Which technique is used to maintain volume when mixing light ingredients into heavier mixtures?

The technique used to maintain volume when incorporating light ingredients into heavier mixtures is folding. Folding is a gentle mixing method that allows air to be retained in the mixture, which is particularly important when working with delicate ingredients like whipped cream or egg whites. This technique involves carefully lifting the lighter ingredients and gently turning them over the heavier mixture, ensuring that the volume and aeration are preserved instead of deflating them.

By using this method, chefs can combine components without losing the airiness that is critical to certain recipes, such as soufflés and mousses. It is essential to maintain that airy texture to achieve the desired final product. In contrast, other methods such as whisking or beating involve more vigorous activity that can cause the lighter ingredients to deflate, which is not ideal in this context. Stirring, while useful for combining ingredients, does not provide the gentle integration required to keep the volume intact.