Tanin

Tanin, often translated as tannin in English, refers to a diverse group of water-soluble polyphenolic compounds produced by many plants. They are known for their astringent taste and their ability to bind proteins, minerals, and other macromolecules. Tanin occur in bark, leaves, seeds, and fruits and contribute to the characteristics of tea, wine, chocolate, and certain woods.

Tanin are broadly classified into two main groups: hydrolyzable tannins and condensed tannins. Hydrolyzable tannins, including gallotannins and ellagitannins, are based on gallic or ellagic acid units esterified to a sugar core and can be hydrolyzed by acids or enzymes. Condensed tannins, or proanthocyanidins, are polymers of flavan-3-ol units and are more resistant to hydrolysis.

Common plant sources include gallnuts from oak and sumac, chestnut wood, tea leaves (Camellia sinensis), grape seeds and skins, and various fruits. In industry, tanin are valued for leather tanning, where they cross-link collagen in hides to yield durable leather. They also influence the color, flavor, and mouthfeel of foods and beverages and can serve as natural clarifying agents or stabilizers in some processes.

In nutrition and health contexts, tanin can bind dietary proteins and minerals, potentially reducing digestibility and mineral uptake when consumed in large amounts. They may also exhibit antioxidant activity, with effects that depend on their specific structure and the context of use.

Overall, tanin are widespread in the plant kingdom, contributing to ecological defense and human uses from traditional leather production to modern food and beverage applications.