Tannins

noun:[TAN-ihns]Any of a group of astringent substances found in the seeds, skins, and stems of grapes, as well as in oak barrels, particularly new ones. Tannins are part of a grouping technically called phenolic compounds. They are important in the production of good red wines because they provide flavor, structure, and texture and, because of their antioxidant traits, contribute to long and graceful aging. Tannins often give young wines a noticeable astringency, a quality that diminishes as the wine ages, mellows, and develops character. Tannins are detectable by a dry, sometimes puckery, sensation in the mouth and back of the throat.