Bitterness

Definition

Bitterness is one of the five basic tastes, sensed by a family of bitter taste receptors (TAS2Rs) on the tongue. In tea, the main bitter compounds are caffeine and the catechins, especially EGCG. Some flavonols and saponins add to it in specific teas. Bitterness and astringency often appear together but are different. Bitterness is a taste; astringency is a drying texture. A tea can be bitter without being drying, as some young sheng pu'er and Dancong oolongs are, or drying without being very bitter. How much bitterness reaches the cup is mostly controlled by brewing. Higher temperatures, longer steeps, more leaf and broken leaf all extract more caffeine and catechins. Green teas are most sensitive because they retain the most catechins; black teas are less so because oxidation has converted most catechins into theaflavins and thearubigins. In some teas a measured bitterness is expected and valued. Chinese tasters prize young sheng pu'er and some Wuyi teas where an initial bitterness (ku, 苦) fades quickly into sweetness (gan, 甘). Bitterness that lingers and builds with each sip is a sign of a flawed brew or a low-grade tea.