Baking Powder

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-pe... read more