Controlled Atmosphere Storage
by Erin Otto
Apples in spring? You betcha! Thanks to some tricky storage.
Starting in about January, and up until the next harvest, most all apples and pears available in markets and from our growers have been kept in special storage called Controlled Atmosphere (CA) storage.
What is Controlled Atmosphere Storage?
CA storage is a non-chemical process that began in England before World War II when farmers noticed that their produce kept longer when it was stored in an airtight room. Now, special CA rooms are designed where apples and pears can be kept crisp and juicy by carefully controlling the temperature, the percentage of oxygen, and the humidity inside.
Apples and pears ripen through the process of taking in oxygen and giving off carbon dioxide. By controlling how much oxygen circulates throughout the storage room, the ripening process can be drastically slowed, almost halted, to keep the fruit fresh and crisp.
The air we breathe contains about 21 percent oxygen and 78 percent nitrogen. In a CA room, the oxygen levels are reduced to 1 or 2 percent, and the nitrogen is increased to replace most of the oxygen. Controlling these oxygen levels literally puts the apples to sleep and keeps them fresh for as long as 10 or 12 months.
Temperatures are also carefully regulated to a constant 32 to 36 degrees, and humidity is maintained at 95 percent (good conditions to shoot for when you store fresh apples at home!).
How is the Quality of the Fruit?
Chosen apples and pears are transferred to CA storage usually within hours of being harvested, locking in their fresh-picked qualities. The juiciness, crunchiness, and flavor of the fruit are very much the same as they were at harvest. The only noteworthy difference is in the storage life of the fruit.
How Long Will My Fruit Keep?
CA storage allows apples and pears to be stored for long periods of time while the fruit is actually in the Controlled Atmosphere rooms. Once it is removed from CA storage, it will start to break down a little bit quicker than freshly harvested fruit.
Our grower thinks you should be able to store your apples for about 2 months, but not much longer. Pears should keep for several weeks or up to a month in the fridge.
Whether you plan to use them all right away or try to store them a bit, it is always a good idea to keep fresh apples and pears cold (32-36 degrees is ideal), humid, and to remove any blemished fruit regularly.
If you do store your spring apples for a while, please come back to this page and tell us how it worked out in the comments section below! We’d love to hear your experience so others can benefit the next time we offer apples in the spring.
Is CA Storage Safe?
Even certified organic fruits can be stored in CA storage, so we think CA storage is very safe. It’s basically a switch-a-roo of the elements that make up our regular atmosphere that slows down the ripening process. It’s also very common. If you have bought apples in the United States between January and September, you have probably already eaten apples from CA storage.
A Familiar Analogy
If you are familiar with buying grains in sealed pails, you might relate the CA storage of fruit to the environment inside the pail. The oxygen absorbers or nitrogen packets inside the pail reduce the oxygen so the grains can be kept in long-term storage. This is a type of mini CA storage that extends the shelf life of the grains and also keeps insects from hatching since they need to breathe oxygen just like we do.
Any questions? Post a comment and we’ll do our best to answer.