tannino

Tannin, in Italian tannino, refers to a diverse group of polyphenolic compounds found in many plants. They are capable of binding proteins and other macromolecules, which contributes to astringency, color stability, and resistance to proteolysis. Tannins are broadly categorized into two main groups: hydrolyzable tannins and condensed tannins (proanthocyanidins).

Hydrolyzable tannins include galloyl and ellagitannins; condensed tannins are polymers of flavan-3-ol units such as catechin and epicatechin. Major natural sources include grape skins, seeds and stems, bark, tea leaves, wood, and various barks used for leather tanning (such as quebracho and chestnut). In wine, tannins come from grape skins/seeds and oak aging; they contribute astringency, structure, and aging potential.

In leather production, tannins act as tanning agents to convert hides into durable leather by forming stable complexes with collagen.

Etymology and chemistry: The term tannin derives from tanning, the historical process for which tannins were first used, and they are chemically characterized as highly polyphenolic compounds capable of forming complexes with proteins and metals. They can oxidize and polymerize, which may alter their sensory impact during aging.

Health and dietary aspects: Tannins have antioxidant properties in vitro and can influence mineral absorption, notably iron, when consumed with meals. Effects vary with tannin type and polymerization; as with many polyphenols, moderate, balanced consumption is typical in diets that include tea, wine, and certain fruits.