Can you reheat coffee?

In this brief guide, we are going to answer the question “can you reheat coffee” with an in-depth analysis of whether or not you can reheat coffee. Moreover, we are going to discuss the chemistry of coffee oxidation.

So without much ado, let’s dive in and figure out more about it.

Can you reheat coffee?

You can reheat coffee as reheating the coffee does not destroy its caffeine content. The difference that it will make is the change in the flavor and freshness of the brewed coffee. The reheated coffee will taste more bitter. 

Green (unroasted) coffee includes chlorogenic acids, which are broken down during the roasting process into quinic acid (which has a flavor similar to quinine in tonic water) and caffeic acid. While chlorogenic acid has a bitter flavor, quinic acid and caffeic acid have a more pronounced bitter, astringent flavor.

When you reheat your coffee, you stimulate the production of quinic and caffeic acid, giving your coffee an even more bitter, astringent, gnarly flavor.

And that is the very reason behind the increased bitterness of reheated coffee but as long as you are okay with it, you can devour a cup of reheated coffee.

The chemistry of coffee oxidation

When coffee beans come into touch with air, they oxidize, and the same is true for cold brew coffee that is kept out in the open for a while. 

This oxidation reaction has a considerable impact on the aroma and flavor of the coffee while having no effect on the color of the coffee.

The oxidation reaction occurs during the brewing of coffee. When coffee beans come into contact with water, they begin releasing aromatics, oils, and acids into the water, resulting in an enriched and flavorful coffee. However, if the oxidation process continues after that, it will result in a strong and bitter flavor, which we do not want.

Why does coffee turn bitter?

At the point when you leave your cold brew coffee to sit for a long time, the reaction between hydrogen and oxygen will raise its pH level, making it taste bitter or stale. Therefore you should never let your cold brew sit for too long in the open.

You can read about different coffee brewing methods here.

Tips to properly store coffee

You can keep your coffee fresh in the fridge by considering the following quick tips

  1. You should not add anything to the coffee if you want to save it for some time in the fridge. The addition of milk or creamers significantly lessens the life of coffee. Therefore you should add them after reheating the coffee.
  1. Coffee loses its characteristic taste and aroma when it comes in contact with the air owing to the oxidation reaction. Therefore to seal the freshness of coffee for quite a long I recommend you to store it in air-tight containers.
  1. An important thing to consider is to always use an airtight container or bottle to store the coffee so that it will not pick up the smell of other foods placed in your fridge as no one will ever want to consume melon scented brewed coffee, right?
  1. If you want to make your coffee last longer in the fridge then it is advised to store it in the fridge as soon as you brew it to preserve its flavor and aroma.

Ways to spot old coffee

Different indicators point out old coffee. Appearance, smell, and taste play an important role as indicators to tell whether or not your coffee has gone bad.


The freshly roasted coffee beans have a shiny appearance, so if the coffee grains you have are dull and matte then it is an indication that they are old and have left their prime age.


The coffee beans that have gone bad will lack the characteristic aroma of the coffee.


In the case of brewed coffee, a lack of flavor or too much bitter flavor points out that your coffee has gone bad.

Health implications of drinking old coffee

Consuming the old brewed coffee without milk or sugar won’t affect your health that much but surely the brewed coffee that has gone bad will have lost its characteristic scent and flavor and will have an awful taste that won’t give you a good mouthfeel. 

But accidentally consuming a brewed coffee that has gone bad and contained dairy products like milk or creamers in it will put your gut health at stake and can cause gastrointestinal issues like nausea, vomiting, diarrhea, and abdominal cramps.

Other FAQs about Coffee that you may be interested in.

How does coffee wake you up?

How does Starbucks decaffeinate its coffee?

What to do if I accidentally bought whole coffee beans?


In this brief guide, we answered the question “can you reheat coffee” with an in-depth analysis of whether or not you can reheat coffee. Moreover, we discussed the chemistry of coffee oxidation.