3. To study the response of fruit held for 1 month at 70° F. after being removed 

 from C.A. storage and fruit held for 1 month at 31° and a week at 70° after being re- 

 moved from C.A. storage. 



4. To compare the condition of fruit stored at 3 percent oxygen and no carbon 

 dioxide with that stored at 3 percent oxygen and 2 to 3 percent carbon dioxide. 



5. To permit commercial shippers of apples from the district to compare the fruit 

 from C.A. storage and from normal air storage. 



6. To evaluate the effectiveness of activated coconut-shell carbon air purification 

 for minimizing odors in C.A. storage. 



PROCEDURE 



Controlled- Atmosphere Cabinets and Their Operation 



The controlled atmospheres were maintained in 3 sheet-metal cabinets, each having 

 a volume of approximately 45 cubic feet. The structure of the cabinets and arrangement 

 of their loading pattern are illustrated in figure 1. The lids were bolted down after the 

 cabinets were loaded with fruit. Fifty c. f. m. of air was circulated by the fan from the 

 top of each cabinet, past the spray nozzle, and discharged tangentially in the glass scrub- 

 ber chamber to separate the spray droplets from the air stream. The air left the scrub- 

 ber chamber through the top center opening and passed through the duct to the plenunn 

 space beneath the false floor in the storage cabinet. Quarter-inch holes in the false floor 

 allowed the air to be distributed uniformly in the spaces between the box stacks. In one 

 cabinet (no. 3), the air at the fan inlet was drawn through an activated carbon filter of the 

 cannister type. Air ducts were made of 3 -inch polyethylene tubing. 



Undesired carbon dioxide was removed by passing the air through a caustic spray as 

 it entered the scrubber chamber. Pyrogallol was added to the caustic solution when it was 

 desired to remove both carbon dioxide and oxygen. The solution was circulated by an all- 

 iron gear-type pump, which had a capacity of 1 gallon per minute against a 10-foot head. 

 Individual pumps were provided for each cabinet, but the 3 pumps were nnounted on a 

 common stand and belt-driven by a single 1/4-hp. motor. Quantities of spray were varied 

 with a bypass around the spray nozzle of each cabinet. The caustic solution was circu- 

 lated in 3/4-inch polyethylene tubing. 



The caustic solution used in these tests was potassium hydroxide, to eliminate the 

 difficulties with the carbonate precipitate encountered with sodium hydroxide. Two of the 

 cabinets developed serious air leaks. In the cabinet having the least leakage, pyrogallol 

 was entirely effective in compensating for the leakage. In the cabinet with the greater 

 leakage, however, control was more difficult, and it was not possible to maintain the 

 oxygen concentration as low as originally intended. Carbon dioxide and oxygen concen- 

 trations were measured intermittently with an Orsat gas analyzer. 



Fruit and air temperatures in each cabinet were read at intervals from a hand- 

 balanced semiprecision potentiometer operated in conjunction with copper-constantan 

 thermocouples placed in and near the boxes marked "T" in figure 1. The cabinets were 

 located in a refrigerated storage room. No refrigeration apparatus was placed within the 

 cabinets. The refrigerated room was kept slightly cooler than the 31° temperature 

 desired in the cabinets to compensate for the respiratory heat of the fruit and heat input 

 from the fans and pumps. The average temperatures for each cabinet for the storage 

 season are listed in table 1. 



Just before the cabinets were opened, an air sample was drawn from each one and 

 analyzed for ethylene and nonethylenic volatiles by the method described by Gerhardt (4). 



