The dilution of egg proteins in a custard Left: An egg is rich in proteins; when unfolded by cooking, they are numerous enough to form a firm solid network Center: When mixed with milk or cream, whose proteins don’t coagulate with heat, the egg proteins are greatly diluted Right: When a custard mix is cooked, the egg proteins unfold and form a solid meshwork, but that meshwork is open and fragile, and the custard’s consistency is delicate Milk, Cream, and Sugar Dilute, Delay, and Tenderize When we dilute eggs with other liquids, we raise the temperature at which thickening begins Dilution surrounds the protein molecules with many more water molecules, and the proteins must be hotter and moving around more rapidly in order to find and bond to each other at a noticeable rate Sugar also raises the thickening temperature, and for the same reason: its molecules dilute the proteins A tablespoon of sugar surrounds each protein molecule in a one-egg dish with a screen of several thousand sucrose molecules Combine the diluting effects of water, sugar, and milk fat, and a custard mix containing a cup of milk, a tablespoon of sugar, and an egg begins to thicken not at 160ºF/70ºC, but at 175 or 180ºF/78–80ºC And because the protein network is stretched out into such a large volume — in a custard, the proteins from a single egg have to embrace not three tablespoons of liquid but 18 or 20! — the coagulum is far more delicate, and easily disrupted by overheating At the extreme, in a concoction like eggnog or the Dutch brandy drink advocaat, the egg proteins are so diluted that they can’t possibly accommodate all the ... effects of water, sugar, and milk fat, and a custard mix containing a cup of milk, a tablespoon of sugar, and an egg begins to thicken not at 160ºF/70ºC, but at 175 or 180ºF/78–80ºC And because the. ..molecules, and the proteins must be hotter and moving around more rapidly in order to find and bond to each other at a noticeable rate Sugar also raises the thickening temperature, and for the same... the same reason: its molecules dilute the proteins A tablespoon of sugar surrounds each protein molecule in a one-egg dish with a screen of several thousand sucrose molecules Combine the diluting