We left an open, half-full bottle of wine out overnight. What happens? Does it lose flavor? Or alcohol content? Is it OK to drink?

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Dear Dr. Vinny,

We left an open, half-full bottle of wine out overnight. What happens? Does it lose flavor? Or alcohol content? Is it OK to drink? If so, for how long?

—PK, Greensboro, N.C.

Dear PK,

After you open a bottle of wine, you expose it to oxygen. Some wines will become more expressive with that initial exposure, but after a while, all wines will fade. Oxygen will eventually cause any fresh fruit flavors to disappear and aromatics to flatten out. Drinking a wine that’s faded due to oxidation won’t make you sick, it will just taste unpleasant. Keep in mind that the wine’s alcohol content was determined during the fermentation process when the sugar in the grapes converted to alcohol, so it won’t be altered with exposure to air.

How much mileage you get out of an open bottle will depend on the wine and on your own personal preference. Older wines will fade more quickly than young, robust ones. Wines higher in acidity or residual sugar might also last a bit longer.

Obviously, putting the cork back in the bottle would have at least partially prevented some oxidation, as would putting the leftover wine in the refrigerator (yes, even if it’s red). I also recommend transferring the wine to a smaller bottler where there will be less surface area. Even in the best-case scenario, most wines won’t retain their youthful fruit flavors for more than a day or two after the bottle is opened.

—Dr. Vinny

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