General Science

  • noun a brownish or yellowish compound formed in leaves and bark, used in the tanning of leather and in dyes and astringents


  • noun a substance capable of changing animal hides to leather, which is resistant to decay, by precipitating the gelatin in the hides as an insoluble compound. All tannins are obtained from plants, including tea, and the bark and galls of oak.


  • A soluble compound found in all woods that can cause staining.


  • A mixture of strong astringent acids found in plants, particularly tea leaves, red grape skins and the bark of trees, with the ability to coagulate proteins. Responsible for the keeping qualities of fine red wines.


  • noun a substance found in the bark of trees and in tea and other liquids, which stains brown


  • a naturally occurring phenolic compound that is found in grape skins, stalks and pips, and, to a much lesser degree, in wooden barrels, that acts as a preservative of the wine. The taste of tannin in a wine is bitter and gives the impression of drying out your mouth, but these tastes soften as the wine ages or if it comes into contact with air and oxidises, when the tannin compound breaks down. A young wine often has a very strong taste of tannin, but this can be reduced before serving by decanting the bottle or, more simply, by swirling the wine in your glass to oxidise the wine slightly, breaking down the tannin.