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Food Science Basics: Egg Structure & Uses

Food Science Basics: Egg Structure & Uses

The Culinary Institute of America

The egg is composed of two main parts, the white and the yolk. Various membranes help keep the yolk suspended at the center of the white and help prevent contamination or weight loss through evaporation.

Whole eggs, as well as whites and yolks separately, play a number of important culinary roles. Whole eggs are used as the main component of many breakfast dishes and can be prepared by scrambling, frying, poaching, baking, or in custards. In baked goods, whole eggs are used as a glaze and to add nourishment, flavor, and color.

The egg white consists almost exclusively of water and a protein called albumen. Its ability to form a relatively stable foam is crucial to the development of proper structure in many items, such as angel food cakes, soufflés, and meringues. Egg whites are a key ingredient in clarifying stocks and broths to produce consommé. They may also be used as a binder in some forcemeats, especially mousselines made from fish, poultry, or vegetables.

The yolk contains protein, a significant amount of fat, and a natural emulsifier called lecithin. The yolk also has the ability to foam. This function, plus its ability to form emulsions, makes egg yolks crucial to the preparation of such items as mayonnaise, hollandaise sauce, and génoise (sponge cake). Yolks are also responsible for providing additional richness to foods, as when they are included as a liaison in sauces or soups.

Reprinted by permission from The Culinary Institute of America, The Professional Chef, 8th Edition (John Wiley & Sons, Inc. 2006).