My father has always drunk old coffee. He will make a cup in the morning then get distracted and finish it later. I remember finding one of these cold cups of coffee on the counter. I was about to throw it away when my father caught me and said “don’t throw that away, it’s still good!”. I couldn’t believe it.
Even back then I used to find old coffee completely disgusting. I have always felt that coffee should be drunk straight away or else it’s ruined. My palate has refined since, after years of tasting good and bad coffee. I can spot a reheated coffee even before tasting it. I bet you can too.
So if old coffee is bad, how long can we keep it on the hot plate, before brewing the next pot? We will show you how long can you drink from your coffee before dumping it and brewing fresh one. Is old, cold coffee ruined or is it still good? Read on to find out!
What Is a Good Coffee?
Coffee as a specialty beverage, has very little margin of error for brewing and manipulation. The days when coffee was a simple caffeine carrier are long gone. It is so easy to make great coffee to settle for average. Following a few simple rules will improve your daily cup tremendously.
So we will mostly address here the impact that time has on coffee from a taste perspective. We will also touch a bit on safety, but that is not our main concern.
What Factors Affect Brewed Coffee Shelf Life?
The brew method determines how long can we drink from fresh batch of coffee. There are various factors that come into play. Each brewing method has its own chemistry, and extracts a different set of compounds from the coffee bean. These compounds expire in a different ratio, depending on the temperature and the amount of time they are in contact with the air. There are two other factors that influence coffee freshness, and one of them might be a surprise for you:
In this article we are going to about three brewing methods - cold brew, espresso and drip coffee. To a certain extent, most other brew methods can be assimilated with one of these three, depending on the extraction temperature and the amount of water used.
Heat and coffee brewing
Heat is the strongest factor in influencing brewed coffee and determining its freshness. If we add heat to the brewing method (ie. hot water) everything is sped up.
Hot water causes the brewed coffee to oxidize quicker. During oxidation, coffee aromatics react with oxygen in the water, forming new compounds with different chemical properties. is the process where oxygen binds to is when the coffee loses its flavor and aroma. More about coffee oxidation here.
Oxidation is happening all the time with coffee but it is sped up by heat. This means that coffee brewed cold, without heat, lasts much longer than coffee brewed hot.
So, if heat speeds up oxidation, the longer we keep coffee hot, the faster oxidizes. Keep this in mind, we'll get back to it later.
Heat has another effect on coffee. Many compounds in coffee are volatile. Some of these compounds start to evaporate even before reaching the brewing temperatures. Why does this matter? Because when we reheat coffee, or we keep it hot longer, the volatile compounds disappear.
How Long Is Cold Brew Good for?
One of the main advantages of drinking cold brew coffee is that it lasts so much longer. Undiluted cold brew can be kept in the fridge for at least a week and even up to two weeks after it has been brewed and it will still taste delicious. Why is this? The main reason for cold brew coffee maintaining its freshness is, the absence of heat during preparation. You’ll notice I said ‘undiluted cold brew’. I’ll talk more about this in a bit.
The message here is that cold brew is a different beverage than your daily hot brew. And cold brew is not necessarily an iced coffee either, but it can be. We showed here the distinction between iced coffee and cold brew. For this reason, cold brew is a drink that can last for weeks in the fridge. In fact, this is strongly recommended for an immersion cold brew batch. But this is another discussion.
Espresso - Drink it within Minutes
Espresso is the coffee drink that expires the fastest. If you are drinking espresso by itself, without any hot milk or hot water, you really only have a few minutes before the coffee looks unappealing. The espresso shot gets cold and it looks unappealing within minutes from preparation.
A common misconception is that espresso should be drunk in one sip, as fast as possible. This is wrong. Drinking any coffee that hot, is not good. Coffee is best tasted when is close to the body temperature, (slightly warmer). Drink it slowly, especially if you have a double shot.
One of the main features of espresso for coffee drinkers is the crema. This layer of foam acts as a lid of sorts for the coffee and locks in the delicious flavors. The crema only lasts for a few minutes, however, and when it dissolves, the delicious coffee notes start to dissipate into the air and the brewed coffee loses its freshness.
The message here is that espresso is a fast coffee beverage. You prepare it fast, you drink it fast, and it expires fast.
How Long Is Brewed Coffee Good for? (Drip Coffee)
Drip coffee is the most interesting one to talk about. A pot of drip coffee will commonly be brewed in the morning in an office or at home and will be used for hours. Most day to day coffee drinkers are very happy to drink coffee in this way.
