Can I drink a bottle of wine that has been open for three weeks?

Q: Will I get sick if I drink a bottle of Merlot that has been open for three weeks? —John B., Ohio

A: Probably not. The unpleasant taste that you detect in a bottle of wine that has been open for more than a day or two is due to the process of oxidation. Oxidation occurs, as you might imagine, when oxygen is introduced to wine. Frequently, the presence of a cork or other sealant prevents oxidation from happening until its removal, though older bottles of wine that remain sealed may become oxidized over time. Tannins serve to prevent oxidation in wine, which explains why red wines, which have many more tannins than white wines, can age longer than their white counterparts.

Oxidation is easy to detect: The wine will lose much of its fruit character and taste bitter. This taste is unpleasant, to be sure, but it’s not necessarily harmful to your body. “Remember that one of the most delightful byproducts of wine oxidation is vinegar,” notes George Skouroumounis, a chemist at the University of Adelaide. But Skouroumounis emphasizes that the formation of vinegar, or acetic acid, from oxidized wine is unlikely to occur—especially in the short time frame of three weeks—without the addition of acetobacter, the bacteria that converts alcohol to acetic acid.

Despite the fact that this Merlot probably won’t make you sick, we certainly wouldn’t recommend that you drink it. It’s not going to taste very good.

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