Eli5 Why does adding whipped egg whites to a batter make a cake rise?

Question

Eli5 Why does adding whipped egg whites to a batter make a cake rise?

In: 8

Answer 1

Whipped egg whites do two things.

First, the whipping of the egg whites fill them with many many many tiny air bubbles, which helps increase the volume of the cake. Plus those air pockets will want to expand when heated.

Second, the proteins in the egg whites will quickly start to solidify when cooking, which helps give the cake extra structure, holding those air pockets open.