Fruit from cabinet 1, with low oxygen and 2.4 percent carbon dioxide, and that from 

 cabinet 2, with low oxygen and only a trace of carbon dioxide, differed little in texture 

 and flavor. Carbon dioxide at these low concentrations apparently has little influence on 

 the fruit, the beneficial effect of the controUed-atmosphere storage being largely due to 

 the low oxygen. Fisher (3) reported that 5 percent carbon dioxide hastens the develop- 

 ment of mealiness. Apparently 2.4 percent is below the concentration which produces 

 this effect. 



The experience with the experimental cabinets demonstrates the importance of elimi- 

 nating air leakage in controlled-atmosphere storage. In cabinet 3 where leakage was 

 excessive, it was impossible to attain the desired low level of oxygen. An oxygen con- 

 centration of approximately 6 percent instead of the desired 3 percent was sufficient to 

 elinninate most of the benefit attributable to controlled-atmosphere storage. 



Some insight into the degree of tightness of stprage chambers can be gained by con- 

 sidering the annount of air leakage allowable to supply the oxygen requirements of the 

 fruit in the cabinet. Cabinet 2 contained approxinnately 300 pounds of Starking Delicious 

 and 265 pounds of Golden Delicious apples. If it is assumed that carbon dioxide produc- 

 tion and oxygen consumption are about half of that in normal air storage, approximately 

 1. 5 mg. of carbon dioxide per kg. of fruit per hour is produced and an equal amount of 

 oxygen is consumed. Therefore, the fruit in the cabinet requires 9, 220 mg. of oxygen 

 per 24 hours. This requirement is satisfied by air leakage of 1.34 cu. ft. per 24 hours 

 when an oxygen concentration of 2, 75 percent exists in the cabinet. When this air leakage 

 value is expressed as air changes per day with respect to gross cabinet volume, it 

 amounts to 0.03 air changes per day. Measurements of air-change rates for comnnercial 

 storages showed that air changed once or twice a day in relatively tight rooms and up to 

 10 times a day in other rooms (9). 



It was observed that the worst leaks occurred following occasional periods of higher 

 than normal temperatures in the cabinets, caused by refrigeration control failure. Pflug 

 and Dewey (7) and Pflug and Southwick (8) called attention to the important part tempera- 

 ture fluctuation plays in the leakage from controlled-atmosphere storage, and the ex- 

 perience with the metal cabinets is in line with their conclusions. 



The ability of the carbon-purification cannister in cabinet 3 to remain operative for 

 the entire season was a surprise; its efficiency probably was due to a diminution in the 

 volatile prodi cing characteristics of the fruit stored under modified atmosphere. Fidler 

 (2) reported that fruit stored in modified atmospheres produces nonethylenic volatiles at 

 a lower rate than similar fruit stored in air at the same temperature. Confirmation of 

 this point is shown by the following calculations: If the fruit produced volatiles at a rate 

 comparable to that observed in air storage early in the storage season, as reported by 

 Gerhardt (5), volatiles equivalent to approximately 1, 200 mg. of Ce(SO^)2 reduced would 

 be produced daily. Air leakage to balance this production and maintain the observed vola- 

 tile concentration in cabinet 2 would be 10.8 cu. ft. per day. The great difference be- 

 tween air leakage to balance oxygen requirements (l. 34 cu. ft. per day) and that to 

 balance the calculated volatile production indicates a reduction in rate of volatile pro- 

 duction similar to that observed by Fidler. 



The concentration of odors fromi the wooden boxes constituted such a serious factor 

 in the cabinets without ca'rbon that an off-flavor was carried by the fruit for some time 

 after its removal from C. A. storage. In keeping box odors and off-flavors from this 

 source at a minimum, air purification can perform an important and necessary function 

 in C. A. storage. On the basis of this experience, the writers recommend its use in such 

 storages and, for further experimental work, have equipped the other two cabinets with 

 carbon filters. 



- 13 - 



