The Food Lab: Better Home Cooking Through Science

browning reactions, adding color (and thus flavor)
to things like pancakes, cookies, and muffins.
Baking powder is sodium bicarbonate mixed with
one or more of the powdered acids and a starch. It
does not require another acid to activate it. As
mentioned earlier, most baking powders are
“double-acting,” meaning they produce carbon
dioxide once upon coming in contact with moisture
and then again when heated. Because of this, baking
powder–leavened goods are generally lighter and
fluffier than those made with baking soda alone. This
doesn’t mean, however, that you can let a baking
powder batter just sit around, expecting the second
batch of bubbles to do all the leavening—the initial
reaction is vitally important to the texture of your
baked goods, and so these batters should be baked
right away too.
Don’t have baking powder on hand? It’s quite
simple to substitute with your own homemade
mixture of baking soda, cornstarch, and cream of
tartar. For every teaspoon of baking powder, use ¼
teaspoon baking soda, ½ teaspoon cream of tartar,
and ¼ teaspoon cornstarch. But do bear in mind that
your homemade mixture will not be double-acting,
requiring you to be extra quick about getting your
pancakes onto the griddle or your zucchini bread in
the oven after mixing the batter.