Mouthfeel
Four of the thirteen ratings are texture rather than flavour: body, smoothness, astringency and mineral. They are detected by touch, not by taste buds, and they are the half of a cup most drinkers never learn to describe.
What it is
The physical sensation of liquid in the mouth. Weight, viscosity, roughness, dryness, how long it coats and how quickly it clears. Tea tasters have a large vocabulary for this and most of it is borrowed from wine: round, silky, velvety, thick, thin, structured, watery. The vocabulary is worth learning because it is the only way to write down a difference between two teas whose flavours are nearly identical.
How to do it
Take a mouthful large enough to coat everything, then stop looking for flavour. Ask three questions in order. How much does it seem to weigh, from watery to syrupy. Does it slide or catch. And after you swallow, is your mouth wetter or drier than it was. The last question is the one people skip and it is where astringency lives.
What to look for
Change over the session. Body usually peaks in the second or third infusion of a gongfu session and falls away after. Astringency often climbs the other way, building as you go. A tea that felt smooth at the start and rough at the end has not changed: your mouth has accumulated something. Noting the arc rather than a single number is more useful than either.
What people get wrong
Filing astringency as a taste. It is not: it travels on the trigeminal nerve, the same one that reports touch and temperature in the face, and anaesthetising the taste nerves leaves it completely intact. That is not a technicality, it is the reason the discrimination test works. Bitterness is over when you swallow because the taste receptors stop receiving; astringency keeps building because your mouth is still drying. The other mistake is calling everything body. A tea can be thin and rough, thick and smooth, or any combination, and collapsing four texture ratings into one throws away most of what the mouth just told you.
Sources
- Astringency is a trigeminal sensation rather than a taste, and survives anaesthesia of the taste nerve. Schöbel et al., 'Astringency is a trigeminal sensation that involves the activation of G protein-coupled signaling by phenolic compounds', Chemical Senses 39 (2014), 471-487