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Where Does Coffee's Bitterness Come From? Does Roasting Increase Coffee's Bitterness?

Published: 2026-07-29 Author: FrontStreet Coffee

Last Updated: 2026/07/29, Professional coffee knowledge exchange. For more coffee bean information, please follow Coffee Workshop (WeChat public account: cafe_style). FrontStreet Coffee briefly describes where coffee's bitterness comes from and whether roasting increases coffee's bitterness. During roasting, chlorogenic acid undergoes changes and decomposes. Although the main bitterness in coffee comes from chlorogenic acid, in fact, chlorogenic acid itself is not bitter! Chlorogenic acid during roasting

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For more coffee bean information, please follow Coffee Workshop (WeChat public account: cafe_style)

Where Does Coffee Bitterness Come From?

FrontStreet Coffee briefly explains the source of bitterness in coffee: Does roasting increase the bitterness of coffee?

During roasting, chlorogenic acid undergoes changes and decomposes. Although the main bitterness in coffee comes from chlorogenic acid, in fact, chlorogenic acid itself is not bitter! During roasting, chlorogenic acid decomposes into "chlorogenic acid lactone" and "phenylindane."

In 2007, pioneering scholar Thomas Hofmann pointed out that phenylindane produces some bitterness, and phenylindane also affects the flavor of coffee roasting.

Coffee roasted from light to medium will have more chlorogenic acid lactone. Hofmann described this roast level as having "pleasant, quality coffee bitterness." Coffee roasted darker will have more phenylindane, with "strong bitterness that lingers in the mouth."

The latest research from German scientists has found that the main reason coffee becomes bitter is due to two special chemical substances produced during the roasting process. Future coffee may potentially not be as bitter through scientific methods.

Brown Pigments: The Root of Coffee Bitterness

One of the sources of coffee bitterness is brown pigments. Based on different molecular sizes, brown pigments also have general classifications, with large-molecule brown pigments having stronger bitterness. As the roast level deepens, the amount of brown pigments increases, and the proportion of large-molecule brown pigments also increases. Therefore, dark-roasted coffee beans have stronger bitterness and texture.

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 。