Just in case you were wondering,
The Role of Egg Whites: Foam!
When
egg whites are used alone, they perform an entirely different role from the yolks, especially when whipped. Whipping and using egg whites in a recipe does not have to be as intimidating as you may think, and we'll be talking much more about this in a few days. For now, just know that whipping egg whites means incorporating millions of little air bubbles within the white. This creates a fairly stable foam that we can use to make everything from a soufflé to meringue. To help stabilize egg whites even further, we can add acidic elements, like cream of tartar and lemon juice.
One of the best ways to use
whipped egg whites is as a natural leavening agent in something like a delicate cake or a soufflé. In the heat of the oven, the air trapped in the foam starts to expand, causing the recipe rise without the need for things like yeast or baking soda. In fact, whipped egg whites are how many classic baked goods, like sponge cakes, got their lift in the days before baking soda and baking powder!
Egg whites can also be whipped with sugar to make meringue, which can then be baked into crunchy meringue kisses, made into billowy pavlovas, or dolloped on top of desserts like baked Alaska. Sugar makes whipped egg whites incredibly stable — you can even pipe it using a piping bag into stars, kisses, and toadstools.
While the idea of "light" and "airy" whipped egg whites might make you think that more is better, it is possible to overdo it. Over-whipped whites will become clumpy, grainy, and difficult to fold into your batter. Also, using too many whites in a batter can wind up making the final product dry.
The Role of Whole Eggs: Fat and Foam
When you use whole eggs in a recipe, you get some of the best properties of both the yolk and the white. While whole eggs aren't quite as good as straight yolks at creating an emulsion, they are still excellent binding agents, especially in cakes, cookies, and other baked goods. Eggs also firm up and solidify when heated, giving crucial structural support to delicate desserts and pastries. At the same time, eggs make baked goods more tender, creating light textures, soft breads, and delicate crumbs.
When mixed with sugar (like in a cake or cookie batter), eggs help trap and hold air — not quite as well as whipped egg whites, but enough to give the finished product some lightness and lift. The combination of eggs and sugar also adds a great deal of moisture and flavor to a recipe.
Yolks and whites can also be used separately in the same recipe. This truly is the best of both worlds, with the yolks providing richness to a base or batter while the whipped whites do their job of lightening and leavening. Chiffon cakes and soufflés are good examples of this kind of recipe.
Thanks Kitchn for the interesting article.
