The study also revealed that alcohol content diminishes with cooking time. After being added to food that then is baked or simmered for 15 minutes, 40 percent of the alcohol will be retained. After cooking for an hour, only about 25 percent will remain, but even after 2.5 hours of cooking, five percent of the alcohol will still be there. Of course, the amount of alcohol in an individual serving will be quite low.
People need to avoid alcohol for various reasons, such as to guard against alcoholic relapse, to protect a fetus, or to avoid adverse reactions that might be brought on by certain medications. The best bet for such people would be to ask if a particular dish is cooked with wine or spirits before ordering in a restaurant. If you’re a dinner guest, you could let the host or hostess know in advance that you’re avoiding alcohol in food as well as drink."
Andrew Weil, M.D