TEMPERATURE OF MECHANECALLY HARVESTED PROCESSING TOMATOES HELD IN DEFFERENT CONTASNERS AND ITS RELATION TO RENT QUALITY Them {or ”'12 Degree of M. S. MICHKGAN STATE UNIVERSE? Eciuardo Gonzaiez Orbegoso 1962 IBEQ’S LIBRAR Y Michigan State University TEMPERATURE OF MECHANICALLY HARVESTED PROCESSING TOMATOES HELD IN DIFFERENT CONTAINERS AND ITS RELATION TO FRUIT QUALITY By EDUARDO GONZALEZ OREEGOSO AN ABSTRACT Submitted to the College of Agriculture of Michigan State University of Agriculture and Applied Science in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE IN AGRICULTURAL MECHANICS Department of Agricultural Engineering 1962 Approved by EA m ABSTRACT EDUARDO GONZALEZ ORBEGOSO The mechanical tomato harvester, under develOpment at MSU for the past five years was used in 1962 to harvest tomatoes into bulk boxes of different materials and construc- tion characteristics. It was important to determine whether any one of the boxes used would keep the tomatoes cooler while exposed to the summer sun. Tomatoes and containers were instrumented to permit recording of the tomato internal and surface temperature as well as the inside surface container temperature. A 16 point recording potentiometer and copper-constantan thermo- couples were used. TWO preliminary runs were conducted to get the equipment prOperly set up and establish procedures. A series of tests were performed throughout the harvesting season. The first test was made to record only the surface temperature of empty containers to provide an idea of their comparative heating during the day. Later tests were made to record surface temperatures of containers filled with tomatoes together with tomato internal and surface temperatures. No meaningful differences were recorded between internal and surface temperatures of tomatoes in a given box, so the internal tomato temperature was used to establish comparisons among boxes. A difference of up to A°F for the mean EDUARDO GONZALEZ OREEGOSO temperature of a 2M hour period was found between the internal tomato temperatures in the wire mesh container as compared to the internal tomato temperature in the steel, wooden and plastic containers. This difference was responsible for a calculated 21% increase in respiration. Very small differences were found between the internal tomato temperature in the steel, wooden and plastic containers. An interesting heat transfer phenomenon found under the conditions of this study was the faur hour lag which existed between internal temperatures of tomatoes and the air temperature. A review of literature was conducted to determine the effect of temperature on tomato quality. Few direct references werefound, but most of the information indicated that overheating of ripe tomatoes is undesirable since respiration is accelerated and losses of organic constituents of the fruit become significant. TEMPERATURE OF MECHANICALLY HARVESTED PROCESSING TOMATOES HELD IN DIFFERENT CONTAINERS AND ITS RELATION TO FRUIT QUALITY By EDUARDO GONZALEZ ORBEGOSO A THESIS Submitted to the College of Agriculture of Michigan State university of Agriculture and Applied Science in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE IN AGRICULTURAL MECHANICS Department of Agricultural Engineering 1962 ACKNOWLEDGEMENTS After a year of graduate work and enjoyable experiences at Michigan State university, the author wishes to eXpress his sincere thanks to the following entities and persons: To the 0.8. Government, for granting him a Fulbright scholarship for an academic year. To the 0.3. Educational Commission in Peru for covering his travel expenses. To the Scholarships Foundation Inc., for granting him an award for continued study. To the U.S. Steel Corporation for sponsoring the research project. To Professor Arthur w. Farrall Head of the Agricultural Engineering Department at MSU, for approving the author's appointment as Special Graduate Research Assistant during the Fall term 1962. To Dr. B. A. Stout, the author's major professor, for his advice and encouragement throughout the academic work and planning of the research project. To Professor D. H. Dewey and Dr. S. K; flies from the Horticultural Department for their suggestions on the research prOject. To Dr. F. H; Buelow for his contributions towards this thesis. 11 111 To Professor C. R. Hoglund for acting as the author's minor professor. To all other members of the Agricultural Engineering faculty and staff who have directly or indirectly contributed towards the author's work. To my fellow graduate students for their friendship. And specially to Veronica, my wife, for her patience and understanding and for the typing of this thesis. TABLE OF CONTENTS MOWCTION oooooooooosoioooooooooosooooooooooooooo REVEW OF LIMA'I'URE 0.00.00...OOOOOOOOOOOOOOOCOOOO Effect of Temperature on the Tomato Fruit Respiration 00.0.0.0000000000000000000000.0.0 Effect of Temperature on Tomato Quality ...... mmEm 000.000.00.00...0.00000000000000000000000 RESULTS AND DISCUSSION 0.00.0000.000000000000000... Comparative Temperatures of Empty and Full containers 00.9.00.00000000000000000000000000 Tomato Temperature as Related to Type of container used OOOOOOOOOOOOOOOOOOOOOO0.000000 Effect of the Observed Temperatures on Tomato Respiration and Quality .............. Keeping Tomatoes Cool in Bulk Boxes .......... CONCLUSIONS ....................................... SUGGESTIONS FOR FURTHER STUDY ..................... REFERENCES ........................................ iv 13 2O 2O 23 30 3h 36 37 38 LIST OF TABLES Heat generated by reSpiration of tomatoes OOOOOOOOOOOOOOOOOIOOOOOO000000000 Description of the boxes used in the tomato temperature studies ............... Sumry Of the tests OOOOOOOOCOOOOCOOOOOOOO Container surface and tomato internal mean temperatures (°F) for a an hour period .0..00.000COOOOOOOOOOCOOOOOOOO0.... Duration of internal temperatures for tomatoes in different containers during a 24 hour period OOOOOOOOOOOOOOOOOO 13 19 26 33 LIST OF FIGURES Tomato temperature study showing the four different types of bulk boxes, the potentiometer and lead wires ......... Manual switching between containers at intervals .....OOOOOOOOOOOOOOOOO0.0...O The position of thermocouples: surface (left), internal (center and right) ...... Surface temperatures of empty containers ... Surface temperatures of containers filled with tomatoes ..................... Tomato internal and surface temperatures compared to container temperatures (wire mesh and sheet steel) .............. Tomato internal and surface temperatures compared to container temperatures . ("00d and plaSt1C) OOOOflOOOOOOOOOOOOOOOOOO Internal temperatures of tomatoes in different containers (2h hour test) ...... Internal temperatures of tomatoes in different containers (12 hour test) ...... vi 15 15 16 21 2h 25 28 29 INTRODUCTION The value of the 1961 U.S. processing tamato crap exceeded 125 million dollars (2”). The cost of harvesting these tomatoes is estimated to be 25% of the dollar value of the crop or over 30 million dollars (19). The difficulty in securing hand labor and the expense involved in harvesting by hand have accelerated the trend towards mechanization and bulk handling of the tomato crap in the last five years. Mechanical tomato harvesting and handling studies have been conducted at Michigan State university since 1958 (20). The third MSU tomato harvester, built in 1960, was used again for the 1962 tests. This machine placed the fruit into bulk boxes holding approximately 500 to 750 lbs. It is important from the standpoint of fruit quality preservation to determine whether some types of bulk boxes would be more advantageous than others in avoiding over- heating of the tomatoes while they are in the field exposed to the summer sun. Containers of different materials and construction characteristics were considered. The different rate of radiant energy absorptivity and thermal conductivity of the materials of these bulk boxes would have an influence on the resulting temperature of the fruits. Variations in the construction characteristics such as solid sides and bottom as compared to spaced sides and bottom (wire mesh) would also be responsible for differences in heat transfer between the tomatoes, the box and the environment. The influence of these factors on the tomato temperature was investigated. ' This study was undertaken to find whether significant temperature differences occurred between tomatoes held in various types of bulk boxes (wood, steel, plastic, wire mesh), and if so, to determine from the literature whether these temperature differences were large enough to affect the quality of the tomatoes. The effect of temperature on tomato respiration and quality was to be considered in evaluating any differences that occurred. REVIEW OF LITERATURE Effect of Temperature on the Tomato Fruit Respiration In any consideration of fresh fruits and vegetables, it should be remembered that these commodities are alive and that they therefore carry within themselves many of the processes characteristic of all living things. The most important of these processes is respiration, by which the oxygen of the air is combined with the carbon of the plant tissues, occurring chiefly in sugars, to form.various decom- position products and eventually carbon dioxide and water. Wright et a1 (27) stated that during the processes of respiration, energy is released in the form of heat, the amount of which varies with the commodity and increases as the temperature increases up to about 100°F. Wright and Whiteman (28) have given the following approximate rates of evolution of heat per ton of ripe tomatoes: Table 1. Heat generated by respiration of tomatoes 0 Ambient Temperature, F Heat Generated, Btu/ton/hr. no . . . . . . . . . 52 6O . . . . . . . . . 235 When determining the temperatures of tomatoes, it should 3 be kept in mind that increases in ambient temperature will produce an acceleration of the rate of respiration with a subsequent increase in tomato temperatures. The rate of production of CO2 is usually taken as a measure of the amount of heat generated by fruits and vege- tables assuming all heat is a result of the combustion of hexose sugar. Since the heat calculated from 002 is difficult -'. c. .-. . to measure, calorimeter measurements of the heat of respiration are made. Green (8) found that the heat measured by calorimeter was higher than the heat calculated from 092 by an amount varying from O to 230 Btu/ton/hour. He also found that the heat produced was always higher at 65°F than at h5°F. From these observations he concluded that the quantity of heat produced by fruits and vegetables varies greatly among samples, to the extent that it is almost impossible to compare independent measurements and expect close agreement. Tomato respiration and ripening has been studied by many researchers (1), (2), (4) all of which have agreed that an increase in temperature brings about accelerated respiration and ripening. Alban (1) measured the respiration rate of tomatoes at three controlled night temperatures: 57°, 62°and 67°F. In general, the respiration was higher at 67°F. The respiration rate for the three different temperatures decreased heavily from O to 72 hours after harvest, maintained itself uniform from 72 to 120 hours after harvest and increased slightly from 120 to lhu hours after harvest. In determining the ripening of tomatoes at different temperatures by observation of color, firmness and acidity, Ayres and Pearce (2) found that the rates of ripening proceeded in the following order: ambient roomq>77°>689>59°>5o°F. He also reported that tomatoes stored at 50°F kept for 2% months and for 2 months at 59°F. The fruits spoiled in less than 1% months at 68°F and in a few days at 77°F or at ambient temperature. Diehl (u) stated that tomatoes were not injured when held for one day at 30° to 31°F. Tomatoes held at 50°F ripened gradually in about nine days, while at 70°F they ripened in five to seven days. Gore (7) in