What are tannins in wine?
Quick answer
Tannins are naturally occurring polyphenols found in grape skins, seeds, and stems that create a dry, slightly bitter sensation on your palate. They give red wine its structure and backbone, and are a key reason why some bottles improve with age.
Detailed answer
If you have ever taken a sip of strong black tea or bitten into an unripe apple, you already know what tannins feel like. That puckering, drying sensation across your tongue and gums comes from the same family of compounds found in red wine.
Tannins are extracted during winemaking when grape juice sits in contact with the skins, seeds, and sometimes stems — a process called maceration. The longer the maceration, the more tannins end up in the wine. That is why a light Pinot Noir, which may macerate for just a few days, feels silkier than a Cabernet Sauvignon that soaks for three weeks or more.
Oak barrels add another layer of tannin. New French oak, for example, can contribute roughly 50-100 mg/l of extra tannin to a wine aged for 12 to 18 months. This is one reason barrel-aged wines often taste richer and more complex.
Here is a useful trick for your next dinner: if a wine feels very tannic and mouth-drying, pair it with a fatty steak or a rich cheese. The protein and fat in the food bind with the tannins and soften the sensation, creating a balanced and satisfying combination.
Over time — sometimes decades — tannin molecules link together into longer chains and eventually settle as sediment in the bottle. This is why aged wines tend to feel smoother and why that dark deposit at the bottom of an old Bordeaux is actually a sign of quality, not a flaw.