How Long Can Coffee Sit Out And Not Go Bad?

It’s not unheard of for a busy individual to brew a pot of coffee in the morning only to take a single sip then start running around doing busy things. This individual will then conceivably keep coming to the same pot of coffee that they brewed in the morning for refills and energy boosts throughout the day.

At least until the pot runs dry, and then repeat. You’ve probably done it more than a couple of times every week. The question is, how long can coffee sit out and not only still taste good but not go bad as well?

How Long Can Coffee Sit Out?

Your coffee can sit for 30 minutes! Once brewed, your coffee can sit out for about 30 minutes and still taste pretty good. It might be slightly cold, but it will still be tasty within that timeframe.

Unfortunately, after that, it starts deteriorating, and the flavor compounds are diminished with every passing hour. By the end of the day, while your coffee will still be good, but it won’t taste quite as good as it did within the first 30 minutes of brewing.

Cold brew coffee can last between 7 and 10 days when refrigerated. If the cold brew starts tasting a bit off, then you will know it has started to go bad. A diluted cold brew only lasts about two days before the flavor changes permanently.

Why Does Coffee Taste Different Once It Sits Out?

To understand why your coffee begins to taste a little different (less flavorful) when it sits out for longer than 30 minutes, you need to understand the process of coffee bean oxidation.

Have you ever sliced an apple in half and eaten only one half leaving the other half to sit for a little while? What did you find when you came back for it? The leftover half had started darkening around the sliced area, right?

That’s oxidation in action. It happens because the slicing of the apple exposed its insides to air which started causing oxidation.

The same thing happens with coffee beans. While this might not be quite as visible to the naked eye, it’s very much the same process. Oxidation typically has a significant effect on the taste of coffee and pretty much every other kind of food affected by this phenomenon.

For coffee, this process starts fairly early on. In fact, the moment coffee beans are ground, they become exposed to oxidation. This process is, however, slowed down when these beans are stored properly.

The brewing process is also actually oxidation in action. Whenever these beans come in contact with air and water, they start releasing their sweet aroma, coffee oils, and acids into that water as it heats. It’s this process that gives you that delicious cup of fresh coffee that you love so much.

Why Does Your Coffee Turn Bitter?

One of the main reasons your coffee begins to taste a little bitter after that magical 30-minute mark is because the oxidization process never stopped taking place. Once the coffee is brewed and in the pot, oxygen and hydrogen reactions will keep occurring, raising the coffee’s pH level in your pot. That’s what eventually makes it more bitter than it was at the start.

While leaving your coffee in a regular pot is a recipe for bitterness, later on, the worst kind of pot to use when you intend to let the coffee sit through the day is a French press.

Brewing your coffee using a French press almost ensures that your coffee will continue brewing even after pressing the plunger down. As long as your coffee is still in the press, it will keep brewing and, in just a few minutes, turn extremely bitter. In this case, your best bet is to simply pour your coffee into a mug or your chosen flask as soon as you are done brewing it.

Can Your Coffee Go Bad?

Can brewed coffee go bad? Yes, black coffee can go bad after sitting in the air for a long time. For example, should you accidentally leave some coffee in your drip machine and go on a trip for a week or so, you will come to find that there are some circles of mold around it. This process will occur much faster if you brew your coffee with milk.

However, the fact that black coffee is made with near-boiling water makes it rather sterile. This means that it can be good to drink for a much longer period. That, however, doesn’t mean that it will taste good. On the contrary, the flavor compounds will be completely ruined.

This means that you can drink your coffee even if it’s about a day old if you don’t mind the taste. However, some people can’t stand that “stale coffee” taste and would rather just brew a fresh cup every time.

Is Day Old Coffee Safe to Drink?

Yes, you can drink day-old coffee. If it’s black coffee, you can pretty much drink it straight from the flask or even cold. However, if mixed with milk, you might want to heat it some before drinking. It won’t taste as good as you are used to, but it will be safe to drink. 

Tips on How to Store Brewed Coffee, So It Lasts Longer

Now and again, you will have more coffee than you can drink within the same day. It happens when you brew a rather large pot thinking you have all the time in the world to drink it only to get called into the office for an emergency meeting.

Should you ever find yourself with too much coffee that you can drink but can’t bear to pour it down the drain, here are some tips that you can use to store it, so it doesn’t go rancid.

Don’t Use Dairy

Unlike pure black coffee, dairy products have a much shorter shelf life. This is especially true when left out at room temperature. Therefore, putting milk or coffee creamer in your coffee is inevitably going to shorten its shelf life too. While it’s not common practice, some people put the milk directly into the fresh pot of brewed coffee. A better approach would be to put milk or coffee creamer in individual coffee cups. This leaves the rest black and with a much longer shelf life.

Put It in an Airtight Container

Your coffee is going to start losing its taste after 30 minutes regardless, thanks to the oxidation process explained above. One way to slow this process down is to put your coffee inside an airtight container. If it’s a vacuumed flask, you will achieve at least two things: your coffee will remain fresh and safe for a much longer period and it will remain warmer for longer.

Here are some of the best vacuum flasks for brewed coffee

Last update on 2025-04-29 / Affiliate links / Images from Amazon Product Advertising API

Put Your Coffee in the Fridge

While this might seem like an obvious tip because people put pretty much everything in their refrigerators to make them keep longer, the truth is when it comes to coffee, we often forget that the same principles apply. One way to ensure that your coffee lasts longer is to keep leftover coffee refrigerated.

However, to do this successfully, you need to use an airtight container to store your coffee. The main reason for this is that should you leave your coffee in the fridge with everything else, including onions and last week’s casserole, that coffee will start tasting pretty much like everything else in that fridge. Imagine having onion-scented coffee in the morning?

The simple truth of the matter is that if you want to have delectable, flavorful coffee, the best approach would be to drink it within 30 minutes of coffee brewing. That, however, doesn’t mean that you can’t have it even 24 hours later. It’s just the taste and coffee flavor that will be slightly awful. When refrigerated in an airtight container, coffee can keep for up to 2 weeks without going bad. Day-old coffee just won’t taste as good, though.

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