What ingredient in angel food cake contributes to its white color, large volume, and tender texture?

The ingredient that contributes to the white color, large volume, and tender texture of angel food cake is cream of tartar. Cream of tartar is an acid that is used in angel food cake recipes to stabilize the egg whites. When beaten, the egg whites develop a foam, and the cream of tartar helps to maintain this foam structure by preventing the proteins in the egg whites from coagulating too quickly. This stabilization is crucial for achieving the cake's fluffy texture and height.

Moreover, the use of cream of tartar also results in a purer white color, as it prevents the egg whites from oxidizing and developing a yellow tint. The combination of proper egg white whipping and the stabilizing properties of cream of tartar results in the signature light and airy quality that characterizes angel food cake.