Tannins, often mentioned when red wine comes up, help provide structure and texture. (iStock)

You know that supple, almost astringent feeling in your mouth after you swallow red wine? That’s the effect of tannins, one of wine’s basic building blocks. Here are five things to know about tannins that can help you understand their influence on your enjoyment of wine.

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1. Tannins are abundant in the plant world. Tannins are polyphenols found in nearly all plants — in bark, skin, seeds and stems. With antioxidant and antibacterial properties, they are one of nature’s defenses against disease. Early mankind figured out how to soak tannins out of plants and use them to “tan” animal hides and make leather, transforming something that would naturally rot into a strong, durable product. The expression, “I’ll tan your hide!” — used to threaten a thrashing — is a bit of an oddity, as tanning doesn’t involve striking the hide. It does require removing flesh from the hide, though, and that may be what the expression means.

Their natural antioxidant properties make tannins a healthy additive to livestock feed, and they have even been touted as a natural alternative to antibiotics. We humans consume tannins, too, in nuts, seeds, vegetables such as spinach and drinks such as tea and, of course, wine.

2. Tannins give wine structure and texture. Just as tannins make leather supple, they add to wine’s texture and mouthfeel. Grapes contain tannins in their skins, seeds or pips, and stems. They leach into the wine during pressing, maceration and fermentation of the juice. Aging in oak barrels also adds tannins from the wood. Powdered tannins, naturally extracted from plants, can also be added to wine, giving the winemaker greater control over the final product.

In wine-tasting parlance, tannins can be ripe, supple, velvety, soft, silky or sweet. They can also be aggressive, chewy, harsh, green, angular or searing. Rustic if we like them, coarse if we don’t.

Tannins are tactile. If you've ever let your tea steep too long, you've felt their astringent, drying effect on your palate and mouth. They make your teeth itch. In big red wines, good tannins — the supple, ripe type — creep up at the finish just as the fruit fades and tickle your teeth with a pleasant caress that reminds you there is more in the bottle. Such wines are said to have “grip.” Aggressive tannins are like a sucker punch to the mouth: They leave the wine tasting bitter.

Some grape varieties contain more tannins than others: cabernet sauvignon, syrah and nebbiolo, for instance, yield wines more tannic than those made from merlot, gamay or pinot noir. Listen to winemakers describe their craft, and sooner or later you’ll hear the term “whole-cluster fermentation,” especially regarding pinot noir. That’s when the winemaker leaves the stems on the grapes, in part to add tannins to the wine.

3. Fat cuts tannins. Tannins bind with protein, leading to the classic pairing of grilled steak and cabernet sauvignon. Richer, more succulent dishes benefit from pairing with tannic wines, as the tannins cut through that richness and their astringency leaves our palates refreshed and ready for the next bite.

4. Tannins help wine age. Tannins’ preservative properties help give wine endurance. Tannins are relatively small, and as wine ages in bottle, they combine to form larger compounds that eventually fall out of solution as sediment. That’s why older wines taste less astringent than when they are young.

But aging wine may not fit the modern lifestyle — in fact, most wine is consumed within days after purchase. And as a society we are moving — albeit slowly — toward a lighter, more plant-based diet. So maybe we don’t need tannic wines anymore? Winemakers have developed techniques for softening tannins and making wines more accessible and drinkable upon release, but maybe our lifestyle and diet call for a more fundamental change in wine style.

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The natural wine movement favors wines with less extraction and reliance on winemaking techniques that emphasize tannins and structure. The result is lighter red wines — lighter in color, alcohol, body and even flavor than modern wines have been the past few decades. Certainly, they are less tannic than our typical cabernets and syrahs. Not that these will replace Napa cult cabernets or Bordeaux First Growths anytime soon, but they make a statement about the direction consumer tastes may be heading.

5. White wines have tannins, too. You’ve probably noticed I’ve only been discussing red wines and their relationship with tannins. Modern whites are made by pressing the juice off the skins, pips and stems — the grape’s source of tannins. Fermenting and aging in barrel, as most chardonnay is, can add a small dose of tannins, but generally the tannic discussion is limited to reds.

The exception is amber wines, also known as orange or skin-contact wines. These are whites fermented and sometimes aged on their skins, much as red wine is made. This imparts color, texture and tannins to the wine. It’s a technique as old as wine itself, from the ancient vineyards of Georgia and Armenia. And it’s a favorite of natural wine adherents, as well as winemakers around the world eager to reconnect with history.

It’s a paradox that the natural wine movement favors lighter reds and heavier whites than the norm, but that’s one of those contradictions that make wine and life so fascinating. Like a soft tannic finish, it leaves me thirsty for more.

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