THE UNIVERSITY 
 
 OF ILLINOIS 
 
 LIBRARY 
 
 (o30.7 
 IfGb 
 
 cop. 
 
 ACRICUITORE 
 
CHECK FOf 
 CIRCULATII 
 
Factors Influencing 
 the Refrigeration of 
 Packages of Apples 
 
 By 
 J. W. LLOYD 
 
 and 
 S. W. DECKER 
 
 University of Illinois 
 
 Agricultural Experiment 
 Station 
 
 Bulletin 410 
 
 V 
 
CONTENTS 
 
 PAGE 
 
 INTRODUCTION 15 
 
 REVIEW OF LITERATURE 15 
 
 EXPERIMENTAL EQUIPMENT AND PROCEDURE 16 
 
 HOW FRUIT WITHIN A PACKAGE COOLS 21 
 
 EFFECT OF AIR VELOCITY ABOUT A PACKAGE ON 
 
 RATE OF COOLING WITHIN 28 
 
 EFFECT OF TEMPERATURE OF FRUIT AT TIME OF 
 
 PACKING ON RATE OF COOLING 32 
 
 SIZE OF FRUIT HAD NO APPARENT EFFECT ON 
 
 RATE OF COOLING 34 
 
 EFFECT OF TYPE OF CONTAINER ON RATE OF 
 
 COOLING OF CONTENTS 36 
 
 EFFECT OF WRAPPING FRUIT ON RATE OF COOLING 45 
 
 SUMMARY AND CONCLUSIONS 48 
 
 LITERATURE CITED.. .50 
 
 The straight-sided tub bushel basket shown 
 on the cover was the standard container 
 used in the experiments reported in this 
 bulletin, except where type of package was 
 being tested. Grimes apples were used for 
 all tests. 
 
 Urbana, Illinois December, 1934 
 
 Publications in the Bulletin series report the results of investigations 
 made by or sponsored by the Experiment Station 
 
Factors Influencing the Refrigeration 
 of Packages of Apples 
 
 By J. W. LLOYD, Chief in Fruit and Vegetable Marketing, and 
 S. W. DECKER, Associate in Fruit and Vegetable Marketing 
 
 MAINTENANCE of perishable fruits and vegetables at low 
 temperatures is generally recognized as the most economical 
 method of extending their life span and reducing losses be- 
 tween the time they are harvested and the time they are offered for 
 sale on a distant market. 
 
 Precooling of these products before shipment in refrigerator cars 
 has been recommended and is used in some localities to reduce their 
 temperatures rapidly to a point where they can safely be transported. 
 In many localities where facilities for precooling are not available, 
 the refrigerator car itself is relied upon to reduce the temperature of 
 the load to a point which allows perishable products to reach distant 
 markets in satisfactory condition. Heavy losses of fruits transported 
 under such conditions are frequent. 
 
 Studies by the Illinois Station regarding factors responsible for 
 losses of non-precooled fruits in transit are reported in Bulletin 334. 5 * 
 Further experiments, with air circulation and temperature conditions 
 in refrigerator cars, 10 * indicated that a knowledge of how the fruit 
 within a package cools and of how certain internal and external fac- 
 tors influence the behavior of the packaged fruit is essential to a com- 
 plete understanding of the refrigeration problem. 
 
 The tests reported herein attempt to answer some of the questions 
 that arise in a study of the phenomena occurring in a package of fruit 
 while cooling, namely: How does cooling of the fruit progress within 
 a package? What is the effect of air velocity about the package upon 
 the rate of cooling of the fruit within? How does the temperature of 
 the fruit at the time of packing affect the rate of cooling? Does the 
 size of the fruit affect the rate at which the package of fruit cools? 
 Does the type of package affect the rate of cooling? 
 
 REVIEW OF LITERATURE 
 
 Many phases of the marketing and storage of apples have been 
 studied. Some of the facts established by earlier workers on the 
 relation of temperature to ripening and of ripeness to decay of fruits 
 are of importance in connection with the studies here reported. 
 
 
16 BULLETIN No. 410 [December, 
 
 Eustace and Beach 2 * pointed out that the ripening process is ac- 
 celerated in a high temperature and retarded in a low temperature, and 
 that early varieties, such as Wealthy, respond more markedly to tem- 
 perature differences than do the late-maturing varieties, such as Wine- 
 sap. Magness and Diehl 7 * found a distinct difference in the response 
 of different varieties of apples to various temperatures, some varieties 
 softening much more rapidly at high temperatures than others. Grimes 
 apples harvested by Magness et a/ 8 * on September 23 were "full 
 eating soft" by October 10 when stored at 70 F., but were not "full 
 eating ripe" until January 1 when stored at 32 F. Morris 9 * found 
 that apples kept in a warm warehouse from one to three days before 
 being placed in cold storage often lost more than a month of their 
 storage life. Smith 14 * showed that rapid cooling of fruit is very im- 
 portant in preventing rapid maturation. 
 
 Brooks and Cooley 1 * found that a slight increase in the ripeness 
 of apples of a particular variety caused a definite increase in suscepti- 
 bility to rot. Earlier studies by the Illinois Station 6 * with Yellow 
 Transparent apples showed that delay in loading the apples after they 
 were picked increased the amount of damage due to internal brown- 
 ing of the tissues. Investigations by Palmer 11 * have shown that the 
 breakdown not caused by low temperature is closely correlated with 
 maturity of the fruit. The Empire Marketing Board 3 * reported that, 
 in general, internal breakdown is more severe in "Extra Fancy" than 
 in lower grade fruit. 
 
 EXPERIMENTAL EQUIPMENT AND PROCEDURE 
 
 Apparatus Used. The equipment used in the experiments reported 
 in this bulletin was so built as to provide conditions as nearly as 
 possible identical with those found within a refrigerator car, except 
 that the temperature and air velocity could be controlled and varied 
 at will. A sketch of the main part of the apparatus is shown in Fig. 1*. 
 For the want of a better term, this portion of the apparatus is desig- 
 nated as a "tunnel." The tunnel is in the form of a large U, the upper 
 parts of which are connected by a comparatively small pipe. 
 
 At the lower left-hand corner of Fig. 1 is shown an electrically 
 driven fan which is the source of air circulation within the tunnel. Just 
 to the rear of the fan is a diaphram which regulates the air flow into 
 the fan. The air passes upward thru a 6-inch tube and around to a 
 draft gage, where the air force or pressure is measured. The draft 
 
 This apparatus was designed and its construction supervised by H. M. 
 NEWELL, formerly Associate in Fruit and Vegetable Marketing. 
 
1934] 
 
 REFRIGERATION OF PACKAGES OF APPLES 
 
 17 
 
18 
 
 BULLETIN No. 410 
 
 [December, 
 
 gage reading is used to regulate the air cut-off diaphram so as to obtain 
 the rate of air flow desired for the various tests. 
 
