I teach the food science application lecture and laboratory at UC Berkeley and one of my favorite weeks is the week where we investigate eggs using angel food cake. Not only because I absolutely love angel food and honestly, even the cakes with recipes that are intentionally messed up still taste good to me, but because I think eggs are amazing. They are amazing for their incredible nutrient density (what other food gives you so much protein, vitamins, and minerals in 75 calories?), but also because they perform such a diverse array of culinary tasks, from aroma to structure. Also, I love the fact that, once out of the shell, they are so fragile and sensitive - just a few degrees can create a completely different product. Unfortunately, not everyone shares this fascination with eggs, be it because of the way they smell or unfounded worries about saturated fat (an average of 1 egg per day is completely fine, the benefits outweigh the saturated fat content). Oh well - more for me!
Angel food cake is the perfect vehicle for evaluating the properties of egg white foams. In lab, we conduct this evaluation with nine different variations in addition to the classic “gold standard” recipe.
Variations include (beginning with arrow and moving counter clockwise). Some worked as they were supposed to and others did not. See below for descriptions of what would theoretically happen to the cake, given the variation:
Cake 1, Classic: Gold Standard
Cake 2, Beat a longer time, until Stage IV: Proteins are overcoagulated, leaving cake "brittle" and stiff.
Cake 3, Beat foam a shorter time, until Stage I: Proteins not denatured/coagulated enough, no structure, does not rise.
Cake 4, Increased manipulation/folding of batter: Collapsed air cells that were created in beating the foam. Cake is dense and flat.
Cake 5, baked at a lower temperature for a longer period of time: Does not rise as high because no initial hot air.
Cake 6, cream of tartar omitted: COT is an acid that helps stabilize the proteins and bleaches anthocyanin, a yellow pigment. Cake without COT has a poorer structure, coarser crumb, and yellower color.
Cake 7, use of hand beaters in place of electric: Totally depends on the skill of the chef! May actually lead to a better, more delicate product because hand blenders often have more blades.
Cake 8, only 1/2 the amount of sugar used: Sugar helps prevent the eggs proteins from denaturing, making it take longer to create a foam and leading to finer air cells and a stronger structure. Without sugar, structure is weak and may not be high in volume, crumb is coarser, and cake is bbviously not as sweet. The lack of sugar also leads to more developed gluten because there's no sugar to draw the water away from the gluten to develop it, which means a tougher cake with less sugar.
Cake 9, lemon juice used in place of cream of tartar: Lemony tasting and structure is weaker, less consistent.