The Functionality of Eggs and Sugar
Eggs have many functions in baked goods. Eggs provide structure, leavening, tenderizing, color, and flavor. The coagulation of egg protein aids in building the structure of cakes, cookies, muffins, and quick breads.
- Protein Coagulation
The yolk portion of the egg contributes to tenderizing the crumb of baked goods, as it contains fats and emulsifiers. The coagulating ability of eggs is also important in the preparation of creams and custards as they aid in the thickening and gelling of these products.
Sugar interacts in a unique manner with eggs. For example, in foam-based cakes, sugar molecules disperse among egg proteins and delay the coagulation of the egg proteins during baking.
As the temperature rises, egg proteins coagulate, or form bonds with each other. The sugar molecules raise the temperature at which bonds form between these egg proteins by surrounding the egg proteins and interfering with bond formations. Once the egg proteins coagulate, the cake "sets", forming the solid mesh-like structure of the cake.
- Custards
Crème Brulee, Crème caramel, pot de crème, and cheesecake, are considered custards. Common ingredients in custards are whole eggs, egg yolks, milk, cream, flavorings, and of course, sugar. The consistency of a custard varies from soft and creamy to firm. The difference in texture is a result of the proportion of ingredients used to prepare it.
Just as most baked products are essentially flour protein structures, custards are egg protein structures. Sugar delays the coagulation of egg proteins in custards and similar cooked egg dishes. If the egg white solidifies too soon from the heat in the cooking process, the liquid ingredients in the custard will be squeezed out in droplets. This is known as syneresis or "weeping."
Sugar in a custard mixture breaks up the clumps of protein molecules so that they are finely dispersed in the liquid mixture. The temperature at which the custard sets is thus raised, permitting the egg proteins to coagulate slowly and enmesh the other ingredients, resulting in a smooth, stable consistency..
Custards with higher amounts of sugar are more tolerant to heat than those with less sugar. Formulas of custards with higher amounts of sugar are less likely to curdle as sugar helps prevent curdling.
Custards should be baked until they are almost set. The proteins of the egg continue to coagulate after the custard is removed from the oven. The final setting of the custard occurs as it is cooling down.
- Foams
Egg foams are formed by whipping whole eggs, egg whites, or egg yolks with sugar to create a light foam. The sugar serves as a whipping aid to stabilize beaten egg foams. Eggs foam are classified into 2 categories: cooked or uncooked.
In foam-type cakes, sugar interacts with egg proteins to stabilize the whipped foam structure. In doing so, sugar makes the egg foam more elastic, so that air cells can expand and take up gases from the leavening agents. Egg foams are used to prepare meringues, buttercreams, and creams, as well as providing the base for many cakes and desserts.
Here are some recipes from some of our baking experts using egg foams to create delicious desserts.