 As the air passes beyond the draft gage it enters an enlarged area, 
 corresponding to one side of the U. At this point, the air comes in 
 contact with a series of cooling coils, composed of 257 feet of half- 
 inch copper tubing (Fig. 2-A). The air then passes around the base of 
 
 Of INTIH.MIDIATI TIIB.S Of COILS 
 
 FIG. 2. INTERIOR SECTIONS OF "TUNNEL" 
 
 (A) Detailed diagram of arrangement of cooling coils; (B) location of a 
 tub bushel basket in the testing chamber; (C) louvers used to distribute the air 
 vertically (a), and laterally (b). 
 
 the U and into the other side. As it comes into the straight side of the 
 U, it strikes two sets of louvers (Fig. 2-C). One set is so regulated 
 as to give an even vertical distribution of air thruout the area (a), 
 the second to give an even lateral distribution thruout the area (b). 
 
 At the upper end of this side of the U is located a testing chamber. 
 In it are placed the packages of fruit to be tested (Fig. 2-B). 
 
 The testing chamber door closes against a rubber seat and is firmly 
 held in place by a series of screw clamps. The air passes by the pack- 
 age and back thru the fan and recirculates, giving a continuous and 
 uniform flow. 
 
 The tunnel, except for the testing chamber, is made of heavy gal- 
 vanized sheet metal which is insulated with l^i inches of wool felt. 
 The testing chamber is of glass in a wooden frame. 
 
1934] REFRIGERATION OF PACKAGES OF APPLES 19 
 
 A Kelvinator cooling unit was attached to the copper coils to re- 
 duce the air temperature of the tunnel. The machine used was large 
 enough to carry the load easily; therefore it was in operation only a 
 portion of the time. The air temperature varied about three degrees 
 with the cutting-in and cutting-out of the machine. 
 
 Instruments for Recording Data. The air temperatures during the 
 tests were recorded by the use of a thermograph, the bulb of which 
 was located just in front of the testing chamber in order to register 
 the temperature of the air that came in contact with the package of 
 fruit. 
 
 Altho the draft gage was used as a guide in regulating the air flow, 
 it could not be relied upon to give an accurate measurement of the 
 rate of air flow about the package of fruit being tested. The kata- 
 thermometer has proved to be a useful instrument for the measure- 
 ment of low air velocities 10 * and it was used thruout these tests. The 
 rate of air movement on either side of the package was measured by 
 five or more kata-thermometer readings for each test. The air velocity 
 for the duration of a single test was found to be very uniform, but 
 the velocity was less uniform for different tests. 
 
 Changes in the temperature of the fruit within the package were 
 ascertained by the use of thermocouples. Chromel and constantan 
 insulated thermocouple wires, No. 30 B and S gage, were used. The 
 ends were twisted and soldered to assure contact between the wires. 
 In order that the exposed wires might not be attacked by the fruit 
 juices, and in order that they might easily be inserted into the fruits, 
 the points were covered with ambroid cement and a thin glass tube 
 drawn to a closed point. 
 
 A portable precision potentiometer designed for measuring ther- 
 mocouple e.m.f. was used in taking the thermocouple readings. The 
 limit of error of the instrument using the slidewire alone was .5 per- 
 cent of the range. With the slidewire and up to 5 studs on the dial 
 switch, the limit of error was from .5 percent to .1 percent. A cold 
 junction of cracked ice in a thermos bottle was used thruout the tests. 
 
 The thermocouples used in obtaining the fruit temperatures were 
 inserted to the center of the fruit. Those used in obtaining the air 
 temperatures between fruits were prevented from coming into contact 
 with the fruits by passing the thermocouple thru a hole in a triangular 
 piece of wood that was wedged between the fruits, thus suspending the 
 point of the thermocouple in midair. Unless otherwise stated, the ther- 
 mocouples were arranged in a cross-section thru the center of the pack- 
 age. In all, twenty-four thermocouples were distributed around and 
 within the package as shown in Figs. 3 and 11. The thermocouple 
 
20 BULLETIN No. 410 [December, 
 
 wires were carried out thru the testing chamber door, and then the 
 door was sealed by clamping it upon the rubber seat. The ends of the 
 wires were then attached to a switch board, from which connections 
 were made with the potentiometer thru the cold junction of cracked ice. 
 By this arrangement the twenty- four thermocouples could easily be 
 read within seven minutes. 
 
 FIG. 3. CROSS-SECTIONS SHOWING THERMOCOUPLE ARRANGEMENTS USED IN 
 
 LINED TUB BUSHEL BASKETS OF APPLES 
 
 The thermocouple arrangement used for tub bushel baskets containing fruits 
 2V4 to 2^4 inches in diameter and 2^4 to 3 inches is shown in A ; for fruits from 
 2 inches to 2i/4 inches in B. The outside row of fruit is referred to in the tests 
 as the first row, the next row as the second row, etc. There are four thermo- 
 couples in each row of fruit, and a composite of the readings is taken as repre- 
 senting the temperature of the row. The air temperature between two rows is 
 obtained by taking a composite of the thermocouple readings between the rows. 
 
 Procedure. The first reading for a test was made just before the 
 fruit was placed in the testing chamber. A second reading was taken 
 after the fruit had been in the testing chamber for 15 minutes. Read- 
 ings were then made at intervals of 30 minutes for 8 hours. After 
 that time the readings were made at 2-hour intervals, except for an 
 8-hour period between the 12th and 20th hours of the test. No read- 
 ings were made during that period. Each test was continued until the 
 temperature of the fruit had reached 45 F. or slightly lower. 
 
 The package being tested was placed on a floor rack in the testing 
 chamber. Considerable space was left on each side of the package and 
 above the package for air circulation (Fig. 2-B). A second and 
 similar package was placed in front of the package being tested ; that 
 is, in the direction from which the circulating air approached the pack- 
 age under test. This prevented the air from striking the test package 
 directly, and thus made the conditions more comparable to those in a 
 loaded refrigerator car. 
 
1934] REFRIGERATION OF PACKAGES OF APPLES 21 
 
 Conditions of the Tests. The straight-sided tub bushel basket with 
 ventilated paper liner and corrugated paper facing pad is a standard 
 container used by commercial growers of apples and peaches thruout 
 the central states. It was therefore selected as the standard container 
 for these studies, except where type of package was under con- 
 sideration. 
 
 In order that conditions might be as uniform as possible, a single 
 variety of apple, the Grimes, was used for all the tests. The fruits were 
 carefully graded into three sizes: (1) below 2 1/4 inches in diameter, 
 (2) 2i/4 to 2^4 inches, and (3) above 2^4 inches. Except when other- 
 wise indicated, the medium-sized fruits (2}4 to 2^4 inches) were used. 
 
