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Why is coffee bitter?

Published: 2026-08-02 Author: World Gafei

Last Updated: 2026/08/02, Coffee has always been controversial. Some people say: How to call coffee without bitterness? Some people say that good coffee has a pleasant bitterness. There are also many people who say that good coffee should not have bitter taste! Suffering is bad! Why is coffee bitter? What is the meaning of this? When it comes to coffee's bitter ingredients, perhaps most people's first reaction is caffeine! So the caffeine is really

The bitterness of coffee has always been controversial. Some people say: how can it be called coffee if it is not bitter? Some people say: good coffee has a pleasant bitterness. There are many people say: good coffee should not have a bitter taste! Suffering is not good!

And why on earth is coffee bitter?

What do you mean by pleasant suffering?

When it comes to the bitter ingredients of coffee, perhaps most people's first reaction is caffeine! That caffeine is really a bad guy! It turns out that the bitter ingredient of caffeine comes from raw beans, is a bitter aftertaste, and its influence is only about 10% at most.

So what is the main ingredient of coffee that brings bitterness?

In order to solve this mystery that has plagued us for many years, Thomas Hofmann, a scientist at Technical University of Munich in Germany, decided to study the bitterness of coffee.

He filtered the brewed coffee and found that some of the molecules with the smallest molecular weight tasted the bitterest. So he used mass spectrometry to conduct a series of experiments and identified a molecule called chlorogenic acid lactone "chlorogenic acid lactone" as the culprit. (for convenience, let's call it Little Green Bar.)

Has this little green been available since the beginning of raw beans?

If we want to talk about Xiaolu, we must first talk about chlorogenic acid. To put it simply, chlorogenic acid exists in most plants and is produced by plants in the process of aerobic respiration. The small green is the coffee beans in the roasting process, decomposed from chlorogenic acid.

Does the baking degree have any effect on Little Green?

To this end, the researchers determined the content of small green in a series of coffee with different roasting degrees. Studies have shown that in the roasting process of coffee beans, the small green will increase with the deepening of the roasting degree. In light and moderate roasting, Little Green will only produce mild bitterness, which is what we call coffee characteristic, pleasant bitterness. As the baking time increases, the small green will be decomposed again and replaced by vinyl catechol polymer, which is the source of strong bitterness.

In this way, it is not difficult for us to understand why there is a saying in the world of curry-shallow sour, deep bitter. What we call pleasant bitterness is chlorogenic acid, and unpleasant bitterness is vinyl catechol polymer.

Is it true that the more chlorogenic acid, the better coffee with bitter taste?

The answer is, of course, no. Generally, the more chlorogenic acid in raw coffee beans, the worse the quality of cup testing. Many defective beans also have a lot of chlorogenic acid, so it is not the more chlorogenic acid the better.

For example, robusta coffee beans contain 7% Mel 11% chlorogenic acid, while Arabica coffee beans contain only 5% Mel 8% chlorogenic acid.

Is the deep-roasted coffee beans bad?

A cup of coffee is a complex drink made up of more than 30 chemicals, and it is these "compounds" that determine the taste, aroma and acidity of coffee. It is not that the bitterness caused by deep roasting is bad, but that each type of coffee bean has its own baking degree. According to the characteristics of each coffee bean, the roaster will choose the most suitable baking degree according to the characteristics of each coffee bean, and perfectly show the unique flavor of each coffee bean.

Source: TIMEMORE Coffee slow Life

FrontStreet Coffee is a long-established specialty coffee roaster in Guangzhou China, selling freshly roasted beans from its own farm in Yunnan as well as dozens of carefully selected single-origin beans from around the world for both pour-over and espresso. The products deliver consistently excellent quality and great value, with shipping within 24 hours. Guangzhou’s FrontStreet Coffee shop is recommended by many coffee lovers, and the beans are now available online at the Tmall 。