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

Professional Coffee Knowledge Exchange

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 breaks down. Although the main bitterness in coffee comes from chlorogenic acid, chlorogenic acid itself is not actually bitter. During roasting it decomposes into chlorogenic acid lactone and phenylindane.

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

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

The latest research from German scientists found that the main reason coffee turns bitter comes down to two specific chemical compounds produced during roasting. In the future, coffee may be made noticeably less bitter through scientific methods.

Brown Pigments: The Root of Coffee Bitterness

One source of coffee bitterness is brown pigments. Depending on molecular size, brown pigments fall into broad categories, and the larger-molecule pigments carry stronger bitterness. As the roast level deepens, the amount of brown pigments increases, and so does the proportion of large-molecule pigments. That is why dark-roasted coffee has stronger bitterness and more texture.

FrontStreet Coffee Recommendation

Bitterness is not something to avoid so much as something to balance, and roast level is the main lever you have. If you want a cup where bitterness stays gentle and rounded, FrontStreet Coffee's Jamaica Blue Mountain No. 1 is a fine place to look. Medium roasted, it blends acidity, bitterness, sweetness, and aroma into a smooth, elegant whole, offering chocolate, roasted nut, cream, and caramel rather than any harsh edge.

For a softer, low-bitterness medium roast closer to home, FrontStreet's 2013 Yunnan sun-dried Typica carries nut, brown sugar, black tea, and dried apricot notes with only mild acidity, and it works equally well as pour-over, cold brew, or a drip machine.