 All tests were run in duplicate under each set of conditions, and 
 some were run a larger number of times. The air temperature of the 
 tunnel varied somewhat, but it was kept as near 35 F. as possible. 
 This is approximately the temperature of air as it comes from the 
 bottom of the ice bunker of a refrigerator car. 
 
 HOW FRUIT WITHIN A PACKAGE COOLS 
 
 In most of the studies conducted on the cooling of fruits in re- 
 frigerator cars the package has been the smallest unit considered. 
 Comparatively little attention has been given to the way in which cool- 
 ing progresses thru the package. Griffith and Awbery 4 * have con- 
 cluded from their experiments that the temperature differences be- 
 tween an individual apple and the air in the immediate neighborhood 
 is quite small at all times. 
 
 In order to obtain a better understanding of the cooling of fruit 
 within a tub-bushel basket a number of tests were made. In these 
 tests the progress of cooling was traced by thermocouples arranged 
 as shown in Fig. 3-A. 
 
 The fruit temperatures recorded at the different points in the 
 baskets are summarized in Table 1. The progress of cooling for all 
 baskets followed closely the averages shown in Table 1. The air tem- 
 perature just outside the package dropped rapidly as soon as the fruit 
 was placed in the testing chamber, and then more slowly as the fruit 
 within the package cooled. An occasional increase in temperature out- 
 side the package shown by the record is explained by the fact that the 
 air temperature of the tunnel varied about three degrees due to the 
 cutting-in and cutting-out of the cooling machine. 
 
 The tests were continued until the package contents had cooled to 
 about 45 F., which is generally agreed to be the most economical 
 temperature for summer apples in transit. 
 
22 
 
 BULLETIN No. 410 
 
 [December, 
 
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1934] 
 
 REFRIGERATION OF PACKAGES OF APPLES 
 
 23 
 
 The way in which the different rows of fruit cooled when placed 
 in the testing chamber is shown in Fig. 4. It is clear that the outside 
 row of fruit cooled the most rapidly. The temperature differences 
 between the first, or outside, row and the other rows were quite large 
 during the early part of the cooling period, tho as cooling progressed 
 the temperatures of the different rows gradually approached one 
 another. 
 
 
 LINED TUB BUSHEL BASKET 
 
 Outside of package 
 First row of fruit 
 -Second row of fruit 
 Third row of fruit 
 
 \Z 16 
 
 HOURS IN COOLER 
 
 FIG. 4. PROGRESS OF COOLING WITHIN A LINED TUB BUSHEL BASKET OF APPLES 
 The first or outside row of fruit cooled more rapidly than the inner rows. 
 The temperature difference between the first and second rows was considerably 
 greater than the temperature difference between the second and third rows. 
 
 The number of degrees of drop in temperature per unit of time 
 (2 hours) for the outside row was greatest during the early part of 
 the cooling period and then gradually decreased (Fig. 5). The second 
 and third rows cooled much more slowly than the first, or outside, 
 row at the start, but after a period of 5 or 6 hours conditions were 
 reversed, and from that time on thruout the test the third row showed 
 a greater drop per unit of time than the second row, and likewise the 
 second row showed a greater drop than the first row. The total drop 
 in degrees during the entire period of the test was about the same for 
 the three different rows. It was only slightly less for the inner rows 
 than for the outside row. 
 
 The difference in the range of temperature between the first and 
 second rows was considerably greater than the difference between the 
 second and third rows. The temperature differences between the first 
 
24 
 
 BULLETIN No. 410 
 
 [December, 
 
 and second rows and the second and third rows increased as the 
 difference between the temperature of the fruit when packed and the 
 temperature of the cooling room increased (Fig. 5). When the fruit 
 
 LINED TUB BUSHEL BASKET 
 
 First row of fruit 
 
 Second row of fruit 
 - Third row of fruit 
 
 FRUIT 75 F. WHEN PACKED 
 
 LINED TUB BUSHEL BASKET 
 
 First row of fruit 
 
 Second row of fruit 
 - Third row of fruit 
 
 FRUIT 90 F. WHEN PACKED 
 
 12 16 
 
 HOURS IN COOLER 
 
 28 
 
 FIG. 5. TEMPERATURE DROP PER TWO-HOUR INTERVALS IN DIFFERENT Rows 
 OF APPLES IN LINED TUB BUSHEL BASKETS WITH INITIAL 
 
 TEMPERATURES OF 75 AND 90 F. 
 
 The .first, or outside, row of fruit when packed at 75 F. and w,hen packed 
 at 90 F. cooled rapidly during the first part of the cooling period and then 
 gradually less rapidly; while the second and third rows cooled slowly at first, 
 reaching a peak after six hours in the cooler, and then cooled at a reduced rate 
 but still at a more rapid rate than the outside row. The outside row of the 
 90 F. fruit cooled more rapidly than the outside row of the 75 F. fruit. 
 
1934] 
 
 REFRIGERATION OF PACKAGES OF APPLES 
 
 25 
 
 was at a temperature of 75 F. when packed, there was a maximum 
 difference in drop per unit of time of 4.98 degrees between the outer 
 row and second row of fruit, and a maximum difference of .82 degrees 
 between the second and third rows. When the fruit was at a tempera- 
 ture of 90 F. when packed, there was a maximum difference in drop 
 per unit of time of 7.38 degrees between the outside and second rows 
 of fruit, and a maximum difference of 1.31 degrees between the second 
 and third rows. 
 
 Air Spaces in Package of Value in Cooling 
 
 The question has been frequently raised as to how a temperature 
 change reaches the center of a package of fruit. Opinions seem to be 
 
 LINED TUB BUSHEL BASKET 
 
 First row of fruit 
 Second row of fruit 
 Air temperature 
 
 40 
 
 8 12 16 
 
 HOURS IN COOLER 
 
 FIG. 6. RELATION OF AIR TEMPERATURE TO FRUIT TEMPERATURE IN LINED 
 
 TUB BUSHEL BASKET OF APPLES 
 
 The air temperature between the first, or outside, row and the second row 
 was nearly midway between the fruit temperatures of the two rows. 
 
 divided, some holding that air circulation is responsible for the tem- 
 perature change, while others are inclined to believe that the tempera- 
 ture change is due to conduction, that is, that the temperature change 
 is carried from fruit to fruit. 
 
