FREEZING INJURY OF FRUITS AND VEGETABLES \7 



MARKET OBSERVATIONS 3 



The average freezing point of onion bulbs is about 30° F. Al- 

 though some onions may freeze at a fraction of a degree higher or 

 lower, this temperature may be taken as the danger point. Under 

 some conditions onions standing on track or in storage may be 

 undercooled to a temperature of 25° or lower for a short time with- 

 out becoming frozen or otherwise injured. A slight jar will cause 

 undercooled products to freeze immediately; therefore onions 

 rarely undercool during transit. 



Individual onions vary considerably in their reaction to low tem- 

 perature. Some bulbs in a lot may freeze quickly when they reach 

 a temperature of 30° F. and show severe injury when they thaw. 

 Others may not freeze, or if they do freeze they may thaw out 

 without injury. 



Onions injured by freezing show water-soaked, grayish-yellow 

 fleshy scales when cut. In slight freezing the outer fleshy scales 

 alone are affected, but when the bulbs are exposed to low tempera- 

 tures for a prolonged period the inner scales may also become 

 water-soaked and discolored. Usually the entire scale is injured 

 all the way around the bulb, but the neighboring scales inside and 

 outside may or may not show injury. Irregularly shaped opaque 

 areas occur in many of the watery transparent scales. 



Garlic bulbs do not freeze until a temperature of approximately 

 25° F. is reached. The frozen tissues are discolored and water- 

 soaked in the same way as those of onions. 



In cases of slight freezing injury of onions and garlic there may 

 be little loss if the bulbs are spread out so that the injured scales 

 can dry thoroughly. Experimental evidence indicates that frozen 

 onions will show less injury and remain in a better general condi 7 

 tion if thawed out at 40° F. rather than at a higher temperature. 



Oranges and Grapefruit 

 experimental observations 



One standard crate of oranges and one of grapefruit were held 

 in an 18° F. room for 25 hours. The crates were not papered, but 

 the fruits in one end of each crate were individually wrapped and 

 those in the other were not wrapped. Immediately after removal 

 from the freezing room all top-layer fruits were found frozen but 

 those halfway down and away from the sides and ends in both the 

 wrapped and the unwrapped lots felt normally soft. Evidently 

 they were not frozen. The crates were held at 45° for 24 hours 

 after removal from the freezing room ; the only marked symptoms 

 in any of the fruits were a definite softening and slight off -flavor 

 of a few from the top layers, both wrapped and unwrapped. 



After 13 days at 36° F. all fruits cut were slightly off in flavor, 

 but otherwise there was no change from the condition noted at the 

 time of the first inspection. No pitting of the peel and no drying 

 or separation of segments was noted. 



s Adapted from Ramsey, G. B., and Wiant, J. S. market diseases op fruits and 



VEGETABLES : ASPARAGUS., ONIONS, BEANS, PEAS, CARROTS, CELERY, AND RELATED 



vegetables. U. S. Dept. AgT. Misc. Pub. 440, 70 pp., illus. 1941. (See p. 10.) 



