One other side effect of the additional ingredients in baking powder is that the mix is less concentrated (and thus less powerful) than baking soda. In fact, 1 teaspoon of baking powder has approximately the same leavening power as just ¼ teaspoon baking soda.
Why do some recipes contain both baking soda and baking powder?
If it’s really as simple as whether or not a recipe has an acid in it, then why all the fuss about when to use baking soda versus baking powder—and why do some recipes call for both? Well, it turns out that reality is a bit more complicated. For one, when you mix baking soda with an acid, it doesn’t just create CO2. It also neutralizes the acid, raising the overall pH and making the batter more alkaline. In practical terms, this lessens the sour flavor of ingredients like lemon juice and apple cider vinegar, meaning less tartness in your final dish. Push this too far by adding too much baking soda, and the recipe could end up with an unpleasant soapy flavor. Not good, right? The amounts of acid and sodium bicarbonate in baking recipes must work in perfect equilibrium for the baked item to reach the right level of airiness. In most cases that means soda plus powder.
Buttermilk biscuits are a useful example. Buttermilk is acidic, so your impulse might be to reach straight for the baking soda. But tangy buttermilk is one of the hallmarks of any good buttermilk biscuit, so you don’t want to completely neutralize the acid in your biscuit dough. Instead, you can use a bit of soda because the immediate chemical reaction with the buttermilk gives the biscuits a big lift right out of the gate. But to get the rise you want without killing the tang (which would be the result of too much baking soda), you’ll need to incorporate baking powder as well, taking advantage of the delayed double-action to add even more levity. Combining the two leavening agents produces a biscuit that is both light and tangy. In baking as in life, it’s all about balance.
Many recipes need both kinds of reactions to achieve the intended overall balance of flavor and texture, which is why you’ll often see both baking soda and baking powder in a recipe. Even though the ingredients are both adding air during the baking process, they’re complements, not substitutes.
If the biscuit example doesn’t have you convinced, you should also know that baking soda enhances browning, which gives baked goods their appealing golden hue. Baking soda also weakens gluten, which helps things like cookies or pancakes spread out while keeping them soft and chewy rather than overly dense.
Some recipes do call for using a single leavener and, in fact, there is a common pneumonic device to help you remember the benefits of using baking powder versus soda: “Powder puffs. Soda spreads.” As in, recipes that call only for baking soda will continue to spread in the oven following the rapid acid-base reaction, while those made with just baking powder will rise, adding lift long after baking soda has given up.
So, in short: Baking powder and baking soda are discrete ingredients with the same primary objective—making your baked goods light and fluffy—that they accomplish in different ways depending on the recipe. They can’t be substituted for each another, and most of the time, they can work as a team, supporting each other. If you take one thing from this article, it should be that if you ever see both on an ingredient list and wonder if you really have to go back to the store to pick up another box of the one you ran out of, the answer is, forever and always: Yes.