 In an effort to obtain data bearing upon this question a series of 
 tests were made in which the relation of air to fruit temperature was 
 followed thruout the cooling period. Records were taken of the tem- 
 peratures of fruits in two consecutive rows and of the air tempera- 
 ture between the fruits. The relation of the fruit temperature to the 
 air temperature in a lined tub bushel is shown in Fig. 6. These records 
 show clearly that the air temperature between the two rows of fruit 
 
26 
 
 BULLETIN No. 410 
 
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 REFRIGERATION OF PACKAGES OF APPLES 
 
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28 BULLETIN No. 410 [December, 
 
 lay between the fruit temperatures. This relationship was found to 
 exist for the three sizes of apples tested, as is shown in Table 2. 
 
 Such data lend some support to the theory that air circulation is 
 of no importance and that the fruit is cooled by conduction. The rate 
 of cooling in the different rows of fruit within the package (Fig. 4) 
 also tends to substantiate the conduction theory. 
 
 Later tests, however, indicated quite the reverse. It was reasoned 
 that if cooling is due entirely to conduction, then the air spaces be- 
 tween fruits would be of no value in the cooling process. Tests were 
 made with packages of fruit in which the spaces between the fruits 
 were filled with mineral wool without interfering in any way with the 
 contact between fruits. Packages so treated cooled much more slowly 
 than packages with open air spaces, the cooling period being extended 
 from 28 to 48 hours (Table 3). It would therefore seem that the air 
 space between fruits is of value in bringing about a rapid change in the 
 temperature of the fruit within a package, and that while the air cir- 
 culation within a tub bushel basket exposed to low air velocity is very 
 slow, it does play an important part in the cooling of the contents of 
 the package. 
 
 EFFECT OF AIR VELOCITY ABOUT A PACKAGE 
 ON RATE OF COOLING WITHIN 
 
 Forced air circulation at a high velocity is commonly used as a 
 means of precooling fruits being prepared for transit. If the fruit 
 is cool at the time of loading, it can be held without difficulty at a de- 
 sirable temperature in the average ice refrigerator car by means of the 
 codling power of the car. However, if warm fruit is placed in a car, 
 difficulty is experienced in reducing the temperature to a point con- 
 sidered desirable for retarding ripening and preventing decay. Results 
 of studies already published show that there is a wide range of tem- 
 peratures within a car of fruit being cooled while in transit, 10 * and 
 that rate of air flow is an important factor in the cooling process. 5 * 
 
 In order to test the effect of the velocity of the air about a pack- 
 age on the rate at which the contents of the package will cool, lined tub 
 bushel baskets filled with Grimes apples were subjected to four air 
 velocities still air, and air moving at the rate of 88.4, 114.4, and 156.2 
 feet per minute. This is a wider range of air velocities than is com- 
 monly found within a refrigerator car. The average temperature of 
 the air before it came in contact with the package varied only slightly 
 in the different tests. The thermocouples were arranged as indicated in 
 Fig. 3-A. 
 
1934} 
 
 REFRIGERATION OF PACKAGES OF APPLES 
 
 29 
 
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30 
 
 BULLETIN No. 410 
 
 [December, 
 
 The rates of temperature drop that occurred at the four different 
 air velocities are shown in Table 4. The records designated "still air" 
 were obtained by placing the fruit in a large coil-cooled storage room 
 in which there was no forced air circulation. The other records were 
 obtained by tests made in the special apparatus already described. 
 
 No differences in the rate of cooling that may be attributed to air 
 movement were shown at the first three velocities ; but when the air 
 velocity was increased to 156 feet per minute, the time required for 
 cooling the fruit within the package was reduced about 8 hours, or 
 about 28 percent. 
 
 A graphic comparison of the temperature drop within the pack- 
 ages subjected to the different air velocities is shown in Fig. 7. The 
 
 TEMPERATURE OF FRUJT IN DEGREES F. 
 
 ^ 171 O) -J 00 
 
 o o o o o 
 
 k 
 
 
 
 AIR 
 
 VELOCITY 
 
 Still air 
 
 
 v 
 
 X 
 
 ^ 
 
 
 34.4ft. per min. 
 14.4ft. per min. 
 56.2ft. per min. 
 
 
 
 - 
 
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 12 16 20 
 
 HOURS IN COOLER 
 
 24 
 
 28 
 
 FIG. 7. EFFECT OF AIR VELOCITY ON RATE OF COOLING IN LINED TUB 
 
 BUSHEL BASKETS OF APPLES 
 
 Air velocities below 115 feet a minute did not influence the rate of cooling 
 of fruit packed in a lined tub bushel basket. As the air velocity was increased, 
 a point was reached at which the rate of cooling increased. 
 
 curve was obtained by taking an average of all the fruit temperature 
 records within the package. The packages subjected to the three lower 
 air velocities show only small temperature differences that are ex- 
 perimentally insignificant. The packages subjected to the higher air 
 velocity show a distinctly more rapid drop in temperature thruout the 
 test. 
 
 Earlier studies 10 * have shown that the rate of air circulation varies 
 considerably in different parts of the refrigerator car. On the average, 
 the highest velocity within any part of a car under normal conditions 
 
1934] 
 
 REFRIGERATION OF PACKAGES OF APPLES 
 
 31 
 
 seldom goes above 80 feet per minute, while in other parts of the 
 same car the velocity may be below 20 feet per minute. The results 
 obtained under laboratory conditions with the tub bushel basket would 
 
 AIR VELOCITY- 100 FT. PER MIN 
 
 First row of fruit 
 Second row of fruit 
 ..-Air temperature 
 
 AIR VELOCITY- 156 FT. PER MIN 
 
 First row of fruit 
 Second row of fruit 
 -Air temperature 
 
 40 
 
 a 12 is 
 
 HOURS IN COOLER 
 
 24 
 
 FIG. 8. EFFECT OF AIR VELOCITY ON RELATION OF AIR TEMPERATURE TO 
 FRUIT TEMPERATURE IN LINED TUB BUSHEL BASKETS OF APPLES 
 
 When the velocity of the air about the package was less than 100 feet a 
 minute, the air temperature between the first and second rows of fruit in a lined 
 tub bushel basket was about midway between the temperatures of the fruit in 
 the first and second rows. An increase in air velocity to 156 feet a minute 
 caused the air temperature between the first and second rows o fruit to ap- 
 proach more nearly the temperature of the fruit in the outside row. 
 
 seem to indicate that the value of increasing the air velocity in a re- 
 frigerator car up to 100 percent above the velocities normally found in 
 such cars is due, not to increased air circulation within the package, 
 but to the lowering of the air temperature about the package. 
 
