Egg whites, when whipped, form a light and airy froth that serves as a topping for pies, the basis for light cookies, and the elegant platform for a fruit-and-cream filled Pavlova. Sugar is an essential ingredient in meringue, serving several functions to turn egg whites into dessert.
Sugar serves as a stabilizer to keep the meringue from collapsing, according to the Exploratorium, a museum of science, art and human perception. Sugar bonds with water molecules and holds them in the meringue. Otherwise, these water molecules would escape in the form of water vapor. By delaying the evaporation of the water, sugar holds the meringue together until it's stiff enough to maintain its shape.
Sugar adds sweetness, so the meringue complements the flavor of your lemon pie or meringue cookies. Without the sugar, meringue would taste bland.
If you add sugar to the egg white before you beat them, the sugar slows the formation of the meringue, according to the Exploratorium. Sugar molecules interfere with the protein molecules, which stretch and form a film around the water bubbles that make meringue light and airy.
In baked meringue recipes, such as meringue cookies or Pavlova, the sugar in the meringue gives the dessert a crisp crunch. Cooking Light Magazine also notes that sugar adds to the melt-in-your- mouth quality of baked meringues.