Tannina

Tannina, in this article, refers to tannin, a class of polyphenolic compounds produced by many plants. Tannins are a diverse group of secondary metabolites characterized by their ability to bind and precipitate proteins and salivary enzymes, and by their tendency to impart astringency to foods and drinks. They are typically soluble in water and polar organic solvents and vary widely in size from small galloylated units to large polymeric structures.

Chemically, tannins are divided into two main groups: hydrolyzable tannins, such as gallotannins and ellagitannins, which can be hydrolyzed to sugars and phenolic acids, and condensed tannins, also called proanthocyanidins, which are polymers of flavan-3-ols. Individual tannin molecules differ in degree of polymerization and substituents.

Occurrence and function: Tannins occur in bark, wood, leaves, fruits and seeds of many plants, often concentrated in bark and tannin-rich tissues. They serve defensive roles against herbivores and pathogens, protect against ultraviolet radiation, and can influence a plant’s microbial interactions.

Uses and effects: In industry and cuisine, tannins are used in leather tanning and as flavoring and coloring agents in foods and beverages. In winemaking and tea production, tannins contribute astringency, color stabilization, and aging potential by interacting with pigments and proteins.

Health and safety: Dietary tannins can act as antioxidants, but high intake may reduce the bioavailability of iron and other minerals and can interfere with protein absorption. Tannins may interact with certain medications.

See also: tannin, hydrolyzable tannins, proanthocyanidins.