By Harold McGee
Because mayonnaise is chock-full of oil, so much so that the droplets press up against each other, its emulsion is easily damaged by extremes of cold, heat, and agitation. It will tend to leak oil in near-freezing refrigerators and on hot rather than warm food. These problems are ameliorated in manufactured mayonnaise by the addition of stabilizers, usually long carbohydrate or protein molecules that fill the spaces between droplets. American bottled “salad dressing” is a very stable hybrid of mayonnaise and a boiled white sauce made with water instead of milk. The texture of such modified sauces, however, is noticeably different from the dense, creamy original. Refrigerated mayonnaise should be handled gently, since some oil may have crystallized and escaped from their droplets. If so, stir gently to reemulsify it, perhaps with the addition of a few drops of water.