Cream of tartar is a white, powdery substance technically named potassium hydrogen tartrate. It is derived from the leftover residue that collects on the inside of wine barrels after grape fermentation. The residue then is processed into a salt. Cream of tartar has acidic properties that make it useful for a variety of culinary purposes.
Stabilizer
Cream of tartar can act as a stabilizing agent in foods and add thickness to prevent ingredients from losing their shapes. One of the most common uses for cream of tartar as a stabilizing agent is with eggs. Egg proteins contain fluids that prevent the incorporation of air. Without incorporated air, foods are dense and lack volume. When cream of tartar is beaten into eggs, the proteins become lighter and easier to shape. Egg whites beaten with cream of tartar often are used to make meringue dessert toppings.
Texture
Mixtures that contain sugar (such as icing or candy) can have a rough texture without the addition of an acidic ingredient like cream of tartar. Sugar naturally has a rough texture that smooths out when it's heated and the molecules separate. When sugar molecules go back to their natural formation, it's known as crystallization and results in a grainy texture. If cream of tartar is added with sugar, the acid will prevent the sugar molecules from separating and make mixtures smooth and glossy.
Baking Powder
Cream of tartar often is an active ingredient in baking powder. Baking powder typically is a mixture of baking soda, cream of tartar and cornstarch. The mixture is added to batters of baked goods to make sure they come out light and airy after being heated. The cream of tartar in baking powder forms air bubbles throughout the batter when it is heated in the oven. The distribution of air bubbles prevents cakes and other baked goods from being dense.
Color Preservation
When vegetables are boiled, they often lose their pigmentation and wind up looking visually unappealing. Cream of tartar can be added to boiling water in order to help prevent boiled vegetables from losing their colors. Since cream of tartar is an acid, it can keep the vegetable pigments intact and reduce browning. Only a small amount of cream of tartar (about a half-teaspoon) is needed to preserve vegetable color without affecting the taste.
Additive
Food additives are ingredients used in processed foods to extend their lifetimes by preventing their ingredients from breaking down or separating. Cream of tartar often is a main additive ingredient in processed goods such as baked goods, candy, carbonated drinks and gelatin. It helps keep sugar molecules intact, so products can maintain their flavors and textures. Without an acidic additive like cream of tartar, products would have shortened shelf lives because they would be visually unappealing and taste bland.