studying fruits held at four controlled temperatures of which 97.7OF was the highest, observed that a rise in temperature was accompanied by a very rapid increase of the respiratory activity. The rate of respira- tion increased from 1.89 to 3.01 times or an average of 2.37 - times for each 18oF rise in temperature for #9 sets of determinations with no different species of fruits. These figures are an indication of changes occurring in respiratory rate, which are to be expected, with the increase in the tomato temperatures influenced by greater ambient and container temperatures. Haller (10) pointed out that in general as temperature increased from 32°to 100°F, the respiration rate also increased. He also emphasized the importance of the respiration rate of fruits in relation to temperature, stating that the respiration rate is a measure of the rate of metabolism and is an index to the rate of deterioration of fruits. Similarly, he stated that the loss of material at high temperature (80°F) may become quite significant and consequently will be to some extent a measure of the rate of deterioration. Effect of Temperature on Jamato 93311131 Since excessive temperature is known to be a limiting factor in the production of many vegetable crOps, an attempt was made to find from.the literature, the correlation between temperature and tomato fruit quality in tenms of color, carotenoid content, ph, acidity, soluble solids and total solidsr It is not unusual to find both the grower and the canner storing tomatoes in the Open where the‘sun shines on them throughout the day. Others place the filled boxes under sheds until they can.market their produce. Tomatoes stored under these conditions are likely to be subjected to different temperatures which should influence their quality. MacGillivray (1h) found that tomato fruits show a gradual continuous loss in weight after they had been removed from the plant. The amount of this loss was greatly influenced by the surrounding temperature and also by the absence or presence of any cuts or cracks. This loss in weight was prOportional to the temperature inasmuch as the greater the temperature the greater the loss in weight. During these experiments fruits were cut across the stylar end to imitate cut or crushed fruits and the tomatoes were held at three controlled temperatures: 57°, 76°, 109.5°F. Slit fruits seemed to suffer greater losses than uncut fruits at the same temperature. The losses of organic constituents such as sugars and acids were found to be directly prOpor- tional to temperature. The quality of the fruit was impaired because of the unequal losses of these two constituents as well as a gain in undecomposed material. Similarly, Haber (9) found that tomatoes stored at 70°F lost weight and acid rapidly. Ripe samples of shaded and unshaded tomato fruits were used by NacCollum (12) to determine the effect of sunlight eXposure on the sugar, total solids, carotenoid and ascorbic acid content of tomato fruits. Analysis were made early and late in the harvesting season. The data showed the unshaded fruits to be higher in ascorbic acid, total solids and sugar than the shaded ones. These constituents vary within a fruit, depending on side exposed. The exposed fruits although high in quality constituents were shown to be low in total carotenoids specially when high temperatures prevailed. Tcmatoes exposed tC sunlight (ften Show deceleratién tr even injury (sun scald) depending upon the conditions of exposure, according to MacCollum (11). In studying light as one of the factors affecting acid content he concluded that the fruits with greater exposure to sunlight had a higher ascorbic acid content. No consistent relationship was found between ascorbic acid, total solids and sugar content. Tomatoes produced for the canner are harvested at red ripe stage as maximum color is required. Forshey (6) emphasizes that color is extremely important in tomatoes that are to be processed. The red tomato pigment, lchpene, deve10ps most rapidly in temperature ranges of 70°—75°F according to several authors (5), (26), (25) and its formation decreases rapidly as the temperature drOps below or rises above this rather narrow range. A number of measurements taken by Skok (23) have indicated that tomato fruits eXposed to the sun will often reach temperatures as high as 100°-l20°F during bright days. Fruit temperatures of 90°F are quite comon during the day- time. He stated that since fruit temperatures are predominantly in the nineties during the latter part of Jul and August and often in the sixties during the latter part of September, conditions for Optimum coloration are unfavorable during a large portion of the tomato season. This means. that fruits must remain on the plants longer for 1yc0pene accumulation than they would if Optimum temperature prevailed. Over-ripe and soft fruits often result and a high prOportion is lost. Losses sustained in the field vary with weather condi- tions. Sometimes only half the crOp is harvestable (23). It is obvious that the longer fruits stay in the field the greater these losses will be; and conversely the earlier the i( fruits are harvested the greater will be the recovery. This problem may be more severe with the once-over mechanical harvest since fruit is required to stay longer in the field to obtain a greater prOportion of ripe fruit. MacGillivray (16) pointed out that in warm.regions in mid-summer, field grown tomatoes would often be subjected to high temperatures during portions of the day which would inhibit lchpene develOpment, but lower temperatures at night would permit 1yc0pene formation during a part of the 2h hours of most days. The temperature of tomatoes was found to vary directly with air temperature. The side of the tomato nearest the sun was higher in temperature than the shaded side. The variation in temperature between the exposed and shaded side ranged from 15° to h7°F. The poorly foliaged fruits ripened more rapidly since they were