Anyone searching for the perfect cup of coffee knows that it starts with the freshness of the bean.
But just how do you go about keeping it fresh?
Lots of people will tell you that the answer is putting it in the freezer.
After all, it does the job for food, right? But does freezing coffee really work in the same way?
Here we put that question to the test.
Read on for a detailed look at what happens to your coffee at very low temperatures.
You may find the results surprising!
Why bother with freezing at all?
Let’s start by reminding ourselves why freezing is even an option.
If you don’t know how long coffee beans last in the bag once opened, you’re about to get a shock. Forget those reassuring expiry dates on the pack. Coffee experts will tell you that for the best flavor, you should use up your beans within two weeks (1).
That’s because once they’ve been roasted, the beans release gases that start to make them go stale. Unless you share your home with lots of coffee lovers, using beans within a fortnight is going to prove challenging.
So begins the search for the perfect solution to prevent your coffee from going stale for as long as possible. Freezing is an obvious choice.
The science behind freezing
The Colonna and Smalls coffee shop in Bath, England teamed up with scientists from around the world to test what affected coffee flavor (2).
One of the factors they tested was the temperature. Would this research finally tell us whether we should freeze our beans?
At first, it seemed that the answer was “yes”. The scientists divided the beans into different sizes, temperatures, and countries of origin.
Then they ground the beans. Finally, they measured the size of the ground coffee particles and the range in size between the smallest and largest.
Why all this interest in the size of the coffee grounds?
Well, the smaller the grounds, the larger their surface area to volume ratio. And what that means is that more flavor and aroma should be extracted from them during brewing (3).
The difference between the sizes of individual grounds also matters because of what happens when coffee brews.
If the particles are in the water for too long or short a time, they can contribute unpleasant flavors. So you need to aim for the perfect brewing period.
That perfect brewing period depends on the size of the coffee particle. Smaller particles release flavor more quickly than larger ones.
As all your coffee particles will be in the water together, you want them as similar in size as possible.
The scientists found that the only factor that affected the size and variation of the particles was temperature.
And guess what? Cold beans produced smaller particles with less variation in size.
So that means freezing works – right?
Outside the lab
After the results of the research were published, a pile of articles popped up telling you to put your coffee beans in the freezer (4).
Unfortunately, the journalists hadn’t read the fine print.
That’s because the scientists were grinding their coffee in a lab. You and I will be making it in our kitchens. Why does that matter?
Well, the beans that the scientists found were associated with better flavor weren’t just cold. They were really cold.
The beans that should have given the best flavor of all had been stored in liquid nitrogen (5).
That’s a temperature of -321 degrees Fahrenheit. The next best were those stored in dry ice at -110.2 degrees Fahrenheit.
Do you have liquid nitrogen or dry ice in your kitchen? Me neither.
The scientists also tested beans stored at a mere -2.2 degrees Fahrenheit, the same temperature as a typical home freezer.
There was virtually no difference to the beans stored at room temperature. In other words, a home freezer just isn’t cold enough to really affect coffee flavor.
Freezing and moisture
It’s not just the temperature of your coffee beans that changes when you put them in the freezer.
The oils that give coffee its delicious flavor don’t respond well to moisture – and there’s plenty of moisture in your freezer.
The seal on the door is never completely airtight. Even if it were, air would be let in whenever you opened the door.
That air carries moisture, and in the cold environment of the freezer, it will form condensation.
If you take out the coffee and then put what’s left-back in the freezer, the problem will get even worse.
However quickly you do it, it won’t be quick enough to stop condensation forming in the container.
Condensation means moisture, and moisture breaks down those precious coffee oils (6).
If that wasn’t enough, there’s another problem with freezer storage…your food.
Coffee is porous. That’s a good thing if you want to recycle your used up coffee grounds to deodorize your freezer. It’s not so good if you haven’t used your beans yet.
They will absorb any smells from the food in your freezer and impair the flavor of your coffee.
The taste test
So all this sounds simple enough. There’s no need to bother freezing your coffee because it’s not cold enough to make a difference to the flavor. Plus you risk damaging your beans with moisture and nasty smells.
But you might argue that this is all a bit theoretical. None of the research we’ve talked about so far has actually involved people tasting coffee! Luckily for us, someone has filled that gap – and the results make for very interesting reading.
Ken Fox of www.home-barista.com carried out a blind espresso tasting to see whether people could tell the difference between fresh and frozen coffee. The fresh coffee he used had been roasted between 4 and 8 days earlier. The frozen coffee had been frozen for either 4 or 8 weeks.
