What Eggs Do in Yeast Bread

Egg Yolks

Egg yolks are the fat in the egg and act as a bridge between other ingredients in bread, allowing other fats to combine with moisture. Fats can be natural fat in the flour or added in the form of oil, shortening or butter. Without this emulsifying action, the yeast breads dry out very quickly because the moisture in them has not been linked to the fats baked in the bread.

Egg yolks combined with fat in a yeast bread tenderize the protein present in wheat flour. This protein forms gluten during kneading, which makes the bread chewy. Reducing the amount of gluten formed creates a softer, more tender bread. When the yolks bind to the protein in the flour, they prevent water from combining with it to form gluten. The result, less gluten, and a more tender loaf of bread. Many yeast breads with egg yolks added also have sugar to further soften the texture, producing a cake-like concoction. Examples of egg breads include brioche and challah.

Egg Whites

Egg whites do not have the emulsifying power of yolks. Instead, egg whites dry bread out to create a crisper texture. This occurs when the proteins in the egg whites cook as the bread bakes. Each protein, when raw, resembles a single spring. Mixing the bread dough unravels these springs, but when the bread bakes in the oven, the springs become entangled with each other. Between these entangled proteins, water hides, but as the bread keeps baking, the proteins tangle even tighter, and the water is pushed out and into the oven as steam. This loss of moisture dries out the bread.

Egg whites also act to help leaven the bread, especially if they have air whipped into them before adding them to the bread dough. The protein structure of egg whites traps air bubbles in it, and when they are mixed into the bread dough, those bubbles incorporate into the bread's structure. By helping the dough hold in more air, egg whites help the bread to rise.

Whole Eggs

With eggs, the whole is greater than the sum of its parts. Whole eggs, like whites, help to bind ingredients and assist in rising and drying, but they also add strength to the bread. Breads made with whole eggs perform best in recipes that require soaking the bread, such as stuffing, French toast and bread pudding. Without whole eggs, the bread would melt in the soaking liquid. Adding several whole eggs to a yeast bread opens the structure of the bread so that there are larger holes in the structure. These holes contain air, which helps to lift the bread.