exposed to higher temperatures during the day and slightly lower temperatures at night. The air temperature for these measurements ranged from 56° to 102°? during the 2!: hours of the day. It was not uncommon for fruits to have temperatures of 96°F or more, ‘but never 90°F for 2“ hours at one time. Sayre et a1 (22) reported that tomatoes ripened within a 10 temperature range of 100°F in the daytime and 85°F at night I would never develop sufficient lchpene to make the fruits sufficiently red. HOwever, tomatoes ripened at a temperature range of 80°F during the daytime and 65°F at night produced a well-colored fruit that was high in lchpene and carotene, regardless of whether the fruits were ripened on the vine or detached at the turning stage of maturity. Under these conditions an average of nine days was required for tomatoes to become red. The carotene content was not greatly affected 'by the different temperature used in these experiments. The amount of red color is an important factor in determining the market value of tomatoes for processing. Several authors (5). (21), (25) have shown that lycopene, the red coloring pigment of tomatoes, does not develOp at tempe- ratures below 50°F and is inhibited at temperatures above 86°F. Duggar (5) stated that when green fruits are ripened at a temperature of 86°F or above, a yellow-orange or orange- red color was produced instead of the red pigment, lchpene. MacCollum (13) found that tomato fruits exposed to direct sunlight in the field often develOp poor color due primarily to a low content of lchpene or a decrease in the develOpment of this red pigment. He stated that at favor- able temperatures (70°-75°F) the rate of development of this pigment is increased by illumination. Light is effective until chlorophyll disappears. It was also found that carotene is increased by illumination of tomato fruits during 11 ripening. Thus, fruits which are exposed to direct sunlight are usually higher in carotene. The effect of heat during processing upon tomato quality was investigated by MacGillivray (15) in color studies of tomato pulp, tomato Juice and canned tomatoes. It was of interest to note that in all cases heating to 212°F was accompanied by an impairment of color. During the concen- tration of the raw Juice to pulp the greatest color impair- ment occurred in the first period of the concentrating time. There was a loss of color during the heating period of sterilization in canned tomatoes. The same sample of pulp was found to have a better color at low temperatures than at high temperatures thus a sample of pulp at 41°F was better in color than one at 86°F. Nutting (17) studied the tomato quality retention among several different concentrations of tomato products during a three year period. He found that samples with 5.6 to 8.8% total solids changed less in flavor and color than those of 21 to 38.u% when held at elevated temperatures for varying periods of time. The effect of temperature on tomato respiration and quality can be approached from several points of view as has been shown. However, most of the authors seem to agree that increased temperatures would bring about an acceleration in the rate of respiration and consequently in the rate of deterioration. 12 Having presented the relationship between temperature and tomato quality, the next step was to arrange the set—up that would allow the recording of temperatures according to the objectives of this study. ““-"1l- A, s — PROCEDURE The materials and methods described in the following paragraphs were used for determining the temperature of mechanically harvested processing tomatoes when handled in bulk boxes made of various materials. The tomatoes for these studies were grown at the MSU horticulture farm and were mostly of the Fireball, Libby 0-52 and Heinz 1370 varieties. Four types of boxes, as described in Table 2, were used throughout the tests. Table 2. Description of the boxes used in tomato temperature studies. Measurements, Inches Material Construction Length Width Depth Wood Slats 47 x R7 x 16 Steel (rusty) Welded sheets bl x ho x 16 Plastic (Polyethylene) One piece #7 x 38 x 15 Wire Mesh* Welded #7 x #7 x 16 * The wire mesh container was aluminum coated and had a 1%" x 1}" bottom and 3" x 1.1;" side design. The tomatoes and containers were instrumented to permit recording of the internal and surface tomato temperatures together with the inside surface temperature of the container. 13 114 A view of the arrangement of the four full containers is given in Figure 1. A 16 point recording potentiometer with a temperature range of -h0° to 140°F and its printing mechanism speed set to allow recordings every 30 seconds was used. The internal tomato temperature was measured by thermocouples inserted half way into the tomato at the calyx end of the fruit (Figure 3). The surface tomato temperature was measured by thermocouples attached with tape to the surface of the tomato. All instrumented fruits were placed in the bulk boxes at mid-level from north to south. All thermocouples measuring inside surface temperatures of the containers were placed symmetrically on the south side of the containers. Thermocouples were made from c0pper-constantan duplex wire with thermOplastic insulation. The lead wires were single COpper and constantan wires insulated by enamel and cotton cloth. All extension wires were put through rubber tubing to facilitate their handling and to protect them (Figure 1). The considerable number of thermocouple wires made it necessary to use independent eleven point connectors for each box to permit consecutive recordings of all points in the four boxes (Figure 2). The c0pper and constantan wires from each box were attached to double sets of female connectors which were attached to four wooden saw horses, one placed next to each box. The lead wires were attached to two male connectors which were manually switched between 15 Figure 1. Tomato temperature study showing the four different types of bulk