Craving dessert? Today’s episode considers some particularly sweet science: the importance of eggs for baking a cake.
Let’s say you’ve got your ingredients ready, your oven’s on, and that cake pan is greased. On to the first step: you cream the butter and sugar. While this action nicely combines your fat and sweetener, it also adds a third ingredient: air. As you fold sugar and butter over and over, tiny air bubbles form, making the mixture lighter and fluffier.
Now, let’s get cracking—cracking eggs, that is, right into your butter/sugar combo. Eggs are full of protein molecules, which are curled up into little globs of amino acids. Some of these amino acids love water; they’re hydrophilic. But other amino acids in the protein despise water; they’re hydrophobic.
When you beat eggs into the sugar and butter blend, you unwind those neat little protein globs. Because water is found in both butter and egg whites, the protein’s amino acids get all in a tizzy—suddenly the hydrophobic amino acids are swimming in the batter’s water! To fix this problem, the proteins wrap themselves around every air bubble. This allows the hydrophobic amino acids to press against air, and the hydrophilic amino acids to face the water of the batter.
The reorganized proteins link up, making a powerful web. When you add flour to your butter-sugar-egg mixture, the flour proteins join the egg proteins and reinforce that web around the air bubbles. As you bake the cake, all that protein coagulates with heat, stopping the bubbles from popping. The result? Structure! Your cake is delicate but firm, and perfectly springy. Want a slice?
