10 CIRCULAR 2 7 8, U. S. DEPARTMENT OF AGRICULTURE 



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 quan- 

 tity of refrigeration 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 

 TVinesap 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 tli an the use of low temperature for checking the ripening and 

 decay so largely responsible for their deterioration— that is, it is 

 impossible in the present state of knowledge to obtain fruits and 

 vegetables that have not been refrigerated but still have not changed 

 in any way since harvest, for comparison with similar lots that have 

 been in cold storage and are eventually removed. However, so far 

 as is now known, it is correct to say that for many fruits and vege- 

 tables cold storage at or near 32° F. is beneficial. Important excep- 

 tions are bananas, sweetpotatoes, tomatoes, cucumbers, melons, and 

 certain other horticultural products mentioned herein, the behavior of 

 all of which in storage is discussed later under appropriate headings. 



Sweating 



When fruits or vegetables are removed from a low temperature to 

 a higher one there is frequently a condensation of moisture from the 

 air on the cool surface of the commodity. This is known as sweating 

 and is more marked the higher the relative humidity of the outside 

 air. It should be prevented whenever possible in the case of onions 

 and the more tender fruits, because it favors the development of decay. 

 This does not mean that when any of these products sweat after 

 removal from an iced refrigerator car or a refrigerated room they 

 are sure to decay; it does mean that they are more likely to decay 



