphological differences McCollum (1955, 1956) recommended that i n sampling f o r colour and/or pigment studies equal and opposite f r u i t sectors should be used when whole f r u i t s were not a v a i l a b l e . Speci f i c a t i o n of Tomato Colour Based on Pigment Studies A number of investigators have attempted to characterize tomato colour on the basis of carotenoid content. Hunter and Yeatman (1961) indicated that because several d i f f e r e n t pigments combined to produce the colour of tomatoes, the colour p o t e n t i a l could not be s a t i s f a c t o r i l y measured by a simple procedure such as the absorption of a single pigment at a single wavelength. Davis (1949) used the l i g h t absorption data from acetone 12 extracts as an index of colour. Kramer and Smith (1946) observed a good cor r e l a t i o n between transmittance readings at 485 millimicrons of tomato benzene extracts and organoleptic colour ratings. Younkin (1954) pointed out that the methods of Kramer and Smith (1946) and Davis (1949) assumed that the r e l a t i v e amounts of the p r i n c i p a l pigments were constant when i n fact Went et a l . , (1942) and Porter and Zscheile (1946b) had established that such was not the case. McCollum (1953) described a method i n which the t o t a l carotenoid to /3-carotene r a t i o was calculated as a chemical index of colour; however, he had noted e a r l i e r (McCollum,1944) that several factors (unspecified) other than t o t a l pigments influenced the colour values of tomato j u i c e to an unknown extent. MacGillivray (1948) and Robinson et a l . (1952) stated that since tomato colour was also dependent upon factors other than carotenoid quantity, s p e c i f i c a t i o n of colour based on pigment concentrations was not recommended. Further, MacGillivray (1948) concluded that colour data could be more accurately interpreted i f expressed i n terms of colour a t t r i b u t e s . Firmness Kattan (1957) pointed out that firmness ranked second only to colour as a q u a l i t y parameter i n fresh market and processing tomatoes. Firmness has been regarded as an important fa c t o r i n the mechanical harvesting, handling, shipping and marketing of tomatoes (Sayed et a l . , 1966). Firmness of the fresh f r u i t determines to a large extent the t e x t u r a l properties of processed tomatoes. For example, Luh et a l . (1960) showed that juices made from s o f t - r i p e tomatoes were thinner i n consistency than those made from firm-ripe f r u i t . Moghrabi (1958) has stated that catsup y i e l d s may vary by as much as 25 percent depending on firmness of f r u i t . 13 Firmness Measurements Several instruments have been devised f o r firmness measure-ments of tomato f r u i t s . Fischer and Sengbush (1935) measured firmness by placing the f r u i t under a cork attached to a fulcrum. A weight was sh i f t e d across the beam u n t i l the f r u i t was seen to s p l i t . The readings were found to be influenced by f r u i t diameter and furthermore, the exact time of s p l i t t i n g was d i f f i c u l t to e s t a b l i s h . West and Snyder (1938) measured firmness of tomato f r u i t s with a C h a t i l l o n penetrometer. The method used by Paech (1938) i n which a plunger was forced against the f r u i t w a l l u n t i l the f r u i t was punctured, required a gradual increase i n pressure u n t i l penetration occurred. Hamson (1952a) c r i t i c i z e d e a r l i e r methods as being too slow and inaccurate. The Cornell pressure t e s t e r developed by Hamson (1952a5b) was designed to measure firmness i n a manner s i m i l a r to hand compression. Since firmness was determined by compression at a single point on the f r u i t , the measurement pos i t i o n presented a problem p a r t i c u l a r l y i n large loculed f r u i t . Kattan(1957 a,b) overcame t h i s d i f f i c u l t y by devising an instrument (Firm-o-meter) based on a multi-point compression p r i n c i p l e . A force was applied to a chain e n c i r c l i n g the f r u i t and the resultant s t r a i n was measured on a scale graduated from zero to ten. The scale readings were inversely related to firmness. The scale values were not influenced by differences i n f r u i t d i a -meter as also found by Hamson (1952a) r e l a t i v e to the Cornell pressure t e s t e r . Further, t h e i r data indicated s i g n i f i c a n t agreement with subjective firmness evaluations. Garrett et al_. (1960) evaluated a number of instruments and found that the Asco Firmness Meter showed exceptionally good agreement with panel 14 measurements. Ang et a l . (1963) compared panel firmness ratings of canned whole tomatoes with Kramer Shear press measurements. The co r r e l a t i o n c o e f f i c i e n t s between the shear press with the Universal c e l l attachment and subjective evaluations were .88 and .92 f o r the two experiments ca r r i e d out. Pectic Substances ' The l i t e r a t u r e on pectic substances i s characterized by c o n f l i c t i n g terminology, broad d e f i n i t i o n s , and i n many cases, questionable methods. Kertesz (1951) and Joslyn (1962) have therefore emphasized the d i f f i c u l t i e s i n the inte r p r e t a t i o n and evaluation of many of the e a r l i e r research reports. Pectic substances may be described as c o l l o i d a l polyuronide macromolecular complexes consisting mainly of D-galacturonic acid residues lin k e d together by a-l,4 glycosidic bonds to form a l i n e a r polymer. The carboxyl groups of the chain are O-methylated to varying degrees. (Bonner, 1950; Kertesz, 1951, 1963). I t has been suggested that c e r t a i n sugars and t h e i r derivatives are covalently attached to the polygalacturonide backbone and could w e l l form an intimate part of the main chain (Albersheim, 1965). Evidence quoted i n support of t h i s proposal includes studies by A s p i n a l l and Canas-Rodriguez (1958) who confirmed the presence of L-rhamnose, L-arabinose and D-galactose i n pectic acid i s o l a t e s of the s i s a l plant (Agave sisalana). Further, A s p i n a l l and Fanshawe (1961) detected L-rhamnose, L-arabinose, D-galactose and traces of L-fucose, 2-0-methyl-L-fucose, 2-0-methyl-D-xylose and a number of oligosaccharides on p a r t i a l hydrolysis of pec t i c acid 15 extracted from a l f a l f a (Medicago s a t i v a ) . •Pectic substances of higher plants have been found to occur i n the intercommunicating c e l l u l o s e i n t e r s t i c e s of primary c e l l walls and have been noted as c o n s t i t u t i n g the major component of the middle lamella (Bailey, 1938). Pectic constituents of the middle lamella are believed to consist p r i m a r i l y of water-insoluble calcium and magnesium pectates which act to cement adjacent c e l l s together thus imparting firmness to tissues (Bonner, 1950). Pectic substances are generally classed as protopectins, p e c t i n i c acids and pectic acids. Pectic substances are also frequently designated i n terms of the solvent systems used f o r t h e i r extractions. Relationship of Pectic Substances to Kinesthetic Properties of Plant Materials  Although present i n l i m i t e d amounts, the quantities and nature of pectic constituents have been found to contribute considerably to the firmness of fresh tomatoes, the s t r u c t u r a l i n t e g r i t y or wholeness of the canned product and the consistency of tomato purees, pastes, catsups, sauces and juices (Kertesz and McColloch, 1950; Kertesz, 1951; Luh et a l . , 1954). Hamson (1952a) correlated instrumental firmness measurements with the various pectic fractions of f i r m and soft tomato l i n e s . He noted that water-soluble, ammonium oxalate-soluble, and acid-soluble pectins were s i g n i f i -cantly correlated with firmness at the f i v e percent l e v e l , while t o t a l pectins were s i g n i f i c a n t at the one percent l e v e l . In addition, i t was found that f i r m v a r i e t i e s were consistently higher i n a l l pectic f r a c t i o n s and i t was therefore concluded that marked quantitative differences i n the uronide 16 constituents were associated with differences i n firmness. Haber and LeCrone (1933) observed that the softening of tissues was accompanied by a conversion of insoluble into soluble forms of pectin. Moghrabi (1958) found that the pectic change most cl o s e l y associated with softening of fresh tomato f r u i t s was the decrease i n protopectin. Foda (1957) and Sayed et a l . (1966) also concluded that the protopectin constituents appeared to be the f r a c t i o n contributing most to the firmness of fresh tomatoes. In reference to processed tomatoes, Appleman and Conrad (1927) observed a r e l a t i o n s h i p between the pectin to protopectin r a t i o of fresh tomatoes and the amount of di s i n t e g r a t i o n of the whole canned product. Deshpande et al_., (1965) found that firmness of canned tomatoes was s i g n i f i -cantly correlated with t o t a l pectic constituents, with the r a t i o of carbonyl to pectic content, and with mineral content. The r e s u l t s indicated that a high content of pe c t i c substances, large molecular s i z e , and low methoxyl con-tent of pectic constituents would r e s u l t i n improved firmness. Kertesz (1940) observed that the firmness of canned whole tomatoes could be improved by the addition of calcium s a l t s , presumably because the calcium reacted with the pectic acid present i n the f r u i t to form a gel which supported the c e l l structure. Rooker (1930) was one of t h e . f i r s t workers to emphasize the significance of pectic substances i n tomato products other than the whole canned f r u i t . McColloch et a l . (1950) indicated that lower pectin contents due to enzymatic a c t i v i t y during processing generally resulted i n tomato pastes of lower consistency. Tomato j u i c e has been described as a diphasic system composed of serum and suspended p a r t i c l e s . Pectic substances i n the f l u i d phase were 17 found to play an important r o l e i n determining the serum v i s c o s i t y and hence, consistency. Pectic compounds i n the suspended p a r t i c l e s were also regarded as contributing to ju i c e consistency, but to a l e s s e r extent. (Kertesz and Loconti, 1944; Kertesz, 1951). Changes i n Pectic Substances with Ripening Appleman and Conrad (1927) reported changes i n pectic substances with maturation and noted that protopectin predominated i n green f r u i t but as ripening progressed, p a r t i a l hydrolysis resulted i n the decrease of protopectin and the corresponding increase i n soluble pectin. The loss of pectate from the middle lamella i s considered to cause softening of the f r u i t as maturation progresses. Kertesz and McColloch (1950) studied pectic transformations during ripening but found no i n d i c a t i o n of any d e f i n i t e quantitative or compositional trend. Moghrabi (1958) pointed out that these negative findings could possibly be explained on the basis that the f r u i t used i n the study had advanced beyond the maturity stage where s i g n i f i c a n t changes i n pectic constituents could be expected and further, that low f i e l d temperatures may have complicated the r e s u l t s . Dalai et a l . (1965, 1966) found that t o t a l pectin concentrations were highest i n green f r u i t between one and three inches i n diameter and gradually decreased with i n -creasing coloration. Soluble pectin increased throughout a l l maturity classes studied. Although Woodmansee et al_. (1959) found ho consistent changes i n the soluble pectin f r a c t i o n of unripe, r i p e and over-ripe f r u i t s , a number of researchers (Haber and LeCrone 1933; Luh et a l . 1960) have demonstrated the gradual increase i n t h i s f r a c t i o n , and i t s subsequent s l i g h t decline with f r u i t deterioration. 18 McClendon et a l . (1959) found that free galacturonic acid increased by a factor of 10 during ripening but the amount present i n r i p e tomatoes was small r e l a t i v e to the t o t a l uronide f r a c t i o n . Spenser (1965) indicated that the small amount present could not account f o r the decrease i n soluble pectic substances during the ripening period. However, she reasoned that once free galacturonic acid was formed, i t was further metabolised and hence, did not accumulate. The exact manner i n which pectic substances are degraded i s incompletely understood. Spenser (1965) pointed out that changes i n pectic substances during ripening involve depolymerization, demethylation and deacetylation. S t i e r et a l . (1956) stated that some evidence suggested protopectin depolymerization into soluble pectin followed by d e - e s t e r i f i c a t i o n and hydrolysis i n t o smaller u n i t s . The degradation of pectic substances during ripening has been att r i b u t e d to two classes of p e c t y o l y t i c enzymes, namely, polygalacturonases (PGs) and Pectinesterases (PEs). Polygalacturonase enzymes act to cleave a-1, 4 1 - g l y c o s i d i c linkages and can be subdivided i n t o three types. Type I PGs are believed to s p l i t g l y c o s i d i c bonds at random and to p r e f e r e n t i a l l y attack pectic substances of high molecular weight and low methoxy content. Type I I PGs are considered to show preference f o r highly e s t e r i f i e d polygalacturonides. Type I I I PGs are believed to hydrolyse pectic substances systematically beginning at one end of the molecule. Pectinesterases catalyse the removal of methyl ester groups from pectic substances. (Deuel and Stutz, 1958). Kertesz (1938) emphasised the importance of pectic enzymes i n a f f e c t i n g the q u a l i t y of tomato products. He noted the rapid increase i n 19 PE with ripening, and attributed the decrease i n v i s c o s i t y of cold pressed tomato j u i c e to demethoxylation caused by extensive PE a c t i v i t y . Other Constituents of Tomato Quality Quality i s dependent upon physical and chemical components and a wide number of compositional studies have been c a r r i e d out on tomato f r u i t s (Bohart, 1940; Winsor and Massey, 1958; Winsor et a l . , 1962a,b; Hanna, 1961; Woodmansee et a l . , 1959; Simandle et a l . , 1966; Yamaguchi et a l . , 1960; Lee and Sayre, 1946; Thompson, 1965; Thompson et a l . , 1962; Dalai et a l . , 1965, 1966). McCollum (1956) pointed out that the composition of tomato f r u i t s varies with such factors as maturity, l i g h t exposure, temperature, morpholo-g i c a l structure and po s i t i o n on the plant. He further stated that "Where the constituents of q u a l i t y are dependent upon so many fa c t o r s , differences between progenies or treatments are d i f f i c u l t to measure without the utmost care i n sampling". The majority of studies appear to indicate that pH, sugars, t o t a l s o l i d s and soluble s o l i d s tend to increase while t o t a l a c i d i t y decreases with ripening. The l i t e r a t u r e on the pattern of changes during ripening presents a somewhat variable picture. Janes (1941) reported that t i t r a t a b l e a c i d i t y reached a maximum at the orange stage of maturity and subsequently decreased. Rosa (1925, 1926), U l r i c h and Renac (1950) and Winsor et a l . (1952a,b) found that t i t r a t a b l e a c i d i t y was highest at the mature green or breaker stages. Janes (1941) reported that sugar contents were maximal at the orange stage of ripening and thereafter decreased s l i g h t l y . Winsor et al.(1962a,b) and Rosa (1925, 1926) concluded that sugars generally increased from 20 the mature green to f u l l y red r i p e stages. I t i s probably that the v a r i a b i l i t y i n findings can be p a r t i a l l y explained i n terms of the factors c i t e d by McCollum (1956). Flavour: Flavour i s an agglomeration of sensations, the perception of which may involve the sense of taste and smell and the chemical sense (Crocker, 1945; Gorman, 1964). The physiological complexity of flavour has precluded the development of adequate objective procedures f o r the thorough character-i z a t i o n of the taste and odour of food materials. Panels provide the most sat i s f a c t o r y method of flavour assessment. However, Kramer (1966) pointed out that c e r t a i n flavour dimensions could be evaluated, at l e a s t i n part, by chemical and instrumental means. For example, sourness can be indicated by pH or t o t a l acid values, while sweetness can be approximated by sugar content or r e f r a c t i v e indices (Kramer, 1951, 1965). Sugars and organic acids (predominantly glucose, fructose, c i t r i c and malic acid) are regarded as the constituents p r i m a r i l y responsible f o r the taste of tomatoes, while l a r g e l y unknown v o l a t i l e compounds account f o r tomato odour (Simandle et a l . , 1966; Dalai et a l . , 1966; Lower and Thompson, 1966, 1967; Winsor, 1966). •Hamdy and Gould (1962) suggested the p o s s i b i l i t y of using a-keto g l u t a r i c to c i t r i c acid and a-amino-nitrogen to c i t r i c a cid r a t i o s f o r the objective determination of processed tomato flavour. Scott and Walls (1947) found that the sugar/total a c i d i t y r a t i o s of r i p e f r u i t and processed j u i c e were i n close agreement with 21 organoleptic flavour ratings. Juices with high sugar/acid r a t i o s were bland, lacked sharpness i n t a s t e , and tended to be " f l a t " . Juices with low r a t i o s were sharp and acid. .Forshey and Alban (1954) considered that tomato f r u i t s with pH ranges of 4.05 to 4.15, t i t r a t a b l e a c i d i t i e s of .45 to .55 per cent, and reducing sugars of 3.20 to 3.50 per cent were of high q u a l i t y . F r u i t s with higher pH's or lower t i t r a t a b l e a c i d i t i e s , and lower reducing .sugars were rather " f l a t " and tas t e l e s s . S i m i l a r l y , Winsor (1966) found that f r u i t s low i n t i t r a t a b l e a c i d i t y and/or low i n sugar content were of i n f e r i o r taste. I t was stated that the best q u a l i t y f r u i t s were those high i n both sugars and organic acids. Winsor noted that the taste of f r u i t at the orange-red stage of maturity was superior to other maturity classes because of the r e l a t i v e l y high sugar content and adequate t i t r a t a b l e a c i d i t y l e v e l . Dalai et a l . (1966) concluded that the i n f e r i o r flavour of greenhouse-grown tomatoes as compared to field-ripened f r u i t could be attr i b u t e d to the lower concentrations of organic acids, sugars and v o l a t i l e reducing substances found i n the former. Temperature Effect of Temperature on Colour and Pigment Concentrations during Ripening  . Duggar (1913) discovered the effe c t of temperature on lycopene synthesis when he observed that constant temperatures of 30 to 37°C resulted i n yellow- to orange-coloured f r u i t . In addition, Duggar indicated that temperatures below 10°C sharply i n h i b i t e d lycopene development. These findings were substantiated by Rosa (1926) who studied the rela t i o n s h i p of temperature to the ripening of green tomatoes as indicated by pigment development. Rosa found that at temperatures of 4 and 8°C, no red, and l i t t l e yellow coloration occurred, thereby establishing a lower l i m i t of 8°C f o r lycopene production. However, i t was noted that f r u i t at the turning stage of maturity did become red when stored f o r 18 days at 8°C. Pigment development was slow and incomplete at 11°C, most rapid at 25°C and i n h i b i t e d at temperatures above 30°C. Hence, i t was evident that ripening temperature not only affected the f i n a l colouring, but also the rate of ripening. Wright et a l . (1931) found that at 15.6°C mature green tomatoes required from 19 to 30 days to ripen. An abrupt f a l l - o f f i n ripening rate was noted below 15.6°C i n a l l v a r i e t i e s studied. At 10°C mature green f r u i t required about 40 days to ripen and were pale i n colour. F r u i t held at 4.4°C f a i l e d to colour and showed considerable low temperature in j u r y a f t e r 10 days. The lowest ripening temperature providing good colour and flavour development was 12.8°C. In comparable studies Ayres and Peirce (1960) found that the rate of ripening proceeded i n the order: ambient room temperature, 25, 20, 15, 10°C. Vogele (1937) noted large differences i n per cent brightness, per cent purit y and dominant wavelength as calculated from spectral reflectance curves of f r u i t ripened at 32 and 36°C. He found that the optimum temperature f o r lycopene synthesis i n tomatoes was 24°C, and that f r u i t exposed to 40°C remained green i n spite of a subsequent return to lower temperatures. Vogele further noted that lycopene formation did not necessarily follow chlorophyll decomposition as previously supposed. MacGillivray (1934) studied coloration of f i e l d tomatoes as affected by diurnal temperature fluctuations and concluded that although 23 day temperatured considerably exceeded 32 C, lycopene formation was permitted because of lower night minimal temperatures. Yamaguchi et_ a l . (1960) and Sayre et a l . (1953) observed a s i m i l a r r e s u l t when tomatoes were exposed to variable d a i l y temperatures. 