How we tested
For such an indispensable ingredient, leavening remains an afterthought to most home bakers. But it’s undoubtedly essential: Without the transformative powers of leavening, many baked goods would emerge from the oven dense, flat, or hard.
Most leaveners work on the same principle: When added to a batter or dough, they release gas, creating air bubbles that lift the mixture. The most familiar natural leavener is yeast, which consumes the sugars in a dough and produces air bubbles. Resilient doughs, like bread doughs, are elastic and can contain gas bubbles for a relatively long period. Quick bread doughs and runny cake batters can’t hold gas bubbles for long, so when making these, we rely on fast-acting chemical leaveners.
There are two commonly available chemical leaveners, baking soda and baking powder. Baking soda is a single-ingredient product, whereas baking powder is a mix, combining baking soda with a powdered acid and a starch.
But the mix isn’t always the same from brand to brand. Since different combinations of ingredients are used in different brands of baking powder, we rounded up six nationally available products and had 21 America’s Test Kitchen staff members assess them in white cake, chocolate crinkle cookies, and cream biscuits.
To keep everything consistent, we carefully measured all the ingredients and baked the cakes in the same oven, one after another. When we lined up the cooled cakes side by side, we were astounded at the differences. Some cakes were tall and airy, while others were dense and squat. The thickness of the cakes varied by up to 20 percent—from 0.89 inch to 1.24 inches—and tasters preferred the delicate, tender crumb of taller cakes. (We baked the cakes three more times, always using freshly opened baking powders, and the results were the same.) What was going on?
Modern baking powders are “double acting,” meaning they release some of their carbon dioxide when moistened and the rest when heated. (True “single-acting” baking powders, by contrast, release all their gas when mixed with liquid and are rarely manufactured anymore.) Although all the baking powders we tested release approximately the same total amount of carbon dioxide gas, brands vary widely in the ratio released at room temperature versus at higher temperatures in the oven. This is important: If too much gas is released at room temperature, cakes won’t bake up tall and airy in the oven.
To get a better idea of the composition of each baking powder, we scrutinized ingredient labels and talked to manufacturers. We learned that the two densest and squattest cakes were made with baking powders that use just one acid, while stronger-performing brands have two forms of acid to bolster lift. Baking powders with just one acid create only 30 percent of their lift in the oven. By contrast, brands with two acids produce 60 to 90 percent of their lift in the oven and create baked goods that are airier, fluffier, and more tender.
But fluffier isn’t better in every application: Lower-rising baking powders actually made moister and chewier cookies. Brands that performed best in cake made cookies that were just a little too fluffy and cake-like. This wasn’t enough to drop these powders from the top of our rankings, but it did push them from the top spot: We were looking for a great all-purpose baking powder, after all. (Don’t worry, our winning baking powder still produces a tall, fluffy cake.)
Finally, since tasters didn’t notice flavor differences in other applications, we tried the baking powders the plainest way we could think of, in cream biscuits. Texture wasn’t an issue in this denser dough, except for one biscuit that took on a speckled, uneven appearance. (Our science editor explained that the baking powder used in that sample includes potassium bicarbonate, which can cause unwanted browning.) Flavor was more contentious, with 30 percent of tasters noting a metallic flavor in two samples. (Ingredient labels showed that the corresponding products contain aluminum compounds.) This wasn’t enough to be off-putting, but tasters preferred options with a clean flavor.
While we didn’t find any products that would ruin a baking project, we did find brands that make the difference between a decent cake and a great one.
Our favorite was an inexpensive all-purpose powder that produced tender cakes, soft biscuits, and perfectly chewy cookies.
What’s the Difference? Baking Powder versus Baking Soda
Baking soda and baking powder both perform the same job (leavening), but each does it in a different way. Baking soda is a single-ingredient product that reacts with acidic ingredients to release carbon dioxide and provide lift. In recipes with a high proportion of acidic ingredients like chocolate, fruit juice, yogurt, or buttermilk, baking soda performs well on its own.
Baking powder is a mix of baking soda (or another carbon-dioxide producing chemical), a powdered acid such as cream of tartar, and a starch to keep the chemicals dry. When moistened, the powdered acid reacts with the soda, releasing carbon dioxide for lift in recipes without a strong acidic component.