Using egg yolks as food thickeners The yolk of an egg has excellent binding properties because it contains lecithin, a natural emulsifier. Egg yolks are essential for emulsifying or binding together classic sauces such as hollandaise and mayonnaise. Egg yolks are also used for their thickening properties. They are often added to custards, puddings, and other mixtures for a richer texture. One egg yolk contains 5 grams of fat (mostly unsaturated), 213 mg of cholesterol, and a range of beneficial B vitamins. Storing egg yolk is simple. Just cover the egg yolk with a small amount of water, seal in an airtight container, and refrigerate for up to 3 days. You can also freeze egg yolks, but they become very thick. If you must freeze them, beat in a speck of salt or a scant 1/2 teaspoon sugar or corn syrup per egg yolk to keep them smooth and usable. Choose salt or sugar depending on how the egg yolk will be used. Thaw overnight in the refrigerator. use 1 teaspoon thawed egg yolk for each fresh yolk called for in the recipe.