The 2014 hops harvest is firmly in the rearview mirror, and, like squirrels caching stores for the winter, many of us are stocking up on fresh hops to sustain us until next autumn. Keeping a few common varieties on hand gives you flexibility to homebrew spur of the moment, but maintaining a stash of Humulus lupulus does mean paying attention to a few storage considerations.
Keep Hops Away from Oxygen
Oxygen is enemy number one in the fight to keep your hops fresh, as it is with pretty much every other aspect of homebrewing (yeast reproduction excepted). Oxygen degrades the precious oils that are responsible for the wonderful flavors and aromas that hops deliver, and over time, oxidized hops take on a distinctive aroma that’s not unlike aged cheese (you’ll know it when you smell it).
Oxygen also breaks down the alpha acids that deliver bitterness, which is why you’ll sometimes hear about the hops storage index (HSI), which quantifies how quickly different hops varieties lose their bitterness with time. The HSI attempts to quantify how much of the available alpha acids remain after six months’ storage. An HSI of 30 percent means that 6 months after harvest, the hops theoretically possesses 70 percent of its original bittering potential.