'Sayre et a l . (1953) compared tomatoes ripened under various diurnal temperature regimes and found e s s e n t i a l l y no difference i n Hunter a/b external colour r a t i o s or pigment concentrations between vine- and s e l f -ripened f r u i t . However, Hood (1959) found that i n the var i e t y Tiny Tim, lycopene development occurred up to 32°C i n f r u i t on the vine whereas the red pigmentation was retarded i n detached f r u i t at temperatures above 21°C. Hanson (1921) noted that ripening f r u i t progressed through a series of changes from green to whitish green (i n d i c a t i n g chlorophyll destruction); to l i g h t yellow as carotene synthesis was i n i t i a t e d ; and then through orange to red as the lycopene concentration increased. Although e a r l i e r researchers had observed colour changes i n tomatoes and attempted to r e l a t e these to carotenoid synthesis (Duggar, 1913; Rosa, 1926; MacGillivray, 1934), l i t t l e attention could be given to compre-hensive investigations on quantitative and q u a l i t a t i v e polyene changes as i n -fluenced by maturity, temperature and other factors u n t i l the development of r e l i a b l e carotenoid extraction and chromatographic resolution techniques ( S t r a i n , 1934; Zscheile et a l . , 1942; Zscheile and Porter 1947). Went et a l . (1942) studied the carotenoid contents of i n d i v i d u a l tomatoes ripened on plant under d i f f e r e n t temperatures and l i g h t i n g conditions and found i t impossible to compare i n d i v i d u a l values f o r the d i f f e r e n t l y treated f r u i t s due to high f r u i t t o f r u i t v a r i a b i l i t y within 24 treatments as indicated by a concomitant 26.5 C day - 20 C night investigation. They concluded that the physiological condition of the plants rather than the various 20°C - 26.5°C temperature combinations controlled carotenogenesis i n attached f r u i t . I t was further noted that a concentration change i n one carotenoid was generally p a r a l l e l e d by s i m i l a r behaviour i n the other f r a c t i o n s . In detached f r u i t , Went and h i s co-workers not only confirmed the temperature effects of lycopene synthesis, but also c a r r i e d out a quantitative study of 10 other carotenoid f r a c t i o n s as affected by ripening temperatures. The majority of the polyene f r a c t i o n s were s u b s t a n t i a l l y lower i n quantity when f r u i t s were stored at 33°C as com-pared to 26.5°C. Meredith and P u r c e l l (1966) determined quantitative changes i n carotenoids i n ripening Homestead tomatoes at s i x d i f f e r e n t maturity stages. The f r u i t were permitted to ripen at 22°C under reduced l i g h t u n t i l the required maturity stage (green, breakers, turning, pink, l i g h t red and red) was attained whereupon one-to two-kilogram samples were analyzed. Mature green tomatoes were found to contain only a and /3-carotene whereas f r u i t at the breaker stage also contained phytofluene, r-carotene, 7-carotene and lycopene. Phytoene appeared at the turning stage o f maturity. A l l pigments progressively increased i n concentration with the exception of a-carotene which gradually decreased with ripening beyond the breaker point and /3-carotene which increased up to the l i g h t red stage and thereafter decreased somewhat. Goodwin and Jamikorn (1952) studied the effect of 0°, 15°, 30° and 37°C temperatures on carotenoid biosynthesis i n excised green tomatoes 25 showing evidence of colour change, at ripening i n t e r v a l s of three, s i x , nine, and twelve days. Temperatures i n h i b i t i n g lycopene synthesis (0°C, and 37 UC) were also found to cause a corresponding marked suppression i n phytofluene, f-carotene and neurosporene production. Lycopene, phytofluene, f-carotene, and neurosporene tended to appear simultaneously during ripen-ing; however, subsequent accumulation rates d i f f e r e d s u b s t a n t i a l l y . a- and (3-carotene syntheses were reduced at 0°C but only s l i g h t l y i n h i b i t e d above 30°C. I t was concluded that a- and /3-carotene syntheses i n tomato f r u i t s were la r g e l y independent of the Porter-Lincoln pathway (Porter and Lincoln, 1950) and possibly coincided with a mechanism found i n leaves. Porter and Lincoln (1950) postulated that the biosynthesis of carotenoids- proceeds through successive dehydrogenation reactions and r i n g closures, thus: tetrahydrophytoene —> phytoene —> phytofluene —*• f-carotene —*- neurosporene lycopene —>• 7-carotene —*• /3-carotene —*- a-carotene. Interpretations of temperature e f f e c t s on the pattern of carotenoid development have been complicated by genetic, physiological and additi o n a l aspects. Thompson et a l . (1962) pointed out the d i f f i c u l t y i n the d i s t i n c t i o n between environmental and heretable ef f e c t s unless adequate sampling and t e s t i n g techniques are applied. Genetic involvement i n temperature ef f e c t s on carotenoids was emphasized by Tomes et a l . (1956, 1958). In temperature i n h i b i t i o n studies with normal red s t r a i n s , Tomes (1963) reaffirmed the finding that lycopene reduction was not accompanied by a s i g n i f i c a n t decrease i n /3-carotene. 26 This suggested that the former pigment did not represent a precursor of /3-carotene. However, i n the s t r a i n s High Beta and Intermediate Beta, a l l carotenoid f r a c t i o n s examined including /3-carotene were highly i n h i b i t e d at temperatures exceeding 30°C. Effect of Temperature on Firmness and Pectic Constituents The rate of decomposition of pectic substances and f r u i t soften-ing have been shown to be d i r e c t l y r e lated to temperature. Carre (1922), i n one of the f i r s t extensive works on pectic changes during storage, found that low temperatures decreased the rate of pectic breakdown i n apples. Haber and LeCrone (1933) measured the changes i n pectic substances of mature green (at point of i n c i p i e n t coloration) and f u l l y r i p e tomatoes stored at 2.2, 10, and 21.1°C f o r extended periods. He found that the rate and extent of change i n pectic constituents was proportional to temperature. At 21.1°C there was an increase i n soluble pectin at the expense of proto-pectin up to three weeks storage but thereafter protopectin, soluble, and t o t a l pectins decreased due to deterioration of the f r u i t . At lower temper-atures, the rate and extent of changes were considerably reduced. At 2.2°C protopectin contents tended to remain constant while the soluble pectin f r a c t i o n showed a s l i g h t increase. Moghrabi (1958) studied rates of change i n pectic constituents and firmness of tomatoes as affected by temperature and maturity. Samples were harvested at the time of i n c i p i e n t colouring and placed under constant temperatures of 15, 20, 30, and 35°C f o r periods of three, s i x , nine and twelve days. The most e f f e c t i v e temperature to retard softening, p a r t i c u l a r l y i n the e a r l i e r phases of ripening, was 15°C. The softness of f r u i t stored f o r nine days at 15° C was found to be equivalent to that of f r u i t stored 27 for. three days at 20 C. Loss of firmness proceeded i n the following order: 30, 35, 20, 15°C. Protopectin contents were found to drop sharply at a l l temperatures during the f i r s t three days with the highest rate of loss occurring at 15 and 20°C and the lowest at 35°C. The rate of decrease of the oxalate-extracted f r a c t i o n at d i f f e r e n t temperatures varied during ripen-ing. At 12 days, these losses varied d i r e c t l y with increasing temperature. Total pectins, as obtained by summation, decreased during ripening. The eff e c t of temperature on t o t a l pectic contents was not s i g n i f i c a n t f o r the variety W.R-3 but f r u i t s of the Stokesdale variety exposed to 35°C were con-s i s t e n t l y higher i n t o t a l pectin than those exposed at 15, 20 and 30°C. Foda (1957) found that tomatoes ripened at 15°C softened more r e a d i l y than at 30°C. Protopectin also decreased more ra p i d l y and water soluble pectin accumulated. The ammonium oxalate f r a c t i o n (low methoxyl pectin) was higher at 30°C due to a more favourable temperature f o r pectin-estrase a c t i v i t y . P a r t i a l i n a c t i v a t i o n of protopectinase at 30°C was indicated. Temperature Effects on Other Components of Quality Rosa (1926) determined compositional changes at four-day i n t e r v a l s i n green tomatoes stored under various constant temperatures. He noted that t o t a l s o l i d s and t o t a l acids decreased r a p i d l y i n f r u i t held at 25°C, while sugars increased s l i g h t l y during the f i r s t four days and then gradually de-creased. At 19°C, compositional changes were less rapid and less extensive. At 4 and 12°C, t o t a l s o l i d s and t o t a l acids showed l i t t l e change with time, but sugar concentrations slowly increased throughout the treatment period. Craft and Heinze (1954) concluded that temperature and duration of storage had l i t t l e or no eff e c t on t o t a l a c i d i t y , soluble s o l i d s , and pH. 28 Lingle et a l . (1965) placed tomato plants i n growth chambers maintained at day-night temperatures of 30-30, 30-25, 30-20, 30-15, 30-10, 30-5, and 23-17°C. F r u i t s at the canning-ripe stage of maturity were analyzed f o r various factors. Results indicated that pH and t i t r a t a b l e a c i d i t y were not influenced by night temperature. Total and soluble s o l i d s were lowest i n f r u i t held at 5°C and highest at 15 and 20°C night temper-atures . Wedding and Vines (1959) studied the eff e c t s of temperature on the development of hormone set f r u i t and found that soluble s o l i d s and t i t r a t a b l e a c i d i t y were s i g n i f i c a n t l y lower at 30-15°C day/night temper-atures compared to 25-15 or 20-10°C. Haber (1931) c a r r i e d out a detailed study that included the influence of temperature on tomato acid contents. He found that low temperatures (2.4,4.4 and 10°C) greatly retarded the rate of acid changes i n stored f r u i t . The t o t a l a c i d i t i e s of green mature tomatoes following four t o f i v e weeks storage were e s s e n t i a l l y the same f o r the three low storage temperatures. The t o t a l a c i d i t i e s of green mature f r u i t stored at 21.1°C decreased r a p i d l y and f e l l to much lower l e v e l s than those of corresponding f r u i t held at lower temperatures. The rate and extent of pH change varied d i r e c t l y with temperature and duration of storage. The pH increase was most marked and rapid at 21.1°C. H a l l , (1968) exposed tomato f r u i t s at the i n c i p i e n t colour stage to temperatures of 3.3, 7.2 or 10°C f o r zero, four or eight days with or without a subsequent s i x day storage period at 21.1°C. The t i t r a t a b l e a c i d i t y o f pericarp portions of f r u i t held at 3.3°C was s i g n i f i c a n t l y higher than that of f r u i t s stored at 7.2 or 10°C. The highest pericarp a c i d i t i e s occurred a f t e r four days at low temperatures. A c i d i t i e s of 29 pericarp and l o c u l a r portions of f r u i t c h i l l e d at four or eight days followed by s i x days at 21.1°C were higher than those of control f r u i t s ripened without p r i o r c h i l l i n g . I t was considered that low temperatures delayed ripening and so delayed acid decomposition. Low Temperature Injury C h i l l i n g i n j u r y has been described as a physiological disorder common to many f r u i t s and vegetables when exposed to non-freezing temperatures below about 10°C f o r an adequate period e i t h e r before or a f t e r harvest. A loss or reduction i n ripening capacity and other c h a r a c t e r i s t i c s has been found to be symptomatic of low temperature injury (Lewis 1961). Wright et a l . (1931) carr i e d out experiments to study c h i l l i n g e f f e c t s on tomatoes at various temperatures. Previously there was i n d i c a t i o n that when tomatoes were exposed to temperatures of 4.4°C or less f o r a very short time, the f r u i t was rendered incapable of ripening when reinstated to a more suitable environment. Diehl (1924) showed that tomatoes could t o l e r a t e exposure to near freezing temperatures f o r as long as f i v e days without i n j u r y , and furthermore, that l e s s damage resulted when c h i l l i n g occurred at the turning point as opposed to the mature green stage of maturity. Wright et a l . (1931) found that exposure of f r u i t to 0°C f o r one to four days di d not prevent subsequent ripening at 21.1°C, but the rate of ripening was retarded to a considerable extent. F r u i t stored f o r eight days at 0°C and then replaced into a 21.1°C environment f o r a period of 19 days showed very incomplete coloration and extensive decay. Lewis (1961) indicated that the extent of c h i l l i n g i n j u r y was prop-port i o n a l to the length of exposure to low temperatures and increased with decreasing c h i l l i n g temperatures. 30 MATERIALS AND METHODS Plant Growth Tomato plants ( c u l t i v a r Early Red Chief) grown i n a greenhouse, were transplanted from f l a t s i n to 9.5 l i t r e p l a s t i c p a i l s four to f i v e weeks a f t e r seeding. The plants were staked and then trimmed p e r i o d i c a l l y to remove excess l a t e r a l shoots and terminal growth. Between October and March supplemental l i g h t i n g was provided (cool white fluorescent; i n t e n s i t y approximately 2.7 klux [250 f t . c ] at plant l e v e l ; 14 hr. photoperiod). The ad d i t i o n a l l i g h t i n g was found to be necessary i n preliminary growth t r i a l s t o prevent flower abortion. The plants were watered d a i l y with Hoagland's solution (macro-nutrients only) (Hewitt, 1966), from age s i x weeks to the termination of each experiment. This was found to circumvent blossom end rot problems which occurred when plants received only water each day, with or without nutrient solution once weekly. Approximately two weeks before the f r u i t were expected to begin ripening (evaluated i n preliminary t r i a l s ) , 16 plants, selected on the basis of o v e r a l l condition, adequate numbers of f r u i t , and adequate s i z e of f r u i t , were divided i n t o four uniform groups (Fig. 1). Each group was then transferred from the greenhouse to a Per c i v a l Model PGC-78 growth chamber i n which plant a l l o c a t i o n was random. Growth chamber photoperiods of 15 hours per 24 hour cycle were maintained. Light from a combination of 16 cool white fluorescent lamps and 10, 40 watt tungsten filament lamps provided an i n t e n s i t y of about 12.9 klux at a distance of 20 cm below the l i g h t b a r r i e r . F i g . 1. Greenhouse Grown Plant Immediately P r i o r to Placement i n a Growth Cabinet 32 The growth cabinets were operated with a d a i l y 17.8-25.6°C minimum-mximum temperature programme u n t i l a number of f r u i t attained the breaker point. At t h i s time, i n d i v i d u a l f r u i t were tagged and temperature treatments i n i t i a t e d . Establishment of Temperature Programmes Thermographic charts covering the period September 8 through October 5 f o r 1964, 1965 and 1966 from Summerland, B.C. were evaluated i n order to es t a b l i s h an average d a i l y temperature curve (Figure 2) on which •the temperature regimes f o r the study were based. Only those days f o r which the temperatures approximated a t y p i c a l diurnal f l u c t u a t i o n (85 per cent of a l l days) were considered i n the determination of t h i s average d a i l y temperature curve. The i n i t i a t i o n and termination of the maximum temperature period was obtained by derivation of the mean times at which a temperature 2F° (1.1C°) below the d a i l y maximum occurred (12.33 p.m. - 4.47 p.m.). S i m i l a r l y , the minimum period was located by c a l c u l a t i n g the mean times f o r which the temperature was 1.1C° above the d a i l y minimum (2.12 a.m. -6.27 a.m.). The average d a i l y maximum and minimum temperatures were obtained f o r the s p e c i f i c period. Four temperature programmes (Figure 3) with selected minimum-maximum temperatures of: 1. 17.8 - 25.6°C 2. 7.2 -18.3 3. 4.4 -15.6 4. 2.8 - 13.9 were patterned a f t e r the calculated curve. Growth chambers equipped with 20.04 12 2 4 6 8 10 12 2 4 6 8 10 12 2 A . M : P .MJ F i g . 