 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.Shortening is responsible for providing tenderness and aerating the dough.In terms of its molecular structure, "a typical shortening that appears solid [at room temperature] contains 15-20% solids and, hence, 80-85% liquid oil ... this small amount of solids can be made to hold all of the liquid in a matrix of very small, stable, needlelike crystals (beta-prime crystals)."