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



and yet not allow them to be damaged by actual freezing. With 

 many products this storage temperature is only 1 or 2 degrees 

 above the actual freezing point. Of course some products, such as 

 berries, may be purposely kept in a frozen condition below freezing 

 temperature, 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 potatoes reported in a previous publication, 1 

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

 without actually having become frozen and 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 further 

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

 such as tomatoes, bananas, and cucumbers are injured if stored at 

 temperatures many degrees above their actual freezing points. This 

 is usually termed chilling injury. It is evident, therefore, that tem- 

 peratures 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 vege- 

 tables 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 

 work is being continued. It has been found in some cases that 

 the freezing points of some varieties are liable to slight variations 

 from year to year, even though the same strain grown in the same 

 locality is used. 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 variation of a fraction of a degree hardly 

 warrants any change in the treatment of the product. It therefore 

 seems advisable to publish the results of these investigations from 



i Wright, R. C, and Taylor, George F. freezing injury to potatoes mthen uxdercooled. 

 XL S. Dept. Agr. Bui. 916, 15 p., 1 fig., 1 p^ 1921. Literature cited, p. 15. 