2. Average Daily Temperature Curve 34 35 Fig. 4. Growth Chamber Temperature Programmer i n Operation f o r the 17.8/25.6 Regine 36 temperature programmers were then f i t t e d with p l e x i g l a s s cams (Figure 4) describing the derived d a i l y temperature curves. Experimental Design Growth chamber experiments were arranged as s p l i t - p l o t designs with a minimum of three r e p l i c a t i o n s . Four chambers representing the four d i f f e r e n t temperature regimes constituted a run or r e p l i c a t e . Each chamber contained four plants from which two f r u i t s per plant were harvested at seven, fourteen, and twenty-one days following the onset of i n c i p i e n t coloration (breaker p o i n t ) . A n a l y t i c a l Sequence Individual f r u i t s were weighed and analyzed as shown i n Figure 5, except that pigment studies were based on pooled samples. F r u i t s that weighed less than 90 grams were not analyzed and another f r u i t was selected to ensure that a l l plants were represented by two f r u i t s per harvest date. 1. External Colour: The Hunterlab Colour and Colour Difference meter was standardized using a black enamel-coated p l e x i g l a s s plate containing a central 1 1/16" bevelled aperture above which was placed a tomato red reference t i l e # D33C-221. The instrument was calibrated to read: L = 10.0, a^ = 7.7 and b^ = 2.8. The red t i l e was then replaced with a f r u i t and three readings taken at about 120° spacings on the lower h a l f of the tomato ensuring that the blossom end scar was not included. Average L, a^ and b^ values were reported. Following the removal of two cubes f o r subsequent pectin and pigment studies, the remaining portion of the f r u i t was blended f o r one minute. A s u f f i c i e n t amount of the macerated material was placed i n a 37 Fruit Washed, Dried, and Weighed EXTERNAL COLOUR Iubed\ PIGMENT STUDIES' <TOTAL PECTIC SUBSTANCES ^Maceratec pH Sieved .INTERNAL COLOUR TOTAL SOLIDS REDUCING SUGARS 'TITRATABLE ACIDITY REFRACTIVE INDEX F i g . 5. Sequence of Analysis 38 sample j a r and stored at -20°C f o r dry matter determination. 2. pH: pH was determined with a Radiometer PMH 26 pH meter previously standardized with a pH 4.0 buffer. The macerate was strained through a 1 mm. mesh sieve t o remove skin and seed fragments. 3. Internal Colour: F i f t y grams of sample was then immediately placed into a p l a s t i c sample tray and colour readings taken on the Hunterlab Colour and Colour Difference meter adjusted to L = 25.1, a^ = 25.5 and b^ = 11.9 with reference standard # D33C-221. 4. Total (Titratable) A c i d i t y : . Ten grams of freshly blended material was placed i n a 250 ml beaker with 150 ml of d i s t i l l e d water and t i t r a t e d with 0.1N NaOH to pH 8.1. 5. Refractive Index: A small amount of material was f i l t e r e d under pressure through Whatman No. 2 V f i l t e r paper and the r e f r a c t i v e index of the f i l t r a t e determined at 20°C on a Bausch and Lomb refractometer. 6. Reducing Sugars: The Lane and Eynon copper reduction method as described by Ruck (1963) was applied t o extracts prepared according to the National Canners Association (N.C.A.) Laboratory manual (1956). 7. Total Solids: A modification of the N.C.A. (1956) method f o r t o t a l s o l i d s determination was used. Approximately 10 grams of thawed, blended sample was placed i n pre-desiccated 9 x 2 cm aluminum moisture dishes, covered, and quickly weighed on an a n a l y t i c a l balance. Excess moisture was driven o f f 39 over a water bath and the samples were then placed i n a vacuum oven operated at 70°C and 25 to 27 inches (125 to 75 mm) mercury. A i r was permitted to enter the oven at the rate of four to s i x bubbles per second, a f t e r having been double dried through s u l f u r i c acid. At the end of three hours, the a i r flow rate was increased to about 8-10 bubbles per second and the samples removed from the oven one hour l a t e r . The moisture dishes were covered, cooled overnight i n a desiccator, and f i n a l weights obtained. Results, as indicated by the i n i t i a l 50 samples, were s u f f i c i e n t l y reproducible so as to obviate the necessity of further duplicate analyses. 8. Total Pectic Substances: Twenty to t h i r t y gram tomato cubes were weighed, placed i n 125 ml 95% eth y l alcohol, and stored at 0°C p r i o r to analysis. The material was blended f o r f i v e minutes and f i l t e r e d on a Buchner funnel using Whatman No. 1 f i l t e r paper. The residue was washed with a d d i t i o n a l 95% ethanol. The residue plus f i l t e r paper was then macerated with 200 ml 0.5% Versene and the pH adjusted to 11.5. The remainder of the preparation procedure and the spectrophotometric determination were ca r r i e d out as described by McComb and McCready (1952a, b). 9. Pigment Analyses: The eight samples representing the same maturity from a given growth cabinet were thawed a f t e r short term -20°C storage and equal weights combined. Thirty grams of pooled material were blended f o r two to three minutes with 100 ml 75 - 60 v/v acetone-hexane. The mixture was f i l t e r e d through a Buchner funnel and the residue washed with 50 ml acetone-40 hexane solution. The residue plus f i l t e r paper was then macerated with a small amount of the solvent system and r e - f i l t e r e d thereby providing a very rapid and e f f i c i e n t means of pigment extraction. The crude extract was p u r i f i e d as described by Tomes (1963). An absorption spectrum was obtained f o r the p u r i f i e d carotenoid solution using a Unicam SP 800 recording spectrophotometer (Fig. 6). The concentration of the extract (expressed as lycopene) was determined i n order to monitor column recoveries. Column recoveries averaged 87%. Immediately p r i o r to chromatography the sample was concentrated to about 10 ml i n a f l a s h evaporator at 40°C. An aliquot of the con-centrated extract was then spotted on a lOx 1.5 cm magnesium oxide - Hyflo SuperCel 1:1 w/w column (Sephadex K 15/30 brand). Duplicate columns were run by stepwise e l u t i o n beginning with 0% acetone i n hexane through to 18% acetone-hexane. E l u t i o n of the f i n a l pigments bands was accelerated by the addition of small amounts of 95% ethanol i n acetone-hexane. The fractions c o l l e c t e d were washed four times with large volumes of d i s t i l l e d water and t h e i r spectra obtained. Pigment concentrations were calculated according to the following formula: 4 C = ?![E X 1 0 ((OD x E V ) + + (OE^ x EV k)) E, 0 x Sv x W lcm where C = concentration i n Mg/gm fresh weight OD = o p t i c a l density at the specified wavelength (refer to Table 1) 1% . . E, extinction c o e f f i c i e n t lcm = EV = eluent volume SV = volume of extract spotted on column wavelength m i l l i m i c r o n s Fig. 6. Typical Absorption Spectrum of a Carotenoid Extract Prior to Chromatography 4 2 T A B L E 1 D a t a U s e d i n Q u a n t i t a t i v e D e t e r m i n a t i o n o f P i g m e n t s 1% P i g m e n t s E n — - 1 c m P h y t o e n e 8 5 0 P h y t o f l u e n e 1 5 0 0 a - C a r o t e n e 2 7 5 0 0 - C a r o t e n e 2 5 0 0 ^ - C a r o t e n e 2 2 0 0 5 - C a r o t e n e 3 2 1 0 Y - C a r o t e n e 2 7 0 0 N e u r o s p o r e n e 2 9 9 0 L y c o p e n e 3 2 0 0 W a v e l e n g t h (m^) 2 8 6 3 4 8 4 4 6 4 5 1 4 0 0 4 5 6 4 6 0 , 4 3 8 5 0 2 R e f e r e n c e R a b o u r n a n d Q u a c k e n b u s h 1 9 5 3 P o r t e r a n d L i n c o l n 1 9 5 0 P o r t e r a n d L i n c o l n 1 9 5 0 L i m e e t a l . 1 9 5 2 P o r t e r a n d L i n c o l n 1 9 5 0 T o m e s 1 9 6 3 P o r t e r a n d L i n c o l n 1 9 5 0 T o m e s 1 9 6 3 P o r t e r a n d L i n c o l n 1 9 5 0 43 W = weight of tomato sample TVE = t o t a l volume of extract a f t e r concentration Pigment i d e n t i t i e s were established by 1. the p o s i t i o n of absorption bands on the column 2. comparison of absorption spectra i n hexane and chloroform with known samples or reported spectra 3. t h i n layer co-chromatography where authentic samples were available Carotenoid S t a b i l i t y Study: Pigment decomposition during sample storage was suspected because of inconsistencies i n the data. An experiment was therefore designed i n order to assess the ef f e c t s of storage form and duration on carotenoid concentrations. F r u i t from tomato plants grown under greenhouse conditions were harvested 14 days following breaker point. Longitudinal sections of 20 to 30 grams were cut from each of three to f i v e f r u i t s , sealed i n containers and placed i n -20°C storage. The remaining portions of the f r u i t s were combined, macerated f o r 2J§ - 3 minutes, 30 gram samples • weighed out (required 2 - 3 minutes) and stored as above. Pigment analyses were conducted on fresh samples, and on pooled material stored f o r 10, 20 and 40 days. 44 RESULTS Effect of Controlled Environment on Vegetative Growth Effects of temperature on vegetative growth and development were r e a d i l y observed (Fig. 7a,7b). Plants exposed to the 17.8/25.6°C night/day diurnal temperature system exhibited rapid and p r o l i f i c shoot growth. Shoots i n i t i a t e d before and p a r t i c u l a r l y during the con-t r o l l e d environment period were very t h i n and showed extreme elongation under growth chamber conditions. Emergent leaves were somewhat reduced i n s i z e . The upper vegetative canopy remained green, while extensive chlorosis and abscission of lower leaves was noted. In contrast, plants grown at 7.2/18.3 showed a growth pattern more c h a r a c t e r i s t i c of plants held under greenhouse conditions. Elongation of both e x i s t i n g and newly developed shoots did not appear to be abnormal. The apparent quantity of vegetative material produced at 7.2/18.3 was less than that produced under the 17.8/25.6 temperature regime. In addition, the death of lower leaves was reduced considerably. At 4.4/15.6, shoot formation was n e g l i g i b l e , while growth of older shoots was sharply i n h i b i t e d . The die-back of lower leaves was very l i m i t e d . Shoot i n i t i a t i o n and growth di d not occur at 2.8/13.9. The 2.8/13.9 environment was obviously below that required f o r plant s u r v i v a l over an extended period. Low temperatures increased the degree of chlorosis (Fig. 7a, 7b). L i t t l e or no di s c o l o r a t i o n was at t r i b u t a b l e to temperature within the 17.8/25.6 treatment. At 7.2/18.3 a l i m i t e d amount of di s c o l o r a t i o n was evident. At 4.4/15.6 considerable c h l o r o s i s , l a r g e l y r e s t r i c t e d to the -F 7a. Plant Responses t o Controlled Environment Treatments of 40 Days Duration. Temperatures: 17.8/25.6 l e f t , and 7.2/18.3 r i g h t . Insert: Flowering and Fr u i t Set at 7.2/18.3. F i g . 7b. Plant Responses to Controlled Environment Treatments of 40 Days Duration. Temperatures: 4.4/15.6 l e f t , and 2.8/13.9 r i g h t . CD 47 upper portion of the plants was r e a d i l y noted. At 2.8/13.9 chlorophyll destruction was general and severe. Effect of Controlled Environment on Reproductive Growth Flowering and f r u i t set continued at the two highest temperatures (Fig. 7b). Some flowering was evident at 4.4/15.6 but no new f r u i t were produced. No flowering occurred at 2.8/13.9. The tomato f r u i t s were found to be very prone to cracking under growth chamber conditions (Table 2). A very high incidence of r a d i a l and concentric cracking was observed at 17.8/25.6. The frequency of cracking decreased with lower temperatures. Cracking was most prevalent at the 21 day harvest. F r u i t tended to be smallest at 17.8/25.6 and weights were somewhat higher at the two intermediate temperatures but these differences, were not s i g n i f i c a n t (Table 3). Effects of Ripening Temperatures on some Chemical Characteristics of Tomato Frui t s  I n i t i a l l y , experiments were designed with a minimum of three r e p l i c a t i o n s . However, growth chamber malfunctions resulted i n unequal r e p l i c a t i o n between the d i f f e r e n t temperature regimes (Table 4) with respect to dry matter, r e f r a c t i v e index, reducing sugar, pH, and t i t r a t a b l e a c i d i t y data analyses. In these instances, s t a t i s t i c a l analyses were car r i e d out on the data from the two complete r e p l i c a t e s R^  and R^  (Tables 5 and 6). The raw data provided by r e p l i c a t e Rg were not considered to be t r u l y i n d i c a t i v e of the influence of temperature during ripening Table 2. Effect of Temperature on the Frequency of F r u i t Cracking at Three Harvest Dates Harvests (days from breaker point) Temperature 7 14 21 17.8/25.6 35.7* 75.6 95.7 7.2/18.3 23.4 41.7 . 66.0 4.4/15.6 14.7 12.5 48.5 2.8/13.9 15.2 17.6 40.6 "Each figure represents the percent of f r u i t having one or more cracks and i s derived from a minimum sample size of 32 f r u i t . Table 3. Effect of Temperature on F r u i t Weight at Three Harvest Dates Harvests (days from breaker point) TemDerature 7 14 21 17.8/25.6 165.6* 160.6 162.4 7.2/18.3 174.6 183.9 172.5 4.4/15.6 177.8 186.5 175.3 2.8/13.9 164.9 169.3 170.8 Each value i s the mean of three r e p l i c a t e s . The means were not s i g n i f i c a n t l y d i f f e r e n t according to Duncan's multiple range t e s t (P = .05). Table 4. Specif i c a t i o n of Controlled Environment Temperature Replicates Replicate Temperature R l R2 R3 R4 R5 17.8/25.6 + + + + + 7.2/18.3 + + + + + 4.4/15/6 + + - + 2.8/13.9 + + + experiment completed experiment not completed because of equipment malfunction Table 5. F Values and the Significances of Main Effects and Interactions on Chemical Characteristics of Tomato F r u i t s Variable Treatment Effect Dry Matter Refractive Index Reducing Sugars pH T i t r a t a b l e A c i d i t y Pectins Temperature 1.82 .54 3.01 10.17* 5.80 2.03 Harvest .42 .09 1.41 66.13* 5.92 1.19 T x H 1.76 1.10 1.30 8.16* .47 .64 + The analyses of variance were based on r e p l i c a t e s R^  and R^, except i n the case of pectins where three complete replicates were used. * Only the F values f o r pH were s i g n i f i c a n t l y d i f f e r e n t (P = .05) 52 Table 6. Effect of Temperature on Chemical Characteristics of Tomato F r u i t s at 3 Harvest Dates Harvests (days from breaker stage) Variable Temperature 7 14 21 6.08* a • 6.07 a 6.13 a 6.69 a 6.50 a 6.43 a 6.69 a 6.62 a 6.44 a 6.75 a 6.53 a 6.19 a 1.3406 a 1.3407 a 1.3409 , 1.3411 a 1.3413 a 1.3412 , 1.3410 a 1.3413 a 1.3410 , 1.3414 a 1.3412 a 1.3406 , 2.99 a 2.81 a 2.69 a 3.11 a 3.19 a 3.09 a 3.27 a 3.08 a 3.06 a 3.38 a 3.26 a 2.88 a 4.37 a 4.48 a 4.66 a 4.26 b 4.38 ab 4.45 b 4.24 b 4.31 b 4.41 b 4.22 b 4.30 b 4.40 b 6.91 a 5.73 b 4.96 b 8.42 a 7.09 ab 6.13 ab 8.31 a 7.32 a 6.47 a 8.68 a 7.65 a 6.75 a 17.8/25.6 Dry Matter 7.2/18.3 (percent) 4.4/15.6 2.8/13.9 17.8/25.6 Refractive 7.2/18.3 Index 4.4/15.6 2.8/13.9 17.8/25.6 Reducing 7.2/18.3 Sugars 4.4/15.6 (per cent) 2.8/13.9 17.8/25.6 7.2/18.3 p H 4.4/15.6 2.8/13.9 17.8/25.6 Ti t r a t a b l e 7.2/18.3 A c i d i t y 4.4/15.6 (ml 0.1 N NaOH) 2.8/13.9 Pectins (per cent A.U.A.) 17.8/25.6 7.2/18.3 4.4/15.6 2.8/13.9 .276 a .304 a .296 a .314 a .260 a .277 a .288 a .306 a .272 a .276 a .289 a .296 a Each value i s the mean of 2 re p l i c a t e s except f o r t o t a l pectins which are means of 3 r e p l i c a t e s . Figures followed by the same l e t t e r within a p a r t i c u l a r measurement and harvest are not s i g n i f i c a n t l y d i f f e r e n t at P = .05, according to Duncan's multiple range t e s t . 53 Harvests (days past breaker stage) 2.60t_J , i_ 7 14 21 F i g . 8a. Influence of Temperature and Harvest Dates on Dry Matter, Refractive Index, and Reducing Sugars of Tomato F r u i t s 54 Harvests (days past breaker stage) 10.00i S-OO-LJ |  7 14 21 Fig. 8b. Influence of Temperature and Harvest Dates on pH and Ti t r a t a b l e A c i d i t y of Tomato F r u i t s 55 on several f a c t o r s , p a r t i c u l a r l y t i t r a t a b l e a c i d i t y , hence supplementary graphs were prepared. The use of means derived from a l l data exclusive of missing values was not s a t i s f a c t o r y as experimental runs (reps.) were s i g n i f i c a n t l y d i f f e r e n t i n almost every case regardless of the manner i n which v a l i d analyses of variance could be done. Table 4-indicates the possible combinations of r e p l i c a t i o n s and temperatures which can be used i n the analyses of variance. Thus, a general l i n e a r hypothesis computer programme (Sampson, 1968) was u t i l i z e d to provide predi c t i o n values f o r the missing data. The temperature x harvest date means which included predicted data were then computed and graph-i c a l l y presented (Fig. 8a and 8b). Dry Matter The dry matter contents of tomato f r u i t s were lowest at 17.8/25.6 f o r each of the three harvest dates (Fig. 8a). In addition, the per cent dry matter tended to decrease with l a t e r harvests at a l l temperatures except 17.8/25.6. The per cent dry matter showed no evidence of change with harvest dates at 17.8/25.6. The analysis of variance using only r e p l i c a t e s and Rg did not confirm the apparent temperature and harvest date effects on the per cent dry matter. Refractive Index Temperature and harvest dates appeared to have l i t t l e or no e f f e c t on f r u i t r e f r a c t i v e indices (Fig. 8a). The s t a t i s t i c a l analysis (Table 5 and 6) also showed that the r e f r a c t i v e index measurements d i d not change s i g n i f i c a n t l y with d i f f e r e n t temperatures or harvest dates. 56 Sugars Preliminary analyses demonstrated that sucrose, when present, occurred only i n trace quantities. Hence, subsequent analyses were done only f o r reducing sugars. The per cent reducing sugars were lowest at 17.8/25.6 and tended to increase with lower temperatures ( F i g . 