Tanninien

Tanninien, commonly referred to as tannins, are a diverse group of polyphenolic compounds produced by many plants. They are characterized by their ability to bind and precipitate proteins, forming complexes with minerals and other macromolecules, which gives tannin-rich foods their astringent taste. Chemically, tannins are divided into hydrolyzable tannins, such as gallotannins and ellagitannins, and condensed tannins, known as proanthocyanidins. Hydrolyzable tannins are esters of gallic or ellagic acid with sugars; condensed tannins are polymers of flavan-3-ols.

Tanninien sources are widespread and include bark, wood, leaves, seeds, and skins of fruits. Notable sources are gall nuts, chestnut wood, myrobalan, sumac, tea leaves, grapes, and quebracho. Industrially important tannins are used in leather tanning and in dyeing and finishing processes, as well as in some beverages and foods as flavoring and buffering agents.

In terms of properties, tannins are typically water- or solvent-soluble to varying degrees and range from lower to high molecular weight. They can form insoluble complexes with proteins and metal ions, contributing to browning color reactions and astringency. In wine and tea, tannins influence mouthfeel, bitterness, and color stability; in leather tanning they cross-link collagen to produce durable skins.

Health and safety: in the diet, tannins contribute antioxidant activity but can impair iron absorption if consumed in excess. Some tannins can interact with drugs and nutrients; high intake may cause digestive discomfort. Environmental and ecological roles include defense against herbivores and pathogens, and tannins influence litter decomposition and soil chemistry.