Q: In Volume I of the MBAA Practical Handbook for the Specialty Brewer, in the hops section, it was stated that freshly harvested hops should be aged for a minimum of 6-12 months before using. This caught me by surprise. I would have figured fresher the better. Really?
A: For some hops, particularly low alpha aroma varieties, the slow oxidation that occurs in baled whole hops kept at freezing storage temperatures (below 0 degrees C) over the course of several months will develop, improve and stabilize their flavors. This is due to the oxidation of certain compounds called sesquiterpenes. The oxidized sesquiterpenes develop complex flavors. However over aging the hops can also produce a harsh bitter quality and cheesy aromas. Most brewers are using pelleted hops so any request for aging would have to be made to the supplier and specified because once pelleted and packed into nitrogen flushed bags, the oxidation process is almost completely shut down.