Baking Soda Needs Acid

• Baking soda, also known as sodium bicarbonate, is the older of the two chemical leavening agents. No one knows for sure what adventurous baker thought to try using baking soda in place of yeast, but it has been employed as a leavener for bread and cakes almost as long as yeast has. Baking soda requires an acid to activate. These acids can be ingredients such as cream of tartar, lemon juice, vinegar, buttermilk, molasses or fruit. The goal is to produce the same kind of chemical reaction that results from yeast fermentation: carbon dioxide bubbles. Baking soda's carbon dioxide enlarges air bubbles that result from beating together the other ingredients (mixing always incorporates air into the batter). These bubbles cause the batter to expand, or rise, when baked.

Baking Powder Can React Twice

• Baking powder was introduced in the mid-19th century in the United States. It's a combination of baking soda, a dry acid powder and cornstarch to inhibit moisture. Baking powder comes in three forms: fast-acting, single-acting and double-acting. Fast-acting and single-acting baking powders typically are made with cream of tartar and release carbon dioxide the moment they combine with a liquid. Batters using fast-acting or single-acting baking powder must be baked quickly or they'll lose their bubbles. However, most baking powder today is double-acting, meaning that it contains acids that react at different rates with the powder's baking soda. Thus double-acting baking powder produces bubbles when first mixed with a liquid, and again when heated in the oven. Recipes made with baking powder don't have to be rushed into the oven, but it's still not wise to let them rest too long once mixed.

Measure Carefully

• Either baking powder or baking soda with an acid is suitable as a chemical leavening agent for quick-breads, muffins, cookies, cakes and other baked goods. However, caution is the byword with either ingredient. Baking soda is four times as strong as baking powder, so less of it should be used. Too much baking soda will give baked goods a soapy taste. Too much baking powder gives baked goods a bitter taste. Neither excess can be corrected successfully once the baking is done.

Going Beyond Lift

• In addition to their properties as leavening agents, baking powder and baking soda contribute to the flavor and browning of baked goods. That's why some recipes call for both ingredients. Baking soda, being alkaline, helps baked goods brown better. Baking powder, having a mix of acid and alkaline, can help preserve tangy flavors in recipes with more acid, such as sour cream cakes or buttermilk pancakes.