Both are white, both are used in cooking and baking, both store well on your cabinet shelf, but are they the same? Not even close!
Baking powder is a leavener containing a combination of baking soda, an acid(such as cream of tartar) and a moisture-absorber(such as cornstarch). When mixed with liquid, baking powder releases carbon dioxide gas bubbles that cause a bread or cake to rise. There are three basic kinds of baking powder. The most common is double-acting, which releases some gas when it becomes wet and the rest when exposed to oven heat. Single-acting tartrate and phosphate baking powders(hard to find in most American markets because of the popularity of double-acting baking powder) release their gases as soon as they’re moistened. Always check the date on the bottom of the can before purchasing it. To test if the baking powder is still active, combine 1 teaspoon with 1/3 cup hot water. If it readily bubbles, it’s okay. Because it is perishable, baking powder should be kept in a cool, dry place. Since moisture causes deterioration, never dip a wet measuring spoon into the baking powder can.
Baking soda is also known as bicarbonate of soda, baking soda us an alkali used as a leavener in baked goods. When combined with acid ingredients such as buttermilk, yogurt or molasses, baking soda produces carbon dioxide gas bubbles, thereby causing a dough or batter to rise. It also neutralizes acidity and produces tender baked goods. Because it reacts immediately when moistened, it should always be mixed with the other dry ingredients before adding to the liquid; the resulting batter should be place in the oven immediately. At one time, baking soda was used in the cooking water of green vegetables to preserve their color. That practice was discontinued when it was discovered that baking soda destroys the vitamin C content in the vegetables. To test if baking soda is still good, combine ¼ tsp with 2 tsp of vinegar. If it bubbles, it’s still good. Baking soda also works well to help remove baked on foods from pans, just sprinkle with baking soda, add a little hot water and allow to sit overnight. The next day they will be easier to clean out.