-5- 



Extensive and careful experiments at Cornell University have demon- 

 strated that Mcintosh apples can be stored for the late spring market much 

 more satisfactorily at 40° F. in controlled-atmosphere storage than at 32° F. 

 in regular cold storage, Exp^-riments at the Massachusetts State College 

 support these findings. 



C on trol led-Atmo sphere Storage - THiat it is. Controlled-atmosphere storage 

 is "a"recently developed type of cold' storage. Instead of the usual air 

 (21^0 oxygen, a trace of carbon dioxide, and 78^0 nitrogen) in most ventilated 

 cold storage rooms, the three constituents of air are maintained at artifi- 

 cial levels. In controlled-atmosphere storage, the oxygen is maintained at 

 approximately 2%, carbon dioxide at 5^o, and nitrogen at 93^. The tempera- 

 ture is kept at 40° F. 



Vrhat it Doe s . 



rr This typo of storage is especially adapted to extend the 

 storage season of Ilclntosh, Apples from controlled-atmosphere storage 

 can be taken out in April and Uay in similar condition to those removed 

 from average 32° F. cold storage in January and February. 



2. Apples taken from controlled-atmosphere storage will usually 

 keep several days longer at room temperature than apples from ordinary 

 cold storage. 



3. The 40° F. temperature elirainates most internal brovming, 



4. Shrinkage losses due to decay are reduced, 



IIovj itWorks. Apples respire and in so doing they use oxygon and give 

 off "carbon 'dioxide. The rate of ripening and breakdovm of apples in stor- 

 age depend largely on the speed of this respiration. Therefore, any storage 

 condition that tends to retard or slow dovm tho respiration process prolongs 

 the storage life of tho fruit. The speed of respiration may be reduced in 

 several vvays, tvio of which are; (1) by lowering the temperature and, (2) 

 by reducing the amount of oxygon. In ordinary 32° F. storage, low temper- 

 ature alone is utilized; in controllod-atnosphoro storage, both 1 )v; temper- 

 ature and low oxygen operate to slov/ dovm respiration and, hence, ripening. 

 In short, apples "live" more sloi-^ljr over a longer period in this nev; type 

 of storage. 



Sp ecial St orage Room Re quirements. The maintenance of the artificial at- 

 mosphere requires that the st orage be practically gas- or air-tight. This 

 is achieved by special gas-proof linings (often galvanized sheet iron), 

 caulking compounds, and special enamel paints in both novz-ly-constructed and 

 remodeled rooras. Most we 11- cons true tod rooms can be made sufficiently gas- 

 tight for controlled aimosphore storage. 



Special Equipment Requirements. An atmospheric vmsher or scrubber to remove 

 carbon dioxide is necessary. V/lien a gas-tight room is filled v;-ith apples and 

 sealed up, respiration of the fruit proceeds quits normally. Oxygen is used 

 up; carbon dioxide is given off. As the room is gas-tight, the oxygen con- 

 tent is gradually lov/ored and the amount of carbon dioxide increased. Since 

 a high accumulation of carbon dioxide may be harmful, the concentration of 

 this gas usuallj'- is not allovrod to go above 5 percent, '^fhen this level is 

 reached, the atmosphere in the room is forced through a simple washer con- 

 taining a solution of caustic soda v/hich has the capacity to absorb carbon 



