Powdered sugar, also called confectioners’ sugar, icing sugar, and icing cake, is a finely ground sugar produced by milling granulated sugar into a powdered state. It usually contains a small amount of anti-caking agent to prevent clumping and improve flow.
Although most often produced in a factory, powdered sugar can also be made by processing ordinary granulated sugar in a coffee grinder, or by crushing it by hand in a mortar and pestle.
Powdered sugar is utilized in industrial food production when a quick-dissolving sugar is required. Home cooks use it principally to make icing or frosting and other cake decorations. It is often dusted onto baked goods to add a subtle sweetness and delicate decoration.
Powdered sugar is available in varying degrees of fineness, most commonly XXX, XXXX, and 10X: the greater the number of Xs, the finer the particles. Finer particles absorb more moisture, which results in caking. Corn starch or tricalcium phosphate is added at 3 to 5% concentration to absorb moisture and to improve flow by reducing friction between sugar crystals.Because of these anticaking agents, it cannot always be used as a substitute for granulated sugar, such as in coffee or tea.