12 CIRCULAR 2 7 8, IT. S. DEPARTMENT OF AGRICULTURE 



As a result of these calculations it has been found that the heat 

 produced by the respiration of fruit while it cools is directly pro- 

 portional to the length of the cooling period. The figures for cooh 

 ing periods of 3, 4, 5, 6, and 8 days are therefore set at 0.3, 0.4, 0.5, 0.6, 

 and 0.8 (to the nearest thousand) of the figure for 10 days. The spe- 

 cific heat has been calculated by the formula S= 0.008a +0.20, in 

 which S signifies the specific heat of a substance containing a percent 

 of water; 0.20 is the value that has been assumed to represent the 

 specific heat of the solid constituents of the substance in question (88) . 



Column 1 of table 2 shows the kind and variety of fruit and col- 

 umn 2 the temperature of the fruit at the time cooling started, in a 

 room held at 32° F. The next column shows the amount of heat 

 evolved by respiration if the fruit reaches 35° at the end of 3 days. 

 The next five columns show the amount of heat if cooling to 35° re- 

 quires 4, 5, 6, 8, or 10 days, respectively. The last column is the 

 sensible heat (obtained by multiplying the specific heat of the fruit 

 by the difference between initial and final temperatures and this 

 result by the number of pounds in a ton). For any one kind of 

 fruit at a given initial temperature, the specific heat is assumed to be 

 the same for all the cooling periods included in the table. 



The values given in table 2 are only approximate. However, in 

 view of the results of the investigations mentioned on page 10, it is 

 believed that the two assumptions that have been made — namely, (1) 

 that the heat of respiration is produced only by the oxidation of a 

 hexose sugar and can be computed from observed amounts of carbon 

 dioxide produced and (2) that the rate of temperature drop is always 

 proportional to the difference between fruit temperature and room 

 temperature — probably lead to fairly accurate results. The figures 

 are presented to help cold-storage-plant operators estimate the refrig- 

 eration required for cooling the specified fruits under the various 

 conditions given. As an example of how the figures can be used, 

 the following calculation may be of interest : A ton of Bartlett pears 

 cooling from 70° to 35° F. in 10 days in a 32° room is shown to be 

 capable of producing about 54,000 B. t. u. Its sensible heat at 70° 

 (35° above its final temperature) is 61,000 B. t. u. The sum of the 

 two is 115,000 B. t. u. If this be multiplied by the capacity of the 

 room in tons of fruit, say 600 (the capacity of some of the commercial 

 cold-storage rooms in the United States) and divided by 288,000 (the 

 number of British thermal units in a ton of refrigeration), the quo- 

 tient 239 is obtained; this is approximately the number of tons of 

 refrigeration required to cool 600 tons of Bartlett pears to 35° in 

 10 days under the conditions specified. The corresponding figure for 

 Winesap apples is 177 and that for Grimes Golden apples 200. 



EFFECT OF COLD STORAGE ON SUBSEQUENT 

 BEHAVIOR OF FRUITS AND VEGETABLES 



The belief is rather common among those concerned with the mar- 

 keting of fresh fruits and vegetables that commodities of this kind 

 that have been in cold storage deteriorate more rapidly after removal 

 from the low temperature than if they had been held at ordinary 

 temperatures. It is difficult, however, to find a basis for judging 

 whether or not they actually do so because there is no means known 

 other than" the use of low temperature for checking the ripening and 



