2 CIRCULAR 447, U. S. DEPARTMENT OF AGRICULTURE 



It is of great importance to the commercial cold-storage man to 

 know the exact freezing points of the fruits and vegetables which he 

 handles. In some instances established commercial-storage practices 

 have been changed after the exact freezing points of certain products 

 have been ascertained. In most cases fruits and vegetables, other 

 than dried or prepared products, when placed in cold storage are 

 alive, and the problem is to keep them alive and healthy throughout 

 their storage period. Since various fruits and vegetables freeze at 

 different temperatures, there is more or less doubt in the minds of 

 those interested as to the proper and safe temperatures at which to 

 hold them in storage. One of the problems in the storage of many 

 products is to hold them at a temperature low enough to slow down 

 the life processes in order to prolong their storage life and yet not allow 

 them to be damaged by actual freezing, which of course is likely to 

 injure their keeping qualities or market value. With many products 

 this storage temperature is only 1° or 2° above the actual freezing 

 point. Of course some products, such as cherries, strawberries, peas, 

 and lima beans, may be purposely kept in a frozen condition below 

 ireezing temperature, but this subject comes under the head of freezing 

 storage and will not be discussed here. 



It should be borne in mind, however that freezing or freezing injury 

 does not always occur when fruit or vegetable products are exposed to 

 temperatures at or below their true freezing points. This is shown 

 in the studies on potatoes reported in a previous publication, 2 where 

 tubers were cooled as much as 10° F. beiow their freezing points 

 without actually having become frozen and were again warmed up 

 without apparent injury. The commonly known fact that some 

 kinds of products may be actually frozen and then thawed out under 

 certain conditions with no apparent injurious effects constitutes fur- 

 ther evidence on this point. On the other hand, certain commodities 

 such as tomatoes, bananas, and cucumbers are definitely injured if 

 stored at temperatures many degrees above their actual freezing 

 points. This is usually termed chilling injury. It is evident, there- 

 fore that temperatures just above the freezing point cannot be 

 regarded as safe for all types or varieties of fruits and vegetables. 

 It is also noticeable that there are variations in the freezing points of 

 fruits and vegetables of the same variety and from the same lot, as is 

 shown in the tables that follow. Furthermore, it is quite probable 

 that different individuals of the same variety and strain when grown 

 under different conditions will have somewhat different average 

 freezing: points. Attention is therefore called to the fact that the 

 freezing points given in the following: tables should be considered as 

 danger points; that is, at or near these temperatures, either above or 

 below them there is danger of injury by freezing if exposed for a 

 sufficient length of time. 



It has been found in some cases, as has been pointed out, that the 

 freezing points of some varieties are liable to slight variations. These 

 variations, however, are probably of more importance in the study of 

 the exact causes and results of freezing injury than from the point of 

 view of the commercial cold-storage and produce man, for the varia- 

 tion of a fraction of a degree hardly warrants any change in the treat- 

 ? lent of the product. 



Wright, R. C, and Taylor. G. F. freezing injury to potatoes when undercooled. U. S. 

 Dept. Agr. Bull. 916. 15 pp., illus 1921. 



