Internet memes may tell you “there’s no such thing as leftover wine.”—a joke about drinking that misses the point that very often in daily life we might not finish an open bottle. If we do have leftovers, the conventional wisdom is that the clock is ticking, since wine is best the same day it’s opened, or should be consumed by the next day at most. This is frustrating, though, if you don’t want to drink that opened wine the very next day or if you don’t have the chance, especially when the leftovers are of a great quality. And pouring “old” wine out feels like a waste. Many of us will ask under these circumstances, But how bad can it be? Understanding how long an open bottle of wine lasts is key to making the most of every last drop—before it turns into vinegar.
The process that starts when you open a bottle of wine is called aeration, which leads to oxidation, which “increases color change and the loss of fruity characteristics,” according to professor Gavin Sacks, Professor of Enology and Viticulture in the Department of Food Science at Cornell University. It also “leads to the loss of sulphur dioxide, which preserves the wine,” he says, and dissipates aromas. Even if you put the cork or a wine stopper back in, the process continues, since no closure is airtight and oxygen has already been introduced.