Q: With so many holiday parties this time of year, we end up with a lot of leftover wine. Are there any negative health effects to be concerned about when it comes to a wine bottle that was opened the night before and has been sitting out at room temperature? —Alan K., Lincoln, Neb.
A: Leftover wine from the night before, or even from a few days ago, won't make you sick, but you might find that it's no longer to your taste. As a wine sits in an open bottle or in a wineglass, it's exposed to oxygen, which will flatten out its fruit flavors and eventually cause it to take on nutty, bruised-apple notes. Opened bottles of wine don't last forever, and in a wineglass or a decanter, where there is more surface area exposing the wine to oxygen, it will fade more quickly. If you're going to try to save a glass of wine, I'd recommend keeping it in the refrigerator as much as possible (which will slow down the process) and covering it with some plastic wrap. Or you can use a wine-preservation system that utilizes argon gas, which protects the wine from oxygen.
Even as a wine oxidizes, becoming less and less pleasant to drink (and everyone's tolerance and sensitivity varies), it won't "spoil" or turn toxic, thanks to its alcohol content. Eventually the wine might turn into your very own homemade vinegar, which can be a great way to repurpose excess old wine!