Tannin

Found in grape skins, pips and stalks, tannins are harsh, bitter compounds which if present in large amounts make a wine difficult to drink as they leave a dry, puckered sensation in the mouth - rather like drinking stewed tea, which is also very tannic. Tannin is a necessary component of good wine, especially good red wine, and is most evident in the first few years of maturity. Eventually, it subsides during the maturation process.