8a). The reducing sugar contents of f r u i t showed a tendency to decrease with l a t e r harvests. Again the s t a t i s t i c a l analysis with r e p l i c a t e s R 3 and Rj-indicated that temperature and harvest e f f e c t s on sugar contents were non-significant (Table 5 and 6). pH The pH of tomato f r u i t s increased as the temperature and the number of days to harvest increased (Fig. 8b). The pH of f r u i t held at 17.8/25.6 was s i g n i f i c a n t l y higher than that of f r u i t at 2.8/13.9, 4.4/15.6 and 7.2/18.3 harvested at a comparable 7 day i n t e r v a l (Table 6). At 14 days, the pH's of 17.8/25.6 and 7.2/18.3 f r u i t did not d i f f e r s i g n i f i c a n t l y but pH's at 17.8/25.6 were s i g n i f i c a n t l y higher than those at the two lowest temperatures. At 21 days, the pH's of f r u i t maintained at the three lowest temperatures were considerably below those of f r u i t subjected to the 17.8/25.6 temperature. T i t r a t a b l e A c i d i t y T i t r a t a b l e a c i d i t y decreased with higher temperatures and l a t e r harvests (Table 8b). The t i t r a t a b l e a c i d i t y values of f r u i t held at 2.8/13.9 and 4.4/15.6 were almost i d e n t i c a l and decreased at the same rate with increasing harvest times. According to the analysis of 57 variance of r e p l i c a t e s and Rj., t i t r a t a b l e a c i d i t y was not s i g n i f i c a n t l y influenced by temperature or harvest date (Table 5). However, when 17.8/25.6, 7.2/18.3, and 4.4/15.6 data were analyzed using R2, R g and R &, temperature and harvest main effects were highly s i g n i f i c a n t . These data also indicated that t i t r a t a b l e a c i d i t y was s i g n i f i c a n t l y lower at 17.8/25.6 irr e s p e c t i v e of the harvest l e v e l . Further, differences between the 7- and 21-day harvests were demonstrated f o r the three higher temperature regimes. Pectic Substances Total pectic substances (per cent anhydrouronic acids) were highest at 2.8/13.9 and tended to decrease with higher temperatures. The pectic substances showed a s l i g h t decrease with l a t e r harvest dates. S t a t i s t i c a l analysis of the data showed that neither temperature nor harvest dates s i g n i f i c a n t l y influenced the t o t a l pectin contents of f r u i t s (Table 5 and 6). Effect of Ripening Temperatures on F r u i t Colour  External Colour Both the temperature and the number of days past the breaker point strongly influenced the surface colour of f r u i t ( Fig. 9). At 17.8/25.6 a minimum period of about 7 days beyond the breaker stage was required,to obtain f u l l red f r u i t . At 7.2/18.3, f r u i t required approximately 14 days following i n c i p i e n t coloration to a t t a i n a f u l l red condition. At 4.4/15.6, a near f u l l red was reached only a f t e r 21 or more days. At 2.8/13.9, f r u i t d i d not surpass a bright orange stage 58 Tig. 9. Temperature-Maturity Tomato Colour Gradients. Above: Side View. Below: Blossom End View. 59 of coloration. Coloration was less uniform at lower ripening temperatures. At the 7-day harvest at 2,8/13.9 and to a lesser extent at 4.4/15.6, f r u i t frequently possessed large green areas. Hunter L, a^ and external colour values were highly s i g n i f i c a n t l y affected by temperature and harvest dates (Table 7 and 8). The temperature x harvest interactions were s i g n i f i c a n t i n a l l cases. Duncan's multiple range t e s t s were done i n such a manner that the e f f e c t s of each temperature at each harvest l e v e l could be assessed (Table 9). Surface lightness, as measured by the Hunter L scale, increased with decreasing temperatures at a l l three harvest times. At 7.2/18.3, 4.4/15.6 and 2.8/13.9, lightness decreased with increasing harvest times. However, at 17.8/25.6, harvest dates had no e f f e c t on surface lightness. Hunter a^ values, a measure of sample greenness to redness, showed a considerable change with temperature. At 7 days, f r u i t redness increased progressively with increasing temperatures. At 14 days, surface redness i n t e n s i f i e d from 2.8/13.9 to 4.4/15.6 and 7.2/18.3. Hunter a L values of f r u i t from 17.8/25.6 were s i g n i f i c a n t l y lower than those of corresponding 14 day f r u i t from 7.2/18.3. At 21 days, a^ values were s i g n i f i c a n t l y greater at the two intermediate temperatures. When examined as a function of the harvest time, sample redness was noted to increase at 2.8/13.9 and 4.4/15.6. At 7.2/18.3, surface redness increased up to 14 days and thereafter decreased s l i g h t l y . At 17.8/25.6, a^ values decreased somewhat with each successive harvest date. Hunter b^ values were inversely related to both temperature and harvest time. The data show that the yellow component of the tomato Table 7. Analysis of Variance f o r L p . Colour Values to Indicate the Complete P a r t i t i o n of Variation i n the S p l i t Plot Analysis Source D.F. Sum Sq Mean Sq. Error F Run 2 12.78 6.39 Pot/RT 8.29** Temp 3 340.79 113.60 R x T 104.52** R x T 6 6.52 1.08 Pot/RT 1.41 n.s. Pot/RT 36 27.77 .77 1.98* Age 2 141.50 70.74 A x R 84.67** A x R 4 3.34 .83 A x P/RT 1.72 n.s. A x T 6 27.19 4.53 A x R x T 5.37** A x R x T 12 10.12 .84 A x P/RT 1.73 n.s. A x P/RT 72 35.03 .48 1.25 n.s. Error 144 56.21 .39 Total 287 661.27 n.s. Not Significant * Significant at P = .05 ** Significant at P = .01 Table 8. F values and the significances of Main Effects and Interactions on Fruit Colour External Colour Internal Colour Treatment Effect L a b L a b Temperature 104.52** 11.51** 117.97** 116.04** 24.96** 112.01** Harvest 84.67** 28.89** 87.39** 15.06* 39.80** 8.81* T x H 5.37** 24.95** 4.06* 4.98** 6.90* 7.40** * Significant at P = .05 ** Significant at P = .01 62 Table 9. Effect of Temperature on Surface Colour Harvests (days from breaker stage) Colour Scale Temperature 7 14 21 17.8/25.6 12.86*c 12.42d 12.30c L 7.2/18.3 14.80b 13.38c 12.91c 4.4/15.6 16.30a 14.34b 13.81b 2.8/13.9 16.26a 15.25a 14.56a 17.8/25.6 10.47a 10.15b 9.45b 7.2/18.3 9.69a 11.33a 10.84a 4.4/15.6 7.77b 10.74ab 11.29a 2.8/13.9 6.25c 8.68c 10.09b 17.8/25.6 4.40c 3.97d 3.88d 7.2/18.3 5.84b 4.86c 4.45c 4.4/15.6 6.84a 5.70b 5.29b 2.8/13.9 6.72a 6.25a 5.83a Each value i s the mean of 3 r e p l i c a t e s . Means followed by the same l e t t e r within a p a r t i c u l a r measurement and harvest did not d i f f e r s i g n i f i c a n t l y according to Duncan's multiple range t e s t at the 5% l e v e l . 63 colour was greatest at the 7-day harvest and was maximal at lower temperatures. Internal Colour Temperature and harvest main effects and the T x H interactions on i n t e r n a l colour measurements were s i g n i f i c a n t i n a l l cases (Table 8). Since the temperature x harvest interactions were s i g n i f i c a n t , the data were re-analyzed f o r simple e f f e c t s . The s i m i l a r i t i e s i n the Duncan's te s t r e s u l t s f o r the L, and a^ and b^ mean values f o r pureed and whole f r u i t samples (Table 9 and 10) suggested that i n t e r n a l colour changes tended to cl o s e l y p a r a l l e l those of f r u i t surfaces. The lightness of 7 and 14 day samples was highest at 2.8/13.9 and 4.4/15.6, lower at 7.2/18.3 and lowest at 17.8/25.6. At 21 days, i n t e r n a l L values decreased with successively higher temperature treatments. Hunter a^ values showed a marked dependence on temperature, p a r t i c u l a r l y at the 7-day harvest. Sample redness attained a maximal l e v e l i n 7 days at 17.8/25.6. At 14 and 21 days, f r u i t macerates from the 17.8/25.6 and 7.2/18.3 treatments were sub s t a n t i a l l y redder than corresponding samples derived from f r u i t s held at lower temperatures. Sample yellowness increased with lower temperatures at a l l three harvests. The highest b^ values were found at 2.8/13.9 at 7 days, while the lowest values were at 17.8/25.6 at 7 and 14 days. The i n t e r n a l L, a^and b^ values were not influenced by the selected harvest times at 17.8/25.6 i n contrast to the eff e c t at the other temperature regimes. When f r u i t colour was expressed i n terms of Lb/a r a t i o s (Fig.10), 64 Table 10. Effect of Temperature on Internal Colour Harvest Interval (days from breaker stage) Colour Scale Temperature 7 14 21 17.8/25.6 32.83*c 30.75c 31.90d 7.2/18.3 44.03b 36.11b 34.55c L 4.4/15.6 48.84a 42.06a 41.68b 2.8/13.9 49.54a 46.20a 45.04a 17.8/25.6 28.21a 28.34a 27.78a 7.2/18.3 20.72b 26.67a 26.68a 4.4/15.6 13.23c 21.98b 23.76b 2.8/13.9 9.67d 16.85c 18.94c 17.8/25.6 11.26c 11.40d 12.74c 7.2/18.3 16.34b 13.16c 12.73c 4.4/15.6 19.09a 15.62b 15.79b 2.8/13.9 21.05a 18.45a 18.10a see footnotes Table 9 -Z2/78.3--178/25.6-14 21 Harvests (days past breaker stage) F i g . 10. Influence of Temperature on Internal Colour Ratios 66 i t was r e a d i l y apparent that temperature effects were most pronounced at the 7-day harvest. From 7 to 14 days, Lb/a r a t i o s showed a very marked decline at 2.8/13.9 and 4.4/15.6, a lesser rate of decrease at 7.2/18.3 and l i t t l e or no change at 17.8/25.6. From 14 to 21 days, Lb/a r a t i o s dropped appreciably at 2.8/13.9, declined only s l i g h t l y at 4.4/15.6 and 7.2/18.3, and showed a small r i s e at 17.8/25.6. The 14-day 17.8/25.6 treatment had the lowest r a t i o . Relationships between Colour Variables When the Hunter values f o r surface colour were graphically compared, a number of in t e r - r e l a t i o n s h i p s between the L, a^ and b^ readings during the ripening process became immediately apparent. The L e x t t > e x t graph (Fig. 11a) demonstrated that the re l a t i o n s h i p between surface lightness and yellowness was e s s e n t i a l l y l i n e a r and that decreases i n surface lightness were consistently associated with losses i n sample yellowness. An o v e r a l l c o r r e l a t i o n c o e f f i c i e n t of .97 was obtained. Further, a high degree of association between and b g x t values persisted over a l l temperature and maturity ranges (Table 11). When L e x t and a e x t values were graphed, a parabolic curve resulted (Fig. l i b ) . The decrease i n surface lightness from a maximum magnitude of about 16 to about 14 was accompanied by a substantial r i s e i n external redness. Surface redness was maxminal when a lightness value of near 13.5 was attained. A further decrease i n lightness was then accompanied by a drop i n sample redness. An o v e r a l l c o r r e l a t i o n of .76 was obtained. The co r r e l a t i o n c o e f f i c i e n t decreased noticeably TABLE 11 Correlation Coefficients f o r External and Internal Colour Variables External Internal y L L a L L a Temperature °C Harvests (days from breaker x stage b a b b a b 7 .94 .30 .37 .67 .24 .55 17.8/25.6 14 .82 .67 .85 .84 .16 .15 21 .82 .65 .64 .84 .10 .28 7 .90 .35 .29 .66 .45 .56 7.2/18.3 14 .88 .31 .32 .79 .28 .10 21 .91 .83 .77 .81 .63 .44 7 .94 .26 .33 .71 .30 .37 4.4/16.5 14 .91 .21 .33 .85 .48 .34 21 .95 .75 .62 .81 .62 .70 7 .93 .46 .32 .34 .23 .47 2.8/13.9 14 .97 .63 .70 .64 .66 .47 21 .94 .56 .39 .85 .79 .74 Fig. l l a - c . Relationships Between Surface L, a^, and Values * Points on the graphs constitute data from one r e p l i c a t e . ** Equations based on three r e p l i c a t e s . oo F i g . 12a-c. Relationships Between Internal L, a^, and b^ Values ! •: Points on the graphs constitute data from one r e p l i c a t e . Equations based on three r e p l i c a t e s . to Table 12. Correlation Coefficients f o r Surface and Internal Colour Measurements at Four Temperatures X ^ext a e x t ^ext Lb/a . ext y L. . m t Lb/a. . mt a. . i n t Lb/a. . ant b. . ant Lb/a. . m t Lb/a. . m t 17.8/25.6 .27** .14 n.s. .08 n.s .05 n.s. .12 n.s. .27* .40** 7.2/18.3 . 69** .67** .63** -.68** .63** .67** .76** 4.4/15.6 .76** .69** .85** -.88** . 68** .63** .85** 2.8/13.9 .72** . 60** .80** -.65** .80**. . 61** .82** n.s. Not Significant * Significant at P = .05 ** Significant at P = .01 Table 13. Correlation Coefficients f o r Surface and Internal Lb/a Indices Harvests (days past breaker stage) Temperature 7 14 21 17.8/25.6 .59** .31* .49** 7.2/18.3 .68** .68** .58** 4.4/15.6 .75** .68** .54** 2.8/13.9 .70** .67** .65** * S i g n i f i c a n t at P = .05 ** Sig n i f i c a n t at P = .01 72 with higher temperatures and l a t e r harvests (Table 11). The re l a t i o n s h i p between surface a^ and b^ measurements was also c u r v i l i n e a r (Fig. 11c). As f r u i t ripened, the rapid increase i n surface redness was accompanied by a moderate f a l l i n yellowness. The t > e x t values declined most r a p i d l y when surface redness was maximal. An o v e r a l l c o r r e l a t i o n c o e f f i c i e n t of .54 was obtained. When i n t e r n a l L, a^, b^ graphs and regression r e s u l t s (Fig. 12a, b, c and Table 11) were compared to the foregoing several differences were noted. The L ^ . to b^^. plots were l i n e a r as anticipated; however, lower c o r r e l a t i o n c o e f f i c i e n t s were obtained. Although s a t i s f a c t o r y parabolic functions could be f i t t e d t o the i n t e r n a l L to a^ and a L to b^ re l a t i o n s h i p s , d e f i n i t e tendencies towards l i n e a r i t y were observed. The equations x = 25.14 +.64y +.02y2 and y = 29.52 +.62x -.07x 2 provided the b e s t - f i t s ( r =.77 and .82 to the L to a^ and a L to b L data re s p e c t i v e l y ) . Although the L e x t , a e x t ' b e x t v a r ^ - a ^ l e s correlated poorly with the corresponding i n t e r n a l colour measurements at 17.8/25.6, the correlations improved s u b s t a n t i a l l y with lower temperatures (Table 12). When the i n t e r n a l and external Lb/a colour r a t i o s were related by regression analysis a c o r r e l a t i o n c o e f f i c i e n t of .88 was obtained f o r a l l data. While the co r r e l a t i o n between surface and i n t e r n a l colour increased with decreasing temperatures i t tended to decrease with time following i n c i p i e n t coloration (Table 13). External and i n t e r n a l colour appeared to be best related at 4.4/15.6 at 7 days ( r = .75). 73 Effect of Temperature on Carotenoid Development During Ripening Pigment analyses of Early Red Chief tomato f r u i t s established the presence of phytoene, phytofluene, a-carotene, /3-carotene, {"-carotene, 7-carotene, neurosporene, and lycopene. A compound with spectral and adsorptive c h a r a c t e r i s t i c s resembling those of 6-carotene was found i n small quantities i n a number of samples, however the presence of 5-carotene could not be confirmed. The analyses of variance of data f o r a l l v a r i a b l e s , as exemplified by Table 14, indicated that i n most instances polyene production was sen s i t i v e to both temperature and ripening period (Table 15). In general, pigment concentrations were maximal under the 17.8/25.6 diurnal temperature regime (Table 16, Part I I ) . Phytoene, phytofluene and f-carotene quantities decreased progressively with lower temperatures. Temperature main e f f e c t means showed that neurosporene and lycopene concentrations were lowest at 2.8/13.9 and 4.4/15.6, and highest at 17.8/25.6. a-Carotene concentration was inversely r e l a t e d to temperature. 7-Carotene synthesis was not affected by temperature. |3-Carotene production was l a r g e l y independent of temperature. In the majority of cases, carotenoid concentrations increased with ripening time (Table 16, Part I I ) . However, a-carotene amounts were maximal at 7 days past i n c i p i e n t coloration and minimal at the 21 day harvest. Neither /3-carotene nor 7-carotene development was s i g n i f i c a n t l y influenced by f r u i t maturity. From the more detailed information provided i n Table 16, Part I ; and F i g . 13a, 13b and 13c, a number of i n t e r e s t i n g situations were evident. Table 14. Analysis of Variance f o r Carotenoid Temperature - Harvest Date Study Source D.F. Sum Sq. Mean Sq. Error F Rep 2 .60 .30 .02 n.s. Temp 3 7376.80 2458.93 T x R ** 38.75 T x R 6 380.78 63.46 ft* 4.90 Harv 2 2479.30 1239.65 95.74 T x H 6 150.10 25.02 1.93 n.s. Error 16 207.18 12.95 Total 35 10594.76 Variable: Lycopene n.s. Not Significant * Significant at P = .05 ** Significant at P = .01 Table 15. F values and the significances of Main Effects on Pigment Concentrations Treatment Effe c t Pigment Phytoene Phytofluene a--Carotene /3-Carotene f-Carotene 7-Carotene Neurosporene Lycopene Temperature ftft 58.36 ftft 174.01 ** Aft qn n c 55.47 4.11 n.s. 207.18 , 3 U n , s * ft 6.86 ftft 38.75 Harvest 82.28** ftft 263.55 ft ftft 7.88 .85 n.s. 54.66 .12 n.s. ft* 10.14 ft* 95.74 T x H ftft 7.16 2.40 n.s. 1.27 n.s. 1.48 n.s. .48 n.s. .59 n.s. .81 n.s. 1.93 n.s. n.s. Not Significant * Significant at P = .05 ** Significant at P = .01 Table 16. Temperature and Harvest Effects on Pigment Concentrations Pigment Concentration (pg/g f. wt.) Temperature Harvest Phy- Phyto- a-Caro- 8-Caro- .C-Caro Y-Caro Neuros- Lyco-toene •fluene tene tene tene tene porene pene 17.8/25.6 7 18.14*b 5.92 b 0.02 a 2.97 a 1.30 b 0.64 a 0.31 a 43.50 c 14 23.05 a 7.87 a 0.02 a 2.18 b 1.70 a 0.51 a 0.32 a 57.68 b 21 19.19 b 8.23 a 0.02 a 2.19 b 1.94 a 0.51 a 0.37 a 64.77 a 7.2/18.3 7 11.82 b 3.99 c 0.06 a 3.81 a 0.67 b 0.65 a 0.23 a 24.33 c 14 18.31 a 6.44 b 0.05 a 3.57 a 1.12 a 0.73 a 0.24 a 43.27 b 21 19.07 a 7.23 a 0.04 a 3.45 a 1.21 a 0.69 a 0.26 a 51.52 a 4.4/15.6 7 6.51 c 2.26 c 0.08 a 3.22 a 0.37 c 0.56 a 0.12 b 16.10 b 14 12.30 b 4.82 b 0.06 ab 3.24 a 0.67 b 0.62 a 0.16 ab 27.60 a 21 15.97 a 6.03 a 0.04 b .3.61 a 0.91 a 0.63 a 0.21 a 31.87 a 2.8/13.9 7 3.91 c 1.26 c 0.07 a 3.56 a 0.25 b 0.54 a 0.08 b 9.30 b 14 9.93-b 3.67 b 0.07 a 3.73 a 0.53. a 0.61 a 0.14 ab 20.49 a 21 13.19 a 4.61 a 0.06 a 3.67 a 0.73 a 0.56 a 0.17 a 24.19 a •Main Eff e c t s Level Temperature 17.8/25.6 20.13 a 7.34 a 0.02 c 2.45 b 1.65 a 0.55 a 0.33 a 55.32 a 7.2/18.3 16.40 b 5.89 b 0.05 b • 3.61 a 1.00 b 0.69 a 0.24 ab 39.71 b 4.4/15.6 11.59 c 4.37 c 0.06 ab 3.36 a 0.65 c 0.60 a 0.16 b 25.19 c 2.8/13.9 9.01 d 3.18 d 0.07 a 3.65 a 0.50 d 0.57 a 0.13 b 21.49 c Harvests 7 10.10 b 3.36 c 0.06 a 3.39 a 0.65 c 0.60 a 0.19 c 23.31 c - 14 15.90 a 5.70 b 0.05 ab 3.18 a 1.01 b 0.62 a 0.22 b 37.26 b 21 16.85 a 6.53 a 0.04 b 3.23 a 1.20 a 0.60 a 0.25 a 43.09 a - * Each value i s the mean of three r e p l i c a t e s , except.for a-carotene, where means of two rep l i c a t e s are reported. Means i n the same column within a p a r t i c u l a r temperature or main effect element, sharing the same l e t t e r did not d i f f e r s i g n i f i c a n t l y according to Duncan's multiple range t e s t (p= 2 5 wt. 2 0 -•*•• _pi "5) a i s -«-» c 0 4- l e -0 k c a> u C s ' 0 V 14 Harvests (days past breaker stage) 21 14 21 -17 .8 /25 .6 -14 21 F i g . 13a. Influence of Temperature at Three Harvest Dates on Carotenoid Pigments. Top: Phytoene. Centre: Phytofluene. Bottom: a-carotene. " Points on the same graph within a p a r t i c u l a r harvest, sharing the same l e t t e r did'not d i f f e r s i g n i f i c a n t l y according to Duncan's multiple range t e s t (P=.05). 1Z8/25.6-14 Harvests (days past breaker stage) 21 17.8/25.6-7.2/18.3-4.4/15.6-2.8/13.°-•b 14 21 Z2/78.3-4.4/15.6-2.8/13.9-17.8/25.6--•a -•a •a -•a 14 21 F i g . 13b. Influence of Temperature at Three Harvest Dates on Carotenoid Pigments. Top: /3-carotene. Centre: f-carotene. Bottom: 7-carotene. 79 F i g . 13c. Influence of Temperature at Three Harvest Dates on Carotenoid Pigments. Top: Neurosporene. Bottom: Lycopene. 80 In most instances, both the temperature and harvest factors behaved i n an approximately s i m i l a r manner at a l l l e v e l s considered. Phytoene, phytofluene, f-carotene, neurosporene and lycopene quantities tended to be lowest at the 7-day, 2.8/13.9 treatment and highest at the 21-day, 17.8/25.6 treatment. However, a highly s i g n i f i c a n t T x H phytoene i n t e r a c t i o n was demonstrated. Data f o r phytoene indicated a marked increase i n the compound with maturity within the 2.8/13.9 and 4.4/15.6 temperature systems. At 7.2/18.3, the phytoene concentration increased s i g n i f i c a n t l y between 7 and 14 days but thereafter did not change appreciably. 