32 BULLETIN No. 410 [December, 
 
 When, however, in the presence of a uniform air temperature, more 
 rapid cooling is obtained by increasing the velocity of the air about the 
 package, it is clear that some other factor than the temperature of the 
 air on the outside of the package must be responsible for the lowered 
 temperature within the package. How the different air velocities out- 
 side the packages influenced the air and fruit temperatures within the 
 packages is indicated by Fig. 8. When the air velocity outside the 
 package was 100 feet per minute, the air temperature within the pack- 
 age was very nearly midway between the temperature of the two rows 
 of fruit; while with an air velocity of 156 feet per minute, the air 
 temperature within the package was considerably closer to that of the 
 outside row of fruit. These results would seem to indicate that even 
 in these lined bushel baskets the air circulation within the package was 
 influenced by the more rapid air velocities outside the package. With 
 more open types of containers, the influence of the air velocity outside 
 the package on the air circulation within the package would of course 
 be more marked. 
 
 EFFECT OF TEMPERATURE OF FRUIT AT TIME 
 OF PACKING ON RATE OF COOLING 
 
 Studies by various investigators have shown that the temperature 
 of the fruit during harvest and packing determines to some extent 
 the amount of mechanical injury it will sustain and the losses that will 
 result during marketing. Many fruits must be harvested and marketed 
 during the summer months when temperatures are high. The question 
 of how the temperature at the time of packing influences cooling may 
 therefore be of considerable importance. A series of tests were con- 
 ducted to obtain information on this point. 
 
 The lined tub bushel basket filled with Grimes apples 21/4 to 2^4 
 inches in diameter was used in all the tests. The fruits at the time of 
 packing were of two general temperatures "medium," or about 75 
 F. when packed, and "warm," or about 88 F. The tests were started 
 immediately after the packing of the fruit. The thermocouple arrange- 
 ment was as shown in Fig. 3-A. 
 
 Under the conditions of these tests, the "warm" fruit cooled at a 
 more rapid rate than did the fruit of "medium" temperature (Table 5). 
 While the initial difference in temperature of the medium and warm 
 fruit was about 12 degrees, this difference was reduced to one degree 
 when the fruit had been in the cooler for a period of 28 hours. The 
 narrowing of the temperature difference was gradual, the difference 
 
1934} 
 
 REFRIGERATION OF PACKAGES OF APPLES 
 
 33 
 
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34 BULLETIN No. 410 [December, 
 
 being 12.1 degrees at the start, 9.9 degrees after 4 hours, 7.2 degrees 
 after 8 hours, 4.8 degrees after 12 hours, 2.5 degrees after 20 hours, 
 and 1 degree after 28 hours. After 28 hours in the cooling chamber 
 the fruit in both groups registered temperatures in the neighborhood 
 of 45 F. These findings are in accord with those obtained in tests in 
 refrigerator cars loaded with bushel baskets of apples. In the earlier 
 studies 10 * cars of fruit that differed about 15 degrees when loaded had 
 temperature differences of about 11 degrees after 10 hours, 9 degrees 
 after 20 hours, 7 degrees after 30 hours, 6 degrees after 40 hours, 
 and 5 degrees after 50 hours. 
 
 In the laboratory tests much more rapid cooling occurred than in 
 the previous tests made in standard refrigerator cars. 10 * The cooling 
 unit in the laboratory had ample power to carry the load, maintaining 
 a uniform air temperature of about 35 F. The cooling power of the 
 refrigerator cars under test 10 * was insufficient to reduce the tempera- 
 ture of the fruit rapidly. It would appear, therefore, that the extent of 
 injury resulting from the packing of high-temperature fruits is largely 
 dependent upon the cooling power of the space, room, or car in which 
 the packages are placed after packing. 
 
 Temperature differences such as occurred in these tests between the 
 fruits in the medium and warm groups during the cooling period 
 (Table 5) may be sufficient to cause considerable difference in losses 
 due to overripeness and decay. Differences in losses between medium 
 and warm fruit are likely to be even greater under the conditions 
 found in refrigerator cars. 
 
 SIZE OF FRUIT HAD NO APPARENT EFFECT 
 ON RATE OF COOLING 
 
 In order to ascertain whether size of fruit has any influence on rate 
 of cooling, a number of tests were made with three sizes of Grimes 
 apples packed in lined tub bushels. The small-sized fruits were 2 to 
 21/4 inches in diameter; the medium, 2 14 to 2^4 inches; the large, 2^4 
 to 3 inches. 
 
 The temperature of the fruits in the different lots was between 
 70 and 75 F. when packed. The thermocouple arrangement for the 
 two larger sizes is shown in Fig. 3-A; the arrangement for the small- 
 sized fruit is shown in Fig. 3-B. 
 
 The tests were conducted in the laboratory with air velocities be- 
 low those found to cause a difference in the rate of cooling due to in- 
 creased air circulation, as discussed on page 28. Each record reported 
 represents a composite of a number of tests for a given size of fruit. 
 
1934-} 
 
 REFRIGERATION OF PACKAGES OF APPLES 
 
 35 
 
 . 
 
 81 
 
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 J I- 
 O j= 
 
 
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 oocso 
 
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 j -c v 
 
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 OWKN ON 
 
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36 
 
 BULLETIN No. 410 
 
 [December, 
 
 The temperature drops for the different rows of fruits, as shown 
 in Table 6, indicate that the outside row cooled most rapidly, the inner 
 rows lagging behind in much the same way as shown in Fig. 4. 
 
 The average temperature drop for each size of fruit is shown 
 graphically in Fig. 9. (The average was obtained by considering all 
 the fruit temperature records within a package.) The temperature 
 
 U.80CT 
 
 SIZE OF FRUIT 
 
 Below 2% inch diam. 
 
 8 12 )6 
 
 HOURS IN COOLER 
 
 FIG. 9. EFFECT OF SIZE OF FRUIT ON RATE OF COOLING IN LINED 
 
 TUB BUSHEL BASKETS OF APPLES 
 
 The size of fruit used in filling a package did not materially affect the rate 
 at which the contents cooled. 
 
 drops for the three sizes nearly paralleled one another, no difference 
 occurring that could be attributed to a difference in the size of fruit. 
 This would lead to the conclusion that the size of the specimens of 
 fruit within a package is not a factor influencing the rate of cooling so 
 long as the total weights of the contents of the packages are similar. 
 
 EFFECT OF TYPE OF CONTAINER ON RATE 
 OF COOLING OF CONTENTS 
 
 Marked changes have taken place during the last few years in the 
 packages used for apples in some commercial producing sections. Evi- 
 dently the old standard package was not entirely satisfactory. Many 
 different types of packages have been tried. 
 
 Cars loaded with rectangular packages were shown in earlier 
 studies 10 * to cool more rapidly than cars loaded with bushel baskets. 
 Eustace and Beach 2 * found that the type of container used had a defi- 
 nite effect upon the rate at which apples placed in storage cooled. 
 
