Egg white foam

Egg whites are very good at holding their shape and building foams because of their proteins. As air is whipped in, the proteins open up and stretch to trap as much air as they can, forming thin walls around each bubble.

Acids can help the foaming ability, and other ingredients such as salt and sugar affect the quality of the foam. Meringue is the combination of air, sugar and egg whites beaten to form a foam, and souffles fold egg white foam and egg yolk foam together with other ingredients before baking.

Heat finishes the job: when the foam is baked, the egg proteins coagulate and set the bubble walls, giving the structure to meringues, angel food cakes and soufflés.