What, Exactly, are Tannins?

Another wine column from Bill Stimmel and me (though I only post here the columns that I'm wholly or primarily responsible for drafting):

It’s the question everybody wants to ask but is too intimidated to: What are tannins? The technical answer is that tannins are bitter-tasting polyphenols that, in grapes, are present in largest quantities in the seeds, skins, and stems. Tannins’ astringent flavors are responsible for the sensation you sometimes get from red wines, or from over-steeped tea—the one where your gums stick to your teeth and you feel like Tom after Jerry tricks him into sucking up a pile of alum.

So why don’t winemakers try to keep tannins out of their wines? Because tannins only make you feel as if your mouth was sandblasted with sidewalk chalk when they are either too “green” or when their levels are so high they overwhelm other elements of the wine. When they are fully “ripe” (which is not the same thing as ripeness of fruit—getting these two levels in sync is one of the signature challenges of great winemaking), tannins provide “structure;” by virtue of the tactile sensation they cause in the mouth, tannins work with a wine’s acidity to keep big, high-alcohol wines from tasting flat and lifeless. Tannins are also preservatives: when a young wine is overpowered by tannins, if they are ripe enough, that same wine ten, even twenty years later will have had time to develop a sensual, earthy depth, while at the same time the tannins will have softened and faded into the supporting role they were meant to play. Finally, tannins can also help red wines stand up to aggressively flavored foods. A tannic wine that is off-putting on its own may sing like the Vienna Boys’ Choir with a char-grilled steak.

One of the most famously tannic grapes is Cabernet Sauvignon, and winemakers often accentuate a truly great Cabernet’s tannins by leaving it in contact with the skins, seeds, and stems for longer than they would if they were going for a fruitier style meant to be drunk young. In fact, world class Cabernets often need ten or more years of aging before their tannins mellow, allowing the grape’s naturally earthy flavors and aromas to emerge in ways that less tannic, fruit-driven Cabernets just can’t match. Think of an aged wine as a stew: you can get good flavor in one or two hours (mostly from showy aromatics, herbs, and spices—things that yield big flavor quickly), but for a stew to achieve true depth and complexity, it needs long, slow simmering. Another grape almost infamous for its tannins is Nebbiolo, the grape responsible for the legendary Italian wines Barolo and Barbaresco.

Not all red wines are tannic beasts, nor do they need to be. We love easy-drinking, fruit-forward reds. But the next time you throw a porterhouse on a blazing grill, try pairing it with a five-to-ten-year-old California Cabernet Sauvignon, or another good-quality tannic wine. You won’t regret it.