Royal icing is a hard white icing, made from softly beaten egg whites, icing sugar (powdered sugar), and sometimes lemon or lime juice. It is used on Christmas cakes, wedding cakes, gingerbread houses and many other cakes and biscuits, either as a smooth covering, or in sharp peaks. Glycerine is often added to prevent the icing from setting too hard. When Icing cakes Marzipan is usually used under the Royal Icing to prevent discoloration of the icing.
Usual proportions are 2 egg whites to 1 teaspoon of lemon juice, 1 teaspoon of glycerine and 1 Pound of sugar. The amount of sugar however must be altered to get the right consistency for application.
As well as coating cakes and biscuits, royal icing is used to make decorations such as flowers and figures for putting on the cake. The Royal Icing is piped into shapes which are allowed to harden on a non-stick surface. These can then be arranged to create edible decorative effects on a variety of sweet foods. The Glycerine must be omitted for this purpose.
Although royal icing has traditionally been prepared with fresh egg whites, many people substitute meringue powder, given the risk of salmonella that using raw egg whites presents.[1] Alternatively, ready-to-use, pasteurized, refrigerated egg whites can be purchased in most grocery stores which should also provide a safe alternative to fresh egg whites.