boxes, the potentiometer and lead wires lFigure 2. Manual switching between containers at intervals 3:an poo mopaoov H8935“ 4:83 nonhuman umrmnmneoooanmfi mo oofifimoa 38 .m mommy“ 17 containers at intervals (Figure 2). A different arrangement was made for continuous recordings during the night by reducing the number of thermocouples in each box so that they all could be covered in one cycle. Daytime recordings were controlled at all times watching for precise switching time, failures due to bad contact or rupture in lines, presence of occasional clouds which would influence recordings unevenly, etc. The general set-up proved to be practical since the installation could be removed completely to allow the fork- lift to handle the boxes every time it became necessary to dump and bring in freshly harvested tomatoes. A nitro- compound fruit fly dust (Pyrethrin) was very helpful in keeping flies away, especially after the tomatoes had been kept for more than one day. The air temperature was recorded during all tests at the same interval as the other recordings. Parallel measurpments of air temperature made by MSU'were available for comparison. The air temperature appearing in the results corresponds to that recorded by MSU on hygro-thermograph charts. A preliminary trial run was conducted with the empty sheet steel and wooden boxes. This test revealed the importance of the symmetric location of thermocouples in one box with respect to another to provide equivalent readings and to avoid the shading of thermocouples by the container's wall. Differences of about 5°F were obtained when thermo- couples were not placed flat on the container surface. 18 A second trial run was conducted using only the sheet steel container partially loaded with tomatoes to determine whether any differences between internal and surface tempera- tures of the tomato could be recorded with the thermocouples used. The results revealed that differences were measurable and the data gave a partial idea of the results to be expected from later experiments. A series of tests were performed throughout the harvesting season. The characteristics of these tests are summarized in Table 3. The first tests were made to record only the surface temperature of the empty containers to provide an idea of their comparative heating at different times during the day. The later tests were made to record surface temperatures of full containers together with internal and external tomato temperatures. After a few tests the effort was concentrated on tomato temperature resulting from different containers during the day, as the higher daily temperatures would be more harmful to the tomatoes than differences observed at night. In all tests a total of 107 hours of records were made corresponding to 6,572 individual readings. The results and conclusions drawn.from this study are based on approxi- mately 65% of this data. The data obtained under inadequate environmental conditions was not used in the analysis. as w l .33 “30: a“ w leMHlm .. one we .. as was: as m 8..me .. mun NH 3 a: moon so w mwnhim a mu: NH I #3 “502 Ed w lewlm = on: m u a: moon .2m w mmumum e .95 m as soon .. as m HHH mpon 85233 7) onspmnoosou no: em .mn: :H ma .oae u so b HH 1 nooaopsoo pom opspmaooaou . u u u ooomnzn nos eh: m .3 use: so m H mm mm m accuses.“ cocoon. .nnn 3H ma .oaa u an r HH mmnmwnw no: am e .93 S as use: .. so m H 8-3% mwoaoaooon mu: m u a: .oaa Ed 0H mmnbmaw onopmnooaop nonempGOo modem Hooch ammunmm powwom uoaom memo mom made a momma open scapounonon puma ooapmnsn poms nonsrz Hm>nopoH once ones mono» on» 90 zhmsaom .m canoe RESULTS AND DISCUSSION Comparative Temperatures of Emptyrand Full Containers The results of the initial tests (No. l and 2, Table 3) measuring surface temperatures of empty containers (Figure u) show that there was a 70°F variation between the hot and cold extremes for a 2A hour period. During these tests the air temperature fluctuated from a maximum.of 88°F at u p.m., to, a minimum of 60°F at 5 a.m. The mean air temperature for the 2A hour period was 73.8°F. The sheet steel bulk box maintained the highest temperature throughout the day followed by the wooden, plastic and wire mesh containers. All containers were hotter than the air temperature through- out the day until 6 p.m., (85°F) after which the air was warmer than the containers since they had radiated their heat to the sky. At 7 a.mu, (67°F) the containers again became warmer than the air. During the night the wire mesh container remained warmer than the others by about 3°F. The sheet steel container reached a maxim temperature of 125°F at 12 noon. The surface temperatures of containers when filled with tomatoes are shown in Figure 5 and the data correspond to test No. 3 in Table 3. During these tests the air temperature fluctuated from a maximal of 87°F at 3 p.m., to a minimum of 58°F at 6 a.mo, with a mean temperature of 20 DEGREES FAHRENHEIT 21 130 WIRE MESH BULK BOX SHEET STEEL BULK BOX WOODEN BULK BOX PLASTIC BULK BOX AIR TEMPERATURE 120 110 100 90 80' 7O 60 SO 9 1 5 9 1 5 9 am am TIME OF DAY Figure A. Surface temperatures of empty containers FAHRENHEI T DEGREES 22 120 WIRE MESH BULK BOX :-- -- SHEET STEEL BULK BO :———— WOODEN BULK BOX : ---- no PLASTIC BULK BOX [4 AIR TEMPERATURE :-—.__ 5O 2 6 1O 2 6 1O 2 pr“ prn TLME OF DAY Figure 5. Surface temperatures of containers filled with tomatoes 23 73.7°F for the 24 hour period. Comparing Figures h and 5, it can be seen that although there was not much difference in air temperature during the recordings for these two groups of tests, there are considerable differences in the surface temperatures between empty and full containers. As would be expected, the surface temperatures of full containers were lower during the day than those for empty containers since part of the heat was being passed on to the tomatoes by conduction. The free circulation of warm air inside of the empty containers during the day contributed towards their higher temperatures. The wire mesh container, because of better ventilation, was the coolest at night among the full containers. Both for the empty and full container tests the surface temperature of the wire mesh bulk box was the closest to the air temperature during the night. The wooden container being a better insulator, had the lowest inside surface temperature during the day and the highest temperature at night. Tomato Temperature as Related to Type of Container Used The internal and surface tomato temperatures as compared to surface container temperatures are shown in Figure 6 for the wire mesh and sheet steel bulk boxes, and in Figure 7 for the wooden and plastic bulk boxes. 