What Are Tannins in Wine?
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When red wine is described as being dry, it's the tannins that are the source of that sensation. To understand that sense of dryness, try an experiment: Pop open a bottle of Cabernet Sauvignon or Syrah — two notably tannic wines — take a sip, and swish the wine around in your mouth like you're auditioning for a Listerine commercial. It won't be pleasant, so consider yourself warned. Spit out or swallow the sip, and then run your tongue across the front of your top teeth and along the insides of your cheeks. They'll feel dry, and a bit like sandpaper, all thanks to the tannins.
The question that naturally follows is: If that's such an unpleasant sensation, then why do we want or need tannins in the first place?
The first answer is that you should not be treating your wine like its mouthwash. Swishing it around your mouth is not proper tasting technique, and if you were to do that at the dinner table, your friends and family would likely get up and leave. Proper tasting technique, which involves swirling, sniffing, and slurping, is about as far from Listerine-ing your Cabernet as a rocking chair is from a rhinoceros.
But tannins are a key component in the structure of red wine, along with acidity. (Acidity, incidentally, is the main structure-giving component in white wine, which generally has no tannins.) It's the component of red wine that frames the fruit and more savory notes. Plus, if the wine is intended to age, tannins allow it to do so.
Where Do Tannins in Wine Come From?
Tannins in wine come primarily from grape skins. They also can be found in stems and seeds, and some producers, most notably of Pinot Noir, might include stems in their winemaking to help build additional structure; Pinot Noir, with its thin skins, produces a less tannic wine than thick-skinned Cabernet Sauvignon and Syrah, for example. Because of how they're each made, red wines possess tannins, while white wines typically don't. As the juice for red wine macerates with the skins, both color and tannins are extracted. For most white wines, skin contact doesn't occur, which means that tannins aren't present in the final product.
It's worth noting that there are tannins in oak, so barrel-fermented and -aged whites, like some Chardonnays, occasionally have subtly perceptible oak-derived tannins, especially if a high percentage of new oak has been used.
At the table, tannins counterbalance fat and protein in food, which in turn soften up the perception of the tannins. This is why tannic red wine with well-marbled steak is such a classic pairing: They each become better alongside the other than they would have been on their own.
Not all tannins are the same, however; they evolve and mature during the growing season. Grapes picked too early often exhibit tannins that have "woody" characteristics, meaning they are assertively astringent. Grapes picked at optimal ripeness tend to showcase tannins that have a vaguely sweeter character, though it's important to note that tannins are never "sweet" in the same sense as, say, the ripe fruit characteristics of the wine might be. Often, wines that are meant to age for an extended period of time are not all that desirable to drink in their youth, because their tannins need to mature and soften.