19341 
 
 REFRIGERATION OF PACKAGES OF APPLES 
 
 37 
 
 From the data available it would appear that the efficiency of the 
 refrigerator car in reducing the temperature of a load of fruit might 
 be greatly improved by the selection of the proper container.' Tests 
 were therefore made of a number of containers commonly used for 
 packing apples. Also a few not in common use, but which are of 
 interest because of some construction feature, were included in the 
 tests (Fig. 10). Each package being tested was protected from direct 
 
 FIG. 10. TYPES OF CONTAINERS USED IN EXPERIMENTS ON RATE OF COOLING 
 
 A Peck basket; B half-bushel basket; C wire-bound slat crate; D tub 
 bushel basket; E western apple box; F unventilated corrugated box; G 
 ventilated corrugated box ; H select apple package ; I bushel hamper. 
 
 exposure to the air by a package of the same type placed on the side 
 toward the wind. Conditions were thus created that were similar to 
 those found in cars loaded with the packages. 
 
 The thermocouple arrangement for each type of container is shown 
 in Fig. 11. In so far as possible, the arrangements were similar in 
 order to have a proper basis for comparing the rate of temperature 
 drop of the contents in the various types of containers. Since the 
 tub bushel basket with a ventilated liner and a corrugated facing pad 
 was used as a standard container for the tests reported in the fore 
 
38 
 
 BULLETIN No. 410 
 
 [December, 
 
 
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1934] REFRIGERATION OF PACKAGES OF APPLES 39 
 
 part of this publication, the other containers tested are compared with 
 this package. 
 
 Ventilated Corrugated Bushel Box Cooled as Rapidly 
 as Lined Tub Bushel Basket 
 
 The corrugated boxes used in these tests were the same as those 
 used in the shipping tests reported in an earlier bulletin of this 
 Station. 10 * The dimensions are approximately the same as those of the 
 western apple box. The ventilated box has seven one-inch holes on 
 each of the long sides and five one-inch holes on each end. There are 
 no openings in the top or bottom. The thermocouple arrangement used 
 is shown in Fig. 11-D. 
 
 In the shipping tests referred to above, the corrugated boxes proved 
 superior to the lined bushel baskets in the rate at which the load was 
 cooled. Under laboratory conditions these two packages proved about 
 equally efficient in permitting cooling of their contents (Fig. 12). In 
 the laboratory a uniform air temperature was maintained thruout the 
 cooling period, while in the refrigerator car the cooling power was 
 insufficient and the air temperature was not uniform but was reduced 
 as the temperature of the load was reduced. A more rapid air move- 
 ment took place in cars loaded with the corrugated boxes than in those 
 loaded with bushel baskets. 10 * The advantage in using boxes in refrig- 
 erator cars would appear to be due to the lower air temperature made 
 possible by the more rapid air movement. 
 
 Unventilated Corrugated Bushel Box Cooled Slowly 
 
 Corrugated boxes were tested that were the same in every respect 
 as the one described above except that there were no holes for ex- 
 change of air. The thermocouple arrangement was the same as for the 
 ventilated box (Fig. 11-D). 
 
 Apples packed in the unventilated corrugated box required about 
 eight hours longer to cool than those packed in the lined bushel basket 
 or the ventilated corrugated box (Fig. 12). The question arises 
 whether this difference in the rate at which the fruit cooled in the un- 
 ventilated and ventilated corrugated boxes was due to a difference in 
 the insulating value of the two containers or to a difference in the rate 
 at which air circulated within the packages. A study of the relation 
 of air temperature to fruit temperature within the two packages shows 
 no differences that might be attributed to a difference in rate of air 
 movement within the packages (Table 7). The difference in the per- 
 formance of the two packages would appear to have been due pri- 
 marily to differences in the insulating value of the containers. 
 
40 
 
 BULLETIN No. 410 
 
 [December, 
 
 60 
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 40 
 
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 HOURS IN COOLER 
 
 24 
 
 32 
 
 36 
 
 FIG. 12. EFFECT OF TYPE OF CONTAINER ON RATE OF COOLING OF CONTENTS 
 Apples packed in a ventilated corrugated box cooled at a rate nearly equal 
 to that in a lined tub basket ; while fruit in an unventilated corrugated box and 
 in a western apple box cooled at a much slower rate. An unlined tub bushel 
 basket and a peck basket cooled more rapidly than the lined tub bushel basket. 
 A "select apple package" cooled more slowly than the lined tub bushel basket, 
 while a slat crate cooled much more rapidly. 
 
19341 
 
 REFRIGERATION OF PACKAGES OF APPLES 
 
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42 BULLETIN No. 410 [December, 
 
 Western Apple Box Cooled Less Rapidly Than 
 Lined Tub Bushel Basket 
 
 The wooden bushel apple box, which is a standard container among 
 western apple growers and used to a limited extent by a few mid- 
 western growers, was found to be similar to the unventilated corru- 
 gated box in its effect upon the cooling of its contents, or about 30 
 percent less efficient than the tub bushel basket (Fig. 12). A cross- 
 section of the box, showing packing and thermocouple arrangement, is 
 shown in Fig. 11 -A. 
 
 Under refrigerator car conditions, however, the wooden bushel box 
 may be as efficient as the tub bushel, owing to the more rapid air move- 
 ment that takes place when rectangular packages are used and are 
 loaded according to standard specifications. 
 
 Ventilated Liner in Tub Bushel Slightly Retarded Cooling 
 
 The liner in an apple basket is considered essential by most packers, 
 especially for tender apple varieties, but oftentimes it is used because 
 the method of packing requires it rather than as a means of protecting 
 the fruit. It is advisable to use liners that will interfere as little as 
 possible with the cooling, especially if the temperature must be re- 
 duced rapidly. 
 
 In tests made with the ventilated liner, ventilation was obtained by 
 two rows of holes located at about one- fourth the distance from the 
 top and the bottom. There were twenty-one ^-inch holes in each liner. 
 Apples packed in an unlined basket cooled in about 15 percent less 
 time than those packed in a lined basket (Fig. 12). It is probable that 
 cooling would have been retarded even more had an unventilated liner 
 been used. 
 
 Cooling of Fruit in Half-Bushel Basket 
 
 The general trend in some apple markets is toward a smaller pack- 
 age. The half -bushel basket is one of the packages being used. In the 
 tests made to determine the rate of cooling in one of these baskets, 
 liners were used that were perforated with one row of eight ^4-inch 
 holes. The thermocouple arrangement used is shown in Fig. 11-E. 
 
 The temperature of the fruit at the time of packing was lower in 
 these tests than in the tests of the bushel packages. The time required 
 to reduce the temperature to 45 F. was about the same as required 
 in the lined bushel basket (Fig. 12). This is not in accord with 
 opinions that have been advanced, 12 * and the data at hand are insuf- 
 ficient to warrant definite conclusions. 
 
