Back to the Beer Simple mail bag this week! More than one person expressed concern over keeping their hops fresh. To which I have this response: don't worry about it. In fact, buy more.
That picture at the top is my newest shipment of hops. Four pounds of pellets. I brew more than most, but I don't really use lots of hops. Altbiers and Pilsners are my usual "hoppy" beers. So have I lost my mind? Am I about to jam out a series of IPAs for the hell of it? Have I discovered that a hop-pellet-eating diet is great for treating hair loss?
Nope. I just don't worry about hop staling. I'll use those hops for at least a year. Maybe two.
When we talk about hop freshness, we're mainly discussing two elements of hops: alpha acid percentage (%AA) and essential oils (since so much of their flavor/aroma components derive from them). Brewers get concerned about a loss of either because it makes recipes unreliable and can significantly impact what you get out of your kegs and bottles.
To which I say, again: don't worry about it.
That's because both of these are highly stable, especially when stored properly. If you're not living in a mobile meth lab somewhere in New Mexico and storing your hops in the outdoor shower area in full sunlight, then in all likelihood you can buy hops with abandon and keep using them almost-forever without any concerns about freshness.
[NB: Before we go on, let me say that I'm always talking pellets here. A lot of this applies generally to whole flower hops, too, but they're not really my thing, so I can't promise anything if that's what you tend to prefer.]
Frozen: Not Just a Terrible Film With Massive Plot Holes Anymore
Storage temperature is the first thing to look at here. Generally speaking, anything that's kept cold takes longer to spoil, stale, develop, etc. Arrhenius' Rule tells us that chemical reactions double in speed for every 10C of temperature we add. If we turn that around, it tells us we can roughly halve the reaction times by reducing temperature by 10C.
So let's take a worst-case. You can find this data yourself from a variety of sources, but generally speaking you'll lose about half of the alpha acid potency and somewhere between 30-90% of essential oils in hops after six months.
"OH MY GOD!!! BUT I JUST BOUGHT A BUNCH OF HOPS! YOU'VE SCREWED ME!"
No, I haven't. Because those numbers assume you're storing the hops in open air at room temperature.
So let's take good ol' Arrhenius out for a spin. If we have a 10% Nugget hop, it'll be at 5% in six months (50% loss). But room temperature is 72F (or just over 22C). Put those hops in the fridge (average temperature being 2C, just to keep the math easy) and we're looking at half of half of that loss, or 12.5%, so our Nugget hops in the fridge are at about 8.75% AA six months later. Put them in the freezer and we drop it by another 20C (to -18C), so we're at half of half of that 12.5% loss, or 3.125%. So our theoretical Nugget hops are still rocking about a 9.7% AA level.
How long would it take to cut the AA% in half, then? Well, at that rate, it's a hell of a lot longer than you'll ever have those hops. Theoretically, we're talking about four half-life doubling steps down in temperature. 6 months at 22C, x 2 (down to 12C) x 2 (down to 2C) x 2 (down to -8C) x 2 (at -18C, or average freezer temperatures). 96 months, or eight years.
Essential oil survival is likewise extended dramatically. It's tough to calculate, but essential oils and their contribution potential is seriously unpredictable anyway, so you shouldn't buy into your own BS on how much you "know" they'll contribute in the first place. But storing them cold WILL reduce the rate at which those oils decay, in the same proportion that our AA% was reduced.
So buy that pound of hops, keep it in the freezer, and don't worry about it.
Everybody Just Hold Their Breath
The other enemy (well, one is light, but if they're in the freezer I doubt they see the light of day very often) is oxygen. Mostly when you buy hop they're vacuum-sealed and/or flushed with nitrogen to prevent staling, which is how hops vendors get away with selling the same crop for a year or more. In that relatively-inert environment, hops last a LONG time, especially when they're also frozen (which they are - and btw, freezer burn isn't possible in hops because of something to do with a lack of "free" moisture - ask a scientist).
Before you run out and buy a vacuum sealer and/or your very own cylinder of nitrogen, you should be aware that at least one study in the journal Comprehensive Review of Food Science & Food Safety found that simply reducing the oxygen by pushing it out mechanically (squeezing the air out of the bag) and then manually sealing it yields about 87% of the total benefit of a nitrogen flush.
So just get as much air out as you can and then seal that puppy up. Done and done.
Time v. Consistency
There's not much risk attached to buying lots of hops and storing them for a long time, but there is a slight loss, as noted herein. So why take the risk? Consistency.
First, the losses are small and predictable (and calculable). You'll have a good sense of about how close to "new" your hops are in terms of Alpha Acids and Essential Oils, and you can account for it in your recipes.
That very slight loss in consistency from batch to batch that we will experience will, in my view, be more than offset by the consistency we'll derive from learning how to use a discrete set of hop varieties. Constantly swapping out ingredients can be fun, but in brewing our goal is usually consistency - there's already a LOT of variability in the process. Why not stick with six or seven hop varieties for a year? You can always sub in specific additions for flavor and aroma, but most of your recipes are looking for a certain hop character - spicy, fruity, floral, herbal etc.
My view is that you'll probably make better beer overall, and more consistently, if you go get yourself a few one-pound bags of pellets and use them as your "base hops" for a year or two. And if anyone asks you about hop staling or aging - just forward them this link.
Keep it simple.