Bitterness

Bitterness is the flavour that bitter compounds such as caffeine and other alkaloids produce, often perceived at low thresholds. It is one of the five basic tastes, mediated by TAS2R receptor proteins on the tongue that evolved partly as a toxin-detection system. In food formulation, controlled bitterness contributes to the identity of coffee, chocolate, beer, and tonic beverages, where its absence would make the product taste flat or bland. Individual sensitivity varies genetically, notably for compounds like PROP, which is why the same dark chocolate can taste pleasantly complex to one person and harshly bitter to another. Skilful formulators treat bitterness as seasoning rather than defect.