10 



A closely related subject is that of ethylene scrubbing in 

 CA storages. Ethylene gas is the hormone that causes apples to 

 begin ripening and it has long been debated whether or not 

 ethylene levels in CA storages were important. The debate exists 

 largely because there has been no way of preventing ethylene build- 

 up, or of scrubbing it down to a very low concentration that is not 

 biologically active. Recently, Dr. Frank Liu and Dr. David 

 Blanpied at Cornell University have had impressive results in main- 

 taining Mcintosh firmness during storage when they have succeeded 

 in preventing ethylene buildup, although they have not always been 

 successful in preventing buildup. They presently think that a 

 commercial ethylene adsorbant plus special harvest and storage 

 management may be commercially successful, but the cost of the ad- 

 sorbant is high. They continue to test this approach. Meanwhile, 

 at Michigan State University Dr. David Dilley is using catalytic 

 burners to remove ethylene from storage atmospheres. His equip- 

 ment is still in the experimental stage, but his results are 

 encouraging. Perhaps "ethylene scrubbing" is approaching reality, 

 and if so a new dimension may be added to CA storage. 



In the early 1970 's, a high CO^ treatment was developed for 

 Golden Delicious apples in Washington State. The apples are 

 treated with a high CO^ environment for a few weeks at the begin- 

 ning of CA and they remain firmer much longer during CA. In 

 neighboring British Columbia, Golden Delicious were severely 

 injured by the treatment. Later tests in a number of areas showed 

 that Mcintosh were also too susceptible to injury from the treat- 

 ment. Dr. George Mattus has now found that Virginia Golden Deli- 

 cious can be successfully treated with high CO^ , so the - treatment 

 is now being used for the first time outside of Washington State. 



In British Columbia, Dr. O.L. Lau has found that "rapid CA" 

 is as effective as high-CO« treatment in retaining firmness during 

 storage. "Rapid CA" simply means reaching CA conditions within a 

 day or 2 after loading the room, and doing so produced fruit that 

 were 2 lbs. firmer at removal from storage than ones that had slow 

 pull-down. However, we believe that it is essential to thoroughly 

 cool the fruit before sealing a room and pulling it down. "Rapid 

 CA" would require very high cooling capacity or else a system for 



pre-cooling. Rapid pull-down makes good sense but not at the 



expense of thorough cooling. 



It should also be noted that in conventional CA, the CO2 level 

 is important to retention of firmness. Dr. D.H. Dewey at Michigan 

 State showed that putting dry lime into the CA room produces softer 

 apples by keeping CO^ too low in the room. 



Humidity in the storage is something that has been given little 

 attention, although it has long been recognized that too high a 

 humidity causes excess rotting and increases breakdown, while too 

 low humidity causes excess weight loss and can cause shrivelling. 



