Controlled Atmosphere Storage

One of the reasons that it is often not understood that even apples have their seasons, is that some varieties are available year round. We have come to expect them, and it has become rare that we have a gap in supply of our favorite apples. The reason we have the luxury of year-round availability is because of a process called controlled atmosphere storage, or "CA."
A simplified explanation of the process is that oxygen in the cooler is reduced from the approximately 21% in our atmosphere down to about 1%, and replaced with nitrogen. The carbon dioxide levels are controlled and the humidity is maintained at a very high 95%. Conditions may vary slightly depending on the particular apple being stored.
As we approach the new year, we may experience some diminishing in quality of the apples that have been stored in regular refrigeration for the 2 or 3 months after their normal harvest time. If we haven't had access to CA apples yet, you may think that your apple was not worth trying anymore. If you don't give up, you will find that the apples are back to their post-harvest quality and will remain pleasing until their supply is exhausted.
Controlled atmosphere storage has evolved since farmers in England began this practice prior to World War II. This is a routine and approved practice for certified organic apples.
—Allen Zimmerman, Produce Buyer