8 CIRCULAR 713, U. S. DEPARTMENT OF AGRICULTURE 



was more noticeable in those that were frozen than in those that 

 were not but it was only slight even in the frozen fruits. After a 

 week at 31° neither the wrapped nor the unwrapped lot showed 

 any change from the condition found when the fruit was removed 

 from the freezing room. 



Many persons think that the presence of ice in an apple is prima 

 facie evidence of freezing injury. Theoretically they are right; 

 practically they may not be. The confusion is due to a failure to 

 distinguish between slight freezing and freezing to death in which 

 enough ice is formed to cause permanent and visible injury. 

 Doubtless the least incipient ice formation injures the apple flesh 

 to some degree, but so far as present knowledge goes there is no 

 visible evidence of injury by such slight freezing and no effect upon 

 the market value of the fruit. If, however, the freezing process is 

 carried somewhat further, a slight noticeable injury results, even 

 though the cells may appear practically normal ; if freezing is car- 

 ried still further, the cells may be killed, in which event they turn 

 brown. Regardless of how much ice appears in the fruit it is inac- 

 curate to say that the apple shows freezing injury unless a signifi- 

 cant proportion of the cells show this browning. 



EXTERNAL AND INTERNAL APPEARANCE OF FROZEN APPLES 



If freezing of an apple has been slight, there may be no marked 

 external symptoms of any sort ; if it has been severe, the general 

 outside appearance is strikingly affected. The surface is discol- 

 ored in irregularly shaped areas — becomes so, in fact, very soon 

 after the apple thaws — and appears considerably darkened. It 

 often assumes a water-soaked, brown color closely resembling that 

 of apple scald, or the color may become much darker, in some cases 

 almost black. When apples are in a frozen condition the skin be- 

 comes slightly shriveled, but the shriveling usually occurs in the 

 form of a network of wrinkles rather than as parallel lines of 

 shrinkage such as are produced by normal evaporation. Careful 

 measurements have shown also that the fruit actually becomes 

 smaller, sometimes by as much as 10 percent of its original volume. 

 On thawing it regains practically its original volume unless the 

 freezing was very severe. 



When apples thaw after having been badly frozen the skin 

 becomes shriveled, particularly if the air in the storage place is 

 very dry. This form of shriveling seems to be due to rapid evapo- 

 ration, after thawing, of the water withdrawn from the cells and 

 changed into ice in the spaces between the cells during the freezing 

 process. Shriveling when slight is accompanied by a reduction 

 chiefly in size and when severe by a marked reduction in both size 

 and weight. 



Apples that have been severely frozen frequently show notice- 

 ably sunken spots, which may be a quarter of an inch or more deep 



i Adapted from Rose, D. H., Brooks, C, Fisher, D. P., and Bratley, C. O. 



MARKET DISEASES OF FRUITS AND VEGETABLES I APPLES, PEARS, QUINCES. U. S. Dept. AgT. 



Misc. Pub. 168, 71 pp., illus. 1933. (See pp. 16, 17, 26-29.) 



