Tea
Astringency Is Not Bitterness
Two sensations that people routinely confuse have different mechanisms, one a taste and the other a physical effect on the mouth, and they respond to different fixes.
Tea drinkers describing a difficult cup often reach for bitter and astringent as though they were interchangeable. They are separate phenomena with separate causes, and telling them apart makes brewing problems solvable.
Bitterness is a taste
Bitterness is detected by receptors on the tongue and registers as a flavour, in the same category as sweet, sour, salt and savoury.
In tea it comes largely from caffeine and from certain polyphenols, and it rises as extraction rises. Longer steeps and hotter water both increase it.
A genuinely bitter cup tastes bitter while it is in the mouth and the sensation fades reasonably quickly once swallowed.
Astringency is a tactile effect
Astringency is not tasted at all. Tannins in the tea bind to proteins in saliva, and the lubricating film in the mouth breaks down as a result.
What you notice is roughness, drying and a slight puckering across the whole mouth rather than a flavour on the tongue.
Because it is physical rather than gustatory, it builds up over successive sips and lingers well after the cup is finished.
The two respond to different adjustments
Bitterness is mostly a function of how much you extracted, so shortening the steep or lowering the temperature reduces it directly.
Astringency depends more on which compounds you extracted, and heavy astringency often signals a leaf that was picked coarse or brewed with too much material for the water.
Reducing the leaf quantity while keeping the time can lower astringency noticeably without making the cup taste thin, which is not true of simply cutting the steep short.
Neither is automatically a fault
A measure of astringency gives tea its structure and its refreshing quality, and a completely soft cup can taste flabby and forgettable.
Some styles are built around briskness, particularly black teas intended to be drunk with milk, where the proteins in the milk bind the tannins and soften the effect.
Judged without milk those same teas seem rough, which is a mismatch of context rather than a defect in the tea itself.
Describing them separately improves your notes
A tasting note that records bitter high, astringency low points to over-extraction of a fine leaf and suggests a shorter steep.
One that records bitterness low and astringency high points instead to the leaf grade or the ratio, and a shorter steep will simply give a weak, still-drying cup.
Keeping the two apart in language is what turns a vague sense that something is wrong into a specific change worth making next time.
