What Are Tannins in Wine?
Tannins are naturally occurring compounds that exist inside grape skins, seeds and stems. The scientific word for these compounds is polyphenols. Polyphenols release from the skins, seeds and stems when they soak in the grape juice just after the grapes have been pressed and are what give certain wines, their characteristic dryness or astringency. You experience the effect of tannins any time you drink a wine that creates a drying sensation in your mouth. Depending on how dry your mouth feels, you can determine whether a wine is high or low in tannins. We say a wine that is high in tannins is tannic.
What makes a wine have strong or weak tannins depends on how long the juice sits with the grape skins, seeds and stems after the grapes have been pressed. The longer the skins, seeds and stems soak in the juice, the more tannin characteristics they will impart. This explains why red wines have stronger tannins than white wines. When producing a red wine, the winemaker wants the skins to impart more color, thereby adding more tannins to the juice. Further, by extracting the characteristics of tannins, they are able to add deeper complexity to the wine.
Wood tannins in wine appear when wine is stored in wooden barrels. Oak barrels are the most popular choice because of the flavors they add to wine such as vanillin.
Winemakers also love tannins because they work as a natural antioxidant to protect the wine. This is actually a key reason why certain red wines, including Cabernet Sauvignon, can be so age-worthy. And, as we know, antioxidants aren’t just useful for helping us age wine; they also have great health benefits for humans!