determined by probing the interior with a toothpick, and is a matter of taste; some people like a creamy interior that still clings to the toothpick, others prefer a more fully cooked consistency, which clings to itself and leaves the toothpick clean Yolk Foams: Zabaglione and Sabayons Yolks Can’t Foam Without Help Beat an egg white for two minutes and it will expand eightfold into a semisolid foam Beat an egg yolk for ten minutes and you’ll be lucky to double its volume Yolks are richer in protein than whites, and have the added advantage of emulsifying phospholipids that do a fine job of coating fat droplets: so why can’t they stabilize air bubbles and make a decent foam? One clue is what happens when you wash out your yolky bowl: the moment you pour in some water, it foams! It turns out that the protein-rich, emulsifier-rich yolk is deficient in water Not only does it contain about half the water that the white does, but nearly all of it is tightly bound to all the other materials In one tablespoon/15 ml of yolk, the volume typical of a large egg, there’s about a third of a teaspoon/2 ml of free, foamable water Add two teaspoons to give it the same free water as a white, and it foams enthusiastically Enthusiastically but fleetingly Put your ear to the foam and you’ll hear the bubbles popping The other deficiency of the egg yolk is that its proteins are too stable Neither the physical abuse of whipping nor the presence of air bubbles causes the yolk proteins to unfold and bond with each other into a reinforcing matrix Of course heat will, as we know from hard-boiled yolks and custards So supplement the yolk with liquid, and the whipping with careful cooking, and the mixture will rise to four or more times its original volume Exactly this procedure is the ... in water Not only does it contain about half the water that the white does, but nearly all of it is tightly bound to all the other materials In one tablespoon/15 ml of yolk, the volume typical of a large egg, there’s about a third of. .. Put your ear to the foam and you’ll hear the bubbles popping The other deficiency of the egg yolk is that its proteins are too stable Neither the physical abuse of whipping nor the presence of air bubbles causes the yolk proteins to... of air bubbles causes the yolk proteins to unfold and bond with each other into a reinforcing matrix Of course heat will, as we know from hard-boiled yolks and custards So supplement the yolk with liquid, and the