Cold coffee - does it make sense to heat it?
The right temperature affects the taste of coffee
Before we talk about how to reheat coffee, let's explain some chemical processes that occur during roasting, brewing and subsequent heating. It is these that have a major influence on the taste and aroma.
The green coffee bean contains more than 800 different compounds. For simplicity's sake, let's divide them into two groups:
- Non-volatile - these are substances that remain stable at any temperature, their quantity does not change. These are caffeine and chlorogenic acid.
- Volatile - this group includes all the compounds that give coffee its typical taste and aroma. They change or disappear with heat.
Roasting coffee
During roasting, thenon-volatile compounds contained in the coffee beans are broken down by heat to form other compounds that directly affect the flavour and aroma of the coffee. However, these compounds formed during roasting are very sensitive to heat and if the coffee is roasted longer, they will burn and the coffee will lose its taste and therefore its quality.
Coffee preparation
The next step in changing the chemical and therefore flavour composition is the final brewing. Hot water again extracts certain coffee compounds that are pleasing to our taste buds and olfactory cells.
However, too high a temperature will release undesirable substances (e.g. chlorogenic acids) which result in a bitter taste. Therefore, it is very important to ensure the correct water temperature in all processes.
Does it make sense to heat the coffee?
What do the preceding lines imply? Clearly that temperature laws work during roasting, brewing and heating in the same way. In all cases, we expose the coffee beans to heat and thus repeat the whole process of releasing coffee acids, compounds and oils.
By reheating, the coffee retains its caffeine content but loses its aroma and flavour. Instead, the bitterness of the caffeic acid will stand out.
For these reasons, it is best to avoid reheating the coffee and instead prepare fresh, fragrant and warm coffee. On the other hand, it's clear that there may be times when you don't feel like pouring out cold coffee and are looking for a way to reheat it.
What to look out for when heating coffee?
From the previous description, it is already clear that the right temperature is crucial. Therefore, always choose the lowest possible heating temperature to avoid negative chemical reactions as much as possible.
Heat the coffee evenly to a temperature of up to 60 °C. This temperature is lower than when brewing fresh. It is usually around 75 °C. This low temperature both mitigates most of the chemical changes and it has been found that most people prefer coffee at 60 °C because it gives the right taste experience.
How to reheat coffee while preserving its flavour and aroma
1. On the stove
Have you brewed a cup of coffee and suddenly noticed it has gone cold? Don't despair.
- Pour the coffee into a teapot, pot or saucepan and heat it on the stove.
- It must not boil. Once it starts to steam, take it off.
- Pour the coffee back into the mug and sip.
This method works only for coffee that is fresh and has not been sitting on the table for several hours. If you try to reheat forgotten coffee, you probably won't enjoy it.
2. In the microwave
Of course, you can also use the microwave to heat it up. However, there are rules to follow here too:
- Set themicrowave to medium power only.
- Place a mug of coffee in it andheat it at 30-second intervals.
This will reduce the likelihood of scorching, and therefore bittering. If this does happen, you can soften the bitter taste with cream or milk.
What to avoid when heating coffee?
- Don't heat coffee with milk or cream
Reheating can precipitate the milk components in the coffee and the resulting effect will not be pleasing to your eye, let alone your palate.
It is also important to remember that dairy products must be kept cool to prevent the spread of unwanted microbes. Just pouring milk or cream into your coffee and leaving it on the table for a long time, out of the fridge, will not add to its quality. If you choose to heat the drink extra, it cancause digestive problems after drinking it.
- Do not use the microwave at full power
Rapid heating to a very high temperature will burn the ingredients in the coffee, giving it aburnt aftertaste.
- Do not use constant heating on your coffee machine
Many drip coffee machines have a feature that keeps the beverage in the potwarm for several more hours after brewing. This may seem like a useful feature at first glance, but believe me, over time it detracts from the quality of the coffee you brew. It loses the integrity of its flavour and becomes bitter.
Although the coffee grounds remain in the filter when brewing drip coffee, some finely ground particles may escape into the pot (as they do when using a French press). The particles continue to boil during the heating process and this long leaching process brings back the unwanted bitterness.
How to prevent the coffee from going cold right away
To avoid unnecessary heating of the coffee, I recommend the following:
- Proper timing - there is nothing better than enjoying a cup of coffee sip by sip and to the fullest. So brew it when you know you will have enough time to drink it.
- Brew small batches - brew just enough to make a big cup of coffee that you can enjoy before it gets cold.
- The right coffee cup - you can also prolong the ideal coffee temperature by choosing the right cup. We found out whether porcelain, glass, ceramic or stoneware is better in our test.
- Thermo mug - You may use it on the road or in the car, but have you thought that the thermal insulation in this cup will allow your coffee to stay hot longer at home? You can do your emails in peace and the coffee doesn't have a chance to get cold in a moment.
- Get your iced coffee ready - Iced coffee or frappuccinos are becoming increasingly popular, especially in the summer months. By adding milk, ice cubes and possibly a flavoured syrup, you can conjure up a refreshing drink in no time and won't regret letting your favourite coffee go cold.