Yes, it does matter if a recipe specifically calls for egg whites, as opposed to using whole eggs. The yolk and white of an egg have different properties and can affect the texture, flavor, and structure of the final baked goods.
Egg whites are primarily composed of proteins and water, and they provide structure and stability to baked goods. They can help create a light and airy texture, especially when whipped to incorporate air. Egg whites are commonly used in recipes like angel food cake or meringues, where a light and fluffy texture is desired.
On the other hand, egg yolks contain fat, proteins, and emulsifiers, which contribute to richness, tenderness, and flavor. They also provide moisture and contribute to the overall structure of the baked goods. Yolks are commonly used in recipes like custards, pound cakes, and cookies, where a moist and tender texture is desired.
If a recipe specifically calls for egg whites, it is usually for a reason, such as achieving a specific texture or avoiding the richness of the yolks. Using the whole egg instead of just the egg whites can alter the balance of ingredients and potentially result in a different texture or flavor in the final product.
However, it's worth noting that there can be variations and substitutions in baking, and some recipes may tolerate minor modifications. If you don't have egg whites on hand but want to try using whole eggs instead, you can experiment, but be aware that the results may differ from the original recipe.