2 BULLETIN 1133, U. S. DEPARTMENT OF AGRICULTURE. 



Knowledge of the exact freezing points of fruits and vegetables 

 is of importance also to the commercial cold-storage man. 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 these various products in storage. 

 One of the problems in the storage of many of these products is to 

 hold them at a temperature low enough to slow down the living 

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

 to be damaged by actual freezing. Of course, some products, such 

 as berries, may be purposely kept at a freezing temperature and used 

 at once on thawing out, but this subject comes under the head of 

 freezing storage and will not be discussed here. It is therefore 

 essential in commercial work of this kind that accurate data be at 

 hand on the temperatures to which these products can be exposed 

 without injuring their keeping qualities or market value. 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 Irish potatoes reported in a previous publication, 1 

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

 and again warmed 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 further evidence on this point. On the other hand, 

 some commodities are injured if stored at temperatures well above 

 their actual freezing points. It is evident, therefore, that tempera- 

 tures just above the freezing point can not be regarded as safe for 

 all types or varieties of fruits and vegetables. It is also noticeable 

 that there are some variations in the freezing points of fruits or 

 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 a possibility that the product will be in danger 

 of injury by freezing if exposed for a sufficient length of time. These 

 are temperatures at which it is unsafe to hold produce which is to be 

 used for food if it is desired to maintain it for any length of time in 

 a living condition. 



The determinations of the freezing points of a number of fruits 

 and vegetables have been made by the Bureau of Plant Industry 

 in connection with its cold-storage investigations. By freezing point 

 is meant the temperature at which ice crystals begin to form within 

 the product, either fruit or vegetable. 



Some 10,000 of these determinations have already been made on 

 many varieties of commercially grown fruits and vegetables, and 



i Wright, R. C, and Taylor, George F. Freezing injury to potatoes when undercooled. U. S. Dept. 

 Agr. Bui. 916, 15 p., 1 fig., 1 pi. 1921. Literature cited, p. 15. 