'At 17.8/25.6, the concentration of t h i s polyene was maximal at 14 days and showed a s i g n i f i c a n t decrease between 14 and 21 days. The pattern of change i n a-carotene quantity was not uniform at a l l temperatures. a-Carotene concentrations were low and constant at 17.8/25.6, were s i g n i f i c a n t l y greater and r e l a t i v e l y consistent at 7.2/18.3 and 2.8/13.9, but decreased r a p i d l y with time at 4.4/15.6. No other anomalous situations were evident with respect to pigment changes with time and temperature. In reference to phytoene, phytofluene, {"-carotene, neurosporene and lycopene, i t was noted that the lower the temperature the greater the difference i n pigment concentrations between the 7-, 14-, and 21-day harvests. Carotenoid S t a b i l i t y Study From the f i r s t growth chamber temperature experiments on tomato pigments, i t was concluded that certain i r r e g u l a r i t i e s i n the carotenoid r e s u l t s , f o r example, the extremely e r r a t i c fluctuations i n phytoene and 81 phytofluene concentrations, could only be attributed to some v a r i a t i o n i n the sampling and/or a n a l y t i c a l methods. A c r i t i c a l review of these • procedures showed that both cubed and macerated samples had been used f o r the analyses and further that the -20° pre - a n a l y t i c a l storage periods had ranged from 10 to 66 days.' Thus, a study on the influence of these two variables on tomato carotenoids was i n i t i a t e d . In the i n i t i a l experiments, f r u i t s of comparable maturity were prepared and analysed as previously described (see Methods and Mat e r i a l s ) , except that the fresh samples consisted of macerated material only. When the fresh, and the 10-day macerated, and the 10-day cubed fractions were compared, i t became obvious that the fresh sample was only equivalent to a "0-day fresh macerated sample". In succeeding experiments, the 0-day fresh cubed sample was derived by placing a quantity of freshly cut sectors d i r e c t l y i n to the extraction solvent p r i o r to blending. The analysis of variance f o r main ef f e c t s demonstrated that storage form was a major fa c t o r a f f e c t i n g pigment concentrations, while storage duration and the main ef f e c t i n t e r a c t i o n appeared to be of minor consequence (Table 17). In comparing the pigment contents of cubed and macerated samples at the same storage times, i t was evident that cubed samples retained much higher l e v e l s of pigments i n the majority of instances. Differences i n the lycopene quantities of cubed and macerated samples at the 0-, 10-, 20-, and 40-day storage periods were not s t a t i s t i c a l l y s i g n i f i c a n t , as was the case with 7-carotene at the 10-day l e v e l and p-carotene at 0 days. When storage duration was evaluated independently f o r each of Table 17. F values and the significances of Main Effects and Interactions for Pigment Losses During Storage at -20°C Variable Treatment Effect Phytoene Phytofluene j3-Carotene f-Carotene Y-Carotene Lycopene Storage Duration 3.27 n.s. .16 n.s. 1.77 n.s. 2.54 n.s. .46 n.s. 1.95 n.s. Storage Form 100.67 ** 151.28 ** 122.24 ** 269.92 ** 90.11 ** .53 n.s. D x F .80 n.s. .01 n.s. 2.69 n.s. .07 n.s. .05 n.s. .20 n.s. n.s. Not Significant ** Significant at P = .01 oo 83 Table 18. Effect o f Sample Condition and Storage Duration on Carotenoid Concentrations Pigments (ug/g f.wt.) Sample Condition Storage Period (days at -20 C) Phy-toene Phyto-fluene ^-Caro-tene f-Caro-tene T-Caro-tene Lyco-pene 0 16.00a* 2.22a 2.86a ' 0.39a 0.59a 67.05a Macerated 10 12.49b 1.91b 2.72a 0.30ab 0.55a 68.53a 20 9.50bc 1.78bc 2.66a 0.20b 0.55a 66.30a UO 7.59c 1.59c 2.45a 0.21b 0.56a 63.92a Cubed 0 26.44a 9.37a 3.38a 1.43a 0.88a 69.33a 10 25.71a 9.28a 3.30a 1.34a 0.86a 68.03a 20 24.76a 9.26a 3.30a 1.19a 0.82a 67.12a 40 23.44a 8.86a 3.42a 1.25a 0.85a 65.04a Each value i s the mean of 3 r e p l i c a t e s . Means within the same column and sample type sharing the same l e t t e r d i d not d i f f e r s i g n i f i c a n t l y according to Duncan's multiple range t e s t (P = .05) 84 the two sample forms, no effects on phytoene, phytofluene, 6-carotene, 5-carotene, Y-carotene or lycopene i n cubed samples were apparent. For macerated samples, 3-carotene, Y-carotene and lycopene contents were not s i g n i f i c a n t l y reduced by the length of the storage period; however, there were appreciable decreases i n the l e v e l s of phytoene, phytofluene and C-carotene (Table 18). Pigment concentrations of cubed samples decreased only s l i g h t l y with storage time, while those of macerated samples generally showed a greater rate of l o s s . With the exception of phytoene, pigment losses tended to be l i n e a r with time. Phytoene degradation i n macerated samples was most rapid during the f i r s t 20 days of storage. 85 DISCUSSION Temperature Effects on Vegetative Growth Light and temperature conditions exerted a pronounced influence on vegetative growth and development. Verkerk (1964) noted that stem and side-shoot growth i n greenhouse-grown tomato plants -was more rapid and resulted i n longer internodes at 23/18 d/n as compared to lower temperatures. However, t h i s could not account f o r the extreme elongation of shoots observed i n the present experiments i n the 1 7 . 8 / 2 5 . 6 ° c growth chamber treatment. Since the 17.8/25.6 temperature regime was considered to be near optimal f o r vegetative growth, the thinness and extreme elongation of shoots was deemed to be largely due to the l i g h t factor. The dense upper vegetative canopy e f f e c t i v e l y reduced l i g h t penetration r e s u l t i n g i n extensive chlorosis and abscission of lower leaves. Light meter readings of less than 0.5 to 0.7 klux were not uncommon at s o i l surface l e v e l s . The fact that elongation of both e x i s t i n g and newly developed shoots appeared to be normal at 7.2/18.3 can be explained on the basis that the effe c t of vegetative growth on the l i g h t f a c t o r was eliminated by lower growing temperatures. The 4.4/15.6 and 2.8/13.9 temperatures were sub-optimal f o r vegetative growth and hence the quantity of vegetative material produced under these regimes was f a r less than that at the two highest temperatures. In the present study, extensive chlorosis of tomato leaves was observed at.4.4/15.6 and p a r t i c u l a r l y 2.8/13.9. One of the e a r l i e s t 86 studies of temperature effects on chlorophyll content was c a r r i e d out by Nightingale (1933) who noted that the quantity of chlorophyll i n tomato leaves decreased following a 10-day exposure to 13°. More recently, McWilliam and Naylor (1967) and Alberda (1969) found that chlorophyll accumulation i n Zea mays L. was i n h i b i t e d at low temperatures. McWilliam and Naylor (1967) pointed out that chlorosis at low temperatures may be due to an i n h i b i t i o n of synthesis of chlorophyll precursors. They concluded that at 16° the f i n a l stage of chlorophyll synthesis i n corn was prolonged and that t h i s coupled with exposure to high l i g h t i n t e n s i t i e s caused photodestruction of the pigment at a f a s t e r rate than i t s synthesis. Temperature Effects on F r u i t i n g Porte (1952) pointed out that tomato f r u i t s continue to increase i n s i z e during ripening and that during the four day period p r i o r to the turning point f r u i t s increase i n s i z e by approximately 12 per cent. The onset and rate of ripening at 17.8/25.6 i n the present studies was very rapid and hence lower f r u i t weights were recorded. In contrast, f r u i t held at 7.2/18.3 and 4.4/15.6 remained i n a green condition f o r longer periods of time and continued to increase i n s i z e . F r u i t s harvested at 7.2/18.3 and 4.4/15.6 were about 10 per cent larger than those at 17.8/25.6 however the differences were not s i g n i f i c a n t . The fact that differences between experimental runs were highly s i g n i f i c a n t indicated that there was a strong pre-treatment 87 e f f e c t . The mean weights f o r the three r e p l i c a t e s (harvested f r u i t only) were 140.4, 177.9 and 197.7 grams. The 140.4 g. mean weight was derived from plants which had been grown i n the greenhouse during the winter season. At t h i s time, greenhouse conditions were somewhat less than optimal f o r plant growth and f r u i t development. I t was also found that during the November to March period, f r u i t sets averaged only 12 per plant as opposed to 22 per plant during the summer months. Tomato v a r i e t i e s vary greatly i n t h e i r a b i l i t y to set f r u i t under low temperatures (Curme, 1962). The c u l t i v a r Early Red Chief was noted i n the present experiments to set f r u i t at 17.8/25.6 and 7.2/18.3. Although flowering did occur at 4.4/15.6 no subsequent f r u i t development was observed. The 2.8/13.9 temperature was sub-minimal f o r flowering and f r u i t s e t t i n g . F r u i t Cracking A very high incidence of f r u i t cracking was noted under growth chamber growing conditions with the frequency of cracking being greatest at higher temperatures and l a t e r harvests. The higher occurrence of cracking at the 21 day harvest i s consistent with the comments of Voisey and L y a l l (1965) who stated that red-ripe f r u i t s were more susceptible to cracking than immature f r u i t . The differences i n the frequencies of cracking between the four treatments could not be associated with differences i n r e l a t i v e humidities between the growth chambers. At 2.8/13.9, f r u i t surfaces 88 were frequently moist with condensation unlike f r u i t grown under higher temperatures and yet the frequency of cracking was lowest under the former regime. The higher occurrence of cracking at the 17.8/25.6 and 7.2/18.3 temperatures may have been due to the d a i l y fluctuations i n s o i l moisture le v e l s although the plants did not w i l t . Voisey and L y a l l (1966) stated that a sudden uptake of water a f t e r a dry period resulted i n the expansion of f r u i t contents which i n turn caused the skin to stretch and fracture. At lower temperatures, s o i l moisture contents remained more uniform and a lower incidence of cracking was recorded. Effect of Ripening Temperatures on Chemical Characteristics of Tomato Fr u i t s  The supplementary graphs were considered to be somewhat more representative of the effects of temperature and harvests on the per cent dry matter, r e f r a c t i v e index, per cent reducing sugars, pH and t o t a l a c i d i t y of tomato f r u i t s than the s t a t i s t i c a l analyses f o r the reason that the graphs u t i l i z e d a s u b s t a n t i a l l y greater amount of data. Furthermore, i n a number of instances, the s t a t i s t i c a l analyses using re p l i c a t e s R^  and Rj. f a i l e d t o show s i g n i f i c a n t differences where obvious and consistent differences existed when a l l data were examined. This was p r i m a r i l y due to the fact that r e p l i c a t e Rj. contained a large proportion of extreme values. For example, t i t r a t a b l e a c i d i t y values f o r Rg were considerably lower than those f o r any other r e p l i c a t e . In addition, the t o t a l a c i d i t y values decreased only s l i g h t l y with harvest dates i n R. whereas other re p l i c a t e s indicated a sharp decline with 89 l a t e r harvests. Differences between experimental runs were s i g n i f i c a n t f o r a l l compositional factors, again suggesting a pre-treatment e f f e c t . This was not e n t i r e l y unexpected since plants used i n the growth chamber experiments were selected from material grown i n the greenhouse throughout the year. Forshey and Alban (1954) have shown that the pH, t i t r a t a b l e a c i d i t y and sugar contents of greenhouse ripened f r u i t s vary markedly with the growing season. The per cent dry matter tended to decrease with l a t e r harvests except at 17.8/25.6, where the s o l i d s content remained unchanged. Previously, Thompson et a l . (1962) noted that the t o t a l s o l i d s content of f r u i t stored at 18.3° decreased from 7 to 14 days past the turning stage. H a l l (1966) found that the t o t a l s o l i d s content showed l i t t l e change from 6 to 12 days past the mature green stage, but subsequently declined. In contrast, Yamaguchi et a l . (1960) reported increases i n t o t a l s o l i d s with ripening under f i e l d conditions, however, t h e i r r e s u l t s may have been complicated by a pre-harvest p r e c i p i t a t i o n factor. In the present study, the per cent dry matter generally increased with lower temperatures. The per cent dry matter of 17.8/25.6 treated f r u i t was considerably lower than that of f r u i t exposed to the 7.2/18.3, 4.4/15.6 and 2.8/13.9 temperatures. Similar findings were reported by Sayre et aL (1953). Temperatures and harvest dates had l i t t l e e f f e c t on f r u i t r e f r a c t i v e indices. The data on harvest effects i s consistent with the findings of Hanna (1961) and H a l l (1966) who reported that soluble 90 s o l i d s of f r u i t s d i d not change s i g n i f i c a n t l y during ripening. In the majority of studies, refractometer measurements are expressed as per cent sucrose, and termed "soluble s o l i d s " . Thompson et a l . (1962) noted that soluble s o l i d s showed a s i g n i f i c a n t decrease with ripening. Moghrabi (1958) observed marked increases i n soluble s o l i d s with ripening but a t t r i b u t e d the increases mainly to losses i n f r u i t fresh weight. Wedding and Vines (1959) noted that soluble s o l i d s increased with lower ripening temperatures whereas Craft and Heinze (1954) showed that storage temperatures had no e f f e c t on soluble s o l i d s . The soluble and t o t a l s o l i d s contents of tomato f r u i t s are of importance i n determining the y i e l d of concentrated tomato products, (MacGillivray and Clemente, 1956; Yamaguchi et aL, 1960; and Lower and Thompson, 1966). Lower and Thompson (1966), have stated that an increase of 0.2 per cent i n soluble s o l i d s of raw f r u i t i s regarded to be of economic significance i n tomato processing. Underwood (1950) has stressed the importance of s o l i d s contents i n influencing the consistency of tomato j u i c e . From these comments, i t i s therefore, evident that f r u i t s ripened at 17.8/25.6 were the least suitable f o r the manufacture of tomato products. The per cent reducing sugars were highest at the three lower temperatures. Learner and Wittwer (1952) pointed out that lower night temperatures reduce r e s p i r a t i o n rates and therefore favour carbohydrate accumulation. Sugar contents showed only a s l i g h t tendency to decrease with " l a t e r harvests. E a r l i e r Craft and Heinze (1954) reported t h a t , i n most 91 instances, sugars tended to increase from 4 to 9 days past the mature green stage and then decreased from 9 to 14 days. Other studies (Yamaguchi et aL, I960; Winsor et aL, 1962) have shown a continued increase i n sugar contents with maturation. Since higher sugar contents are associated with good flavour q u a l i t y , f r u i t harvested at the three lowest temperatures would be considered somewhat superior to 17.8/25.6 treated f r u i t . The pH of tomato f r u i t s was found to increase with l a t e r harvests as demonstrated e a r l i e r by Yamaguchi et a l . (1960) and Hanna (1961). The pH of f r u i t s was also observed to be temperature dependent with the highest values occurring at 17.8/25.6 and the lowest at 4.4/15.6 and 2.8/13.9. No pH differences existed between f r u i t exposed to 4.4/15.6 and 2.8/13.9. The pH of f r u i t held at 17.8/25.6 tended to increase^ more r a p i d l y with l a t e r harvests than those subjected to lower temperatures. These findings are contrary to those reported by Craft and Heinze (1954). They exposed mature green tomatoes to temperatures of 0, 4.4, 8.9, 18.3, and 23.9 f o r 4, 9, and 14 days and concluded that temperature and storage duration had no ef f e c t on f r u i t pH. S i m i l a r l y , Lingle et al.(1965) noted that night temperatures ranging from 5 to 30° had l i t t l e or no ef f e c t on the pH of tomato f r u i t s . The t i t r a t a b l e a c i d i t y was influenced by both temperature and harvest dates. The t o t a l a c i d i t y declined with harvests i n the study c a r r i e d out by H a l l (1966). Winsor et a l . (1962b) was unable to e s t a b l i s h a consistent trend i n a c i d i t y changes of f r u i t walls following the stage of i n i t i a l 92 col o r a t i o n , however, Winsor et a l . (1962a) did f i n d that the t o t a l a c i d i t y of juices expressed from whole f r u i t s declined with ripening. The highest t i t r a t a b l e a c i d i t y values were found at 2.8/13.9 and 4.4/15.6. At higher temperatures, lower t o t a l a c i d i t y values were evident. Haber (1931), Wedding and Vines (1959) and H a l l (1968) also noted that lower temperatures resulted i n higher t o t a l a c i d i t i e s . The fa c t that t o t a l a c i d i t i e s were highest and almost i d e n t i c a l at 2.8/13.9 and 4.4/15.6 suggests a close approach to the minimum temperature required f o r the metabolism of organic acids. From the data i t was r e a d i l y apparent that pH increased uniformly as t i t r a t a b l e a c i d i t y decreased. Much attention has been devoted to the study of pH and t o t a l a c i d i t y i n tomatoes because of the importance of a c i d i t y i n determining the q u a l i t y of raw tomatoes and processed products. Lambeth et a l . (1966), Gould (1957), and Leonard et a l . (1959) have pointed out the requirement of high a c i d i t y i n f a c i l i t a t i n g a reduction of processing times and temperatures thereby permitting improved colour, flavour, texture, and ascorbic acid retentions. Lower and Thompson (1967) indicated that pH's above 4.5 and t o t a l a c i d i t i e s below .35 per cent were not conducive to the maintenance of high processing q u a l i t y . In the present study, pH values exceeding 4.5 and t i t r a t a b l e a c i d i t y values of less than .35 were encountered only at 17.8/25.6 at 21 days and occasionally at 14 days. This indicated that f r u i t s harvested at 17.8/25.6 at 7 days and at lower temperatures ir r e s p e c t i v e of harvests could be processed with a minimal loss i n q u a l i t y . 