Heat-Stabilized Foams: Sabayons

Both the method and the name of the French sabayon derive from the Italian zabaglione, a sweet, winy foam of egg yolks. Though rich in proteins and phospholipids, egg yolks don’t foam well on their own because they don’t contain enough water. Add water and beat and they foam prodigiously but temporarily; heat while beating and the yolk proteins unfold and bond to each other into a thickening, stabilizing network. This is how sabayons are made, with the water replaced by a flavorful liquid of some some sort, a broth or juice or puree for example. The hot egg-emulsified butter sauces can be made in the style of a sabayon, with the butter folded in gently at the end so as not to pop too many of the foam bubbles. (The butter doesn’t need to be beaten in because the foam has created a large surface area over which the butter can spread and stay suspended, much as a vinaigrette is spread over lettuce leaves.) The proteins in aerated yolks thicken around 120°F/50°C, and may coagulate and separate if heated much above that, so many cooks prepare sabayons over a pot of hot water rather than over direct stovetop heat.