Coffee Knowledge Base

20 February 2024

How does excessive bitterness in coffee occur?

How does excessive bitterness in coffee occur?

Like acidity is bitterness another important component of coffee's flavour. A minimal level of bitterness is always present and is a positive trait, because it balances the acidity and ensures that it comes through less sharply. As soon as the bitterness level is too strong, it starts to dominate the other flavours, and is perceived as a negative experience.

Bitterness is linked to over-extraction. The more you extract your coffee, the more the bitter substances can develop. The degree of extraction is also expressed as Total Dissolved Solids (TDS). You can use a TDS meter to measure it. Extraction is influenced by the water, roasting, temperature, extraction time, degree of grinding, number of grams used and brewing method.

Causes of bitterness include the following:

Degree of roasting

A darker roast eventually breaks down the positive acidity and reduces the sweetness of the coffee while increasing its bitterness.



A higher water temperature can increase the sense of bitterness.

Degree of grind

The finer the coffee is ground, the slower the water will seep through the coffee. Consequently, the contact time is longer and the level of extraction is higher.


The contact time/flow-through time/extraction time is mainly regulated by the number of grams used and the degree of grind. The more grams or the finer the grind the longer the flow-through time. In addition to that, you will notice that the flow-through time varies per type of coffee. Some coffees flow through faster than others. This is related to the bean’s porosity.

The importance of the type of coffee

Of course, you cannot overlook the importance of the type of coffee you choose. Lightly roasted coffee gives a broader flavour palette with very many different aromas. A dark roast destroys many aromas. A lighter roast will also accentuate the freshness , which contributes to a broad and soft but extremely aromatic and tasty coffee with a limited number of bitter substances.