Freezing roasted coffee can help to prolong its freshness, but it’s a tricky business. Here are some guidelines on when and how to do it.
When?
As you will see below, getting your coffee safely through a freeze/thaw cycle is a bit complicated. Because of all the work involved, you wouldn’t want to do it unless you really have to.
You should only freeze coffee that you want to store for a long time (about 2-12 months). Your plan should be to pack it away for a while, then get it out and use it all up. You really want to avoid freezing a large amount of coffee then getting it out periodically to brew a bit and put it back. Why, you ask? Because every time you open the package, you expose the coffee to oxygen and maybe even moisture.
How?
The most important thing to remember about freezing coffee is that it needs to already be rested (see the Freshness page) and placed in an airtight container with very little air in it. The less space there is in your container, the less oxygen and moisture there is to degrade your coffee. A vacuum sealed bag is a good option.
In this image, the bag on the left was properly rested before vacuum sealing, while the bag on the right was sealed immediately after roasting. The picture was taken 2 days after the bag was sealed. Notice that the unrested coffee has released so much CO2 that the bag is about to burst.
Once your coffee is sealed in a container with very little oxygen and moisture, it can be safely placed in the freezer for up to a year, or so.
To prepare your coffee for use after it has been frozen, all you need to do is thaw it out. Thawing should be at room temperature in the unopened container it was frozen in. This is important because cold coffee beans exposed to room temperature air will immediately begin to form condensation. Oops, now you’ve started brewing coffee!
Give your coffee a good long time to thaw. 24 hours seems like a good bet, though overnight might be long enough. After thawing, you can open the container, grind, and brew as usual. If you have coffee left, store it normally. Refreezing is not recommended.
