A mixture of one liquid with another with which it cannot normally combine smoothlyoil and water being the classic example. Emulsifying is done by slowly (sometimes drop-by-drop) adding one ingredient to another while at the same time mixing rapidly. This disperses and suspends minute droplets of one liquid throughout the other. Emulsified mixtures are usually thick and satiny in texture. Mayonnaise (an uncooked combination of oil, egg yolks and vinegar or lemon juice) and hollandaise (a cooked mixture of butter, egg yolks and vinegar or lemon juice) are two of the best-known emulsions.
From The Food Lover's Companion, Fourth edition by Sharon Tyler Herbst and Ron Herbst. Copyright © 2007, 2001, 1995, 1990 by Barron's Educational Series, Inc.