EFFECTS OF FREEZES ON CITRUS IN CALIFORNIA 



313 



machines have been ^perfected and are used in packing houses to make 

 this separation. 



3. Severely frozen fruit will usually show a marked decrease in 

 specific gravity within a week; less severely injured fruit changes 

 more slowly. In lemons the changes in specific gravity are more rapid 

 than in oranges. 



4. Holding the fruit for two weeks after picking increases the 

 specific gravity of good fruit very markedly. A month is generally 

 long enough to make a recognizable difference, but better separations 

 can be obtained after six weeks or two months. 



Fig. 19. Badly frozen orange showing growth of rind when fruit remains 

 on tree. Photo by Smith, March 7, 1913. 



5. Frozen fruit decreases in specific gravity whether stored or left 

 on the tree. Sound fruit, however, remains fairly constant on the 

 trees, but gradually increases in density when stored. 



6. The excessive loss of moisture in citrus fruits caused by freezing 

 is due to the killing of the walls of the cells in the fruit, thus changing 

 them form semi-permeable membranes to a porous substance that 

 freely allows the liquid to evaporate from the interior without de- 

 creasing its volume. This loss in weight and not in volume decreases 

 the specific gravity. 



7. The specific gravity of the juice of frozen citrus fruit is some- 

 what lower than that of the unfrozen. 



