bitter aftertaste

Bitter aftertaste is bitterness remaining after swallowing or spitting out, or emerging when suppression by a mixture ends. In an experiment adapting participants to a quinine-sucrose mixture and then presenting individual solutions at the same molar concentrations, those adapted to the mixture perceived stronger residual bitterness (or residual sweetness when sucrose alone was presented) than those adapted to an individual solution.

This suggests that bitterness and sweetness suppressed each other in the mixture; the authors locate the suppression in peripheral sensory mechanisms. The view that bitterness hidden during suppression emerges as 「後味」 (in translation: "aftertaste") when the mixture breaks apart helps consider bitterness over time rather than only as an isolated intensity. The experiment, however, presented stimuli to the front of human tongues, and direct applicability to aftertaste in actual dishes remains untested.

In Chinese tea, 「回甘」 (in translation: "huigan") denotes sweetness becoming dominant after bitterness or astringency; its definition explicitly describes a time course in which sweetness overtakes bitter-astringent taste and ends in sweetness. Bitter aftertaste describes 「苦味が残る、または再び現れる」 (in translation: "bitterness remains or reappears"), whereas huigan describes the opposite direction, 「甘味へ転じる」 (in translation: "turns toward sweetness"). Both concern an aftertaste time window but point to opposite sensations. This distinction is editorial; no study tracking both time curves together has yet been confirmed.

A time-intensity study of caffeine and quinine at 4 concentrations adjusted to equal bitterness reported, for both compounds, a correlation between greater bitter intensity and longer aftertaste duration, but no change in time to peak intensity. At equal bitterness, caffeine aftertaste lasted longer than quinine aftertaste. Only the abstract has been checked.

A sip-and-spit study of 63 adults compared 3 bitter solutions—quinine, sucrose octaacetate (SOA), and tetralone—matched for in-mouth intensity. At 15 seconds after spitting out, quinine aftertaste was consistently weaker than that of the other 2, suggesting it dissipated faster. Compared with in-mouth ratings, aftertaste intensity at 15 seconds fell significantly for all 3 substances at the front of the tongue; for quinine, it fell at all sites: front, middle, and back of tongue, palate, and lips.