How long can coffee sit out

How Long Can Coffee Sit Out + Pro Tips & Hacks

It’s happened to all of us i.e. not drinking your entire coffee. But what happens to your poor half-consumed cups of coffee after you leave for work? Is it safe to drink it once you get back home? How long can coffee sit out?

Although it will start going bad after 30 minutes of so, coffee can still sit out for a couple of hours – but only if refrigerated or stored in an airtight thermos.

If black coffee is a part of your morning routine, it might not taste as good in the afternoon, although it will still be drinkable.

Even coffee with milk can make for a perfectly fine drink after hours of sitting out if you refrigerate before you come back from work.

All that you have to do is simply put your drink in the microwave to make it nice and hot and it’ll still have a very good taste.

Honestly, you don’t have to waste a single cup of your precious coffee anymore… and here is how!

The Process of Coffee Oxidation Explained

As soon as you expose roasted coffee grounds to oxygen, heat, and/or moisture, the associated oxidization process kicks off.

Now, although you can’t see oxidization happening, you can most certainly taste it as this is what makes your coffee go bad.

Once coffee gets in touch with the air, the chemical process starts and it makes the flavor compounds deteriorate.

But what you might not know is that brewing coffee encourages oxidization as water makes the coffee beans release acids, oils, and aromatics.

So when you brew fresh ground coffee, oxidization helps with producing flavorful cups.

How long can coffee sit out, woman drinking coffee

Is Freshly-Brewed Coffee Immune to Oxidation Though?

No – even freshly brewed coffee is subject to oxidation, which is the main reason why your coffee doesn’t taste the same after sitting out longer than 30 minutes!

Another factor that should be taken into account is the freshness of your grounds that can affect the oxidation process as well.

In essence, the higher the exposure to air – the staler your coffee grounds will be.

If you are using already-stale grounds, then your coffee will oxidize much faster once you brew it.

Thus, if you’re after a full-bodied and great tasting coffee, make sure to store the roasted beans properly and you will ensure they remain good for at least a couple of weeks.

How long can coffee sit out, coffee splash

Will My Coffee Turn Bitter After 30 Minutes?

Yes, although it will only turn slightly more bitter i.e. not entirely bitter.

Yet, the longer your coffee sits, meaning the longer the oxidation process works, the pH level in your cup will continue climbing.

The result?

Bitter or stale-tasting coffee that you won’t be too happy about.

With that being said, the way how you store your coffee after brewing it also plays a significant part.

For example – coffee that sits out for a couple of hours in a brewing pot at room temperature will definitely taste bitter.

But if you are really in a rush, store it in a thermos bottle or any other type of airtight container.

This will slow down oxidation and help your coffee retain most of its amazing original flavor.

Is it Safe to Drink Day-Old Milk Coffee?

Yes, it is – but only if you refrigerate it beforehand.

If you let that cup sit out for the whole day, it is likely that it will turn rancid.

That’s because milk accumulates mold when you keep it outside the fridge for more than 2 hours, which applies especially to coffee that has milk in it.

Not only will your coffee with milk taste and smell rather unpleasantly, but the mold can actually make you sick.

As a general rule of thumb, stay away from coffee that you haven’t stored properly (e.g. in an airtight container) once brewed.

But what if you have a coffee that’s starting to go bad?

Take it out of the fridge, put it in the microwave and enjoy a hot cup of Joe.

Microwaving will kill most of the bacteria so the beverage will be safe to consume.

How to Tell if Your Coffee Is Bad?

If you notice rancid or bitter notes in your cup of Joe, then this means that it went bad.

Rancid beans can and will make your coffee taste differently and not in a good way.

And the same goes for coffee beans that might have mold or mildew on them.

Thus, discard all of the beans that show off any signs of mold or discoloration as they can spoil your beverage.

This applies to both instant and ground coffee too.

Keeping ground coffee in a wet container will make the powder change its color and you will probably spot some mold.

Unfortunately, when you’ve already steamed your coffee, there is no other way to tell if it went bad but to have a sip or two.

How long can coffee sit out, woman enjoying a cup of coffee

How to Improve the Taste of My Cups?

You can make your coffee taste better by adding cinnamon, nutmeg and salt to your coffee grounds.

These ingredients can slow down oxidation or mask the stale flavor of your coffee.

Yet, how do you improve the taste of your freshly-brewed cups?

You can partially restore its flavor by adding some more coffee and sugar to it.

That’s doable due to the fact that stale coffee usually has a bland taste but it is still drinkable.

However, if you notice no difference after adding more coffee and sugar, it could be that your ground coffee was already bad so there is nothing you can do about it other than discarding it.

Can You Leave Coffee Overnight?

Yes you can, but only if it’s refrigerated.

For example, non-refrigerated black coffee will go bad within 24 hours.

Sure – bacteria, fungi and yeast grow slowly and you can’t really see them.

But that doesn’t mean your coffee will be drinkable after you leave it out of the fridge overnight.

Still, we don’t recommend making this a rule since nothing can beat the fresh and bold taste of a freshly-brewed cup.

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What Material Is Best For Storing Coffee?

Airtight containers, tainted glass and porcelain are the best options, as both will retain most of the original taste of your java.

Storing it in a plastic container will make the content smell plastic-like after only a couple of hours and that’s a big no-no.

On the other hand, stainless steel is a so-so option, as the coffee might change its taste, although not as much as when stored in a plastic container.

Can You Use Coffee Grounds Twice?

You can, but only in a short time interval.

If you, for whatever reason, can’t finish your cup within 15 minutes after it’s been brewed, you can reuse the same grounds to make a new cup within the next couple of hours.

However, it is almost certain the taste of your coffee will be nowhere near as close to that of freshly-brewed grounds.


Now that you know the answer to ‘how long can coffee sit out’, you should be much more alert when it comes to not finishing your cup of Joe.

So from now on, you will either store it properly or simply brew another cup when you are back home.

Now – have you ever left your favorite beverage unrefrigerated?

And could you spot any difference?

Leave your answers in the comments section below!

Last update on 2023-09-23 / Affiliate links / Images from Amazon Product Advertising API

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