18 CIRCULAR 713, U. S. DEPARTMENT OF AGRICULTURE 



MARKET OBSERVATIONS 4 



Freezing injury in transit is likely to occur in the fruit next 

 to the side walls and along the floor of the car rather than in that 

 in the body of the load. It seldom shows in the form of drying out 

 so characteristic of fruit frozen on the tree. Oranges and grape- 

 fruit are often bitter in flavor for a time after thawing, but this 

 is not a consistent condition. If the freezing has been severe, the 

 rind may show effects ranging in severity from almost typical 

 brown stain to leaden-gray discolored areas of varying size, which 

 greatly resemble watery break-down. The affected rind tissues 

 may or may not be sunken, but when severely frozen they usually 

 become soft and mushy and are underlain by mushy pulp tissue. 



Freezing damage is best seen by cutting off both ends of a fruit, 

 then cutting lengthwise through the rind of the central portion re- 

 maining, and pulling the segments apart. If the fruit has been 

 frozen the membrane between the segments will show a soaked 

 condition and usually a number of white specks, which are hes- 

 peridin crystals (naringin in grapefruit) resulting from the freez- 

 ing. However, the presence of crystals is not necessarily an indi- 

 cation that the fruit has been frozen. They may also result from 

 the application of heat to the fruit or from rapid drying out of the 

 tissues. In tangerines the hesperidin crystals occur in the pulp as 

 well as on the segment walls and are seen even more readily than 

 in oranges when a cross-section cut is made. Freezing damage 

 may be confined to a part of the fruit, in which case the signs sug- 

 gested will be found in the affected part. The method of examina- 

 tion just described is particularly useful for California oranges. 

 Florida oranges are not so easily examined in this way but are 

 more likely to show the mushy condition in cross section. 



Lemons and grapefruit show the damage in cross section much 

 more plainly than oranges do, although it is desirable at times to 

 pull grapefruit sections apart as recommended for oranges. If 

 lemons have been seriously damaged the pulp becomes mushy at 

 once after thawing. 



In addition to the symptoms just described grapefruit shows a 

 milky appearance of the pulp, which is in marked contrast to the 

 very light amber color and the almost transparent condition of un- 

 frozen pulp. The contrast is especially noticeable in fruits that 

 have been frozen in small spots or on one side only. The milky ap- 

 pearance of the pulp is also found in grapefruit that has been in 

 storage for 8 to 10 weeks, and it may be accompanied by a bitter 

 taste. However, such fruit is not mushy and watery unless af- 

 fected by watery break-down ; in such a case a positive diagnosis 

 must depend on a consideration of the history of the fruit and the 

 conditions under which the injury is found. 



Citrus fruits frozen on the tree show a number of symptoms 

 similar to those described under transit freezing if examined 

 soon after the freezing occurs. After a few days, however, addi- 

 tional symptoms appear. First and most characteristic among 

 these is a buckling of the partition walls at the stem end of the 



4 Adapted from Rose, D. H., Brooks, C, Bratley, C. O., and Winston, J. R. 



MARKET DISEASES OF FRUITS AND VEGETABLES I CITRUS AXD OTHER SUBTROPICAL FRUITS. 



U. S. Dept. Agr. Misc. Pub. 498, 57 pp., illus. 1943. (See pp. 27 and 28.) 



