Eggs are wonderful. They are used in so many baked products and in so many ways. Most cakes are not possible without eggs and cookies are also difficult to make without eggs.
An egg is composed of three main parts plus membranes and two white strands called chalazae that hold the yolk in the center of the white.
The shell that contains the egg is fragile and porous. It is important to remember that eggs absorb flavors and odors through the shell and therefore they must be protected from strong smelling substances and unsanitized surfaces. When baking, make sure that your eggs are odor free. A tainted egg will spoil your product.
The yolk is high in both fat and protein and is a natural emulsifier. It is rich in vitamins and minerals and contains cholesterol. The color of the yolk varies depending on the diet of the chicken but color is not an indicator of food value or quality.
The white is primarily albumin protein. It is clear and soluble before it is cooked. It contains sulfur and becomes odorous when old.
About 3/4’s of the egg by weight is water, hence when you add eggs to the batter you add a great deal of water into the product. The remaining portion is nearly equal parts of fat and protein.
So what role do eggs really play in the process of baking Here is a list of nine different functions of eggs in baking:
Structure: As eggs cook, the protein coagulates and provides stiffness to the product.
Leavening: Eggs help in leaven by trapping air cells in whipped eggs or egg whites. Angel food and chiffon cakes are often entirely leavened using eggs.
Tenderizing: The fat in the egg yolk shortens gluten strands in batters and dough to tenderize the product.
Moisture: Since eggs are mostly water, they moisten the products to which they are added.
Wash: Egg whites and egg yolks are used as washes on baked goods like croissants and Danish pastries to give them a glossy finish and on rustic breads to hold sesame seeds and other accouterments in place.
Emulsifying: Eggs act as natural emulsifiers that help in making the batter smooth.
Flavor: They add a unique taste and flavor to the baked goods.
Color: Most lemon meringue pie recipes rely entirely on egg yolks for color.
Nutrition: They add nutritional value such as protein, Vitamin D, and choline (an important nutrient for the brain, nervous system, and cardiovascular system).