The idea that putting coffee in the freezer will help preserve it has been around for quite some time. In fact, I can remember my mom storing her pre-ground, store-bought coffee in the freezer for just this reason. I can also remember her abandoning the practice because she heard it was bunk.
So what’s the truth?
Can you freeze coffee to extend its shelf life? The short answer is “yes, but only if you do it properly.” What does “properly” mean when you’re trying to get the most out of your specialty coffee purchases? Let’s start by examining what happens chemically as coffee loses “freshness.”
The Chemistry of Coffee at its Peak
First things first: “fresh coffee” is actually not the best phrase to describe a coffee’s optimal brewing condition. Technically, the “freshest” coffee is one that has literally just been roasted. However, coffee needs to sit for a period of time after roasting before it’s going to live up to its flavor potential.
What we’re really talking about when we say “fresh roasted coffee” is coffee at its peak. Just like a piece of fruit has a window during which it’s going to be the best to eat, there’s a window during which roasted coffee is going to produce the best coffee tastes and aromas when brewed. You could brew it before the window opens (or after it closes), but the experience just isn’t going to be quite as good.
There are many factors that determine when and for how long a coffee maintains its peak. A couple of the most important ones are off-gassing and oxidation.
Off-Gassing
Off-gassing (a.k.a. “degassing”) is the process by which gasses (mostly CO2) trapped inside roasted coffee seep out over an extended period of time. A certain amount of off-gassing is beneficial. However, if coffee degasses too much, it begins to lose its flavor, aroma, and ability to produce crema.
Oxidation
Exposure to Oxygen causes a chemical reaction that sours flavor in roasted coffee. This is oxidation, and it’s the same process that causes metal to rust, fruit to over-ripen, and fire to burn.
Other Factors
It’s largely agreed that oxidation is the most impactful variable when it comes to a coffee’s staling. But it’s not alone. Temperature and moisture both affect a coffee’s degradation rate, as do a variety of other factors.
Ultimately, the hotter and wetter an environment is, the faster coffee will become stale.
Preserving Coffee’s Peak
So, the ideal environment for extending the life of roasted coffee is cold, dry, and devoid of Oxygen.
But how to create such an environment?
Storing coffee beans in the freezer may seem like a great option, but unless you have a commercial-grade chest freezer capable of reaching temperatures far lower than your standard Frigidaire, you’re not going to stall oxidation enough to matter much.
So, if you’re opening a bag of coffee to use every day and putting it back in the freezer (like my dear misinformed mother circa 2002), you’re constantly re-introducing Oxygen and moisture into the coffee’s environment, which will actually exacerbate the rate at which it stales.
There are, however, ways to freeze coffee “correctly” such that even regular folks can successfully save a beloved batch of coffee for later by storing it in the freezer.
Freezing Coffee Correctly
In order for freezing coffee to effectively slow down its staling, a few conditions must be met: first, you should only freeze whole beans. The surface area of ground coffee is great enough that it will absorb too much moisture and Oxygen, even when frozen, to maintain its peak.
Second, ensure the containers you’re using to freeze your coffee have as little moisture and Oxygen as possible. Basically, this means one of two things: either put whole, unopened bags of coffee directly in the freezer (assuming they’re air-tight and have one-way degassing valves), or portion single doses into smaller, resealable bags (zip lock bags are fine) and squeeze the air out before freezing.
If you want to ensure that every cup of coffee you brew is as “fresh” as possible, the single-dosing option is your best bet. This way you can keep your beans frozen as long as you need to and only take it out once you’re ready to use them.
Quick note: if you store coffee in freezer bags, you may notice the bags expanding—this is normal! As the coffee off-gasses in the freezer, the CO2 will fill the bags and actually help prevent oxidation. So, don’t let the CO2 out (unless the bag’s about to explode, of course).
There’s actually an added benefit of this storage plan—studies have shown that grinding frozen coffee improves consistency, so you’re likely to get better results overall.
If you do end up storing larger doses, it’s important to thaw them properly before opening the bags. Take the bag out of the freezer and let it sit until it’s close to room temperature (usually 1–3 hours, depending on the size of the bag), then wipe the outside of the bag down to remove any condensation—this will prevent the moisture from leaching directly into the super-dry beans when you open the bag.
When To Freeze Your Coffee
Ultimately, most people probably don’t have a compelling reason to be freezing coffee. If you’re picking up a bag at the coffee shop and finishing it over the course of a week or so, you’ll be just fine keeping it in a vacuum container on your shelf, or even leaving it in its bag (assuming it’s got a zip lock top and a one-way degassing valve).
If, however, you tend to acquire way more specialty beans than you could ever brew coffee with before they go bad (maybe you went to CoffeeCon or the SCA Expo and couldn’t control yourself), storing your unopened bags in the freezer until you have the opportunity to enjoy them is a great way to ensure you’ll actually be able to enjoy them when you get around to brewing—provided you do it properly, of course.
FAQ
Is freezing coffee beans a good idea?
Freezing coffee beans is a good idea if you do it right. Storing vacuum sealed coffee (i.e. no moisture or oxygen in the bag) in your freezer long-term will help to prevent it becoming stale like it would in your room temperature cabinet. However, storing open bags of coffee in the freezer will actually make it go stale faster than normal.
Can you freeze coffee beans in original packaging?
You can freeze coffee beans in their original packaging if you purchased your coffee in a vacuum sealed bag, or in one with a one-way degassing valve. If your coffee came in a paper bag, or one that otherwise allows air and moisture in and out, you’ll want to re-package it if you plan on freezing it.
How do you thaw frozen coffee beans?
The best way to thaw frozen coffee beans, if you’ve frozen them in single-doses, is to put them right into the grinder. Studies show that grinding frozen beans actually improves the consistency of your grind. If, however, you have a larger bag frozen, you’ll need to let it rise to room temperature and dry the bag thoroughly before opening it up—this will prevent the beans from absorbing too much moisture.