93 Total pectic substances showed only a s l i g h t tendency to decrease with higher temperatures and l a t e r harvests. Previously, Moghrabi (1958) found that there was very l i t t l e difference between the t o t a l p ectic contents of f r u i t held at 15 and 20°. Kertesz and McColloch (1950) and Woodmansee et a l . (1959) were unable to demonstrate any consistent quantitative changes i n pectic constituents with ripening while Dalai et a l . (1965, 1966) observed a minor decrease i n t o t a l pectins between the large green and red r i p e stages of maturity. Foda (1957) and Moghrabi (1958) noted that t o t a l p ectic substances decreased considerably during ripening, but t h i s resulted p r i m a r i l y from changes occurring during the f i r s t 3 to 6 days following the turning stage. In the present study, f r u i t s were harvested at 7, 14, and 21 days past the turning point and thus, with the possible exception of the 2.8/13.9 treatments, a major decrease i n t o t a l p ectic substances with harvests was not anticipated. The important r o l e of pectic substances i n influencing the t e x t u r a l properties of tomato f r u i t s i s w e l l recognized. Forshey and Alban (1954) made use of t o t a l pectic content as a chemical index of f r u i t t e x t u r a l q u a l i t y . Foda (1957) noted that protopectin contents and instrumental measurements of firmness of tomato inner pericarp tissues were correlated to the extent of .93 to .99, however, t h i s was not necessarily i n d i c a t i v e of the firmness of whole f r u i t s . Deshpande et a l . (1965) and Sayed et a l . (1966) observed highly s i g n i f i c a n t correlations between firmness measurements of canned and whole tomatoes respectively, and t o t a l pectic substances, but i n no case d i d the 94 c o r r e l a t i o n c o e f f i c i e n t s exceed .71. In the present study, treatment effects on t o t a l pectic substances were non-significant, and yet, based on subjective assessments, differences i n f r u i t firmness were considered to e x i s t . Since a chemical analysis does not account f o r such factors as pericarp thickness, carpel s i z e , number and arrangements, i t i s doubtful that measurements based on an analysis of f r u i t constituents alone would serve as an adequate objective measure of tomato firmness. Effect of Temperature on Surface Colour The Hunterlab Color and Color Difference Meter equipped with a D25L circumferential l i g h t i n g unit but used f o r small area evaluation provided a s a t i s f a c t o r y means f o r the assessment of the surface colour' of tomato f r u i t s . In spite of a reduction i n instrument s e n s i t i v i t y due to the decrease i n the viewing area, differences i n surface redness, yellowness and lightness were r e a d i l y detected. Although the CDM-D25L i s designed f o r the measurement of f l a t surfaces and u t i l i z e s a four inch diameter specimen area (Hunter Associates Laboratory, 1966) the fact that 1 1/16" curved surface readings of a series of yellow to orange to red specimens were highly correlated with four inch diameter f l a t surface colour readings indicate that the modified instrument can be used to measure adequately the surface colour of tomato f r u i t s . External redness was c l e a r l y dependent on the ripening temp-erature and the number of days from the turning point to harvest. The highest a^ values were attained at the. 17.8/25.6 temperature regime i n the 7 day harvest, at 7.2/18.3 i n the 14 day harvest, at 4.4/15.6 and 2.8/13.9 i n the 21 day harvest i n d i c a t i n g that the rate of red c o l o r -95 ation of f r u i t surface accelerates with increasing temperatures. These findings are consistent with those of Ayres and Peirce (1960) who observed that f r u i t s ripened at 10° required greater than 30 days to a t t a i n a u ni-form red state while f r u i t s ripened at 20° coloured i n 7 to 10 days. H a l l (1968) noted that coloration at 20° assumed a c u r v i l i n e a r r e l a t i o n s h i p with respect to time, being most rapid between 3 and 5 days following the turning stage. With the apparent exception of the 17.8/25.6 regime, a s i m i l a r r e l a t i o n s h i p was observed when a^ values were related to the 7, 14, and 21 day harvest. F r u i t held at 17.8/25.6 f o r 7 days a f t e r the turning point had already advanced through the main phase (breaker stage to uniform red) i n the coloration sequence and hence showed l i t t l e subsequent change i n a^ readings, whereas f r u i t stored at 2.8/13.9, 4.4/15.6 and to a l e s s e r degree, 7.2/18.3 showed a continued increase i n redness from 7 to 21 days. The e f f e c t of the'lower temperatures was to extend the period of maximum colour change beyond the 7 day harvest. Temperatures during ripening not only influenced the rate but also the extent to which L, a^, and b^ changes took place. The de-creases i n sample redness with lower thermal regimes were d i r e c t l y a t t r i b u -table to the i n h i b i t o r y e f f e c t of temperatures on carotenoid synthesis. The highest a^/b^ values, i n d i c a t i v e of good colour development, occurred at 17.8/25.6 and 7.2/18.3. The s l i g h t l y less intense coloration of 21 dav - 4.4/15.6 f r u i t was r e f l e c t e d bv lower a T/b T ,. „ L L readings. The maximum value of the hue component of 2.8/13.9 treated f r u i t was considerably lower than those of 21 day f r u i t at higher temperatures. The best colour development at 2.8/13.9 was a bright orange. These findings are generally i n agreement with those of Sayre et a l . (1953) who noted that the best 96 coloration occurred at 23.9/15.6 d/n, while f r u i t s ripened at 15.6/7.2 d/n were f a i r l y red but not of s u f f i c i e n t i n t e n s i t y to rate U.S. No. 1 i n colour. S i m i l a r l y Ayres and Peirce (1960) noted that the f r u i t s stored at 10° tended to be more pink than red i n hue. The re s u l t s of the present experiments are not i n f u l l agreement with the constant temperature study carr i e d out by Wright et a l . (1931). They reported that the lowest temperature to f a c i l i t a t e good colour development was 12.8°. The present study made use of diurnal temperature systems and hence both the minimum and maximum temperatures as w e l l as t h e i r dur-ation became factors of importance. The r e s u l t s suggest that MacGillivray's (1934) conclusion (confirmed by Sayre et a l . 1953, and Yamaguchi et a l . 1960) that lower night temperatures permitted s a t i s f a c t o r y coloration when day temperatures exceeded the maximum f o r lycopene development can be ex-panded to include the s i t u a t i o n where night temperatures f a l l below that necessary f o r lycopene synthesis while day temperatures remain within the range required f o r adequate pigmentation. Temperature exerted a pronounced e f f e c t on surface yellow-ness values at a l l harvest dates. Hunter b^ readings were greatest under low temperatures and showed a decline with ripening time. The increase i n b T values with lower temperatures was in d i c a t i v e of the progressive delay i n the ripening process. The differences i n b^ values f o r the various treatments were att r i b u t a b l e to changes i n carotenoid constituents. The d i s t i n c t l y yellow appearance of f r u i t at low temperatures and e a r l i e r harvest dates was due to a preponderance of /3-carotene. McCollum (1955) noted that a /3-carotene content of 2 to 10 per cent of the t o t a l carotenoids was more than s u f f i -97 cient to a l t e r the chromaticity of tomato f r u i t s . At 2.8/13.9 - 7 days, 3-carotene constituted approximately 25 per cent of the t o t a l carotenoids. The decrease i n surface yellowness with ripening might be expected to be p a r a l l e l e d by substantial losses i n 8-carotene, however, when carotenoid analyses were ca r r i e d out t h i s d i d not prove to be the case. 3-carotene concentrations at 7.2/18.3, 4.4/15.6 and 2.8/13.9 were not only comparable but showed l i t t l e consistent evidence of decreasing with l a t e r harvests. The reports of Goodwin and Jamikorn (1952), Thompson et a l . (1965), Dalai et a l . (1966), and Meridith and P u r c e l l (1966) demon-str a t e that 3-carotene quantities usually increase from the mature green or breaker stages up to the pink or l i g h t red stages of maturity. I t i s thus obvious, that as chlorophyll decomposition i n mature green f r u i t s occurs, the colouring e f f e c t of g-carotene becomes im-portant. 3-carotene continues to represent the main pigment contributing to the yellowness of the f r u i t , but with further ripening, lycopene concen-t r a t i o n s become a c r i t i c a l factor. As lycopene quantities increase ex-pression of 3-carotene decreases. Hence the redness rather than yellowness component becomes the dominant factor governing the appearance of f r u i t s . Surface lightness changes c l o s e l y p a r a l l e l e d those of ^ex^. under a l l treatment conditions. The highest lightness values were found at the lowest temperatures and the e a r l i e s t harvests. The v i s u a l l y apparent darkening of f r u i t s with ripening was confirmed by lower readings. The advantages i n using a t r i s t i m u l u s colorimeter f o r the determination of pigment concentrations are numerous. Such instruments have previously been reported f o r the s p e c i f i c a t i o n of carotenoid concentrations i n sweet potatoes and squash and also the pigment (predominantly anthocyanins) 98 contents i n cranberry products (Francis, 1969). Surface redness might be expected to constitute a measure of the concentration of red pigments i n tomato f r u i t s , however, the a n a l y t i c a l data indicated that t h i s was not e n t i r e l y the case. At low temperatures, increases i n surface a^ values coincided with increases i n lycopene concentrations, but at the two highest temperatures increases i n lycopene quantities were not associated with a consistent change i n a^ values. Since the 3-ex^. readings d i d not r e f l e c t the lycopene contents of red-ripe f r u i t s , measurement of surface redness as a basis of prediction of carot-enoid concentrations would be of questionable value. Thompson et a l . (1965) noted that Hunter values of raw pericarp, locule and whole f r u i t j u i c e s confirmed t h e i r carotenoid data i n most respects, but f a i l e d to d i s t i n g u i s h quantitative carotenoid differences i n 14 day - 18.3° ripened crimson from e i t h e r high pigment or standard red tomatoes. Internal Colour and the Relationship to Surface Colour The effects of temperature and harvest dates on i n t e r n a l colour were s i m i l a r to those on surface colour values. In both instances, L and b^ values increased with lower temperatures and decreased with l a t e r harvests. S l i g h t differences between surface and i n t e r n a l L, a^ and b^ measurements were evident where conditions permitted over-ripening. Thus at 17.8/25.6 i n t e r n a l a^ values remained at a maximal l e v e l f o r a l l harvest dates while external a^ values declined somewhat from 7 to 21 days. S i m i l a r l y , a^ i n t e r n a l values remained constant and maximal at 7.2/18.3 from 14 to 21 days while surface redness declined. 99 Although i n t e r n a l and surface colour could not be compared i n terms of absolute values because of the differences i n measurement techniques, i t was noted that f r u i t stored at 2.8/13.9 f o r 7 days had an i n t e r n a l redness of only 33.7 per cent of that of 17.8/25.6, 7-day f r u i t while surface redness was 59.7 per cent of that of 17.8/25.6, 7-day f r u i t . At 2.8/13.9, 14-days, i n t e r n a l and surface a^ readings were equivalent to 59.5 and 85.5 per cent of the corresponding 17.8/25.6, 14-day f r u i t . S i m i l a r l y , i n t e r n a l and surface yellowness values of f r u i t s at 2.8/13.9, 7 days were 1.9 and 1.5 times greater than b^ values at 17.8/25.6, 7 days. This indicated that at lower temperatures i n t e r n a l colour development lagged behind that of f r u i t surfaces. Ayres and Peirce (1960) also noted that colour within the f r u i t d i d not keep pace with surface colour under low temperature conditions. Correlation studies showed that surface redness, yellowness and lightness were best associated with the i n t e r n a l variables at lower temperatures. The lower correlations at 7.2/18.3 and the non-significant relationships at 17.8/25.6 indicate that independent L, a^ and b^ surface values are of n e g l i g i b l e value i n estimating the i n t e r n a l colour at higher temperatures. When i n t e r n a l and external Lb/a r a t i o s were compared, a very high o v e r a l l c o r r e l a t i o n c o e f f i c i e n t was obtained suggesting that surface colour expressed as the Lb/a r a t i o could be used to accurately specify i n t e r n a l colour. The highest Lb/a c o r r e l a t i o n c o e f f i c i e n t s obtained f o r the four temperature treatments were found at 2.8/13.9 and 4.4/15.6. Although the Lb/a c o r r e l a t i o n c o e f f i c i e n t at 17.8/25.6 was highly s i g n i f i c a n t i t was evident that surface colour could not be used 100 to predict•accurately the i n t e r n a l colour at t h i s temperature. Desrosier (1954) has stated that surface colour i s as good a measure of i n t e r n a l colour as cross-sectional colour but can occasionally be misleading. When Lb/a r a t i o s were correlated f o r each of the temperature and harvest treatments, the c o e f f i c i e n t s were found to be highly s i g n i f -icant with one exception. The highest c o r r e l a t i o n c o e f f i c i e n t s occurred at lower temperatures and e a r l i e r harvests demonstrating that both the ripening temperature and harvest date influenced the r e l a t i o n s h i p between surface and i n t e r n a l colour o f tomatoes. In no case did the c o r r e l a t i o n c o e f f i c i e n t s exceed .80. Part of the d i f f i c u l t y i n c o r r e l a t i n g surface and i n t e r n a l colour may have been due to the fact that raw j u i c e samples were not deaerated p r i o r to colour evaluation. Previously, Yeatman and Sidwell (1958) reported that although deaeration improved the colour of tomato juices "the improvement was so constant and predictable that i t was found l o g i c a l to discontinue deaeration". When aerated and deaerated samples were tested t h i s was found not t o be e n t i r e l y the case. The e f f e c t of aeration was greatest but least predictable on sample L values ( r = .51). In contrast, the c o r r e l a t i o n c o e f f i c i e n t s f o r the a^ and b^ values were .95 and .77. Association between Tristimulus Colour Coordinates of Tomato F r u i t s , Comparatively few studies have been done on possible r e l a t i o n -ships between the colour coordinates of tomato f r u i t s . Asselbergs et a l . (1951) determined the colour range of a series of raw juices derived from 101 tomato f r u i t s of various ripeness l e v e l s using a spectrophotometer equipped with a d i g i t a l t r i s t i m u l u s integrator. They observed a very high l i n e a r c o r r e l a t i o n ( r = .90) between luminous reflectance Y and x-chromaticity measurements. They considered the high corre l a t i o n between "lightness" and "redness" to be an important c h a r a c t e r i s t i c of the colour range of raw tomato j u i c e . In the present study, i n t e r n a l lightness was also noted to decrease with increasing redness, but a cor r e l a t i o n c o e f f i c i e n t of only .77 was observed between the Hunter L and a^ values. Sample aeration may have represented a f a c t o r contributing to t h i s lower degree of association. The difference i n the cor r e l a t i o n c o e f f i c i e n t s may also have been due to the fact that the range of j u i c e colours used by Asselbergs et a l . included only l i g h t , medium and dark red samples, whereas a sub s t a n t i a l l y wider range of colours was encountered i n the present growth chamber experiments. When surface L and a^ values were examined, the relationship was found to be non-linear, p a r t i c u l a r l y at higher temperatures and l a t e r harvests. Yeatman et a l . (1960) and Yeatman (1969) studied the d i s t r i b u t i o n of raw tomato j u i c e colours i n terms of Hunter L, a^ and b^ dimensions. The data presented by Yeatman et a l . :(1960) indicate the existance of a r e l a t i o n -ship between sample lightness and yellowness values. In the present study, a good l i n e a r r e l a t i o n s h i p between j u i c e lightness and yellowness was demon-strated , except where conditions resulted i n poor colour development. Sur-face L and b^ values correlated to the extent of .97. Further, a high degree of association between surface lightness and yellowness persisted over the extreme range of treatments. 102 These findings indicated that the surface colour, and to a l e s s e r extent, the i n t e r n a l colour of tomato f r u i t s could be very ade-quately s p e c i f i e d through the use of two (a^, and b^ or L ) , rather than three colour scales. The high degree of association between L and b^ values would also permit the s i m p l i f i c a t i o n of three variable colour indices. The a^, b^ chromaticity diagram given by Ayres and Peirce (1960) f o r a range of immature to over-ripe tomatoes i l l u s t r a t e s t h a t , with ripening, the decrease i n b^ values f o r outer w a l l and skin portions, and f o r section walls was accompanied by a marked increase i n sample redness values. The present studies showed s i m i l a r relationships between redness and yellowness values up to about the red stage of ripeness. The r e s u l t s of Ayres and Peirce demonstrated that, with over-ripening, redness values continued to increase with no change or an increase i n b^ values. In the present growth chamber experiments, over-ripening was found to be accompanied by a continued decrease i n i n t e r n a l b^ and' an increase i n i n t e r n a l a^ values. Further, surface b^ and a^ values declined with ripening beyond the red stage, giving r i s e to a parabolic r e l a t i o n s h i p between surface redness and yellowness. Effect of Temperatures and Harvests on F r u i t Carotenoids Lycopene and 3-carotene represented the dominant carotene pigments i n the tomato f r u i t s at a l l temperatures and harvests. Lycopene generally accounted f o r greater than 80 per cent of the t o t a l carotene content. The increase i n the proportion of lycopene to t o t a l carotenes with increasing temperatures and l a t e r harvests was l a r g e l y a r e f l e c t i o n 103 of treatment ef f e c t s on lycopene concentrations i n the absence of corresponding changes i n p-carotene contents. Thus, at 17.8/25.6 at 21 days, lycopene constituted 92.8 per cent of the t o t a l carotene f r a c t i o n , as opposed to 67.4 per cent at 2.8/13.9. Data presented by Tomes (1963) and Meredith and P u r c e l l (1966) show that lycopene constitutes i n excess of 90 per cent of the t o t a l carotenes of r i p e red v a r i e t i e s . a-Carotene, y-carotene, neurosporene and £-carotene were present only i n small amounts. Previously, Porter and Lincoln (1950) reported that ct-carotene i s present i n commercial v a r i e t i e s usually i n trace quantity only, while y-carotene i s found i n red tomato v a r i e t i e s i n concentrations r a r e l y exceeding 5 ug/g. Substantial quantities of phytoene and phytofluene were en-countered i n the majority of treatments, p a r t i c u l a r l y where conditions were conducive to adequate ripening. Comparable concentrations f o r r i p e f r u i t s of a number of other red v a r i e t i e s have been reported by Tomes (1963) and Thompson et a l . (1965). Temperatures and/or harvest dates influenced the concentrations of a l l pigments i s o l a t e d with the exception of y-carotene. Phytofluene, S-carotene, neurosporene and lycopene increased while a-carotene concentrations declined with harvests. Phytoene concentrations increased with l a t e r harvests except at 17.8/25.6 from 14 to 21 days, where a s i g n i f i c a n t decrease was observed. The findings concur with those of Meredith and P u r c e l l (1966) except that they observed continued increases i n y-carotene and phytoene during ripening. Since many of the f r u i t s harvested at 17.8/25.6 at 21 days showed evidence of 104 "deterioration, i t seems