What are tannins in wine?

The first sip of a nice red wine gives you plenty to decode. You’ll get at least one of the five basic tastes (sweet, salty, bitter, sour and umami) along with a cascade of other flavors. This is where fruit and floral notes will interplay with non-food tastes like tobacco.

Taste is just the beginning. You’ll also experience the texture of the wine in your mouth and a puckering, drying sensation. That dryness — known as astringency — comes from tannins. Wine isn’t the only tannic thing we consume. Coffee, tea and dark chocolate all have tannins.


What are tannins?

Tannins are chemical compounds in grape skins, seeds (also called pips) and stems. They’re common in bark, leaves, wood and fruits. The fact that we’re talking about tannins in something we drink goes against everything tannins stand for. Their purpose is to gross out any animal who wants to eat part of their plant. A mouthful that dries your mouth and tastes bitter doesn’t typically inspire another bite.

These chemical compounds are so good at drying that tannins from tree bark have long been used to make leather. Tannins bind to the proteins in an animal hide and dry it out.

In a much milder way, this is how tannins work in wine. The polyphenols, a type of organic compound, attach themselves to the protein in our saliva, coating our mouths. Tannins can be overpowering and off-putting, but in the hands of a skilled winemaker, they add structure and complexity.


What do tannins do in wine?

The flavor of wine is more than just how it tastes. The aroma and texture — or mouthfeel — play a significant role as well. Texture can be challenging to separate from taste because it all happens in the mouth. Tannins are sometimes misread as a bitter taste, but you’re really just experiencing astringency.

When we talk about the texture of a wine, we’re describing what it feels like in our mouths. Words like velvety, silky, chalky or rough describe mouthfeel and are impacted by tannins.

The structure of wine expands on texture to include the balance of tannins, acidity, sugar and alcohol. You’re most likely to notice that a wine has poor structure if it is unbalanced. A wine with low tannins will almost taste watered down. Wine that is unbalanced in the other direction will be heavy and firm. Too many tannins will make wine extremely astringent like oversteeped tea.

The layers of aroma, flavor, texture and acidity should harmonize, making the wine more complex.


What kinds of wine are most tannic?

Red wine is most associated with tannins. This is because red wines spend much more time in close contact with the skins, pips and stems. Maceration is the part of the process where the grape juice is in contact with the other components of the fruit. At this time, tannins and color are imparted into the wine.

White wine is typically made by pressing grapes right after they are harvested. With barely any contact with the skins, the finished wine has a white color. Some whites, like Riesling, have a short period of skin contact to pull out the aromatic characteristics of the grape skins. Rosé gets its pink color from a short maceration period. It spends enough time with the skins to impart some color, but very little tannin.

Reds made with Cabernet Sauvignon, Petite Sirah, Syrah, Merlot and Nebbiolo grapes, among others, are considered tannic wines. Wines made from Pinot Noir and Grenache grapes tend to be less tannic because those grapes have thinner skins.

While naturally occuring tannins provide the baseline, the end product depends on winemaking decisions, like length of maceration and fermentation temperature. Some winemakers will ferment the wine with the grape stems. Whole-bunch or whole-cluster fermentation is often used for Pinot Noir to add structure.

Tannins help shape the red wines we love by influencing the mouthfeel, balance and structure. But for some people, tannins are a headache —  literally. Some people are sensitive to tannins. If you are prone to red wine headaches, tannins may be to blame.  Learn how to test your tannin sensitivity in our blog about red wine headaches.

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