This post (in keeping with the entirety of this blog so far!) is not an authoritative post, but more a way for me to store information I’ve learned so far which may possibly be of use to others. There will undoubtedly be inaccuracies and incoherence – if any readers spot such things please drop me a line through the comments and I’ll be only too happy to update where necessary!
As I mentioned in my last post, for my next brew I’m going to attempt brewing from a malt-extract recipe, rather than the pre-hopped all-in-one kits I’ve been using so far.
This, to me, represents a good next step between the simplicity of the kit approach (“just add water”) and the complexity of a full-grain mash. Using a malt-extract enables the home-brewer (ie me!) to get a feel for the effects of different types of hops and malts over the flavour, while still skipping past some of the more complex issues of water quality and mash-tun operation.
Using a recipe from the CAMRA Brew Your Own British Real Ale book, I’ve purchased four different types of hops for my next brew alongside various other ingredients.
All of the hops have come in 100g vacuum packs, yet in some cases a little as only a few grams of hops are required for the recipe. This leaves the obvious conundrum – what do I do with the rest of ’em?
As with everything brewing-related, the hops are (or at least, very recently were) a living thing, and as such are susceptible to degradation and contamination. Storing them for any length of time must be done correctly to avoid them not only becoming poor quality, but potentially (shock! horror!) ruining a future batch of beer (nooooooooo!).
I’m no chemist, so I’m not going to go into the details of a-acids, b-acids and essential oils – there are a number of sites on the internet which do this in far more detail and far more clearly than I would be capable of – it’s enough to understand that the a-acids are responsible for bitterness, the oils are responsible for aroma, and both begin to degrade as soon as the hops are harvested.
Different varieties of hops degrade at different rates and there are complex calculations for working out storageability and a-acid degradation rates. For our purposes as small-scale home brewers (as opposed to commercial hop harvesters) it’s enough to simply understand the reasons for degradation and have a rough estimate of storage times…
The main culprits in accelerating hop degradation are temperature, oxygen and light. For this reason, hops should ideally be stored in vacuum bags in a darkened freezer.
How long can I keep hops for?
For all the complex reasons I’ve skipped over above, it’s impossible to give a one-size-fits-all answer to this question.
- If you can’t find vacuum bags and just have access to zip-lock plastic bags, up to 1 month in the freezer should be ok.
- If you have a kitchen vacuum sealer and store the hops in the freezer, the hops should remain useable up to 6 months, although I would certainly advise using them sooner if possible.
- Storing hops reliably for any longer than 6 months will require a nitrogen gas flush and aluminised barrier bags.
Again – these timescales are a guideline only and your specific storage conditions / hop varieties may return a fairly wide range of results.
Another useful tip for hobbyist home brewers who don’t want to get too bogged down in calculations: table 1 on this page shows the percent lost (a standardised measure of hop degradation explained further here) for common hop varieties. Without needing to understand the details, you can quickly see which types of hops degrade faster than others by comparing the values in the Percent Lost (%) column – the higher the value, the faster the hops will degrade (all other variables being equal) and therefore the quicker you should use them…
If you want to know more, I recommend the following articles as a good starting point (all were used in the collation of information above…):
- Hop Storage: How to Get – and Keep – Your Hops’ Optimum Value
- Gorst Valley Hops: Hop Quality
- Brewing Hops Storage: Preserving Precious Hops