Why does coffee taste bitter ?

Extraction determines the taste

During brewing, hot water gradually extracts the various compounds from the ground coffee. Fruity acids and sweet flavours are extracted first, while the more pronounced bitter compounds emerge later. If the water passes through the ground coffee for too long or the grind is too fine, the coffee becomes over-extracted, resulting in a noticeably more bitter taste. Conversely, an extraction time that is too short often produces a coffee that is overly acidic and lacks balance.

The grind size makes all the difference

Grind size is a key factor. If the coffee is ground too finely, the contact time with the water increases, causing more bitter compounds to be extracted. If the grind is too coarse, on the other hand, the water flows through almost unhindered, resulting in coffee that tastes thin and often unpleasantly acidic. A useful rule of thumb is: the shorter the contact time with the water, the finer the grind can be. Espresso requires a much finer grind than filter coffee or French press coffee.

The roast influences bitterness

The roast has a significant influence on the character of a coffee. While lighter roasts often bring out fruity and vibrant flavours, darker roasts develop intense roasted aromas with a pleasant bitterness. At the same time, acidity decreases with longer roasting times. What matters is not whether a coffee has been roasted light or dark, but whether the respective roast profile is optimally suited to the beans. The aim is always to achieve a harmonious balance of sweetness, acidity and roasted aromas.

Keep an eye on temperature and brewing time

Water that is too hot can also have a negative effect on the taste. For most brewing methods, a water temperature between 92 and 96°C is recommended. Boiling water can extract more undesirable bitter compounds and mask subtle aromas. The correct brewing time is equally important. Even small adjustments can noticeably affect the taste.

Bitterness is not a sign of poor quality

A slight bitterness is part of the natural flavour profile of many coffees and is particularly desirable in espresso. It is only when bitter compounds become dominant and mask other flavours that the balance between the beans, grind size, amount of water and brewing time is no longer right.