Tannins are phenolic compounds that affect wine texture and mouthfeel by creating the drying sensation or bitter taste in your mouth when you drink a red wine. Tannins naturally leach into wine from the grape skins, seeds and stems pressed during the winemaking process and from the barrels the wine is stored in, When a wine has a pleasant amount of tannins, it’s often described as “grippy.” “Green” tannins will taste bitter, with unpleasant astringency. “Resolved” tannins in mature wines are described as “smooth” or “soft,” and are no longer astringent.