The experiment was tightly controlled so that the tasters didn’t know which coffees they were tasting. They were also given long intervals between each tasting to avoid their ability to appreciate differences in flavor diminishing over time.
The tasters were asked to drink two shots of espresso in each tasting. They were then asked to mark each coffee in terms of its crema and intensity of aroma and flavor, and to say which they preferred.
Despite all three tasters being expert baristas, none of them could consistently distinguish between fresh and frozen coffee (7).
This YouTube video gives the result of one other person’s taste test, conducted under somewhat less scientific conditions.
Fresh vs frozen coffee
If even trained baristas can’t tell the difference between fresh and frozen coffee, maybe we can do what we like? Or maybe we shouldn’t worry about coffee storage at all?
Before you throw away your airtight containers, it’s worth noting that – as with the Colonna research – there were other factors that might limit the usefulness of Ken Fox’s findings when making coffee in your own home.
First of all, Ken roasted his own beans and froze them straight away. If you buy pre-roasted beans, there may be a delay in freezing that may (or may not) affect flavor.
Ken also said that his freezer was able to maintain low temperatures, though he didn’t say how low. Neither do we know how often he opened his freezer door. Of if had a bag of seafood next to his coffee jars.
Ken also noted that another barista, Jim Schulman, had undertaken less formal experiments “cupping” fresh and previously frozen coffee.
Jim reported correctly identifying the fresh coffee more often than was attributable to chance. But he went on to say that the differences were very subtle and difficult to describe.
In fact, he felt there was no more difference than between different roasting batches of the same coffee.
The right way to freeze your coffee
There’s a wealth of research into the way coffee grows stale after roasting. Keep it at room temperature, and it will be past its best after about two weeks.
But while there’s also plenty of theoretical reasons why freezing coffee should impair its flavor, the Ken Fox experiment suggests that in practice that need not happen – at least, not if you follow certain steps.
So if there’s a great offer on your favorite beans, don’t rule out buying more than usual and freezing them. Just make sure you follow these rules to get the best results.
1. Use whole beans and freeze at the correct interval from the roasting date
You want to capture the best possible flavor at the point of freezing.
That means getting the right balance between giving the beans time to let out gas and not losing their aromatics.
Some baristas maintain you should let lighter roasted beans rest for about a week after their roast date before freezing (8).
Medium and dark roasted beans, which degas more slowly, should be frozen within one or two days.
2. Split your beans into portions with enough for about a week in each one
Splitting your beans into batches will avoid the need to replace them in the freezer once they’ve been taken out.
You’ll reduce the risk of condensation forming in the container and causing moisture damage.
3. Store the beans in airtight containers
Ideally, vacuum seals the coffee beans. Alternatively, use Ziplock bags and remove as much air as possible before putting them in the freezer.
Don’t use the bag the beans were packaged in. It won’t be designed for freezer use, and you won’t be able to use all the beans in one go.
This YouTube video shows a range of different bagging options.
4. Keep your beans as far as possible from any smelly foods in the freezer
You don’t want strong smells to contaminate your coffee, so keep them as far away from your beans as possible.
You can also recycle used coffee grounds to deodorize your freezer.
Just put them in a couple of bowls and place them in the freezer to absorb the smells.
5. Allow the beans to reach room temperature before opening
Opening the bag as soon as it’s outside the freezer can cause condensation to form inside it, so be patient.
Beans should also be thoroughly defrosted before you use them. Any moisture in your frozen beans will cause your grinder to rust (9).
Beyond the bean
So far we’ve focussed on freezing whole coffee beans. There are, though, other ways your freezer can preserve the life of your favorite drink.
If you’ve ever wondered, “Can you freeze brewed coffee,” the answer is yes – sort of.
Don’t try heating it up and drinking it as you would have done at the time it was made. The flavor won’t be the same. You can, though, freeze the coffee in ice cube trays.
Add the frozen cubes to your iced coffee to keep it cool whilst avoiding diluting the flavor.
Although it horrifies coffee purists, some people can’t face grinding their own beans. If you’re one of them, you may be wondering how to store ground coffee.
The simple answer is that the freezer can help in much the same way as for whole beans.
For the best results, place the coffee in a vacuum-sealed bag. Leave about an inch of space at the end of the bag to allow for opening and resealing.
Then just pop it in the freezer away from any strong smells.
The question of whether or not to freeze coffee divides opinion. Scientific evidence suggests that very cold beans are more flavorful.
Others claim that condensation and freezer smell damage the taste of your drink.
Why not put it to the test yourself? Next time you buy coffee beans, put half in the freezer, and compare the results.
Follow our instructions for freezing and we challenge you to tell the difference!
If you have any questions, let us know in the comments.