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How Long Can Leftover Coffee Sit Out?
Read to discover how long you are safe to leave the coffee out for.
Published November 11, 2021
Erik Hedlund
Coffee experts@The Coffee Lab
We’ve all drunk coffee that’s been sat out for a while, whether it has been sat on the counter all night or you’ve had that unlimited Americano they sell in restaurants. Yes, we’re all guilty of sipping old coffee, but do we know if it’s safe for us? When it comes to answering the question ‘how long can coffee sit out for?’, there are several factors that impact the shelf life. Typically, black coffee can be sat out for around 4-5 hours, but the flavour will change dramatically. If you’ve added any dairy products, including non-dairy milk, you’re looking at having a two-hour window before it’s no good. If you’re looking for absolute clarity on how long you are safe to leave the coffee out for, you’ve come to the right place. Continue reading for the ultimate guide on, ‘how long can you leave coffee out?’
Can You Drink Coffee That Has Been Sitting Out?
After you’ve brewed your coffee, you’ve got a 30-minute window to drink it before the taste begins to change notably. If the taste is that important to you, don’t be leaving your coffee out. Once you get past the two-hour mark, the coffee will lose its aromatic compounds alongside developing an off flavour.
Despite the changes taking place, you can leave your black brewed coffee out for over 24 hours at room temperature and it will still be safe to drink. That said, at that point, you can say goodbye to its original flavour. If you’ve added milk or other dairy products to your coffee, you can’t leave it out for longer than two hours at room temperature.
After brewing a pot and pouring yourself a coffee, you can put the leftovers in the fridge and you’re safe for around one week. Alternatively, if you’re storing cold brew, you can leave it in the fridge for 10-14 days.
No matter how you store your leftover coffee, the question of ‘how long can brewed coffee sit out’, isn’t as black and white as we first thought. You need to consider the container and the location of storage, as well as the colour of the coffee. Below, we will explore the lifecycle of your leftover coffee.
The Lifecycle of Your Leftover Coffee
Like most food and drink products, if you leave your coffee out for too long, it will go bad eventually. However, every person’s definition of ‘going bad’ is different. For example, some people will chuck food out once it’s past the “best before date”. Whereas, other people will examine the food and use it for an extra week if it smells and looks fine.
When it comes to coffee, the people that are particular about flavour will tell you not to leave your coffee out for longer than 30 minutes after brewing. On the flip side, some people will brew an entire pot and drink it throughout the week (without storing it in the fridge). This is all well and good, but how does coffee go bad if you leave it out? Below, we will examine each factor that contributes to making your coffee go bad.
Say Goodbye to Flavour
One of the fastest processes to take place in leftover coffee is oxidisation, which is the transference of electrons between different molecules. When it comes to your coffee’s amazing taste, it comes down to the aromatic compounds. Unfortunately, when they hit oxygen, these ‘aromas’ begin to break down. The hotter your coffee is, the faster the oxidisation process will happen. This is why the optimal window for leaving coffee out and retaining taste is 30 minutes.
With this in mind, if you reheat the coffee in the afternoon, you’re promoting even higher oxidisation rates. To avoid this happening, you should invest in a thermal mug that will help retain heat. These mugs are a great asset to any coffee lover, especially if they enjoy a hot coffee on the go.
To reduce oxidisation, you should be storing your coffee in an airtight container. If you can, go ahead and put it in the fridge. The low temperatures will slow down the rate of oxidisation. Even after taking these measures, your coffee will inevitably lose its taste once it has been brewed and sat around.
Bad Milk
To be deemed safe, milk should be stored at around 4.4°C. If milk and other dairy products rise in temperature, there is evidence to suggest that bacteria will begin to rapidly reproduce. If you consume it at this point, you’re more likely to get ill. As we’ve mentioned already, when you put milk in your coffee, this window puts the sit-out time at around two hours.
So, how long can oat milk sit out and other alternatives? When it comes to oat milk, the same rules apply because of the way the bacteria spreads through the milk. When it comes to non-dairy milk, although it can be left out longer, it’s best to follow the same rules. When you brew black coffee, you should add milk to each mug as opposed to the entire pot.
Rancid Oils
If you do any further reading on leaving coffee out, you will find mentions of oils in the coffee spoiling after around 4-5 hours - but what does this mean?
Rancidity is related to the oxidisation process but is to do with the oils in the coffee coming into contact with oxygen. When this reaction takes place, it will drastically change the taste of your coffee. Further, the process of rancidification can cause free radicals to form, which can have a diverse impact on human health. Through research, there has been no indication to suggest that the process takes place within 4-5 hours, but there is no doubt that it will happen eventually.
If you want to avoid rancidification, or at least slow it down, you should invest in an airtight container and store your brew in the fridge. Alternatively, you can pour your cuppa into a thermal mug that will keep your coffee warmer for longer.
Caffeine Will Survive
If you’re an absolute powerhouse that just loves coffee for the boost of caffeine, you’ll be relieved to know that caffeine will not deteriorate in your leftover coffee. Even if your coffee has been left out for weeks, you will still get an energetic buzz from it - but we wouldn’t suggest drinking coffee this old.
Despite still containing caffeine, if you’ve made a brew with freshly ground coffee, it will have a high antioxidant level. However, if your coffee is left out for a long time, the antioxidants will break down. This means that yes, your coffee will have caffeine, but it won’t hold the same benefits as the original coffee.
The Mould Stage
We’ve talked a lot about “does black coffee go bad?” and told you that black coffee will keep perfectly fine for weeks. However, this is only true if you keep it in the fridge. If you leave black coffee out at room temperature for around a week, you will start to see mould growing. Luckily, this process is fairly slow because it doesn’t have a high protein or carbohydrate content. When talking about whether you can drink day old coffee or not, it’s safe to say that you can without the risk of high bacteria levels.
Even though coffee takes a long time to go mouldy, you should remember to clean out your coffee machine and coffee pot regularly. If you fail to clean out your machine, you are inviting colonies of bacteria to make their home. Eventually, when you pour that fresh morning coffee, you will be consuming harmful bacteria and you may get ill.
What Impacts Shelf Life?
There are plenty of ways to alter the shelf life of your coffee, as mentioned above. One of the most effective ways to increase your coffee’s survival rate is by making a cold brew. The reason a cold brew lasts longer is that you aren’t exposing it to heat, meaning that oxidisation isn’t exacerbated. Typically, you need to store your cold brew at the same temperature as milk (4.4°C). If you do this, you can drink your cold brew for up to 14 days. However, if you leave it at room temperature, you should pour it away after three days max.
When it comes to the beans used to make coffee, everyone has a different preference. However, if you’re going to be leaving your coffee out, you should know that dark roast beans will lose flavour more rapidly than light roast. This is especially true if you’re reheating coffee because the dark roast bean has already had higher levels of heat applied.
Summary
Throughout this article, we’ve answered the questions ‘how long can black coffee sit out?’ and ‘how long can white coffee sit out?’. Essentially, if you’re dealing with black coffee, you can leave it out for extended periods before it starts to go off. You can extend the shelf life by using airtight containers and keeping your brew in the fridge. When it comes to coffee with milk or creamer added, you should consume it within two hours.
About the author
Erik Hedlund
With Era of We and The Coffee Lab, I hope to share knowledge, increase the value of coffee – and secure the future of coffee.
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