A hot mug of fresh coffee is a great way to keep yourself going whenever you're having a stressful day, but if you have leftover coffee you didn’t have time to finish, then it’s vital to know how long your coffee can sit out before going bad.
I'll cover everything you need to know, including the consequences of leaving out different types of brewed coffee, the lifecycle of the leftover coffee, and what happens to the taste.
Read on to find out all the details about the popular question, "how long can coffee sit out?"
How Long Can Coffee Safely Sit Out At Room Temperature?
The length of time leftover coffee can sit out varies depending on the coffee you're drinking. Cold brew coffee, iced coffee, and black coffee will all differ.
The average times vary from 2-24 hours, depending on the type of leftover coffee you've got. I'll explain more below.
1. Black Brewed Coffee
One of the most popular styles of coffee is the classic plain black coffee. It's simple, easy, and practical to make and drink.
Assuming you don't add dairy at a later stage, then your leftover coffee should last for 24 hours.
It's important to note, though, that brewing coffee creates a unique flavor that dissipates after roughly 30 minutes.
2. Coffee With Milk In It
Whole bean coffee has a long shelf life, including when you produce ground coffee from it and make it into black coffee.
However, if you've added milk to leftover coffee, your drink will last for far less time.
When you let leftover coffee sit with milk, it will only be suitable for 2 hours. After that, the milk in your coffee will curdle.
3. Iced Coffee
Iced coffee is hot coffee with added ice, and when it becomes leftover coffee, it lasts for about as long as plain black coffee before the flavor begins to degrade completely.
Because the ice melts, it will be watered down and not taste as good, but you will still be able to drink it.
4. Cold Brew Coffee
Cold brew coffee has a shorter lifespan than iced coffee, which surprised me, but there's a good reason for it.
Starting cold means it goes bad sooner. The average lifespan for leftover cold brewed coffee is roughly 12 hours.
5. French Press Made Coffee
Brewing coffee made with a French Press is more volatile in terms of leftover coffee.
The extraction process continues if you leave the coffee inside the French Press, so you'll need to take your brewed coffee out and set it aside.
If you do this without adding milk, it should last 24 hours.
6. Starbucks Coffee
If your leftover coffee is a commercial purchase from Starbucks, leave it for a few days maximum. Just like your own brewed coffee, it will lose its flavor and freshness within 30 minutes.
The longer you leave it, the worse it will taste when you get around to it. If it has dairy in it and has been sitting there a few hours, it's time to toss it.
7. Coffee Creamer
In my opinion, leftover coffee creamer doesn't last long because it degrades fast. Left on the kitchen counter, it won't be worth using after about 2 hours.
This means if you're having coffee with creamer, you should finish your cold coffee within a few hours. It may still taste off, but it will be drinkable.
The Lifecycle Of Your Leftover Coffee (Oxidization Explained)
Freshly brewed coffee has a lifecycle from when the coffee beans are harvested to when you finish the last sip from your coffee pot.
After your roasted coffee beans have been processed into your morning coffee, they won't stay fresh for long!
You can drink day-old coffee without any health risks, but I wouldn't recommend drinking coffee any older than that.
The reason is that coffee has a shelf life before it's processed and then a short window after when it's not stale.
Assuming your coffee beans have been made into cold brew, ground coffee, black coffee, or another preferred variety, the next 30 minutes are vital.
Its signature aromatic compounds will degrade, even at room temperature. You’re then left with stale coffee, which is still safe to drink but won’t taste good at all.
One major reason for this is oxidization. Once brewed, coffee is immediately assaulted by heat, moisture, and airborne scents.
The longer that coffee leftover from your last drink remains like this, the worse things become.
Eventually, the flavor compounds break down, and your cup of coffee develops a bitter and stale taste.
Specifically, the oils, aromas, and flavors in a fresh cup of coffee are known as the 'solubles.' These oxidize once exposed to the air, so it's best to keep coffee grounds in a tightly sealed container.
It limits the oxidization of the highly volatile aromatic compounds in your coffee.
This means that after 24 hours, plenty of oxidization will have taken place in your old coffee, and you’ll find it has a sour taste even if it was a flavorful cup at the beginning.
It’s again worth bearing in mind that if you have coffee with milk, this will curdle as the oxidization occurs, making it taste bad very fast.
What Happens To Coffee That's Left Out
Now that I've covered some of the basics about what happens to a perfect cup of coffee after 30 minutes, regardless of the brewing method, I'll get into some extra detail about the specific changes. So when you notice an unpleasant smell and poor taste, this is what's happening.
The Flavor Will Deteriorate
Whether you've got store-brewed coffee or cold-brewed coffee, you'll notice one of the first things to go is the flavor. Within a few hours, your fresh pot of coffee just won't be the same.
The compounds that give your coffee its delicious taste break apart. When making coffee, the flavor comes under attack from the elements as soon as your coffee maker starts pouring it into the cup.
The Milk In Your Coffee Will Go Bad In Only 2 Hours
Whether you’ve had a fine Starbucks latte or used coffee grounds from an airtight container, it doesn’t make a difference to the milk added.
