What are two functions of cream and tartar in angel food cake?

1. Stabilization of Egg Whites: Cream of tartar is an acidic ingredient that helps stabilize the egg whites when they are whipped. Egg whites contain proteins that tend to unfold and form bonds with each other, leading to the formation of a stiff foam. However, adding cream of tartar lowers the pH of the egg whites, which inhibits the unfolding of the proteins and allows them to remain dispersed. This results in a more stable foam that can hold its structure and volume during baking.

2. Leavening Action: Cream of tartar also acts as a leavening agent in angel food cake. When combined with baking soda, it undergoes a chemical reaction that produces carbon dioxide gas. This gas becomes trapped in the batter and expands during baking, causing the cake to rise and become light and fluffy. However, unlike baking powder, cream of tartar provides a slow and steady leavening action, which is crucial for angel food cake's delicate texture.