0n the whole, no meaningful differences were recorded between internal and surface temperatures of tomatoes in a given box. There was 2h WIRE MESH BULK BOX TOMATO INTERNAL TEMPERATURE :----- TOMATO SURFACE TEMPERATURE :-——-— CONTAINER SURFACE TEMPERATURE: -———— AIR TEMPERATURE :-— —— \ /~ g; \ . C) DEGREES FAHRENHEIT Q) ‘C) 70 \fi \ ‘ " ‘~-—.. ...... j,‘ ------ / 50 2 6 TO 2 6 ’IO 2 pm TIME OF DAY Pm SHEET STEEL BULK BOX l.— E Z110 LlJ 0: 3% so Ll. L...— “: T“:\T—) \- 4:-_ N ‘ L3 \\ °-°:°‘ "‘------._._ L|J 7O '- L‘J \ R 50 2 6 TO 2 6 10 2 pm TIME OF DAY pm Figure 6. Tomato internal and surface temperatures compared to container temperatures FAHRENHEIT DEGREES FAHRENHEIT DEGREES HO 25 WOODEN BULK BOX TOMATO INTERNAL TEMPERATURE TOMATO SURFACE TEMPERATURE CONTAINER SURFACE TEMPERATURE: -———— AIR TEMPERATURE 50 2 6 10 2 6 10 2 pm TIME OF DAY pm PLASTIC BULK BOX 110 D \J C) “I\:*\\ \k— 50 2 6 IO 2 6 10 2 Pm TIME or DAY Pm Figure 7. Tomato internal and surface temperatures compared to container temperatures 26 only 1 or 2 degrees difference during the day and usually a smaller difference at night. The data used for plotting these curves were recorded simultaneously for each box and at an interval of 8 minutes between boxes on the same day. A difference of up to h degrees for the mean temperatures of a 24 hour period was found between the internal tomato temperatures in the wire mesh container as compared to the. internal tomato temperatures in the other three containers, Table A. HOwever, no meaningful difference was found between the mean internal temperatures of the tomatoes in the steel, wood and plastic containers.. The mean temperatures of the _containers and tomatoes were above the mean air temperature for the steel, wooden and plastic boxes, while for the wire mesh container and its tomatoes these means were below the mean air temperature. Table A. Container surface and tomato internal mean temperatures (°F) for a 2A hour period. Mean air temperature . 73.7°F Wire Mesh Sheet Steel Wood Plastic Full Container Inside surface 72.7 77.0 7M.5 75.2 (south) Internal tomato temperature 72.6 75.5 76.7 75.7 _— 27 Figure 8 shows comparative internal temperatures of tomatoes in different containers for a 2h hour test (test No. 3). A marked difference between internal temperatures of tomatoes in steel, wooden and plastic containers and the temperature of tomatoes in the wire mesh box existed from 7 p.m., to 9 a.m. Again it can be seen that the tomatoes in the wire mesh container approached the air temperature at night. The internal tomato temperature during the day is best explained by Figure 9 which corresponds to the data on test No. 7. A steady increase can be appreciated from 8 a.m. to a peak in the mid seventies at 8 p.m. Figure 8 does not show the peak at 8 p.m. clearly because the thermocouples and tomatoes to be instrumented were exposed to the sun before they were placed in the box and covered by other tomatoes at 2 p.m. This did not happen for the test corresponding to the curves in Figure 9 since all the instrumentation was done the previous day. Nevertheless, a noticeable rise in all curves at 8 p.mo for Figure 8 is an indication that the peak temperatures should have occurred at that time. Both Figure 8 and 9 show the minimum internal temperatures occurr- ing around 9 a.m. for all tomatoes except those kept in the wire mesh container which reach minimum.temperature at 7 a.m. since they start getting heated earlier as air temperature starts going up at 6 a.m. An interesting heat transfer phenomenon illustrated by DEGREES FAHRENHEIT 28 90 WIRE MESH BULK BOX :-—-—. SHEET STEEL BULK B0 :————- / \ \ WOODEN BULK Box .--“ , 85 PLASTIC BULK BOX : ....... J 55 p2m 6 10 2 s 10 2m TIME OF DAY 8 Figure 8. Internal temperatures of tomatoes in different containers FAHRENHELT DEGREES 29 90 85 80—— WIRE MESH BULK BOX : - SHEET STEEL BULK BOX:-———— WOODEN BULK BOX PLASTIC BULK BOX AIR TEMPERATURE / / /’ / / 75 55 Figure 9: 12 2 THWE OF 4 DAY containers Internal temperatures of tomatoes in different 30 these curves is that under these conditions there exists approximately a four hour lag between the internal tempera- tures of tomatoes and the air temperature. This is known as temperature lag. It could help in arriving at a solution for keeping the tomatoes cool. One possibility is that of blowing air through the mass of tomatoes in each box to study the effect on the tomato temperature. Effect of the Observed Temperatures on Tomato Respiration and Qualigy A systematic study of tomatoes eXposed to controlled temperatures, accompanied by an analysis of carotenoid content, acidity, soluble solids, total solids and other standard measures descriptive of quality, as well as a calori- metric measure of the heat of respiration at different temperatures would be necessary to define precisely the effect of varying temperatures upon tomato reapiration and quality. It was not planned to enter into this area which falls outside the field of engineering. Nevertheless, an attempt was made to correlate the information available in the literature on these points with the results obtained on the various tests performed. The observed internal temperatures of tomatoes ranged from about 80°-85°F at 3 p.m. to 65°-75°F at 6 a.m. The variation between the average maximum and average