COMMERCIAL STORAGE OF FRUITS AND VEGETABLES 9 



It might be thought that respiration could be used as a basis for 

 judging the effects of cold storage on fruits and vegetables, since this 

 process is one of the important factors in bringing about deteriora- 

 tion. Certain starchy products such as potatoes and bananas that 

 have been held in cold storage respire more rapidly after removal; 

 they produce more carbon dioxide and give off more heat than those 

 which have been held at ordinary temperatures. However, so far 

 as can be discovered, fruits such as peaches, strawberries, oranges 

 grapefruit, and apples do not. In the case of potatoes and bananas, 

 the reason is thought to be that when these commodities are held at 

 low temperatures, sugar accumulates in their tissues; then when they 

 are removed to higher temperatures, this sugar is readily respired, 

 so that they produce more carbon dioxide and give off more heat 

 than similar lots that have been held continuously at 50° to 60° F. 

 With potatoes, however, the criterion used does not necessarily mean 

 more rapid deterioration. That is, the increase in respiration is 

 not necessarily accompanied by wilting, decay, or discoloration of 

 the flesh. 



It can be stated that for many fruits and vegetables, as far as is 

 now known, cold storage at 32° F. is beneficial. Important exceptions 

 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 than if they were dry after being unloaded and remained dry 

 until consumed. In this connection dryness means merely the ab- 

 sence of liquid water on the surface. 



Sweating can be prevented to some extent, as in the British prac- 

 tice with eggs and certain other commodities, by allowing the fruits 

 or vegetables to warm up gradually. Under commercial conditions in 

 the United States this is rarely practicable, however, and the best 

 thing to do in very damp weather is to realize the risk, handle the 

 product carefully, and get it into consumption without undue delay. 



The storage conditions recommended herein for certain commodi- 

 ties represent either a compromise between two undesirable extremes 

 of temperature or humidity or a choice of the least harmful of two 

 such extremes. Grapefruit, for example, suffer less from decay at 

 low humidities than at high; on the other hand, at low humidities 

 they are subject to a pitting which is usually more damaging to the 

 market value of the fruit, because it is more common under commer- 

 cial conditions than is decay. Therefore, it is recommended that 

 grapefruit in storage be held at about 85 percent relative humidity. 



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