Separating eggs is a process used in cooking, in which one removes the egg yolk from the egg white in order to use them separately which is required in many recipes such as meringues, sponge-cakes, mousses, mousselines and mayonnaise, among many others.
Many recipes require frothing egg whites to make a foam, which will not work if the yolk is also included, as fat prevents eggs from foaming. Since egg yolks are high in fat, it is best to separate them before whisking. However, some recipes, such as genoise and zabaglione do include the yolk in the whisking procedure, but it is not possible to incorporate as much air and therefore to achieve as much volume.
All methods for separating eggs make use of the fact that the yolk can hold itself together while the white is much more runny. Since older eggs have more watery yolks which make separation difficult, it is a good idea to begin with the freshest eggs available. Old eggs can be used for other dishes that do not require separation, like omelettes.
An egg is fresh if it lies flat at the bottom of a glass of water. It is old if it floats.
It is easier to separate eggs immediately after removing them from the refrigerator. If the recipe calls for room temperature eggs, which allows for more volume, separate them immediately and then let them sit at room temperature for about thirty minutes.
- Break the egg and use your fingers to strain out the yolk, while the whites run into the bowl below. This is very quick but messy.
- Crack the egg in half and cradle the yolk in one half of the shell (using the other half of the shell to keep it from slipping out) while draining the white into a bowl. If some white is left with the yolk, carefully pass the yolk back and forth between halves until it is all drained, being sure not to break the yolk on the sharp edges of the shell. Then deposit the yolk into another bowl.
- Break the egg on to a plate, and trap the yolk under a glass. Carefully, drain off the whites, lifting the glass slightly.
- Use a needle to pierce the egg and run the whites out, leaving the yolk inside.
- Break the egg into a funnel, thus capturing the yolk.
Specialized tools are also available for this process. See: Egg Separator