Once it’s mixed with a hot drink like coffee, it doesn’t do well after 2 hours. The milk just spoils.
Coffee Oils Will Go Rancid With Time
Even if you’ve ensured you’re not using stale grounds for the process of brewing coffee, there’s still a huge difference in the quality of the coffee oils as time goes on.
As your drink sits, the old coffee oils degrade sharply.
It's still safe to drink for 24 hours at room temperature, but day-old coffee won't taste nice at all. The reasons are oxidization and its effects on day-old coffee, as covered in the previous section.
The Caffeine Content Will Be Preserved
When you drink coffee hot, a big part of the satisfaction comes from the caffeine kick it gives. That's why it's my favorite drink in the morning before work.
Some even better news is that it will still have that effect. The caffeine in your drink will be preserved for as long as you leave your cold brew concentrate or black coffee to sit.
Just make sure you don't have too much coffee!
Molds or Bacteria Could Start To Appear
Storing brewed coffee is vital for another reason: if you leave it too long, it can get moldy and infected by bacteria.
Aspergillus and fusarium are described as "natural coffee contaminants" in a study featured in the Pathogens journal.[1]
It can grow on old coffee, so it's important to be vigilant about this if you're dealing with leftover coffee. The best practice I recommend is to leave it no longer than one full day before drinking it.
Failing that, you can make coffee safe to drink by storing that coffee in the fridge as a last resort.
According to Healthline, if placed in a sealed container, this should keep it “safe to consume for 3-4 days”.[2]
Why Does Coffee Taste Stale After Sitting Out?
If you find that your coffee is stale after leaving it to sit out at room temp for a while, then there are several reasons.
I've gone through the main aspects in the previous parts of the article, but there are some special cases to keep in mind.
When you have too many coffee grounds gathered inside your coffee maker, you’ll find that even your fresh coffee might taste stale.
This is because the oils from the grounds have decayed and been left inside the machine. If you have coffee with dairy or iced coffee, the time you have is much less.
Milk curdles fast, and iced coffee melts.
If you have a coffee start to your day each morning, you'll probably be used to drinking it quickly. If it goes stale, then it's definitely been left too long.
The different elements which make up the coffee, besides the hot water, will degrade. This includes the oils, the aromas, and the flavor compounds.
Generally, your coffee will go cold after 30 minutes, and the taste will be pretty rancid. However, if you need to keep it sitting out for longer, then 24 hours is as long as you should leave it.
Tips To Store Brewed Coffee
If you’ve wondered how long is brewed coffee going to last because you need to store it, here are some helpful tips to keep it fresher for longer.
However, you should only do this if you really need to, as I think it’s best to consume your coffee sooner rather than later.
1. Don't Put Dairy In It
This tip may seem obvious, but it’s worth doing.
If you want to keep brewed coffee good for as long as possible, then the first thing you can do is not mix milk with your hot water and coffee grounds.
This way, you can extend the life of your coffee from 2 hours to 24.
2. Put It In The Refrigerator
I mentioned this in regards to protecting your coffee from mold and bacteria, but the reason it’s effective for that is that it increases the lifespan of your old coffee.
Refrigeration slows down decay and gives you more time to drink your coffee.
3. Use An Airtight Container (Thermos)
It's always wise to keep your fresh coffee in an airtight container when you store it. This vastly slows down the oxidization process.
It also means you have a handy way to transport your coffee if you need to take it with you on a commute, and you can even drink day-old coffee if you have to.
I still wouldn't recommend it as it won't taste good.
Common Questions About Coffee Going Off
Does coffee go bad in the refrigerator?
Eventually, your drink will go bad even if you keep coffee in the fridge. It's not a permanent solution, so you can expect to get about 6 extra days maximum. However, it may start to go off after just 3-4 days. If you add milk, the time will be considerably less.
When can you drink day-old leftover coffee?
In most cases, you won't want to drink coffee after a day old. It will taste off, and it's more efficient to make another cup than to use an existing one. If you need to, just ensure you haven't added any dairy.
How long does the caffeine stay in brewed coffee?
Caffeine content stays roughly the same in coffee, even after you’ve brewed it and left it sitting for a while. The oils, aromas, and compounds degrade, but caffeine doesn’t follow this pattern.
How long can coffee beans sit out?
Unlike freshly made coffee, the whole beans decay far slower. You can leave them on the kitchen counter for 1-2 weeks, even if they're not in an airtight container. Still, you should make use of them within that period to get the freshest possible coffee.
Conclusion
Coffee can sit out for varying lengths of time depending on whether it’s in bean form or dispensed into a cup and whether it contains dairy.
Still, it should now be clear why there is a fixed 2-24 hour window for coffee that’s brewed, regardless of the style of coffee you’re drinking.
The only exception is if you refrigerate it, in which case you get 2-6 days more time.
References:
1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9024902/
2. https://www.healthline.com/nutrition/how-long-does-coffee-last
