Baking Powder

A chemical leavening agent that works on the principle of carbon dioxide gas. Its ingredients include baking soda, an acid, such as cream of tartar, and something that absorbs moisture, such as cornstarch. The leavening comes from the interaction of the basic salt (baking soda) with the acid and produces a more controlled reaction than does baking soda alone. Baking powder can be bought commercially or made at home. It must have liquid added in order for the release of carbon dioxide to take place.

In North America, virtually all baking powder sold is double-acting, which means it contains two types of acid: one that activates upon contact with liquid and the other when exposed to heat in the oven. Single-acting baking powder is much harder to find and is only active immediately after being exposed to liquid, so the batter must be instantly put in a preheated oven or else the rising action is lost. Double-acting baking powder dominates the market because it turns out more reliably light and airy baked goods than the more quickly exhausted single-acting baking powder.

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