When I’m making a pot of espresso I sometimes have a cup of brewed black coffee left over. Will it keep its caffeine if I put it in the fridge for later?
Brewed black coffee will keep its caffeine and flavor for up to five days if stored in a sealed glass container in the refrigerator. If you’ve already added milk, cream or sugar then this time will be cut to just a couple of days.
Let’s dive down into the subject of refrigerating brewed coffee in more detail, and discover how long the caffeine lasts when you do this, and how you should store your coffee to keep it fresh when in the fridge…
Does Refrigerated Coffee Lose Caffeine?
Good news: refrigerated coffee doesn’t lose caffeine. If you store your brewed coffee in the fridge, even for as long as a week, it may lose flavor but the caffeine kick will still remain.
Why doesn’t caffeine degrade or disappear over time? The chemical caffeine is water soluble, and won’t evaporate in ambient or refrigerated temperatures.
If you take a swig of your refrigerated coffee, it won’t taste as strong as it used to. This has nothing to do with the levels of caffeine, which remain unchanged. It’s because the oils that give coffee its flavor will gradually deteriorate.
You may have heard that cold brew coffee has less caffeine than a hot cup of Joe. This is only because cold brew coffee tends to be made with a lower ratio of coffee to water. The cold brewing and refrigeration process doesn’t change the quantity of caffeine at all.
How Long Does Caffeine Last in the Fridge?
The refrigerated caffeine will last as long as the coffee does. Actually, caffeine would outlast the other components of your brewed and refrigerated coffee, because it’s such a stable chemical.
However, by the time the coffee has lost a lot of its original flavor, there’s little point being left with a flask of tasteless chilled caffeine: brew a fresh batch.
How long will the coffee last? Certainly a day or two, and it can really help your morning schedule to brew and refrigerate your coffee the night before.
Some folks day up to five days is fine, while a few go for the whole week. We’re not convinced that it would still taste as good after seven days in the fridge, but certainly, a day or two is absolutely fine.
What about coffee that’s been made with milk or had milk or cream added? This will shorten its life considerably. If you want to make coffee in advance and store it in the fridge, keep it black.
Also, if you’re reheating the coffee, a brew that already has milk, cream, or sugar added might curdle as it warms up again: not pleasant.
What Happens if You Refrigerate Coffee?
Made too much coffee? Always refrigerate any excess that you hope to save. Coffee will keep oxidizing long after it’s brewed, becoming more and more bitter in flavor. Refrigerating it as soon as it’s cooled will pause this process, preserving your coffee.
As we’ve discussed, the caffeine component of your coffee won’t evaporate or sublimate in the fridge. However, with time, the delicious oils will start to deteriorate, and while this won’t harm you in any way, the coffee will lose some flavor and strength.
The coffee may also start to pick up other tastes and aromas. You know that “fridgy” taste that things get if you keep them in the refrigerator too long? Your brewed coffee will start to take on that flavor if stored for more than a few days.
It can also take on some taste from the container. Never store brewed coffee in something plastic, as it will take on a plasticky aroma. Metal flasks or something like a Chilly Bottle are better than plastic; however, you may still detect a metallic tang in your beverage.
The best way to store brewed coffee is in a glass container. If you can get hold of a sealed glass jar, that’s ideal. The quality of the seal is important: it keeps flavors in (and out) and prevents spills. You really don’t want to be mopping coffee out of your refrigerator.
What happens if you don’t put your excess coffee in the fridge? In terms of being safe to drink, brewed black coffee lasts up to 24 hours in ambient temperatures.
However, by then it will taste disgusting because it will have continued to oxidize. If you had already added the milk or cream before abandoning the brew, it shouldn’t be touched after a couple of hours.
How Long Does Coffee Hold Its Caffeine? (Even When Out of the Fridge)
Caffeine really is one tough chemical. Even after a week in the fridge, the caffeine level in the coffee won’t have gone down one bit.
Those old coffee grounds that you’ve added to the compost? The caffeine’s still there. (Don’t bother composting decaf grounds: they’re not as nutritious for the worms.)
So, whatever other chemical processes are happening to your coffee, stable caffeine hangs in there to the bitter (get it?) end.
So if you really, really need a caffeine hit and you have some five-day-old brew in the fridge, you’ll still get that kick, but the flavors won’t be as pronounced as they would be with a freshly brewed cup.
Try adding cream, sugar, and syrup to perk the flavors up again.
At What Temperature Does Caffeine Break Down?
We now know that caffeine easily survives in the refrigerator, but what about at high temperatures? The melting point of caffeine is around 460°F, which is higher than even a dark roasting (most roasts don’t go over 430°F).
Roast any higher than the super-hot 460°F point, and the coffee would be so cooked it would be virtually undrinkable, so the caffeine is pretty safe.
Given that caffeine is so stable and robust, how do they actually manage to make decaf coffee? There are two main ways: a chemical process and the newer Swiss Water method.
Both begin by soaking the coffee beans at the “green stage” (once the beans have been roasted, attempting to strip the caffeine out will also remove the flavor).
With chemical decaffeination, the soaked beans are covered with a food-safe solvent that draws out the caffeine. The Swiss Water method uses carbon to capture the caffeine.
This short film tells the history of decaf coffee (just be pleased that the decaffeination process doesn’t use the original chemicals…)
Even with these complex processes, some caffeine remains behind (decaf typically contains 2-3%). It really is one stubborn chemical.