Why do you fold in egg whites over other mixtures?

* To incorporate air and create lightness: Egg whites, when whipped, trap air and form a stable foam. Folding them into a batter or mixture gently incorporates this air, resulting in a lighter and airier texture. This is crucial for cakes, soufflés, meringues, and other recipes that rely on a delicate, airy texture.

* To prevent deflation: Overmixing can deflate the whipped egg whites, causing them to lose their structure and airiness. Folding them in gently ensures that the air bubbles are preserved.

* To retain volume: Folding instead of stirring helps prevent the mixture from becoming dense and compact. This is especially important for recipes where volume is essential, like angel food cake.

The folding technique itself involves using a spatula to gently lift and fold the mixture over itself, incorporating the egg whites while preserving their airiness.

Here are some examples of when folding egg whites is crucial:

* Angel food cake: The airy texture of angel food cake is entirely dependent on the volume and stability of the whipped egg whites. Folding them into the batter gently ensures that the air bubbles remain intact.

* Soufflés: Folding egg whites into a soufflé batter adds volume and helps create the characteristic airy texture that rises dramatically in the oven.

* Macarons: The iconic "foot" of a macaron is achieved by gently folding whipped egg whites into the almond flour mixture.

So, while folding egg whites might seem like a simple technique, it's essential for creating airy and delicate textures in many beloved desserts and baked goods.