1934] REFRIGERATION OF PACKAGES OF APPLES 43 
 
 Rectangular Corrugated Peck Basket Cooled More 
 Rapidly Than Lined Bushel Basket 
 
 A peck basket made of single-cell corrugated paper material, folded 
 in such a way that the sides are of double thickness, is proving quite 
 popular on some of the midwestern markets. The cover is made of the 
 same material as the basket, and a large opening left in the center is 
 covered with cellophane in order that the contents may be displayed to 
 advantage. The peck basket is an attractive package of convenient 
 size for the average family. The thermocouple arrangement used in 
 the peck basket is shown in Fig. 11-G. 
 
 The records show that this package cooled in about 30 percent less 
 time than a lined bushel basket (Fig. 12). It is questionable, however, 
 whether this difference would be maintained in carload lots. The way 
 in which these packages are loaded in the car would be of considerable 
 importance in determining the rate of cooling. 
 
 Open-Slat Crate Permitted Rapid Cooling 
 
 Among the containers tested which are not in common use for 
 apple packaging is a strong wire-bound open-slat bushel crate. This 
 crate is a little shorter than the bushel box and a little wider. The 
 thermocouple arrangement used in the tests is shown in Fig. 11-C. 
 
 Fruit in this package cooled to 45 F. in 10 hours, as compared 
 with 24 hours in the lined bushel basket (Fig. 12). This very rapid 
 rate of cooling was accompanied by a low air temperature about the 
 fruit. The air temperature between two rows of fruit was below that 
 of the outside row (Fig. 13), which is a marked contrast to the rela- 
 tionship of fruit and air temperatures in a lined bushel basket (Fig. 6). 
 This condition was undoubtedly caused primarily by a combination 
 of two factors: the low insulating value of the container and the air 
 circulation among the fruits in the package. 
 
 This package may prove of considerable value for carload ship- 
 ments of perishable products that must be cooled rapidly. 
 
 Bushel Hamper Cooled as Rapidly as Lined Bushel Basket 
 
 Tests with apples packed in a bushel hamper showed that the rate 
 of cooling in the hamper was about the same as in the lined bushel 
 basket (Fig. 12). The thermocouple arrangement used was the same 
 as for the bushel basket (Fig. 11-B). 
 
 The hamper used in these tests is of much stronger construction 
 than the hampers commonly used for shipping vegetables. It has a top 
 
44 
 
 BULLETIN No. 410 
 
 [December, 
 
 about the same diameter as the bushel basket, but the package is taller 
 than the basket and considerably smaller at the base (Fig. 10-1). 
 
 WIRE-BOUND SLAT CRATE 
 
 First row of fruit _i 
 
 Second row of fruit 
 Air temperature 
 
 40 
 
 468 
 HOURS IN COOLER 
 
 FIG. 13. RELATION OF AIR TEMPERATURE TO FRUIT TEMPERATURE 
 
 IN WIRE-BOUND SLAT CRATE OF APPLES 
 
 The air temperature between the first and second rows of fruit in the wire- 
 bound slat crate was lower than the fruit temperature of the outside row. This 
 is a marked contrast to the conditions in a lined tub bushel basket, where the air 
 temperature was found to be midway between the fruit temperatures of the 
 two rows. 
 
 Apples Shipped in "Select Apple Package" Need Precooling 
 
 The "select apple package" tested in these studies is composed of 
 twelve boxes, each holding twelve apples. The boxes are made of 
 heavy-grade paper, are lined with a single-celled corrugated paper, 
 and are divided into twelve individual compartments with corrugated 
 paper (Fig. 10-H). The twelve boxes are then packed in a larger 
 single-celled corrugated box. 
 
 Fruit placed in this package cooled very slowly (Fig. 12). Three 
 times as much time was required to cool the contents as was required 
 in a lined bushel basket. The thermocouple arrangement shown in 
 Fig. 11-F was used in tracing the rate of cooling. 
 
 While the select apple package may be used to advantage in market- 
 ing a limited quantity of fancy apples, these studies show strongly 
 the advisability of cooling the fruit before packing it. Apples placed in 
 this package while at a high temperature are liable to damage from 
 overripeness and decay even under the best refrigerator car conditions. 
 
1934] REFRIGERATION OF PACKAGES OF APPLES 45 
 
 EFFECT OF WRAPPING FRUIT ON RATE 
 OF COOLING 
 
 It is a common practice in some regions to wrap the higher grades 
 of fruit. Especially is this true of apples packed in bushel boxes in the 
 West and to a less extent of fancy apples packed in bushel baskets in 
 other regions. Advantages claimed for wrapping apples include the 
 preservation of their bright color, checking of transpiration, reduction 
 in amount of wilting, prevention of bruising, prevention of spread of 
 rot, 13 * and in some varieties, prevention of scald in storage. In spite 
 of these advantages in wrapping apples for long-time storage, there is 
 some question regarding the desirability of the practice from the stand- 
 point of its effect on the rate of cooling of apples packed and shipped 
 during warm weather. 
 
 To determine the effects of wrapping upon rate of cooling, tests 
 were made in lined tub bushel baskets with apples wrapped in 20- 
 percent oil paper wraps and others without wraps. The arrangement 
 of thermocouples in the baskets is shown in Fig. 11-B. Thirty-six 
 hours were required to reduce the temperature of the wrapped fruit 
 to 45 F., while only 24 hours were required to bring about an equal 
 change in the temperature of the unwrapped fruit (Fig. 14). 
 
 Other tests were made to determine the rate of cooling of wrapped 
 apples in a western wooden apple box. The fruit was packed in the 
 same way as the unwrapped box apples (Fig. 11 -A). The box in 
 which the wrapped fruit was packed was not lined, while the one in 
 which the unwrapped fruit was packed contained a liner. The un- 
 wrapped fruit cooled in 34 hours, while the wrapped fruit cooled in 
 46 hours, a difference of about 35 percent (Figs. 12 and 14). How 
 much a liner in the box of wrapped fruit would have still further 
 retarded cooling was not tested. In a lined bushel basket the retarding 
 effect of the oil-paper wraps was equivalent to about 50 percent of the 
 time required to cool the unwrapped fruit. 
 
 These findings are in accord with those of Eustace and Beach, 2 * 
 which show that wrapping materially retards the rate of cooling and 
 that the type of container, to some degree, determines the extent of 
 retardation. 
 
 Under the conditions found in the average refrigerator car, it 
 would probably require two days longer to reduce the temperature of 
 a carload of wrapped fruit to the desired degree than a carload of un- 
 wrapped fruit, when shipped during the summer months. 
 