Is drinking from a pot of drip coffee for a few hours more acceptable than drinking an espresso an hour after it has been brewed? No. The message is the same. Brew only what you drink. This is why single serve coffee makers are so popular today. This is why we can see a return to brewing with manual drippers.
Coffee is Meant To Be Hot
Coffee is meant to be hot. That is what our parents and our culture tell us. We have been conditioned to expect coffee to be hot, unless it is an iced coffee or a cold brew that is!
If coffee is luke warm we are thoroughly unsatisfied and will most likely throw the coffee away, with the exception of the odd weirdo like my dad!
Drip coffee makers come with seemingly the best invention ever: the hot plate. It keeps the coffee hot, which is priority number one for most of us. If the coffee is hot, we are generally more forgiving about the taste, so even though the coffee has oxidized, we will still drink it.
I personally think that hot plates should not exist, period. Coffee on a hot plate keeps brewing and it slowly changes the taste. In the first 10 minutes the changes are minimal, but the longer we keep it on the hot plate, the worse the coffee becomes.
What Is the Solution?
The solution is to brew less coffee at a time. Just brew what you are going to drink. This may seem like a pain but we are only talking about an extra few minutes a day. It is easy to make this time and it is so worth it for a tasty cup of coffee every time.
What you really don’t want to be doing is adding extra hot water to brewed coffee in order to heat it up. This brings me onto the last factor in brewing that can influence the freshness of the coffee.
The Amount of Water
Firstly, when we add water to coffee after it has been brewed we are diluting the recipe. I have talked about this before so I won’t now, but basically the coffee won’t be balanced and it will taste bitter or wrong as a result. With drip coffee, it is already hot so we don’t need to add water and dilute the recipe when it goes cold.
Secondly, when we add water after brewing we are increasing oxidation. Any contact of coffee with foreign molecules found in air or water after brewing will cause more oxidation, will raise the ph level of the coffee which will cause it to taste bitter. This is why we can’t add cold water to our cold brew concentrate after it has been brewed when we are storing it!
The life of coffee
There are two major life stages in brewed coffee. The first stage is the oxidation stage. After about 30 minutes left out in the open, hot brewed coffee will have oxidized. This means that, technically, any coffee we drink after this time is ‘bad’ coffee.
There is, however, another stage when hot brewed coffee will deteriorate further. This happens at the 4 hour mark. This is when the oils go bad and the coffee becomes too acidic.
OK, there is a a third stage, but I am talking about it later in the page.
Tips for fresh coffee
You may be thinking: “well that’s all well and good but I don’t have the luxury of always brewing fresh coffee. I’m a busy person!” That is a good point and it is absolutely fair enough. Luckily, we have some tips for keeping your coffee delicious after it has been brewed.
Invest in a good thermos
This is really the most important thing we can do if we want to preserve our coffee. If you invest in a good thermos flask you will cut out the contact of the coffee with the air and the taste will last much longer, not to mention the heat.
Coffee health and safety
Now, we are moving beyond the taste of the coffee and talking about how long it is safe to drink for.
I hope none of my readers drink coffee older than a day. This is when mould starts to grow and bacteria to develop. After one day, you have a higher risk to drink infested coffee, even though at first sight, coffee looks good.
My sister in law’s grandmother (a tenuous connection) likes to keep a pot of coffee on the go for a few days, reheating each cup of coffee in the microwave. This is enough to make anyone shudder, but is it unsafe?
There is a myth that coffee left on the hot plate for a long period of time or reheated coffee can be carcinogenic or cancer causing. However, there is no scientific evidence to support this.
The real things we need to be wary of from a heath point of view are milk and mould. If you have added milk to your coffee, that milk will go off within two hours and you will give yourself food poisoning if you drink old, milky coffee.
The other health risk is mould. If you are drinking coffee from the day before, there could may be mould on the coffee, which is obviously not good for you.
Although I have seen this maybe a couple of times in my life, coffee can spoil. Bacteria can grow and spoil coffee, if mould doesn't before.
So, as it turns out, granny has it right. If you are determined to drink day old coffee, or old (hopefully not day old) milky coffee, it is best to put it in the microwave to heat it up. Then you will kill the harmful bacteria at any rate, though you won’t do much for the taste!
The answer to the question depends on your priorities. If you are a coffee aficionado, drink your hot coffee straight away or at the very least within half an hour. At 4 hours, hot brew coffee tastes and notes are completely ruined. If you’re not picky, you love lots of coffee and you’re anti-waste, drip coffee is a good solution. If you’re determined to drink old coffee, put it in the microwave to make sure it’s safe. Or you could just drink cold brew and not worry about any of it!