Eggs…are magic in baking. Seriously. They truly are. The whites mimic little clouds that mystically lift and elevate anything they come in contact while egg yolks are so succulent and transform humble ingredients into the most luscious creams, curds and custards. Can you tell that I just am a bit enamored with these little guys?
The Science. Let’s have a look at the main components of eggs, their structure and function, shall we?
Whole eggs: Whole eggs in baking serve a multitude of purposes, from acting as binders, to leaveners, to adding richness and stability. When whisked, eggs are aerated which is the incorporation of air into batter and thus build in volume up to four times their original volume. Eggs are emulsifiers which stabilize liquids that naturally repel one another such as oil and water, and coagulators which help bind ingredients to one anther through their transformative properties from liquids to solids. Arguably, the most significant contribution eggs make to bakes are the structure they provide. The building blocks of this structure come from the protein found in eggs. When heated or agitated by methods such as whisking, the tightly wound proteins molecules, unwinds and reconnect with other nearby proteins giving the bakes structure.
Egg Whites: Egg whites which are also known as albumen (originating from the Latin word albus meaning white) are comprised of 90% water and 10% protein, mainly the protein albumin. In baking, egg whites act as leaveners and provide structure and stability to bakes.
When whisked, egg whites can increase to eight times their volume. This is the showstopper of the magic show. Watching a few eggs white in the bottom of a bowl slowly begin to increase in volume and then resulting in billows of airy clouds is so captivating. The dramatic increase in volume is attributable to the physical whisking action that forces the protein molecules to unfold and in turn create foam. In addition to the structural change in the egg white proteins, the whisking action also incorporated air into the whites which adds to the volume as well. Warming the egg whites initially by gently heating them over a water bath until warm to the touch slows down the process of unwinding the protein molecules which maximizes the structure. Also, beginning the whisking process on low and gradually increasing the speed creates more a more uniform and thus stable structure. When whisked the unraveled proteins hold in the air, thereby creating foam that is categorized by the stages the egg whites transform into: soft, firm and stiff peaks.
Egg yolks: Egg yolks are comprised of predominantly protein, with fat and water. Yolks not only add moisture and richness to bakes, they are also a natural binder. The yolks are also where the vitamins and minerals of the egg are concentrated, including lecithin which is a natural emulsifier that adds creaminess and flavor to bakes, custards and sauces. Egg yolks can also be aerated, however due to their composition and fat content will only double in volume.
It is important to bring eggs, as well as other ingredients to room temperature when baking, unless the recipe specifically calls for otherwise.
Fat is your nemesis when whisking egg whites and building volume. Any fats, from even a trace of egg yolk to remnants in the whisking bowl while sabotage the entire batch of whites. To avoid this collapsing calamity, make certain you use a copper, metal or glass bowl that free of any traces of fat and that there are no egg yolks in your egg whites.