 The rate of temperature drop per unit of time for the different 
 rows within the baskets of wrapped and unwrapped fruits is shown 
 
46 
 
 BULLETIN No. 410 
 
 [December, 
 
 
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1934} 
 
 REFRIGERATION OF PACKAGES OF APPLES 
 
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48 BULLETIN No. 410 [December, 
 
 in Table 8. During the first part of the cooling period the temperature 
 drop in the outside row of fruit was about equal for the wrapped and 
 unwrapped fruit, but in the later periods the wrapped fruit cooled 
 more slowly than the unwrapped. The second and third rows of 
 wrapped fruit cooled much more slowly than the corresponding rows 
 of unwrapped fruit during the early part of the cooling period; but 
 as cooling progressed, the rates of cooling of the wrapped and un- 
 wrapped fruit gradually approached each other. 
 
 After five or six hours in the cooling chamber the two inner rows 
 of unwrapped fruit were cooling more rapidly than the outer row. 
 The corresponding rows of wrapped fruit were in the cooling chamber 
 nine or ten hours before they showed a similar relationship. In an 
 attempt to ascertain the value of the air spaces in the cooling of fruits, 
 tests were made with lined bushel baskets of fruit in which the air 
 spaces were filled with mineral wool (page 27). The results were very 
 similar to those obtained when the fruit was wrapped (Fig. 14). The 
 effect of the wrap on the cooling of the fruit does not seem to be due 
 entirely to its power to insulate the fruit it seems also to be due to 
 the filling of the air spaces between the fruits. 
 
 Most of the data regarding the value of the wrap in improving 
 the keeping quality of apples have been obtained by tests upon fall and 
 winter varieties. It is a question whether equally good results would 
 be obtained with wrapping if the fruit was packed while at a high tem- 
 perature and then loaded into a refrigerator car and sent to market 
 during the summer months. The high temperature of the fruit would 
 tend to overcome any value of the oil wrap in checking physiological 
 processes. 
 
 SUMMARY AND CONCLUSIONS 
 
 1. In this study special apparatus was constructed to produce 
 conditions similar to those found in refrigerator cars. 
 
 2. Lined tub bushel baskets filled with Grimes apples and placed 
 in a cooling chamber developed comparatively large temperature gradi- 
 ents between the outer and inner rows of fruit during the early part 
 of the cooling period. As cooling progressed, the temperatures became 
 more nearly uniform thruout the package. 
 
 3. The temperature difference between individual apples in a 
 lined tub bushel basket and the air in the immediate neighborhood is 
 quite small thruout the cooling period. Packages that permit much 
 
1934] REFRIGERATION OF PACKAGES OF APPLES 49 
 
 more rapid cooling, such as the wire-bound slat crate, have an air 
 temperature below that of the fruit in the immediate neighborhood. 
 
 4. The air spaces between apples packed in a lined tub bushel 
 basket exposed to low air velocities materially contribute to the cooling 
 of the fruit even tho the temperature in these air spaces resembles the 
 fruit temperature. As the air velocity is increased, a point is reached 
 at which it causes the contents of a package to cool more rapidly, 
 owing apparently to the lowering of the air temperature about the 
 fruits as the result of the increased rate at which the air contents of 
 the package are exchanged. 
 
 5. Air velocities below 100 feet per minute are not sufficient to 
 affect the rate of air movement within a lined tub bushel basket and 
 therefore do not influence the rate at which the contents cool, provided 
 the air temperature remains constant. 
 
 6. The higher the temperature of the fruit when packed, the 
 more rapidly it drops, given similar conditions of temperature and air 
 velocity. 
 
 7. The size of apples used in filling a lined tub bushel basket 
 does not alter the rate at which the package cools. 
 
 8. The type of container may alter greatly the behavior of a 
 package of apples under refrigeration. The contents of a lined tub 
 bushel, a ventilated corrugated bushel box, and a bushel hamper be- 
 haved similarly in cooling tests. The contents of an unventilated cor- 
 rugated bushel box and a lined western apple box cooled more slowly 
 than the contents of the lined tub bushel basket. The contents of a 
 wire-bound slat crate cooled much more rapidly than the contents of 
 the lined tub bushel basket. 
 
 9. The use of oil wraps in the packing of apples materially re- 
 tards the rate of cooling. 
 
50 BULLETIN No. 410 
 
 LITERATURE CITED 
 
 1. BROOKS, CHARLES, and COOLEY, J. S. Temperature relations of apple-rot 
 
 fungi. Jour. Agr. Res. 8, 139-164. 1917. 
 
 2. EUSTACE, H. J., and BEACH, S. A. Cold storage for Iowa grown apples. 
 
 Iowa Agr. Exp. Sta. Bui. 108. 1909. 
 
 3. Empire Marketing Board, Economic Section. Report of an investigation into 
 
 the deterioration in transit of imported Canadian fruits, 1927-29. Gt. 
 Brit. Empire Marketing Bd. Pub. 30. 1930. 
 
 4. GRIFFITH, EZER, and AWBERY, J. H. Gt. Brit. Dept. Sci. and Indus. Res. 
 
 Food Invest. Bd. Rpt. (1925 and 1926), 74-76. 1926. 
 
 5. LLOYD, J. W., and NEWELL, H. M. Observations on the refrigeration of some 
 
 Illinois fruits in transit. 111. Agr. Exp. Sta. Bui. 334. 1929. 
 
 6. ' Some factors influencing the keeping quality of fruits in transit. 
 
 111. Agr. Exp. Sta. Bui. 350. 1930. 
 
 7. MAGNESS, J. R., and DIEHL, H. C. Physiological studies on apples in storage. 
 
 Jour. Agr. Res. 27, 1-38. 1924. 
 
 8. et al. The ripening, storage, and handling of apples. U. S. 
 
 Dept. Agr. Bui. 1406. 1926. 
 
 9. MORRIS, O. M. Studies in apple storage. Wash. Agr. Exp. Sta. Bui. 193. 
 
 1925. 
 
 10. NEWELL, H. M., and LLOYD, J. W. Air circulation and temperature con- 
 
 ditions in refrigerated carloads of fruit. 111. Agr. Exp. Sta. Bui. 381. 
 1932. 
 
 11. PALMER, R. C. Recent progress in the study of Jonathan breakdown in 
 
 Canada. Sci. Agr. 11, 243-258. 1931. 
 
 12. POWELL, G. H. Relation of cold storage to commercial apple culture. U. S. 
 
 Dept. Agr. Yearbook 1903, 225-238. 
 
 13. and FULTON, S. H. The apple in cold storage. U. S. Dept. Agr. 
 
 Bur. Plant Indus. Bui. 48. 1903. 
 
 14. SMITH, A. J. Temperature conditions in refrigerated holds carrying apples. 
 
 Gt. Brit. Dept. Sci. and Indus. Res. Food Invest. Bd. Spec. Rpt. 27. 1926. 
 
6.05O 12-34 6528