Unpolished Grape 101: Tannins Explained

Have you ever tasted a glass of wine and your mouth felt like you just chewed a cotton ball? It was probably the tannins!

Tannin in Grape Skins

Tannins are not a flavor. Rather, they are polyphenols (astringent chemical compounds) found in grape skins. They are also found in fruits, veggies, wood, seeds, stems, leaves, bark, and a plethora of other livings plants. The compound results in a cottony mouthfeel when we eat grapes or drink wine.

The best way to understand how tannin influences grapes or wine is to peel the skin off of a black table grape and put it in your mouth, without the juicy pulp. When you chew the skin, you should be able to feel the cottony effect of tannin on your teeth and around your mouth.

Black grapes have higher levels of skin tannin than white grapes. And even within the black-grape category, all tannin levels are not the same. Cabernet Sauvignon, Nebbiolo, Syrah and Tannat have some of highest tannin levels. Whereas Pinot Noir and Grenach have relatively lower levels. In addition, smaller berries, i.e. Syrah, may contribute even more tannins to a wine due to it’s high skin/pulp ratio.

Any time grapes are fermented with their skins, the tannins make their way into the final product of wine.

Tannin in Grape Seeds and Stems

Tannin is also found in grape seeds and stems. A winemaker may choose to ferment the grape juice along with their seeds and stems to further extract tannin and additional flavor compounds existing in a grape cluster. This method may be more common for red wine, but some winemakers also choose to ferment white grapes along with skins, seeds and stems for more complexity.

Tannin From Oak

As mentioned earlier, tannins are also found in wood and bark. When any wine is aged in an oak vessel, it extracts the natural tannins found in that particular barrel and increases that cottony feel and flavor complexity of the final wine. Keep in mind, barrels lose their impact and impart lower tannin levels each time they are used.

Softening Tannins for Easy Drinking

Even though tannin is present in wood, extended periods of oak-aging may help to soften the natural tannins found in the grapes themselves. If you were to taste a Tannat wine before barrel-aging, the tannins may be so astringent that your lips pucker and the wine isn’t very drinkable. This is why many red wines need to age a bit.

Although barrels are tightly sealed, they are not 100% air-proof. Placing wine in barrels is a form of deliberate oxidation. As the oxygen seeps in the tiny barrel openings and crevices over time, it will slowly interact with wine and begin to soften the tannin astringency. When the tannins are softer and balanced the wine is more enjoyable.

Some people like tannic wine, others not so much. But we can’t deny the major role they play in the finished product!


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