What does bitter mean in coffee?

Bitter is one of the five basic tastes - detected primarily at the back of the tongue - and is a natural component of roasted coffee. A degree of bitterness is normal and expected in coffee; it becomes problematic when it dominates the cup or creates an unpleasant harshness.

In coffee, bitterness comes from several sources: caffeine (which is inherently bitter), degraded chlorogenic acids produced during roasting, and certain compounds produced through over-extraction or overly dark roasting. Darker roasts are intentionally more bitter than lighter roasts, as the extended roasting time produces more bitter compounds while breaking down the acids that provide brightness and sweetness.

As a defect descriptor, bitter implies an unpleasant, sharp harshness that overwhelms other cup attributes - typically the result of over-extraction (grinding too fine, water too hot, or brew time too long), over-roasting, or poor-quality green coffee. The distinction between acceptable bitterness (which provides balance and structure) and defect bitterness (which dominates and detracts) is one of the key calibrations in developing sensory skills at the cupping table.