probable that the lower phytoene concentrations resulted from oxidative decomposition. The g-carotene contents of f r u i t at 17.8/25.6 and 7.2/18.3 tended to decrease with harvests, but a s i m i l a r trend was not evident at lower temperatures. Dalai et a l . (1965) and Meredith and P u r c e l l (1966) found that 8-carotene increased up to the l i g h t red or pink stage of maturity and thereafter decreased. Phytoene, phytofluene, f-carotene, neurosporene and lycopene concentrations were highest at 17.8/25.6 and decreased progressively with lower temperatures. The low concentrations of carotenoid pigments at 2.8/13.9 indicated a nearness to the mimimal temperatures f o r caro-tenoid synthesis. E a r l i e r workers (Rosa, 1926, Wright et a l . , 1931), using constant temperature systems established lower l i m i t s of between 4.4 and 8° f o r lycopene development. Went et a l . (1942) found that f r u i t stored at 2° showed no evidence of lycopene synthesis. From the present study, i t was r e a d i l y apparent that, i n spite of very low night temperatures, the higher day temperatures d i d permit carotenoid synthesis to a l i m i t e d extent. a-Carotene contents were inversely r e l a t e d to temperature i n contrast to the r e s u l t s presented by Goodwin and Jamikorn(1952). They found the a-carotene concentrations, not only increased with ripening, but were somewhat higher at 15° as compared to 0°. From t h e i r temperature maturity study, Goodwin and Jamikorn (1952) concluded that the Porter-Lincoln pathway was only of minor importance i n the synthesis of a-carotene 105 and B-carotene. In the present study, i t was found that a-carotene, 3-carotene, and Y-carotene did not respond to temperatures and harvests i n accordance to the treatment e f f e c t s on the other carotenoids. Thus, the r e s u l t s not only seem to support the contention of a d i f f e r e n t pathway f o r a-carotene and 8-carotene, but also tend to suggest the p o s s i b i l i t y that Y-carotene production may be independent of the Porter-Lincoln pathway. Relationship of Carotenoids to Tomato Colour Since lycopene and 3-carotene generally accounted f o r 95 per cent or more of the t o t a l carotene f r a c t i o n , the other carotenoid pigments were of l i t t l e consequence i n influencing f r u i t colour. At 2.8/13.9 and 4.4/15.6, p a r t i c u l a r l y at the 7-day harvests, 3-carotene represented a substantial portion of the t o t a l carotenes. For t h i s reason, and owing to i t s high e x t i n c t i o n value, B-carotene would therefore have contributed greatly to the f r u i t colour. Hence, the high proportion of S-carotene to lycopene was associated with f r u i t o f a yellow to orange hue. At higher temperatures, B-carotene concentrations tended to decline with delayed harvest, while lycopene quantity increased, and thus the significance of 3-carotene i n influencing f r u i t colour decreased. There was a marked increase i n colour i n t e n s i t y and a great change i n hue as lycopene concentrations increased up to about 32 ug/g fresh weight. Between 32 and 43 pg/g colour i n t e n s i t y increased to a lesser extent and f r u i t changed from an orange to red hue. When lycopene concentrations exceeded about 40 pg/g, Hunter i n t e r n a l and external values and r a t i o s showed l i t t l e appreciable change. 106 F r u i t harvested at 7.2/18.3 - 14 days and 17.8/25.6 - 7 days were judged to have a s a t i s f a c t o r y f u l l red coloration. At these t r e a t -ments the mean t o t a l carotene contents were 49 pg/g. Compensating f o r column losses, then actual concentrations of about 56 pg/g would have existed. I t i s thus apparent, that s a t i s f a c t o r y red coloration requires a t o t a l carotene concentration i n excess of 55 pg/g of which lycopene accounts f o r approximately 90 per cent of the carotenes. Effects of Sample Condition and Storage Duration on Carotenoid Pigments L i t t l e research has been directed towards the study of the carotenoid pigments of tomato tissues as affected by aeration, and/or low temperature factors. Yeatman(1959) reported that the colour of whole red tomato f r u i t s remained stable at -10° f o r Ih years; however, colour i s not a good c r i t e r i o n of the carotenoid status of f r u i t s , e s p e c i a l l y where carotene contents exceed 55 pg/g. In the present study, storage form was found to be the main fa c t o r a f f e c t i n g carotenoid concentrations. Cubed samples retained much higher l e v e l s of phytoene, phytofluene, 6-carotene, f-carotene and Y-carotene than macerated tissues. Lycopene content was not affected by sample maceration. Chichester and Nakayama (1965) commented that lycopene i n tomato f r u i t s i s r e l a t i v e l y stable even under the most adverse condi-tions . The greatest loss of carotenoids i n macerated tissues occurred before storage at -20°. The high loss of carotenoids excepting lycopene at 0 days storage was largely a t t r i b u t a b l e to the i n c l u s i o n of oxygen during the 2h - 3 minute blending phase p r i o r to solvent extraction. 1G7 The pigments i n order of s e n s i t i v i t y to decompostion were phytofluene, ^-carotene, phytoene, y-carotene, B-carotene and lycopene. Thus, the r e l a t i v e l y common procedure of blending tomato f r u i t s f o r pigment analysis p r i o r to extraction with solvents cannot be recommended. The carotenoid concentrations of cubed samples showed only a s l i g h t tendency to decrease with storage at -20° demonstrating that pigment contents of i n t a c t tomato tissues were reasonably stable. Phytoene, phytofluene and c-carotene losses were considerable i n stored macerated tissues but t h i s was most l i k e l y due to oxidative losses before the temperatures of the tissues reached -20°. I t i s therefore evident that carotenoid analysis should be preferably c a r r i e d out on fresh material or samples stored f o r a minimal time period. Where samples cannot be. analysed immediately, whole f r u i t or f r u i t sections rather than blended samples should be stored. 108 SUMMARY AND CONCLUSIONS Controlled environment experiments were conducted to study the effects of a i r temperatures at harvest dates of 7, 14, and 21 days past the breaker stage on tomato f r u i t q u a l i t y . Emphasis was placed on the assessment of temperature e f f e c t s , notably low temperatures, on f r u i t colour, the pigments responsible f o r the colour c h a r a c t e r i s t i c s , and the relationships of colour parameters to each other during the ripening process. In addition, controlled temperature ef f e c t s on vege-t a t i v e and reproductive growth and f r u i t c h a r a c t e r i s t i c s were examined. An investigation was also undertaken to determine the eff e c t s of sample maceration and storage duration at -20° on carotenoid concentrations of tomato tissues. From the r e s u l t s of these experiments the following conclusions can be drawn: 1. Decreasing temperatures suppressed vegetative grox^rth. The 4.4/15.6°C night/day thermal regime was d e f i n i t e l y sub-optimal f o r vegetative growth while the 2.8/13.9 temperature system was sub-minimal f o r vege-t a t i v e growth and development. Prolonged exposure to low temperatures caused extensive and severe chlorosis of leaves. 2. The minimal temperature f o r flowering i s lower than that required f o r f r u i t set. Flowering continued at 4.4/15.6 but was prevented at 2.8/13.9. The c r i t i c a l niinimum temperatures f o r f r u i t set i n the c u l t i v a r Early Red Chief l i e s between 7.2/18.3 and 4.4/15.6. The sub s t a n t i a l l y higher frequency of f r u i t cracking at 17.8/25.6 was probably due to an in d i r e c t e f f e c t of temperature on s o i l moisture l e v e l s . 3. The t o t a l s o l i d s contents of f r u i t s were lowest at 17.8/25.6 and showed 109 only a s l i g h t tendency to decrease with delayed harvest. Treatment effects on f r u i t r e f r a c t i v e indices were l a r g e l y negative demonstrating that ripening temperatures had l i t t l e e f f e c t on a net change i n t o t a l soluble constituents. 4. The per cent reducing sugars generally showed a s l i g h t decline with delayed harvest. Sugar contents were lowest at 17.8/25.6 presumably because of respiratory losses. 5. The a c i d i t y of f r u i t s was dependent on both temperature and harvest dates. T i t r a t a b l e a c i d i t y declined while pH values increased with l a t e r harvests and higher temperatures. The higher t i t r a t a b l e a c i d i t y and lower pH values with decreasing temperatures indicated that organic a c i d losses through r e s p i r a t i o n were progressively retarded by lower temperatures. 6. There were only very minor differences i n the t o t a l p ectic substances of f r u i t s between the various treatment l e v e l s . Since appreciable firmness differences existed, i t may be concluded that t o t a l p ectic substances do not serve as a suitable index of the t e x t u r a l properties of whole f r u i t . 7. Temperatures and times of harvest had a pronounced influence on surface and i n t e r n a l f r u i t colour. Surface and i n t e r n a l lightness and yellow-ness decreased while redness values increased with higher temperatures and l a t e r harvests. Temperatures influenced the rate and extent to which colour changes took place. F r u i t showed a f u l l red colour development at 17.8/25.6 i n 7 days, and at 7.2/18.3 i n 14 days or l e s s . The near f u l l red coloration of f r u i t harvested at 4.4/15.6 110 at 21 days was r e f l e c t e d i n somewhat higher Lb/a r a t i o s than those obtained at 17.8/25.6 and 7.2/18.3 at 21 days. F r u i t exposed to 2.8/13.9 ranged from yellow to bright orange depending on the harvest date. 8. Changes i n f r u i t colour were due almost exclusively to temperature and harvest effects on lycopene synthesis. At low temperatures and p a r t i c u l a r l y at the 7-day harvests, B-carotene constituted a sub-s t a n t i a l portion of the t o t a l carotenes and exerted a pronounced influence on the colour of f r u i t s . The importance of g-carotene decreased progressively with increasing temperatures and l a t e r harvests. A t o t a l carotene content of approximately 55 pg/g fresh weight was required f o r s a t i s f a c t o r y red coloration. Total carotene contents i n excess of 55 ug/g had l i t t l e e f f e c t on colour. 9. Temperatures and harvests influenced the relationships between surface and i n t e r n a l colour measurements. Surface L, a^ and b^ readings and Lb/a r a t i o s were best related at low temperatures and e a r l i e r harvests. In s p i t e of the very high o v e r a l l c o r r e l a t i o n between surface and i n t e r n a l Lb/a r a t i o s , the fact that the c o r r e l a t i o n c o e f f i c i e n t s were considerably lower where temperatures f a c i l i t a t e d s a t i s f a c t o r y colour development indicates that surface colour cannot be conclusively r e l i e d upon i n the colour grading of tomatoes at the processing l e v e l . Surface colour cannot be used to specify accurately the i n t e r n a l colour of f u l l y ripened tomatoes. 10. The consistently high c o r r e l a t i o n c o e f f i c i e n t s between surface lightness and yellowness values demonstrated that one measurement could be used to I ' l l determine both lightness and yellowness. Thus, three parameter surface colour indices may be s p e c i f i e d by the use of two measurements and a constant, the constant accounting f o r the r e l a t i o n s h i p between L and b^ values. 11. Temperatures exerted a marked influence on phytoene, phytofluene, x,-carotene, neurosporene and lycopene contents but had l i t t l e or no e f f e c t on g-carotene and Y-carotene concentrations. a-Carotene concen-t r a t i o n s were highest at the e a r l i e s t harvest at the lowest temperature. The decrease i n phytoene with over-ripening at 17.8/25.6 between 14 and 21 days may have been due to oxidative decomposition. The fact that a-carotene, g-carotene and y-carotene concentrations d i d not respond to temperature and harvest effects i n the same manner as di d the other pigments seems to support the contention that more than one pathway i s involved i n the biosynthesis of carotenoids. 12. In spite of higher dry matter, sugar contents, t o t a l a c i d i t y ; lower pH values; and s l i g h t l y higher p e c t i c contents and r e f r a c t i v e i n d i c e s , f r u i t ripened at 4.4/15.6 and 2.8/13.9 were of i n f e r i o r q u a l i t y because of reduced colour development. F r u i t s ripened at 7.2/18.3 and 17.8/25.6 were of high colour q u a l i t y . However, f r u i t s ripened at 7.2/18.3 were of superior t o t a l q u a l i t y f o r reasons of higher a c i d , sugar and dry-matter contents. The treatment providing the best q u a l i t y as indicated by objective measurements was 7.2/18.3 at 14 days. 13. Carotenoids of i n t a c t tissues were r e l a t i v e l y stable when stored from 10 to 40 days at -20°C. Macerated tissues stored at -20 contained sub-s t a n t i a l l y lower concentrations of a l l carotenoids except f o r lycopene. 112 The major portion of the losses found i n macerated tissue occurred during the blending procedure rather than during low temperature storage periods. For t h i s reason, maceration of tomato f r u i t s at room temperature p r i o r to extraction cannot be recommended when analysing tissues f o r carotenoid constituents. 113 BIBLIOGRAPHY Alberda, T.H. 1969. The effe c t of low temperature on dry matter production. chlorophyll concentration and photosynthesis of maize plants of d i f f e r e n t ages. Acta Bot. Neerl. 18 (1): 39-49. Albersheim, P. 1965. Biogenesis of the c e l l w a l l . In: Plant Biochemistry. J . Bonner and J.E. Varner, eds. Academic Press, New York. Ang, J.K., J . Hartman and F.M. Isenberg. 1963. New applications of the shear press i n measuring texture i n vegetables and vegetable products. I I . Correlation of subjective estimates of texture of a number of whole and cut vegetables, and objective measurements, made with several sensing elements of the shear press. Proc. Amer. Soc. Hort. S c i . 83: 734-740. Appleman, CO. and CM. Conrad. 1927. The pectic constituents of tomatoes and t h e i r r e l a t i o n to the canned product. Maryland Agr. Expt. Sta. B u l l . No. 291. A s p i n a l l , G.O. and A. Canas-Rodriguez. 1958. S i s a l pectic acid. J . Chem. Soc. Part IV: 4020-4027. A s p i n a l l , G.O. and R.S. Fanshawe. 1961. Pectic substances from lucerne (Medicago s a t i v a ) . Part I. Pectic acid. J . Chem. Soc. Part I I I 4215-4225. Asselbergs, E.A., G.W. Wyszecki and W.P. Mohr. 1961. The color of raw tomato j u i c e . Food Technol. 15: 156-159. 114 Ayres, J.C. and L.P. Peirce. 1960. Eff e c t of packaging films and storage temperatures on the ripening of mature green tomatoes. Food Technol. 14: 648-653. Bailey, I.W. 1938. C e l l w a l l structure of higher plants. J . Ind. Eng. Chem. 30: 40-47. Bohart, G.S. 1940. Studies of western tomatoes. Food Res. 5: 469-486. Bonner, J . 1950. Plant Biochemistry. Academic Press, New York. Carrasco, 0. 1937. Color of tomato products. Food Ind. 9: 405 and 423. Carre, M.H. 1922. An investigation of the changes which occur i n the pectic constituents of stored f r u i t . Biochem. J . 16: 704-712. Clydesdale, F.M. 1969. The measurement of color. Food Technol. 23: 16-22. Commission on the Nomenclature of B i o l o g i c a l Chemistry. 1960. D e f i n i t i v e rules f o r the nomenclature of amino acids, s t e r o i d s , vitamins and carotenoids. J . Amer. Chem. Soc. 82: 5575-5584. Craf t , C.C. and P.H. Heinze. 1954. Physiological studies of mature-green tomatoes i n storage. Proc. Amer. Soc. Hort. S c i . 64: 343-350. Crocker, E.C. 1945. Flavor. McGraw-Hill, New York. C u r l , A.L. 1961. The xanthophylls of tomatoes. J . Food S c i . 26: 106-111. Curme, J.H. 1962. Eff e c t of low night temperatures on tomato f r u i t set. In: Proc. Plant S c i . Symp. Campbell Soup Co., Camden, New Jersey. 115 D a l a i , K.B., D.K. Salunkhe, A.A. Boe and L.E. Olson. 1965. Certain physiological and biochemical changes i n the developing tomato f r u i t (Lycopersicon esculenturn M i l l . ) . J . Food S c i . 30: 504-508. D a l a i , K.B., D.K. Salunkhe and L.E. Olson. 1966. Certain physiological and biochemical changes i n greenhouse-grown tomatoes. (Lycopersicon esculentum M i l l . ) . J . Food S c i . 31: 461-467. Davis, W.B. 1949. Estimation of the co l o r of tomato paste. Anal. Chem. 21: 1500-1503. Davis, R.B. and W. A. Gould. 1955. A proposed method f o r converting Hunter Color Difference Meter readings to Munsell hue, value and chroma renotations corrected f o r Munsell value. Food Technol. 9: 536-540. Deshpande, S.N., W.J. KLinker, H.N. Draudt and N.W. Desrosier. 1965. Role of pectic constituents and polyvalent ions i n firmness of canned tomatoes. J . Food S c i . 30: 594-600. Desrosier, N.W. 1954. Color measurements with tomatoes. Color i n Foods -Symposium. Nat. Acad. S c i . Nat. Res. Council. Deuel, H. and E. Stutz. 1958. Pectic substances and pectic enzymes. Adv. Enzymol. 20: 341-382. Dieh l , H.C. 1924. The c h i l l i n g o f tomatoes. U.S. Dept. Agr. Dept. C i r c . No. 315. Duggar, B.M. 1913. Lycopersicum, the red pigment of the tomato, and the-ef f e c t of conditions upon i t s development. Wash. Univ. Studies. 1: 22-45. Duncan, D.B. 1955. Multiple range and multiple F t e s t s . Biometrics 11: 1-42. i i 6 E l l i s , G.H. and K.C. Hamner. 1943. The carotene content of tomatoes as influenced by various factors. J . N u t r i t i o n 25: 539-553. Fischer, A. and R. Sengbush. 1935. Die zuchtung von tomaten mit nicht platzenden und druckfesten fruchten. Zuchter 7: 57-62. Foda, Y. 1957. Pectic changes during ripening as related to f l e s h firmness i n the tomato. Ph.D. t h e s i s , Univ. of I l l i n o i s . Forshey, CG. and E. K. Alban. 1954. Seasonal changes i n greenhouse tomatoes. Proc. Amer. Soc. Hort. S c i . 64: 372-378. Francis, F.J. 1969. Pigment content and col o r i n f r u i t s and vegetables. Food Technol. 23: 32-36. Garrett, A.W., N.W. Desrosier, G.D. Kuhn and M.L. Fi e l d s . 1960. Evaluation of instruments to measure firmness of tomatoes. Food Technol. 14: 562-564. Goodwin, T.W. 1952. The comparative biochemistry of the carotenoids. Chapman S H a l l , London. Goodwin, T.W. 1955. Carotenoids. In: Modern methods of plant analysis. Vol. 3. K. Paech and M.V. Tracey, eds. Springer Verlag, B e r l i n . Goodwin, T.W. and M. Jamikorn. 1952. Biosynthesis o f carotenes i n ripening tomatoes. Nature 170: 104-105. Gorman, W. 1964. Flavor, taste and the psychology of smell. Charles C. Thomas, S p r i n g f i e l d , I l l i n o i s . Gould, W.A. 1953. A p r a c t i c a l approach to color grading of tomato and other food products with a disc colorimeter. Food Packer 34 (10): 22 and 26. Government of Canada. 