Monoglycerides and diglycerides, which replace eggs in the Twinkie recipe, are compounds that act as emulsifiers. They stabilize the cake batter, enhance flavor and extend shelf life.
A very small amount of egg is used to leaven the cake. Polysorbate 60 serves a similar function to the glycerides, keeping the cream filling creamy without the use of real fat. Hydrogenated shortening replaces butter, giving the cake some of its texture and flavor and prolonging shelf life.
Taste tests by flavor experts have revealed that artificial butter flavoring is used in the cake and artificial vanilla flavoring goes into the cream filling.
Both flavorings are chemicals derived from petroleum…. How Stuff Works