baking powder 

It’s happened to us all at least once in the kitchen: you’ve decided on double chocolate brownies, and you’ve pulled out the eggs, the milk, the cocoa and the sugar. But wait, uh, baking powder, or baking soda? What if you only have one; are they interchangeable? And really, what the heck are they? Quick, now, only 30 minutes before movie night with the girls begins!

It all starts with sodium bicarbonate. This handy little chemical is used in lots of applications (like green cleaning), but for culinary purposes, it does one brilliant thing in baking: leavening. What’s leavening, you ask? Think of a wet cupcake batter poured into muffin tins. Approximately 22 minutes later, when you pull out the muffin tin from the oven, that wet batter has become light, fluffy, risen bread. That’s leavening.

Baking soda is simply sodium bicarbonate, and it works by reacting with an acid in a recipe, like buttermilk or lemon juice.

When there is no acid in a batter, baking powder is called upon. Baking powder is basically just baking soda (remember sodium bicarbonate?) with a bit of acid salt and cornstarch added. The acid salt (cream of tarter and sodium aluminum sulfate) is necessary for the leavening action to take place, since there is no acid in the batter. The cornstarch is there to absorb moisture so that leavening doesn’t occur until a liquid goes into the batter (i.e. so that the baking powder doesn’t shoot its load too soon).

As many a sad baker-in-training has discovered (as they pulled out limp or fallen cakes from the oven), baking powder and baking soda are not interchangeable. Technically, baking soda can be used in place of baking powder, but you’d have to add cornstarch and cream of tarter to the mix—kind of a pain when you’ve got just 30 minutes to whip up double chocolate brownies before the girls come by for romcom movie night. Best to simply cough up the 2 to 3 dollars for each and keep them smartly stocked in your baking cupboard.

Image: Mel B.