minimum internal tomato temperatures was approximately 15°F for most 31 of the tests performed with all four types of containers. As was pointed out before, differences of up to h°F were found between tomatoes in wire mesh and those in the steel, wooden and plastic containers. The significance of these differences in terms of tomato respiration can be eXplained objectively by the theory of the temperature coefficient (3). The temperature coefficient is designated by the symbol Q10 and defined as the number of times that the rate of a process increases with a 18°F rise in tempera- ture. Since the rate of reSpiration is increased 2 to 3 tumes for each 18°F rise in temperature, within the range 32° to 95°F, the temperature coefficient Q10 for respiration is 2 to 3. The equations defining the reSpiration process are as follows: _ A A R 7' (.6 - 1) 100 o o o o o o o o (1) T2 - Tl ‘I'IB" .6. = (Q10) 0 e o e o o o o (2) B where [3R = % increase in respiration ratio of respiration rate of process at T2 tn >-lfi“> rate of process at T1 Q10 : temperature coefficient 32 T2 ; higher temperature in degrees Fahrenheit T1 ; lower temperature in degrees Fahrenheit Taking Q10 : 2.37 as given by Gore (7) for fruits, and the 4°F difference observed between T2 and T1 and substituting in equation (2): 4. IB' _A_ = 2037 B 0.22 B' 5_ = 1.21 B Therefore the ratio of reapiration between the observed temperatures is 1.21. Substituting this value in equation (1) gives the following result: % increase in respiration = (1.21 - 1) 100 = 21% This computation shows a 21% increase in respiration for tomatoes held in steel, wood and plastic as compared to those held in wire mesh because of the A°F difference in temperature. Haller (10) has emphasized that respiration is a measure of the rate of metabolism and an index of the rate of deterioration. Since increases in temperature bring about increases in respiration, keeping the tomatoes cooler W111 minimize respiration and consequently maintain a better . _ 33 fruit quality. The tomato internal temperatures corresponding to the curves in Figure 8 are summarized in Table 5. Table 5. Duration of internal temperatures for tomatoes in different containers during a 24 hour period Time above stated temperature, Hrs. Tempesgtures, Wire Mesh Sheet Steel Wood Plastic Over 67.5 24.0 24.0 24.0 24.0 " 70.0 16.0 24.0 24.0 24.0 " 72.5 9.0 15.5 18.0 16.0 " 75.0 7.0 11.5 13.0 12.5 " 77.5 5.5 9.0 9.5 8.5 " 80.0 3.5 6.5 7.0 2.0 " 82.5 0.0 0.0 2.5 1.0 " 85.0 0.0 0.0 0.0 0.0 From this Table it can be seen that the tomatoes in the wire mesh box were exposed to temperatures over 67.5°F for shorter periods of time than the tomatoes in the other three containers. MacGillivray (14) indicated that tomatoes showed a continuous loss ianeight after they had been removed from the plant. These losses were influenced by temperature and cracks. Losses of organic constituents were directly pr0portional to temperature. Haber (9) stated that tomatoes lost weight fast at 70°F and Haller (10) indicated 34 that losses at 80°F were significant for this fruit. The tomato temperatures observed during the warm days fell within the range considered critical by these authors, in terms of tomato quality preservation. Keeping_Tomatoes Cool in Bulk Boxes Conduction, convection and radiation play a part in the heat transfer between the bulk boxes, the tomatoes and the environment. The cooling or heating rate of the tomatoes is influenced primarily by the distance from the center of the box to the face or faces of the mass of tomatoes where heat can be transfered to or from the air. Patchen and Sainsbury (18) have indicated that when conduction is the sole means of heat removal, cooling occurs almost as the square of the distance from the center of an apple container to its nearest face. If there are more than two parallel faces the heat is conducted primarily through the nearest face and the influence of the farthest pair is slight. This is an important consideration when stacks of bulk boxes are placed tightly together in rows. The depth of the bulk boxes is usually about 2 feet which is almost one half their length or width. Consequently most of the cooling should occur from the tap and bottom areas when the air temperature is lower than the tomatoes or containers. If the box depth were increased the circulation of air through the tomatoes should diminish and temperatures 35 would increase inside the box. A provision to let air into the bulk boxes to accomplish as much cooling as possible by convection is of prime importance as was proved by the results obtained for the wire mesh container. Variations in construction of the bulk boxes to provide comparisons among them should be considered, such as slots, spaced sides, Spaced bottom or combinations of these. _The thermocouples placed inside the boxes at mid-level measured temperatures of tomatoes at symmetrical locations. However, no measurements were made for those tomatoes in the tap layer being additionally heated by radiation nor for the tomatoes on the sides adjacent to the container's wall which undoubtedly were exposed to more intensive heating. Skok (23) indicated that tomatoes exposed to the sun reached temperatures averaging 90°F and MacGillivray (16) claims there is a difference of 15° to 40°F between the exposed and shaded side of the tomato. nevertheless, the same tomatoes which had been exposed to the sun and in contact with the container's wall would be those which would be cooled faster when the air temperature started drapping. Patchen and Sainsbury (18) Showed that when thermocouples were placed in apples at the outer edge, at bottom, t0p and middle positions and in the air at the center of a pallet box, the sides, bottom and t0p were found to cool the fastest in cold-storage rooms. CONCLUSIONS 1. A difference of up to 4°F for the mean temperatures of a 24 hour period was found between the internal tomato temperatures in the wire mesh container as compared to the internal tomato temperatures in the steel, wooden and plastic containers. 