The Science of Bitterness in Coffee: A Taste Like No Other

Did you know that the bitterness of coffee is far more complex than other basic tastes? According to Behrens et al. (2007), bitterness is detected by 25 distinct receptors (TAS2Rs), each specialized to sense different bitter compounds.

In coffee, some key bitter compounds include:
🔸 Caffeine: The familiar stimulant responsible for coffee’s characteristic bitter kick.
🔸 Chlorogenic Acids: Found in green coffee, these break down during roasting into phenylindanes, which add both pleasant and harsh bitterness.
🔸 Maillard reaction products: Created during roasting, these compounds contribute to the roasted, nutty, and chocolate-like bitterness.
🔸 Over-extraction: Brewing too long or using water that’s too hot can extract excessive bitter compounds like tannins, overwhelming the cup’s balance.

What Makes Coffee Bitterness Unique?

Unlike sweetness or saltiness, which rely on only one or a few receptors, bitterness is sensed by a diverse set of receptors. Each person’s sensitivity depends on which TAS2R genes they express and how these receptors are distributed on their tongue.

For example:

  • Supertasters (those with more TAS2R receptors) often find dark roasts or high-caffeine coffees overly bitter.
  • Others may enjoy the dark chocolate-like bitterness of a well-roasted Ethiopian coffee.

What is a Supertatster ?

A supertaster is a person who has an enhanced sensitivity to certain tastes, particularly bitterness, due to a genetic variation in taste perception. This heightened ability to perceive flavors can make them more sensitive not only to bitter compounds but also to other strong tastes, including sweet, sour, and salty. The concept of supertasters is often evaluated using the compound propylthiouracil (PROP) or a related compound, phenylthiocarbamide (PTC), which are used as markers to assess bitter taste sensitivity.

Managing Bitterness in Coffee

Understanding the science of bitterness can help coffee professionals craft the perfect cup:
✔ Choose the right roast: Medium-light roasts highlight sweetness and acidity, while dark roasts emphasize bitterness.
✔ Adjust your brewing: Keep water temperatures between 90–95°C (194–203°F) and avoid over-extraction to balance bitter and sweet notes.

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