Eggs function as emulsifiers, foaming agents, and tenderizers in the dough. The egg white proteins, mainly ovalbumin, "function as structure formers. Egg solids, chiefly the egg white solids combined with the moisture in the egg, are considered structure-forming materials that help significantly to produce proper volume, grain, and texture." The egg yolk contributes proteins, fats, and emulsifiers to the dough. Emulsifying agents are essential to doughnut formation because they prevent the fat molecules from separating from the water molecules in the dough. The main emulsifier in egg yolk is called lecithin, which is a phospholipid. "The fatty acids are attracted to fats and oils (lipids) in food, while the phosphate group is attracted to water. It is this ability to attract both lipids and water that allow phospholipids such as lecithin to act as emulsifiers." The proteins from both the egg yolk and the egg whites contribute to the structure of the dough through a process called coagulation. When heat is applied to the dough, the egg proteins will begin to unfold, or denature, and then form new bonds with one another, thus creating a gel-like network that can hold water and gas.