sweet aftertaste

Tea-culture media articles repeatedly explain huigan as a sensation in Chinese tea tasting in which slight bitterness and astringency on entry are followed, over time, by dominant sweetness and ultimately a sweet aftertaste. A tea-trade article also quotes a definition attributed to the national standard 『茶叶感官审评术语』 (in translation: "Terminology for Sensory Evaluation of Tea") (GB/T14487): 「茶湯を飲んだ後、舌根と喉部に甜感があり、滋潤の感覚を伴う」 (in translation: "After drinking the tea liquor, there is sweetness at the root of the tongue and in the throat, accompanied by a moistening sensation"). NIGAMI LAB has not checked the standard’s original text, so this is treated as a quotation from a secondary source.

Some tea-trade articles distinguish huigan from huitian, explaining huigan as the result of 「化学因素」 (in translation: "chemical factors"), an interaction of bitterness and astringency with sweetness, and huitian as the result of 「物理因素」 (in translation: "physical factors"), the action of tea polysaccharides. Another article, however, explains huitian as physical stimulation by soluble sugars, sweet-tasting amino acids, and thearubigins, so the details of the proposed distinction differ across sources. Some articles explaining Pu-erh tea tasting terms also equate the 「甘」 (in translation: "sweetness") of houyun directly with huigan, suggesting that boundaries between these terms are not always strict even within the tea trade.

Tea-culture media articles introduce several theories about how huigan arises. One proposes that tea polyphenols bind to salivary proteins and form a film in the mouth, perceived as astringent bitterness; when the film breaks, the oral muscles relax and huigan and shengjin are felt. Another proposes that tea polysaccharides, not sweet in themselves, remain in the mouth because of their viscosity and are gradually hydrolyzed by salivary amylase into sweet maltose, creating a time delay that produces huigan. A further contrast-effect theory holds that, after sensory adaptation to bitterness and astringency, sweetness that had been in the background feels relatively stronger. NIGAMI LAB did not confirm experimental studies based on direct observations or measurements for any of these; they are presented as common explanations.

Among the few experimental studies of sensitivity to huigan is a 2022 paper involving 6 participants classified as highly sensitive. It reports significant positive correlations between huigan intensity in this group and both total salivary protein and lipase activity. In a comparison of green-tea-derived compounds, an aqueous mixture of epicatechin (EC) at 400 ppm and epigallocatechin (EGC) at 100 ppm received higher huigan scores than L-theanine or trilobatin (5.2 points in both the oral and oropharyngeal phases, significantly different from the other samples at p<0.05). EC and EGC were always tested as a mixture, however, so the study cannot separate their individual contributions. The abstract of another paper from 2019 describes an especially strong correlation between the friction coefficient of a saliva–tea-component mixture and perceived huigan intensity in the sensitive group at sliding speeds below 0.5 mm/s; only the abstract was checked, not the full paper.

These sensory studies each assessed huigan at a single time point, such as 10 seconds after swallowing. No study of tea was confirmed that tracked huigan as a continuous temporal curve using time-intensity (TI) or TDS methods. There are time-intensity studies of individual tea catechins, but they concern only bitterness and do not connect it with sweetness. As an editorial distinction, huigan refers to 「苦渋味の後に優勢になる甘味」 (in translation: "sweetness that becomes dominant after bitterness and astringency"), whereas terms for bitterness persisting in the aftertaste concern the opposite sensory quality, bitter rather than sweet. Many tea-trade articles explaining huigan focus mainly on Pu-erh tea.