What Makes Coffee Bitter? Extraction Explained

what makes coffee bitter

If, like me, you are an avid coffee drinker, then you will know that feeling when you take a sip of a freshly brewed cup and realize that for some reason it has become incredibly bitter. The taste has been ruined, and you don’t simply want to add loads of sugar to make it drinkable.

While coffee may be associated with a bitter taste, this is not supposed to be the dominant note- for sure there are variety of flavors that may come through depending on the particular beans that you use, but what makes coffee bitter?

Why Is My Coffee Bitter?

There are actually four different reasons why this may occur. As you’ll probably know- there’s a particular art to making the perfect cup of coffee. It isn’t as simple as just adding boiling water to ground beans, and the way that you prepare your drink has major implications on how the final product turns out.

It all comes down to what is known as ‘extraction’. This is the process by which the flavors are released from the coffee into the water. Chemical reactions allow the flavor compounds to dissolve into the water. By extracting only the right chemicals you will be rewarded with a perfect brew, but if you over extract the coffee, too many of the wrong chemicals are released and you’ll be left with a bitter tasting mess.

The four main reasons over extraction can occur are:

1. Steeping the coffee for too long

Simply leaving the ground coffee in the water for too long will cause more and more chemicals to release from the bean, and the drink will become bitter. This often happens when making coffee in a Cafetiere because once you have pushed down the plunger the coffee is still exposed to the water and continues to release its compounds.


You have probably noticed that sometimes the first cup you pour tastes perfect, but each subsequent one tastes gradually more bitter. To avoid this effect I’d recommend pouring all of the coffee into another container once it has been brewed, and that way it will remain perfectly fresh.

2. The water is too hot

It may come as a surprise to some, but coffee has an optimal temperature at which the beans release their flavor, and it can be very easy to burn the bean. There are various theories as to the perfect temperature, but they tend to range between 195°F and 205°F.


Important to note here is that water boils at 212°F so you should never pour recently boiled water onto your ground coffee. Leave it for a few minutes before you do, and you’ll find your coffee tasting far better.

3. The wrong size of ground coffee

As I said earlier, the trick to making the perfect brew is all about extracting the right chemicals from the bean. Getting the perfect grind is crucial to ensuring this process happens in the best way possible. If it is too coarse then it will under-extract- causing the drink to be flat and sour tasting. If it is ground too fine then you will get an over-extracted, bitter brew.

 There is no right or wrong answer to getting the perfect grind. Through trial and error you will be able to find the perfect amount for you.

4. Dirty Equipment

Often you’ll want your brew as quickly as possible in the morning to get going, but don’t forget to give your equipment a thorough clean after each use. This can often be the cause of bitter coffee because residue from previous blends can ruin your new batch.

What Makes Coffee Bitter? Conclusion

To conclude, bitter coffee can ruin your favorite pick-me-up, but is easily avoided if you take time to understand the brewing process and how to maximize its efficiency. The combination of flavors all comes from extracting the coffee bean in the right way and should never taste only bitter. Luckily if it does there are a few things to watch out for to prevent it from happening again:

  • Water temperature (do not use boiling water)
  • Clean your equipmen
  • Grind the bean differently
  • Don’t let it continue to brew when sitting in a Cafetiere

Following these steps will help you achieve the best tasting coffee, and never again will you wonder what makes coffee bitter.


If you have any further questions then please ask them in the comments section below, and be sure to let us know if the advice here has helped you to achieve the perfect brew.

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