1966. Processed f r u i t and vegetables regulations. P.C. 1966-599. Canada A g r i c u l t u r a l Products Standards Act. 11.7 Haber, E.S. 1931. A c i d i t y and .color changes i n tomatoes under various storage temperatures. Iowa State College J . S c i . 5: 171-184. Haber, E.S. and F. LeCrone. 1933 Changes i n the pectic constituents of tomatoes i n storage. Iowa State College J . S c i . 7: 467-476-H a l l , C B . 1966. Quality changes i n f r u i t s of some tomato v a r i e t i e s and l i n e s ripened at 68°F f o r various periods. Proc. F l a . State Hort. Soc. 79: 222-227. H a l l , C B . 1968. Changes i n t i t r a t a b l e a c i d i t y of tomato f r u i t s subjected to low temperatures. Hort. S c i . 3 (1): 37-38. Halsey, L.H. and F.S. Jamison. 1958. Color development c h a r a c t e r i s t i c s of several tomato v a r i e t i e s . Proc. Amer. Soc. Hort. S c i . 71: 344-348. Hamdy, M.M. and W.A. Gould. 1962. V a r i e t a l differences i n tomatoes: a study of alpha-keto acids, alpha-amino compounds and c i t r i c acid i n eight tomato v a r i e t i e s before and a f t e r processing. J . Agr. Food Chem. 10: 499-503. Hamson, A.R. 1952a. Measuring firmness of tomatoes i n a breeding programme. Proc. Amer. Soc. Hort. S c i . 60: 425-433. Hamson, A.R. 1952b. Factors which condition firmness i n tomatoes. Food Res. 17: 370-379. Hanna, G.C. 1961. Changes i n pH and soluble so l i d s of tomatoes during vine storage of ri p e f r u i t . Proc. Amer. Soc. Hort. S c i . 78: 459-463. Hanson, J . 1921. Tomato color. Canner 52: 35-36. Hewitt, E.J. 1966. Sand and water culture methods used i n the study of plant n u t r i t i o n . 2nd ed. rev., Eastern Press Ltd., London. Hood, K.J. 1959. The relationship between flowering and ripening i n 118 tomatoes (Lycopersicon esculentum and L. pimpinellifolium) with emphasis on carbohydrate metabolism and ethylene responses. Ph.D. Thesis, Univ. C a l i f . , Davis. Hunter Associates Laboratory Inc. 1966. Instructions f o r Hunterlab D-25 Color Difference Meter. F a i r f a x , Va. Hunter, R.S. 1942. Photoelectric t r i s t i m u l u s colorimetry with three f i l t e r s . J . Opt. Soc. Amer. 32: 509-537. Hunter, R.S. 1948. Photoelectric Color Difference Meter. J . Opt. Soc. Amer. 38: 661. Hunter, R.S. 1958. Photoelectric Color Difference Meter. J . Opt. Soc. Amer. 48: 985-995. Hunter, R.S. and J.N. Yeatman. 1961. Direct-reading tomato colorimeter J . Opt. Soc. Amer. 51: 551-554. Janes, B.E. 1941. Some chemical differences between a r t i f i c i a l l y produced parthenocarpic f r u i t s and normal seed f r u i t s of tomato. Amer. J. Bot. 28: 639. Jensen, L.S. 1967. Recent advances i n the chemistry of natural carotenoids. In: Symposium on carotenoids other than vitamin A. Butterworths, London. Joslyn, M.A. 1962. The chemistry of protopectin: a c r i t i c a l review of h i s t o r i c a l data and recent developments. Adv. Food Res. 11: 1-107. Karrer, P. 1948. Sur l a nomenclature des carotenoids. I I . Regies de nomen-clature des carotenoids. B u l l . Soc. Chim. B i o l . 30: 150-156. Karrer, P. and E. Jucker. 1950. Carotenoids. Translated and revised by E.A. Braude. E l s e v i e r , New York. 119 Kattan, A.A. 1957a. Changes i n c o l o r and firmness during ripening of detached tomatoes and the'use of a new instrument f o r measuring firmness. Proc. Amer. Soc. Hort. S c i . 70: 379-384. Kattan, A.A. 1957b. Firm-o-meter f o r measuring firmness i n tomatoes. Ark. Agr. Expt. Sta. Farm Res. 6 (1): 1-7. Kattan, A.A., F.C. Stark and A. Kramer. 1957. Effect of c e r t a i n preharvest factors on y i e l d and q u a l i t y of raw and processed tomatoes. Proc. Amer. Soc. Hort. S c i . 69: 327-342. Kertesz, Z.I. 1938. Pectic enzymes. I I . Pectic enzymes of tomatoes. Food Res. 3: 481-487. Kertesz, Z.I. 1951. The pectic substances. Interscience, New York. Kertesz, Z.I. 1963. Polyuronides. In: Comprehensive biochemistry, Vol. 5. M. F l o r k i n and E.H. Stotz, eds. E l s e v i e r , New York. Kertesz, Z.I. and J.D. Loconti. 1944. Factors determining the consistency o f canned commercial tomato j u i c e . N.Y. Geneva Agr. Expt. Sta. Tech. B u l l . No. 272. Kertesz, Z.I. and R.J. McColloch. 1950. The pectic substances of mature John Baer tomatoes. N.Y. Agr. Expt. Sta. B u l l . No. 745. Kramer, A. 1950. This meter gives better c o l o r evaluations. Food Ind. 22: 1897-1900. Kramer, A. 1951. Objective t e s t i n g of vegetable q u a l i t y . Food Technol. 5: 265-269. Kramer, A. 1952. The problem of developing grades and standards of q u a l i t y . Food Drug Cosmetic Law J. 7: 23-30. 120 Kramer, A. 1965. Evaluation of q u a l i t y of f r u i t s and vegetables. In: Food q u a l i t y : Effects of production practices and processing. G.W. I r v i n g , J r . , and S.R. Hoover, eds. Amer. Soc. Adv. S c i . Pub. No. 77, Washington, D.C. Kramer, A. 1966. Parameters of q u a l i t y . Food Technol. 20: 1147-1148. Kramer, A. and H.R. Smith. 1946. Preliminary investigation on measurement of color i n canned foods. Food Res. 11: 14-31. Kramer, A., B.A. Twigg and B.W. Clarke. 1959. Procedures f o r determining grades of raw tomatoes f o r processing. Food Technol. 13: 62-65. Kuhn, R. and C. Grundmann. 1932. Die Konstitution des lycopins. Ber. Deut. Chem. Ges. 65: 1880-1889. Lambeth, V'.N., E.F. Straten and M.L. Fi e l d s . 1966. F r u i t q u a l i t y a t t r i b u t e s of 250 foreign and domestic tomato accessions. Univ. Missouri Agr. Expt. Sta. Res. B u l l . No. 908. Lee, F.A. and CB. Sayre. 1946. Factors a f f e c t i n g the acid and t o t a l s o l i d s content of tomatoes. N.Y. Agr. Expt. Sta. Techn. B u l l . No. 278. Leonard, S., R.S. Pangborn and B.S. Luh. 1959. The pH problem i n canned tomatoes. Food Technol. 13: 418-419. Lewis, T.L. 1961. Physiological studies of c h i l l i n g i n j u r y i n tomato f r u i t s . Ph.D. t h e s i s , Purdue Univ. Lime, B.J., F.P. G r i f f i t h s , R.T. O'Connor, D.C. Heinzelman and E.R. McCall. 1952. Spectrophotometric methods f o r determining pigmentation -beta-carotene and lycopene i n Ruby Red grapefruit. J . Agr. Food Chem. 5: 941-944. 121 Lingle, J . C , M. Yamaguchi, B.S. Luh, and A. U l r i c h . 1965. The ef f e c t of night temperature and nitrogen n u t r i t i o n on y i e l d , time of maturity and q u a l i t y of tomato f r u i t s . Veg.Crop Series 139, Univ. C a l i f . , Davis. Lower, R.L. and A.E. Thompson. 1966. Sampling v a r i a t i o n o f a c i d i t y and s o l i d s i n tomatoes. Proc. Amer. Soc. Hort. S c i . 89: 512-522. Lower, R.L. and A.E. Thompson. 1967. Inheritance of a c i d i t y and s o l i d s content of small-fruited tomatoes. Proc. Amer. Soc. Hort. S c i . 91: 486-495. Luh, B.S., S. Leonard and W. Dempsey. 1954. Pectic substances of Pearson and San Marzano tomatoes. Food Res 19: 146-153. Luh, B.S., F. V i l l a r r e a l , S.J. Leonard and M. Yamaguchi. 1960. Effe c t of ripeness l e v e l on consistency of canned tomato j u i c e . Food Technol. 14: 635-639. MacGillivray, J.H. 1928. Studies of tomato q u a l i t y . I I I . Color of di f f e r e n t regions of a tomato f r u i t and a method f o r c o l o r determination. Proc. Amer. Soc. Hort. S c i . 25: 17-20. MacGillivray, J.H. 1931a. Tomato color as related to q u a l i t y i n the tomato canning industry. Purdue Agr. Expt. Sta. B u l l . No. 350. MacGillivray, J.H. 1931b. Tomato col o r as affected by processing temperatures. Proc. Amer. Soc. Hort. S c i . 28: 353-358. MacGillivray, J.H. 1934. The v a r i a t i o n i n temperature of tomatoes and t h e i r color development. Proc. Amer. Soc. Hort. S c i . 32: 529-531. MacGillivray, J.H. 1937. Spectrophotometric and coiorimetric analysis of tomato pulp. Proc. Amer. Soc. Hort. S c i . 35: 630-634. 122 MacGillivray, J.H. 1948. Color s p e c i f i c a t i o n of the federal canning tomato grade as related to h o r t i c u l t u r a l c o l o r determination. Proc. Amer. Soc. Hort. S c i . 52: 415-429. Mackinney, G. and A.C. L i t t l e . 1952. Color of foods. A v i . , Westport, v Conn. Mackinney, G., A.C. L i t t l e and L. Brinner. 1966. Visual appearance of foods. Food Technol. 20 (10): 60-68. Mavis, J.O. and W. A. Gould. 1954. Objective c o l o r measurements of tomato pulp (puree). Proc. Amer. Soc. Hort. S c i . 64: 379-389. McClendon, J.H., C.W. Woodmansee and G.F. Somers. 1959. On the occurrence of free galacturonic acid i n apples and tomatoes. Plant Physiol. 34: 389 McColloch, R.J., B.W. Nielson and E.A. Beavens. 1950. Factors influencing the q u a l i t y of tomato paste. II. Pectic changes during processing. Food Technol. 4: 339-343. McCollum, J.P. 1944. Color and pigment studies with d i f f e r e n t grades of tomato j u i c e . Proc. Amer. Soc. Hort. S c i . 44: 398-402. McCollum, J.P. 1953. A rapid method f o r determining t o t a l carotenoids and carotenes i n tomatoes. Proc. Amer. Soc. Hort. S c i . 61: 431-433. McCollum, J.P. 1955. D i s t r i b u t i o n o f carotenoids i n the tomato. Food Res. 20: 55-59. McCollum, J.P. 1956. Sampling tomato f r u i t s f o r composition studies. Proc. Amer. Soc. Hort. S c i . 68: 587-595. McComb, E.A. and R.M. McCready. 1952. Colorimetric determination of pectic substances. Anal. Chem. 24: 1630-1632. 123 McCready, R.M. and E.A. McComb. 1952. Extraction and determination of pectic substances. Anal. Chem. 24: 1986-1988. Meredith, F.I. and A.E. P u r c e l l . 1966. Changes i n the concentration of carotenes of ripening Homestead tomatoes. Proc. Amer. Soc. Hort. S c i ; 89: 544-548. M i t c h e l l , J.S. 1935.' Comparative composition and color of commercial tomato j u i c e . J . Assoc. Off. Agr. Chem. 18: 128-135. -Moghrabi, H.M. 1958. Physical and chemical changes during the ripening of tomatoes as affected by temperature. Ph.D. t h e s i s , Univ. of I l l i n o i s . Nauman, H.D. 1965. Evaluation and measurement of meat q u a l i t y . In: Food q u a l i t y : Effects of production practices and processing. G.W. I r v i n g , J r . , and S.R. Hoover, eds. Amer. Soc. Adv. S c i . , Pub. No. 77, Washington, D.C. National Canners Association Research Labs. 1956. A laboratory manual f o r the canning industry. 2nd ed. Nat. Canners Assoc., Washington, D.C. Newhall, S.M. 1940. Preliminary report of the O.S.A. subcommittee on the spacing of the Munsell colors. J . Opt. Soc. Amer. 30: 617-645. Newhall, S.M., D. Nickerson and D.B. Judd. 1943. F i n a l report of the O.S.A. subcommittee on the spacing of the Munsell colors. J . Opt. Soc. Amer. 33: 385-422. Nickerson, D. 1946. Color measurement and i t s application to the grading of a g r i c u l t u r a l products. A handbook on the method of disc colorimetry. U.S. Dept. Agr. Misc. Publ. No. 580. 124 Nightingale, G.T. 1933. Effects of temperature on metabolism i n tomato. Bot. Gaz. 95: 35-57. Nimeroff, I. 1968. Colorimetry. U.S. Dept. Commerce, Nat. Bur. Stand. Monogr. 104. McWilliam, J.R. and A.W. Naylor. 1967. Temperature and plant adaptation. I. Interaction of temperature and l i g h t i n the synthesis of chlorophyll i n corn. Plant Physiol. 42: 1711-1715. Paech, K. 1938. Pflanzenphysiologische grundlagenforschung. Landwirtsch. Jahrb. 85: 653. Cited by A.R. Hamson In: Measuring firmness of tomatoes i n a breeding programme. Proc. Amer. Soc. Hort. S c i . 60: 425-433. Porte, W.S. 1952. Commercial production of tomatoes. U.S. Dept. Agr. Farmers' B u l l . No. 2045. Porter, J.W. and R.E. Lincoln. 1950. I. Lycopersicon selections containing a high content of carotene and colorless polyenes. I I . The mechanism of carotene biosynthesis. Arch. Biochem. 27: 390-403. Porter, J.W. and F.P. Zscheile. 1946b. Carotenes of Lycopersicon species and s t r a i n s . Arch. Biochem. 10: 537-545. Porter, J.W. and F.P. Zscheile. 1946a. Naturally occurring colorless polyenes. Arch. Biochem. 10: 547-551. Rabourn, W.J. and F.W. Quackenbush. 1953. The occurrence of phytoene i n various plant materials. Arch. Biochem. Biophys. 44: 159-164. Robinson, W.B., T. Wishnetsky, J.R. Ransford, W.L. Clark and D.B. Hand. 1952. A study of methods f o r the measurement of tomato j u i c e color. Food Technol. 6: 269-275. 125 Rosa, J.T. 1925. Ripening o f tomatoes. Proc. Amer. Soc. Hort. S c i . 22: 315-322. Rosa, J.T. 1926. Ripening and storage o f tomatoes. Proc. Amer. Soc. Hort. S c i . 23: 233-242. Ruck, J.A. 1963. Chemical methods f o r a n a l y s i s o f f r u i t and vegetable products. Pub. 1154. Res. S t a . , Sunimerland, B.C. Sampson, P. 1968. BMDX64 general l i n e a r hypothesis programme. He a l t h S e r v i c e s Computing F a c i l i t y , Univ. C a l i f . , Los Angeles. Sayed, M.N.K., H.T. E r i c k s o n , and M.L. Tomes. 1966. I n h e r i t a n c e o f tomato f r u i t f i rmness. Proc. Amer. Soc. Hort. S c i . 89: 523-527. Sayre, C.B., W.B. Robinson and T. Wishnetsky. 1953. E f f e c t o f temperature on the c o l o r , lycopene and carotene content o f detached and o f v i n e r i p e n e d tomatoes. Proc. Amer. Soc. Hort. S c i . 61: 381-387. S c o t t , L.E. and E.P. W a l l s . 1947. A s c o r b i c a c i d content and sugar-acid r a t i o s o f f r e s h f r u i t and processed j u i c e o f tomato v a r i e t i e s . Proc. Amer. Soc. Hort. S c i . 50: 269-272. Simandle, P.A., J.K. Brogdon, J.P. Sweeney, E.O. Mobley and D.W. Davis. 1966. Q u a l i t y o f s i x tomato v a r i e t i e s as a f f e c t e d by some co m p o s i t i o n a l f a c t o r s . ' Proc. Amer. Soc. Hort. S c i . 89: 532-538. Smith,.T.J. and R.A. Huggins. 1952. Tomato c l a s s i f i c a t i o n by s p e c t r o -photometry. E l e c t r o n i c s 25: 92-94. Spenser, M. 1965. F r u i t r i p e n i n g . I n : P l a n t b i o c h e m i s t r y . J . Bonner and J.E. Varner, eds. Academic P r e s s , New York. S t i e r , E.F., CO. B a l l and W.A. Maclinn. 1956. Changes i n p e c t i c substances o f tomatoes d u r i n g storage. Food Technol. 10: 39-43. 126 S t r a i n , H.H. 1934. Carotene. VIII. Separation of carotenes by adsorption. J . B i o l . Chem. 105: 523-535. Thompson, A.E. 1965. A technique of selection f o r high a c i d i t y i n the tomato. Proc. Amer. Soc. Hort. S c i . 87: 404-414. Thompson, A.E., R.W. Hepler, R.L. Lower and J.P. McCollum. 1962. Characterization of tomato v a r i e t i e s and strains f o r con-stituents of f r u i t q u a l i t y . 111. Agr. Expt. Sta. B u l l . No. 685. Thompson, A.E., M.L. Tomes and E.V. Warm. 1965. Characterization of Crimson tomato f r u i t color. Proc. Amer. Soc. Hort. S c i . 86: 610-616. Tomes, M.L. 1963. Temperature i n h i b i t i o n of carotene synthesis i n tomato. Bot. Gaz. 124: 180-185. Tomes, M.L., F.W. Quackenbush and T.E. Kargl. 1956. Action of the gene B i n biosynthesis of carotenes i n the tomato. Bot. Gaz. 117: 248-253. Tomes, M.L., F.W. Quackenbush and T.E. Kargl. 1958. Synthesis of 8-carotene i n the tomato f r u i t . Bot. Gaz. 119: 250-253. Trombly, H.H. and J.W. Porter. 1953. Additional carotenes and a colo r l e s s polyene of Lycopersicon species and s t r a i n s . Arch. Biochem. Biophys. 43: 443-457. U l r i c h , R. and J . Renac. 1950. Le metabolism des f r u i t s de tomate et son a l t e r a t i o n sous 1'effect des blessures. Comptes Rendus L'Acad. S c i . 230: 567-569. Underwood, J.C. 1950. Factors influencing q u a l i t y of tomato paste. Food Res. 15: 366-372. Verkerk, K. 1964. Additional i l l u m i n a t i o n before and temperature a f t e r planting of early tomatoes. Neth. J . Agr. S c i . 12 (1): 57-68. Vogele, A.C. 1937. Effect of environmental factors upon the co l o r of the tomato and the watermelon. Plant Physiol. 12: 929-955. Voisey, P.W. and L.H. L y a l l . 1965. Methods of determining the strength of tomato skin i n r e l a t i o n t o f r u i t cracking. Proc. Amer. Soc. Hort. S c i . 86: 597-609. Voisey, P.W. and L.H. L y a l l . 1966. Measuring tomato cracking. Can. Agr. 22-23. Wedding, R.T. and H.M. Vines. 1959. Temperature e f f e c t s on tomato. C a l i f . Agr. 13 (11): 13. Weedon, B.C.L. 1965. Chemistry o f the carotenoids. In: Chemistry and Biochemistry o f Plant Pigments. T.W. Goodwin, ed. Academic Press, New York. Wegener, J.B., E.R Thompson and L.S. Fenn. 1957. Color evaluation of canned tomato j u i c e with natural and a r t i f i c i a l i l l u m i n a t i o n . Food Technol. 11: 196-199. Went, F.W., A.L. LeRosen and L. Zechmeister. 1942. Eff e c t of external factors on tomato pigments as studied by chromatographic methods. Plant Physiol. 17: 91-100. West, E.A. and G.B. Snyder. 1938. The e f f e c t of storage methods on ripening and q u a l i t y of tomatoes. Proc. Amer. Soc. Hort. S c i . 36: 695-700. Winsor. G.W. 1966. Some factors a f f e c t i n g the composition, flavour and firmness of tomatoes. S c i e n t i f i c Hort. 18: 27-35. 128 Winsor, G.W., J.N. Davies and D.M. Massey. 1962a. Composition of tomato f r u i t . I I I . Juices from whole f r u i t and locules at d i f f e r e n t stages of ripeness. J . S c i . Food Agr. 13: 108-115. Winsor, G.W., J.N. Davies and D.M. Massey. 1962b. Composition of tomato f r u i t . IV. Changes i n some constituents of the f r u i t walls during ripening. J . S c i . Food Agr. 13: 141-145. Winsor, G.W. and D.M. Massey. 1958. The composition of tomato f r u i t I. The expressed sap of normal and 'blotchy' tomatoes. J . S c i . Food Agr. 9: 493-498. Woodmansee, CW., J.H. McClendon and G.F. Somers. 1959. Chemical changes associated with the ripening of apples and tomatoes. Food Res. 24: 503-514. Wright, R.C, W.T. Pentzer, T.M. Whiteman and D.H. Rose. 1931. Eff e c t of various temperatures on the storage and ripening of tomatoes. U.S. Dept. Agr. Tech. B u l l . No. 268. Yamaguchi, M., F.D. Howard, B.S. Luh and S.J. Leonard. 1960. Eff e c t of ripeness and harvest dates on the q u a l i t y and composition of fresh canning tomatoes. Proc. Amer. Soc. Hort.Sci. 76: 560-567. Yeatman, J.N. 1969. Tomato products: read tomato red? Food Technol. 23: 618-627. Yeatman, J.N. and A. P. Sidwell. 1958. Judging q u a l i t y of tomatoes f o r processing by objective color evaluation with subjective estimation of defects. U.S. Dept. Agr. Mktg. Res. Rept. No. 235. Yeatman, J.N., A. P. Sidwell, and K.H. Norris. 1960. Derivation of a new formula f o r computing raw tomato j u i c e color from objective c o l o r measurement. Food Technol. 14: 16-20. 129 Younkin, S.G. 1950a. Color measurement of tomato purees. Food Technol. 4: 350-354. Younkin, S.G. 1950b. Measurement of small c o l o r differences i n tomato purees. J . Opt. Soc. Amer. 40: 596-599. Younkin, S.G. 1954. Application of c o l o r indcies to the tomato color measurement problem. Color i n Foods - Symposium. Nat. Acad. S c i . , Nat. Res. Council. Zechmeister, L. 1962. Cis-trans isomeric carotenoids vitamins A and arylpolyenes. Academic Press, New York. Zechmeister, L. and A. Polgar. 1943. Cis-trans isomerization and spectral c h a r a c t e r i s t i c s of carotenoids and some related compounds. J . Amer. Chem. Soc. 65: 1522-1534. Zscheile, F.P. and J.W. Porter. 1947. A n a l y t i c a l methods f o r carotenes of Lycopersicon species and s t r a i n s . Anal. Chem. 19: 47-51. Zsheile, F.P., J.W. White, J r . , B.W. Beadle and J.R. Roach. 1942. The preparation and absorption spectra o f f i v e pure carotenoid pigments. Plant Physiol. 17: 331-346. 

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