Foaming

Heat is not the only thing that causes eggs to coagulate; agitation can also bring about coagulation. Whipping not only adds air to an egg white, it also opens the proteins and causes them to link together to form an interconnected web.

The reason foaming is done with egg whites and not with yolks is because yolks have a high concentration of fat and fat inhibits foaming. Foaming is used to make soufflés, meringues, mousses, and sponge cakes such as génoise. The texture of mousseline preparations also benefits from this technique.