Here's what the great Chef Thomas Keller says in his award winning The French Laundry Cookbook: "If your marinating anything with alcohol, cook the alcohol off first. Alcohol doesn't tenderize; cooking tenderizes. Alcohol in a marinade in effect cooks the exterior of the meat, preventing the meat from fully absorbing the flavors in the marinade. Raw alcohol itself doesn't do anything good to meat. So put your wine or spirit in a pan, add your aromatics, cook off the alcohol, let it cool, and then pour it over your meat. This way you have the richness of the fruit of the wine or Cognac or whatever you're using, but you don't have the chemical reaction of 'burning' the meat with alcohol or it's harsh raw flavor."