Why Does Black Coffee Taste Bitter?

We all know that coffee-making is not as easy as it sounds, as getting a perfectly sweet-tasting cup of black coffee takes a lot of effort. However, despite their greatest efforts, all coffee lovers have ended up with a bitter-tasting drink instead and probably have gone back and forth trying to understand what went wrong during the process. So, why does black coffee end up tasting bitter?

Black coffee can taste bitter for many reasons. These reasons include the over-extraction of the coffee and using the wrong grind size for the wrong brewing method. Using dark roasted coffee beans and water that is too hot or cold can also make black coffee taste bitter.  

There is nothing worse than having a cup of black coffee that has an unfavorable bitter taste, especially when you spent a lot of time and effort brewing it. As mentioned above, there are many reasons why your black cup of coffee tastes bitter. However, we have selected four reasons to discuss in more detail. We will also explore ways to reduce the bitterness of the coffee.

Why Does Black Coffee Taste Bitter?

Although there is a scientific explanation for why coffee, in general, is bitter, that being due to its caffeine content. However, caffeine only accounts for about 10-15% of the bitterness of the coffee. There are many other reasons why coffee can be bitter. These reasons include the following:

  • Over-extraction of the coffee.
  • Using the wrong grind size for the wrong brewing method.
  • Using dark-roasted coffee beans.
  • The temperature of the water is too hot or cold.

Let us discuss these reasons in more detail.

Over-Extraction Of The Coffee

One of the most common reasons for black coffee being bitter is when it has been over-extracted. Over-extraction means that too much soluble material in the coffee beans has been dissolved in the water. These soluble materials impact the flavor and aroma of the coffee.

The following table presents the various soluble materials found in coffee beans and the flavor each one brings.

Soluble MaterialFlavor
CarbohydratesBitterness And Viscosity
CaffeineBitterness
LipidsViscosity
AcidsSour And Sweet Flavors
SugarsViscosity And Sweetness

Over-extracted coffee occurs when:

  • Grounded coffee beans and water have been in contact for too long.
  • The water-to-ground coffee ratio is not right.

Therefore, when over-extraction of coffee occurs, the water breaks down the soluble materials of the coffee beans and causes them to disintegrate in the water resulting in an unpleasant bitter, and thin-tasting cup of black coffee.

The Wrong Grind Size For The Wrong Brewing Method

Each brewing method requires a particular grind size, and using the wrong grind size will indeed result in a bitter cup of black coffee. Although grinding coffee beans help extract most of the flavors out of the coffee beans, having them too fine or coarse result in bitterness.

The table below presents the correct grind size for each brewing technique.

Grind SizeBrewing Method/Technique
Extra CoarseCold Brew
CoarseFrench Press
Medium (Similar to grains of sand)Pour-Over/Drip
Medium To FineMoka Pot
Fine (Similar to salt)Espresso
Extra FineTurkish

Dark Roasted Coffee Beans Were Used

When it comes to the different roasts of coffee beans, it is evident that each one will have its own unique aroma and flavor. Light, medium, and dark-roasted coffee beans also vary in bitterness, with dark-roasted coffee beans being the most bitter. Therefore, if you have brewed a black cup of coffee with dark-roasted coffee beans and it has an unfavorable bitter taste, the roast is definitely the culprit.

The bitterness of dark-roasted coffee results from the breakdown of sugars that eventually carbonize in the roast process. Once the sugars in the coffee beans start to carbonize, they become bitter and burnt.

Furthermore, the longer the coffee beans are roasted, the more soluble they become, which ultimately increases the chances of over-extraction, which, as discussed above, is another reason for black coffee tasting bitter.

The Temperature Of The Water Is Too Hot/Cold

When it comes to brewing a black cup of coffee, the temperature of the water plays a significant role in taste and flavor. If the water is overboiled, the end result will, without a doubt, be a bitter-tasting cup of black coffee, as water that is too hot releases the bitter compounds found in coffee beans. Black coffee can also taste bitter if the water used in the brewing process is too cold.

It is ideal to have the water between 195 and 205 degrees Fahrenheit, approximately two to three minutes off the boil. Keeping the temperature of the water within this range will give you a sweeter-tasting cup of black coffee.

Ways To Reduce The Bitterness Of Black Coffee

Although a bitter-tasting cup of black coffee is extremely frustrating, there are ways to reduce the bitterness to at least make it a little more enjoyable. Let us look at how you can get rid of that nasty bitter taste.

  1. Add Milk Or Cream To Black Coffee. Adding milk or cream to bitter black coffee reduces the bitterness as the fat content counteracts the bitterness.
  2. Add Salt To Black Coffee. Putting a dash of table salt in your bitter black cup of coffee suppresses the bitterness and enhances the other favorable flavors of the coffee.
  3. Add Sugar To Black Coffee. Adding white or brown sugar will overpower the bitterness and give the coffee a sweeter taste.

Conclusion

While some coffee lovers might enjoy a bitter cup of black coffee, others find it frustrating, especially if they do not know the reason for the bitterness in the coffee. Over-extraction of the coffee, using the wrong grind size for the wrong brewing method, using dark-roasted coffee beans, and having the water too hot or cold are all valid reasons for a bitter-tasting cup of coffee.

Although bitterness in coffee is unfavorable for most coffee lovers, there are ways to reduce the bitter flavor. Add a splash of cream or milk, a dash of salt, or simply some white or brown sugar for a sweeter-tasting cup of black coffee!

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