Soda science

When you inspect almost any cookie recipe other than shortbread, you’ll probably find baking soda in the ingredient list. Most people generally understand how baking soda works to make cakes rise, but why do cookies need this pantry staple since they don’t really rise that much? Stella Parks at indexed blog Serious Eats has the scoop and explains the multi-faceted role of baking soda in cookies.

It turns out that leavening isn’t the only effect soda provides; it “also raises the dough’s pH, and that’s a pretty big deal. Creating an alkaline environment slows protein coagulation, which gives the dough more time to spread before the eggs set. This promotes a uniform thickness from edge to center, helping the cookies bake more evenly,” says Parks. Additionally, the alkalinity of the soda impedes gluten formation, which helps tenderize the cookies. But wait, there’s more! Baking soda even speeds up the Maillard reaction, causing the cookies to brown faster and develop more flavor. That’s a lot of work for one simple ingredient.

Parks illustrates the different roles for soda using a gingersnap recipe. She changes the amount of soda from none to a full teaspoon, noting the changes to the cookies after each tiny bump. Since even a small change to the amount of soda can have a big impact, Parks warns not to go overboard when making changes to any cookie recipe.

Many times when cookies or cakes fail, stale baking soda is often blamed. Chances are that the baking soda is not the culprit, as it can last almost indefinitely at room temperature in most climates. It would have to be held at high temperatures and/or at very high humidity levels for extended periods for it to significantly diminish in quality. So if your soda is past its “expiration” date, it’s probably still good to use.

Photo of The best gingersnaps from indexed blog Serious Eats