What does it mean to fold egg whites into batter?

Folding egg whites into batter is a cooking technique used to incorporate air into a mixture, creating a lighter and fluffier texture. Egg whites are separated from the yolks and beaten until stiff peaks form. Stiff peaks occur when you lift the whisk out of the egg whites, and the peaks hold their shape without folding over. Once the egg whites reach this stage, they are gently folded into the batter with a spatula or wooden spoon. Folding involves cutting through the egg whites with the utensil and then gently lifting and turning them over the batter until just combined. This is done to maintain the air incorporated into the egg whites and prevent it from being deflated. Folding egg whites into batter is commonly used in recipes such as meringues, soufflés, angel food cakes, and sponge cakes to achieve their characteristic airy and light texture. Folding is crucial because stirring or mixing too vigorously would cause the air to escape and result in a denser texture.