https://kidsinthesink.wordpress.com/page/12/

Why add vodka to a marinade (I almost always do)? Just like salt, alcohol brings out the flavor in food. Alcohol does this by evaporation and molecular bonding. Food is also the beneficiary of alcohol’s ability to bond with both fat and water molecules. In this way, alcohol bridges the gap between our aroma receptors (which respond only to molecules that can be dissolved in fat) and food (which consists primarily of water). This is very important because most of the great “flavor” in food comes from aromas in the nose rather than tastes in the mouth. In terms of a marinade or a brine with both water and fat soluble ingredients, by taking the flavor compounds in certain aromatics such as garlic, herbs or other fat soluble ingredients, alcohol helps carry those compounds into the meat that’s soaking in the marinade or brine. But alcohol also helps carry water soluble flavor compounds into the meat as well. Water soluble flavors would include sour, sweet, salty and bitterness. With alcohol’s effort, the result is more flavor and aroma into the marinated food. Even one tablespoon of a neutral-tasting vodka considerably improves the flavor penetration of any given marinade.