Recently, a reader of Craft Beer and Brewing Magazine asked us the following question:
Some of my club members are doing a bulk buy of hops. What is the best way to break them up and store them, and how long will they last?
You can certainly save some money by buying hops in bulk, especially if you have a few friends who can split the purchase. The downside, of course, is what to do with several pounds of hops you may not be able to use immediately.
The first thing you want to remember is that heat, light, and oxygen are all enemies of fresh hops. Heat and direct sunlight will break down many of the chemicals in hops more rapidly, both reducing their alpha- acid content and impacting their flavor. Oxygen accelerates the aging process, as well, which is why you find most commercial hops packaged now in foil barrier packages that are often purged with an inert gas such as nitrogen. The form of hops also matters. Whole-leaf hops, being loose and more exposed to oxygen, will not fare as well as pellet hops, which are compressed.
In an ideal world, you want to store your bulk hops in oxygen-purged, foil-lined packages at freezing temperatures. In reality, you’ll likely have to break up and repackage your bulk hops to use in individual batches and to share with friends. The best method for preparing your hops for storage is to use a vacuum-sealing machine; they are available for food storage at many home-goods stores. Some even work with foil and polyester film (e.g., Mylar) pouches. If you don’t have access to such a device, you want to get as close as you can. For example, you can purchase small polyester film pouches, add a prepackaged desiccant to each pouch to reduce the oxygen and moisture and then seal it. Even plastic freezer bags offer some protection, if you take care to remove as much oxygen as possible. Store these in the freezer to minimize the degradation that light and heat will cause over time.
How long your hops will last is determined by something called the Hop Storage Index (HSI), which varies by hops variety as well as by the temperature and packaging you use. The HSI measures the percentage of alpha acids lost in six months if the hops are stored at 68°F (20°C). From the HSI, you can use software or an online tool to estimate your alpha loss over time, but in practice, if you package, freeze, and store the hops properly, most varieties will last a year or more.