Freezing coffee is widespread nowadays and is a great way to preserve freshness. There have been numerous studies which show that freezing coffee halts deterioration. I don't know about you, but I find it rather distressing to know that I have several bags of coffee open on my shelf and that they will be past their best by the time I can drink them. In this short article I do not want to argue that freezing coffee is a good idea but rather take this as a starting point and give you some practical pointers and freezing best practices.
The container for freezing coffee should be as airtight as possible and contain as little air as possible, in other words don't use a big container for a small amount of beans. We need to decide whether we want to freeze single doses or larger amounts of beans which can be consumed in a week or less. I'll discuss both options below but first I'll outline my basic approach.
When I buy a new bag of coffee or have some beans I have just roasted myself, I first let them degas. In the first few days, coffee may still taste one-dimensional or flat. Brewed as espresso it might a sharp or biting edge to it. The topic of how long coffee should rest and how to rest it best is another big topic and I think I should discuss this in a separate blog post, but as a very general rule of thumb one to two weeks is a good starting point for many coffees. Very dark coffees need less time and very light coffees might need longer. Some roasteries might give you guidance for their coffees here. La Cabra, for example, recommend on their website: "We recommend resting our coffees for at least 10 days and maintain that often find excellent results, especially for particularly dense coffees, beyond 6 weeks." When I suspect that a coffee might be approaching a good drinking age (based on past experience with similar coffees), I will open the bag and brew a cup. If it still tastes a little closed still a little, I might give it a few more days. This in itself is a very interesting experience. After a while you get a good sense of when a coffee is at its peak. Don't get too hung up on this at first thought, because even if you don't drink or freeze your coffee at its absolute peak it will be better than leaving an open bag in the cupboard and coming back to it 8 weeks later.
When the coffee is at its peak it's time to freeze it. I then decide whether I want to freeze an amount that I'll defrost and then use for a few days or whether I'll freeze individual doses. This decision is made on the basis of how special it is, how I'll be brewing it, and how much time I have to fiddle around with weighing and freezing coffee.
Freezing larger amounts
I'd recommend freezing an amount that you can drink in a few days to a week. After all the coffee was frozen at it's peak so once you defrost it, it's decline will commence. The simplest way to do this is just squeeze the air out of the bag, put a little sticky tape over the degassing valve, put this bag into a further ziplock freezer bag for good measure and pop it in the freezer. Job done. When you defrost it be sure that it has completely defrosted before you open the bag! Otherwise, water condenses on the beans and spoils them. Here you just defrost the coffee once and then store the beans at room temperature in an airtight container. Simple. You will often hear that they will deteriorate more quickly after freezing. I'm not sure that this is really the case - I can't say I've ever noticed this. You will often also hear that re-freezing is a mortal sin. I'm also not convinced, and have been forced to do this following longer power cuts for example. But what you definitely don't want to do is keep opening a bag of frozen coffee, taking out your coffee and then putting it back in the freezer!
Freezing single doses
The second option is freezing single doses of coffee beans. You can freeze them in centrifuge tubes (50ml tubes will fit 20g of most medium or light coffee in at a push) or fancy single dosing coffee tubes, or you can use a vacuum sealer. If you use a vacuum sealer, do remove the air but do not remove the air to the extent that you crush the beans. If you freeze coffee in single doses, you might well want to grind your beans straight out of the freezer. It is often suggested that grinding frozen beans creates less fines. I'm not sure if this is apparent in the cup, but one could test this fairly easily in a blind tasting on a rainy afternoon (see my suggestion below). In any case, it is certainly very practical to not have to plan ahead and instead to just pluck a single dose from the freezer, grind and brew.
Keeping track of what's in the freezer
For larger bags of coffee I normally just write on the bag with a marker. (If I'm freezing in the bag the coffee came in, then even this might not be necessary.) For single dose tubes/bags I tend to number them and keep a little notebook in which I record the following information for each coffee:
name of coffee
origin and process
roaster
date roasted and date frozen
grind setting for brew method
(tasting notes)
little notebook from @lushwd
Ideas for experimentation
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Further reading
For those of you who want to dive deeper into the topic then I highly recommend this article