II. THE RIPENING OF APPLES IN STORAGE AS INFLU- 

 ENCED BY TEMPERATURE 



.By J. R. Magness, Physiologist. M. H. Hallee, Junior Pomologist, and H. C. 

 Diehl, Assistant Physiologist, Office of Horticulture, Bureau of Plant In- 

 dustry 



Following the removal of apples from the tree, the ripening proc- 

 esses which go on are to a considerable extent a continuation of 

 those in progress while the fruit was still attached to the tree. The 

 most outstanding change which occurs in apples between the time of 

 picking and that of ultimate consumption is in the structure of the 

 cell walls which results in the softening of the flesh. At the time of 

 picking most varieties of apples are too firm and hard to be in prime 

 eating condition. As softening proceeds, however, the apples pass 

 through a prime eating condition and ultimately become mealy or 

 overripe. This softening process in storage is, of course, accom- 

 panied by other changes in the fruit. The unblushed portion usually 

 becomes more yellow in storage. There is also a change in the chemi- 

 cal composition of the fruit. The starch disappears, changing to 

 sugar; consequently the sugar content usually increases slightly be- 

 tween the time of picking and the time when the fruit is soft ripe. 

 The acid content of the fruit decreases during the storage period. 



Magness and Burroughs (10) and Magness and Diehl (11) have 

 reported that under normal storage conditions the rate of softening 

 of apples while in storage is apparently almost entirely controlled by 

 the temperature at which the fruit is held. Other factors, such as 

 humidity, ventilation, and type of package, have little influence on 

 the actual rate of softening or ripening of the apples. In the in- 

 vestigation here reported a comprehensive and detailed study has 

 been made of the exact influence of different temperatures on the 

 rate of softening and other changes which occur during ripening in 

 a large number of important commercial apple varieties. This in- 

 formation is fundamental to a proper understanding of the factors 

 involved in handling apples in storage, regardless of whether the 

 fruit is being handled in cold storage or in air-cooled or common 

 storage. 



INFLUENCE OF TEMPERATURE ON RATE OF SOFTENING 



Since softening in apples is the most obvious change during the 

 period between picking time and ultimate consumption, it has been 

 studied in greater detail than any other. The apples used in the 

 tests were picked at approximately the commercial picking season 

 for the varieties. The fruit of the different varieties was taken as 

 quickly as possible to the storage plant and in most cases placed in 

 storage the day following that of picking. The Yellow Newtown, 

 York Imperial, and Arkansas (Mammoth Black Ticig) apples had 



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