Hooray for science!
If you’ve ever tried substituting baking powder for baking soda (or vice versa), you’ve discovered that you can’t use the two interchangeably. We’ve all learned that the hard way and ruined a whole weekend’s baking efforts, so don’t be too hard on yourself. Baking soda and baking powder are easily confused, as they have annoyingly similar names and look exactly alike. Both leavening agents do indeed break down in moisture and/or heat to help baked goods rise instantly without yeast, but baking soda and baking powder are not at all the same.
You may have heard it said that baking is a science, and that’s no lie. Both reactions produce carbon dioxide gas to help dough rise up, but baking soda and baking powder have completely different chemical compositions. Here’s what you need to know.
Let’s start with the simpler of the two. Baking soda is an alkaline base with only one ingredient: sodium bicarbonate. When it’s combined with an acidic ingredient (like buttermilk, yogurt, chocolate, lemon juice, maple syrup, molasses, sour cream, applesauce, or honey), it produces carbon dioxide gas to leaven baked goods. Remember that science experiment you did in elementary school, making a baking soda and vinegar volcano and watching bubbles erupt? That exact chemical reaction occurs in your baked goods, just not as dramatically. The trapped carbon dioxide fizzes and expands with liquid—not heat—to help the dough rise. The chemical reaction begins as soon as the wet and dry ingredients are mixed, so don’t wait to bake. Slide your cookies in the oven ASAP, or else they’ll fall flat.
Also, baking soda spreads, so adding more does not mean more lift. It can leave a metallic, soapy taste if it’s not balanced with enough acid, or if you use too much.
On the other hand, baking powder is basically baking soda with an acidic element already built in, usually in the form of cream of tartar and a little bit of cornstarch. The acids may be slow-acting, which only react when heated, and fast-acting, which only react when wet. Baking powder is available as both single-acting and double-acting powders. Single-acting powders include either slow-acting acids or fast-acting acids. Double-acting powders have both acids and their effects come into play at two different stages throughout the baking process. The first reaction occurs when the dry and wet ingredients are mixed together, and the second starts when it’s exposed to heat. Because of this, the batter can stand for a while before baking.
When you’re using baking powder, try to avoid over-mixing the batter. You want to incorporate the dry ingredients into the wet just enough without letting too many bubbles escape from the mixture.
I know, I know. The million-dollar question still remains: Can you use baking soda instead of baking powder, and vice versa? Not exactly. If you swap baking powder for baking soda, expect the taste of your baked goods to change for the worse. Baking soda is much stronger than baking powder, so you’ll have to triple the amount of baking powder to meet the amount of baking soda that’s required. You can, however, make your own baking powder at home, using a 2:1 ratio of cream of tartar to baking soda. Still, only use the exact amount the recipe calls for. In general though, it’s much better to run to the store and grab the right one.