We’ve all been there: you made too much coffee, and now you’re wondering how long coffee can sit out before it goes bad.
Well, you’re in luck. Black coffee can sit out for more than 24 hours and often up to one week before it starts to go bad. Meanwhile, coffee with cream or milk goes bad after only 1-2 hours.
Let’s dive deeper into how and why coffee goes bad and when you should think about maybe making a new cup instead of drinking old coffee.
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Plain Black Coffee
First of all, you need to know that black coffee doesn’t ever really go bad. Coffee is pretty stable, and even drinking days-old coffee won’t hurt you. Just make sure there’s no visible mold or bacteria growth.
A lack of protein and carbohydrates means there isn’t much for bacteria to work with.
That’s good news for those who often forget our morning coffee on the counter!
The truth is your leftover coffee won't kill you if you drink it a few hours after you brewed it. It will just be cold and bland (more on that later). But it will still give you that caffeine kick.
Keep in mind, though, that this only applies to black coffee. If you add anything like cream, sugar, or flavoring syrups, you’re working with a much shorter timeframe.
Coffee With Cream And Sugar
While the coffee itself won’t go bad quickly, the cream does. The cream starts to go bad in only 1-2 hours.
Potentially hazardous foods like milk must be stored outside the so-called “danger zone” of 40-140 degrees Fahrenheit.
Any food that sits in the danger zone for longer than two hours should be discarded.
Foods with a higher risk of rapid bacteria growth need to be consumed quickly to prevent discomfort.
So, as a general rule of thumb, I like to drink my lattes within an hour. But let’s be honest for a second, if you’re taking longer than one hour to drink a latte, you’re not getting the best experience.
If you want to save your leftover coffee with cream for tomorrow morning, stick it in the fridge. And it’s probably best to avoid the microwave and simply drink the leftover coffee cold.
What happens when you leave coffee out?
Any barista worth their weight in espresso will be able to tell you that coffee tastes better once it cools.
That’s right, coffee that’s allowed to cool down a little bit after brewing actually tastes better than piping hot coffee right off the pot.
In professional cuppings, we taste each coffee for five minutes to understand how a coffee’s taste changes as it cools down.
The result? Slightly cooler coffee actually tastes sweeter, fuller, and smoother than hot coffee. Coffee tastes best about 5 minutes after it’s finished brewing.
This happens due to oxidation, the process of oxygen breaking up compounds. The aroma and taste in your morning cup are comprised of chemical compounds susceptible to oxidation.
So, the oxidation process starts as soon as you start brewing, and it peaks around 3-5 minutes after you brew. Or at least the taste of the coffee peaks.
Anything after about 5 minutes starts to taste bland, flat, and cold.
Ever wonder why restaurants and gas stations serve scalding coffee? That’s to mask how stale the coffee is already. If you want to know how fresh a restaurant’s coffee is, let it cool down for a few minutes before taking your first sip.
The good news? After about 30 minutes, your coffee’s flavor will stop changing and stabilize. That’s why cold coffee almost always tastes the same.
Another thing to note is that caffeine doesn’t change. Caffeine is more stable than aroma and taste, so it will remain the same no matter how long your coffee has sat out.
Can you reheat coffee?
This question has sparked much debate in my life over the years.
In my opinion, there’s only one right answer, but there is a nuanced viewpoint that makes a lot of sense.
I believe that you should absolutely not reheat your leftover or extra coffee. As a trained barista and coffee lover, it hurts my soul when coffee gets popped into the microwave.
Reheating your coffee will degrade the flavor and leave you with bland and flat coffee.
Pro Tip: Instead of reheating leftover coffee, make a new drink! Add a couple of ice cubes, a splash of cold milk, and a spoonful of sugar to create a delicious iced coffee.
However, I understand that not everyone treats coffee the way I do. And I recognize that sometimes there are circumstances beyond our control.
In those cases, you most certainly can reheat your coffee. It’s not harmful or dangerous. It’s just a little strange. If you must reheat your coffee, the microwave is fine.
How does the brewing method change leftover coffee?
The truth is that the brewing method has a rather big impact on how long coffee stays fresh. Two brewing methods make the biggest difference: hot and cold brewing.
You see, heat plays a big part in the oxidation process that makes leftover coffee go stale. As in, heat speeds up the oxidation process.
So brewing hot will mean your coffee goes bad faster than cold brew.
Cold brew stays fresh for up to two weeks after brewing. That means you can enjoy delicious coffee up to two weeks after you brewed it. That’s impossible when brewing hot.
My advice: make batches you can drink within a week or so. And always store your cold brew in an airtight container in the fridge.