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Dear Dr Vinny,

Are tannins a preservative in wine?

—W.P., Tulsa, Okla.

Dear W.,

There are a few natural preservatives in wine, including tannins, acidity, alcohol and sulfites. Tannins come from the skins, seeds and stems of grapes, as well as from oak barrels. Some types of acid are found in grapes; others are a byproduct of fermentation, which is also where alcohol and sulfites come from.

All of these components help keep a wine from turning into vinegar, and in the best cases, allow it to age well. It’s still a wine lover’s responsibility to make sure the bottle has the best chance for survival, in cool, constant temperatures. Once the bottle is open and the wine is exposed to oxygen, no amount of natural preservatives will keep it from fading.

—Dr. Vinny

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