8 CIRCULAR 65 9, U. S. DEPARTMENT OF AGRICULTURE 



tendency on the part of growers to delay picking until the apples do 

 color, with attendant danger of loss from dropping and of the fruit's 

 becoming too mature for storage. Because this is particularly true 

 of Jonathan, Delicious, and Rome Beauty, red bud sports of these 

 varieties have been eagerly sought and largely substituted wherever 

 possible. Many large plantings of the original varieties will doubt- 

 less remain in heavy production, however, and in such cases there 

 will continue to be problems of color, dropping, and overmaturity. 

 Use of hormone sprays, which prevent apples from dropping, meets 

 the problem of slow coloring only in part, since there is danger that 

 apples thus held on the tree to color may become too far advanced in 

 maturity or may be fully ripe at time of picking. Overmature apples 

 are particularly susceptible to water core, soft scald, internal break- 

 down, and Jonathan spot and are more subject to stem punctures, 

 bruising, and other mechanical injuries through which blue mold 

 infection takes place. Blue mold infection through lenticels is also 

 more likely to occur in overmature apples than in those picked at 

 proper maturity. 



Storage Temperature 



The life processes of apples that have to be considered in the suc- 

 cessful storage of the fruit after harvest are essentially chemical, and, 

 as with other chemical processes, the rate at which they proceed de- 

 pends largely upon the temperature at which they can be carried out ; 

 i. e,, upon the temperature of the apples. Apples freeze at a tempera- 

 ture of about 28.5° F. (17) ; hence, it is necessary to keep them above 

 this temperature. In practice, storage temperatures of 30° to 32° have 

 been found most satisfactory (15). 



Magness and others (10) found that the rate of respiration largely 

 governs the rate of ripening and softening of apples in storage. They 

 found that at 40° F. this rate is approximately twice as rapid as at 32°, 

 at 50° it is almost double that at 40°, and at 70° it is about twice as fast 

 as at 50°. At 30°, on the other hand, 25 percent longer time is required 

 for apples to ripen than at 32°. From these results, therefore, the 

 extreme importance of quickly cooling apples to the minimum safe 

 temperature for storage is readily apparent, because the apples will 

 ripen as much in 1 day at 70° as they will in 10 days at 30°. Holding 

 apples at 70° for only 3 days after harvest thus will cut off about a 

 month of their potential storage life at 30°. If 30° storage is not im- 

 mediately available, every opportunity should be used to cool the fruit, 

 such as stacking it in the shade and providing good ventilation, espe- 

 cially at night (fig. 1, A). The same principle applies after storage. 

 It is therefore inadvisable to remove from cold storage at one time more 

 apples than can be used or marketed before they deteriorate seriously. 

 It must also be remembered that after storage the span of life remain- 

 ing for the fruit is much shortened, and as the end point is uncertain, 

 the gamble in holding at warm temperatures is much greater. 



Cooling the fruit means the transfer of heat from the fruit to the 

 air surrounding the fruit. The effectiveness of the cooling depends on 

 the difference between the temperature of the air and that of the fruit 

 and the rate at which the air moves over the fruit. In common stor- 



