Effect of an agent (lat. astringent) whose ingredients cause skin tissue or mucous membranes to contract (lat. astringere = to contract). The astringent bonds with the proteins of the skin and the mucous membranes, forming a protective wall (membrane). In medicine, such agents as alum are used to stop bleeding. In the context of a wine description, astringent is understood to be a complex of sensations that manifests itself through a rough effect that dries out the mucous membrane of the mouth or "contracts the mouth". This is caused by high contents of phenols(tannins), which are particularly found in the woody parts of fruits such as stems, pods, skins and seeds. These are, for example, almonds, chestnuts, green nuts, artichokes and anthocyanin-rich (colouring rich) grape varieties. The latter mostly have a dark (black) berry colour like the ones shown in the picture.
The astringent substances cause a contraction of the organic tissue in the oral cavity, inhibit saliva secretion and thus have a roughening effect on the mucous membranes. However, this is (although it seems so) not a sensation of smell or taste, but a tactile or trigeminal stimulus (concerning the sense of touch) to the mucous membranes of the inner sides of the cheeks and the nasal cavity and must not be confused with bitter or sour. The sensation also depends on the wine temperature and is intensified at low temperatures. It can range from weak to the just positively charged obtrusive to the already negative aggressive.
Astringency is usually mainly a characteristic of young red wines. This impression can be significantly softened during bottle ageing or in the course of the ageing process and even disappear completely due to the precipitation of the causative substances. The astringent effect has a positive effect on low acidity red wines in most cases and can also stimulate the appetite. With white wines, on the other hand, this is usually an undesirable negative characteristic and is called phenolic. See also under wine appeal.
Pictures: Ursula Brühl, Doris Schneider, Julius Kühn Institute (JKI)