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Hops
Hop Perishability
Hop components (such as alpha acids and essential oils) undergo changes as soon as they are harvested. The rate of loss is dependent in part on storage conditions and on the variety and condition of the hops when baled.
Although hops deteriorate with storage, the aging process can be slowed with refrigeration, anaerobic packaging, and minimizing contact with light. Of these three, refrigeration is the most important, followed by anaerobic packaging. For optimum preservation, hops should be stored at a temperature of 2ºC. The hops should be packaged in barrier bags that are either vacuum packed or flushed with an inert gas such as nitrogen or carbon dioxide. Badly stored hops cause the alpha acids to oxidize, and some of the oxidation components are responsible for off tastes in the beer, such as "rancid" or "cheesy" odors or "oily" or "sour" flavors.
Click on the following topics for more information on hops.