2. No meaningful differences were found between the mean internal temperatures over a 24 hour period for tomatoes I held in steel, wooden and plastic containers. 3. The variation between the average maximum and the average minimum internal tomato temperatures was approxi- mately 15°F for most of the tests performed with all four containers. 4. There was approximately a four hour lag between the internal temperatures of tomatoes and the air temperature. 5. A provision to let air into the boxes to accomplish as much cooling as possible by convection is of prime importance as indicated by the results obtained for the wire mesh container. 6. A difference of 4°F in tomato temperatures accounted for a calculated.21% increase in tomato respiration. 36 (I) . ...; «Um-hall“ .1 (‘T"I."‘-"»".’_TTV',"“".".“‘ r37," , 7‘7'11:L »._ , ‘1‘7' ... 31 . - ‘4 < .: .\‘ \v‘ 'x.- kl STA—4k.) ... |VJ I U 4. Kan L, F ... ,L Li 4 a _ U __ [J _L 1" ‘.r\""-. ‘xr‘ - e I T ‘ --.—-. 7" --~ 3' . --« ~\ -' 1‘. t, r -‘ \ v,-\ 011 1‘. l. VBTlaLiOho in tne CUMS«FUL310L cl bulk Luxes such s '7‘ slots, spaced lides, spaced bottom or combinatitns cf ( '5)" T (1) (*T“ H. :1 I L, OFdRI‘Tfl)IHlKlH Zr H‘ H . .J ccnsid-red If) D. I”: ,C‘, H Cl» 5“ ( [I T, -. .. (16:51.18 3. of produce. 2. Future tests should inclule a larger number Cf reccrd— ings per Dex Tc enacie to measure tomato temperatures 8L Q) (T: *1 01 Q) Q: mid-level as well as on the 10p ard bottom 1 transfer analySls could then be made. ‘\ l_J . Tests should be accompanied by an analys's cf carctenci content, acidity, soluble sclids, total solids and other standard measure" descriptive of Quality. bu k handlin: conditions shculd Since the tomatoes in the wire mesh cox remalred Tl cooler because of better veutilaticn, an attcmot cculd he IT;"d: on stud the suggested slots of the tomato Drxes. 2) 3) a) 5) 6) 7) 8) 9) 10) 11) REFERENCES Alban, E. K., H. W. Ford and F. S. Hewlett (19h8). A preliminary report on the effect of various cultural practices with greenhouse tomatoes on the respira— tion rate of the harvested fruit. Am. Soc. Hert. Sci. Proc. 52 : 393-398. Ayres, J. C. and L. C. Pearce (1960). Effect of packag- ing films and storage temperatures on the ripening of mature-green tomatoes. Food Tech. 1h : 6&8-53. Buchele, W. F. (1957). The engineering aspects of the temperature coefficient. Special paper Agr. Eng. 8&0, Mich. State Univ. Diehl, H. C. (1942). The chilling of tomatoes. U.S. Dept. Agr. Circular No. 315. Duggar, B. M. (1913). Lyc0persicin the red pigment of the tomato and the effect of conditions upon its develOpment. Wash. Uhiv. Studies Part 1. 22-h5. Forshey, C. G. (l95h). Seasonal quality changes in greenhouse tomatoes. Am. Soc. Hort. Sci. Proc. 64 : 372-378. Gore, H. C. (1911). Studies of fruits respiration. U. S. Dept. Agr. Bur. Chem. Bull. 142. Green, W. P., W. V. Hukill and D. H. Rose (19fll). Colormetric measurement of the heat of respiration of fruits and vegetables. U.S. Dept. Agr. Tech. Bull. 771. 22 pp. illus. Haber, E. S. (1931). Acidity and color changes in tomatoes under various storage tegfieratures. Iowa State Col. J. Sci. 5 : 171-1 . Haller, M. H., P. L. Harding, J..M. Lutz and D. H. Rose (1931). The respiration of some fruits in relation to temperature. Amt Soc. Hort. Sci. Proc. 28 : 583-589. flbCollum, J. P. (19uu). Some factors affecting the ascorbic acid content of tomatoes. Am. Soc. Hort. Sci. Proc. 1&5 : 382-386. 38 12) 13) 1a) 15) 16) 17) 18) , 19) 20) 21) 22) 23) 39 McCollum, J. P. (19h6). Effect of sunlight eXposure on the quality constituents of tomato fruits. Am. Soc. Hort. Sci. Proc. MB : hl3-416. MbCollum, J. P. (195A). Effect of light on formation of carotenoids in tomato fruits. Food Research MacGillivray, J. H. (1926). Studies of tomato quality and effect of temperature on storage losses. Am. Soc. Hort. Sci. Proc. 23 : 208-21“. MacGillivray, J. H. (1931). Tomato color as related to quality in the tomato canning industry. Purdue Agr. Exp. Sta. Bull. 350. Macoillivray, J. H. (193“). The variation of tempera- ture in tomatoes and their color deve10pment. Am. Soc. Hert. Sci. Proc. 32 : 529-531. Nutting, M. D. (1955). Stability of tomato Juice and concentrates held at elevated temperatures. Food Tech. 9 : 466-70. Patchen, G. 0. and G. F. Sainsbury (1962). Cooling apples in pallet boxes. USDA Agr. Marketing: Service. Marketing Research Report 532. Ries, S. K. and B. A. Stout (1960). A progress report on horticultural problems associated with a mechanical tomato harvester. Am. Soc. Hort. Sci. Proc. 75 : 632-637. Ries, S. K., B. A. Stout, C. L. Bedford and M. E. Austin (1961). - Mechanical harvesting and bulk handling tests with processing tomatoes. Mich. Agr. Exp. Sta. Quarterly Bull. No. 2. Vol. nu. Rosa, T. J. (1926). Ripening and storage of tomatoes. Am. Soc. Hort. Sci. Proc. 23 : 233-2h2. Sayre, c. B., w. B. Robinson and T. Wishnetsky (1953). Effect of temperature on the color, lchpene and carotene content of detached and vine-ripened tomatoes. Am. Soc. Hort. Sci. Proc. 61 : 381-387. Skok, J. (1951). Quality of artificially ripened tomatoes for canning purposes. Food Research 16 : 1h7-53. 2h) 25) 26) 27) 28) MO Statistical Reporting Service. CrOp Reporting Board (1961). Acreage, production and value of principal commercial crOps. USDA Vegetables - Processing, Vg. 3-2. Vegele, A. C. (1937). Effect of environmental factors upon the color of the tomato and the watermelon. Plant Physiology 12 : 929-955. Wright, R. 0., w. T. Pentzer, T. M. Whiteman and D. H. Rose (1931). Effect of various temperatures on storag§6§nd ripening of tomatoes. USDA Tech. Bull. . Wright, R. C., D. H. Rose and T. M. Whiteman (1938). The commercial storage of fruits, vegetables and florists stocks. U.S. Dept. Agr. Cir. 278, 43 pp. Wright, R. c. and T. M. Whiteman (19u5). Unpublished report. Reference in Agr. handbook No. 66. USDA. MICHIGAN STATE UNIVERSITY LIBR l H! lllllllilll 3 1293 03146 3163 III)”