As the name suggests, a vinaigrette is a mixture that usually includes vinegar for flavor. Traditionally, it is made by whisking together vinegar and oil until the mixture is slightly thickened, or emulsified. Emulsions are basically combinations of fat (in this case, the oil) and water (vinegar is 95 percent water), beaten together to form a thickened, relatively homogeneous mass. Examples of other emulsion sauces are mayonnaise and the hollandaise family, in which fats like egg yolks, butter, and oil are blended with watery acids like lemon juice to make a smooth sauce.
Unlike mayonnaise, a vinaigrette is an “unstable” emulsion. This only means that it will not stay emulsified for very long. If you make your vinaigrette ahead, you may have to whisk or blend it again at serving time. When you use a blender or food processor to make a vinaigrette, it will be thicker and stay emulsified longer than the same version whisked by hand. (If you want to learn more about emulsions and indeed the whole fascinating world of the science of food and cooking I recommend Harold McGee’s book On Food and Cooking: The Science and Lore of the Kitchen and Shirley Corriher’s more recent book Cookwise.)
© 2004 John Ash. All rights reserved.