On leavening: baking soda
During a surprisingly memorable middle school talent show act, a classmate of my older sister staged a sort of cooking show where she “demonstrated” how to bake something–maybe cookies? Under the requisite floppy chef’s hat, she mixed and stirred and muddled her way through the recipe, doing just about everything wrong. I don’t actually remember where it fell on the middle school talent show spectrum of excruciating to hilarious, but I do remember her getting to the part about baking soda and throwing in some Dr. Pepper.
For those of us baking to make food and not to stage a comedy show, hopefully we recognize baking soda as something entirely different from Coke and its ilk. Although it makes magic in baked goods, giving us light, airy cupcakes and perfectly crisp cookies, the chemistry here is super simple.
Baking soda, also known in scientific circles as sodium bicarbonate, has two parts: a positively charged sodium atom (Na+), which we pretty much ignore, and a negatively charged bicarbonate molecule (HCO3–). That negative part acts as a base and desperately wants another hydrogen to complete it (chemistry is a lot like match-making, as it turns out), so it steals hydrogen from anything around it. Acids are usually a good source of hydrogen; in the kitchen think vinegar, lemon juice, buttermilk, and sour cream. In addition to fulfilling their destinies and all that, bringing hydrogen and bicarbonate together also creates carbon dioxide (CO2). These tiny gas bubbles puff up your dough and create the air pockets that make baked goods fluffy.
The most important lesson here boils down to this: baking soda plus acid gives you air bubbles. Baking soda without acid gives you a bad taste in your mouth. So baking soda works well in recipes where an acid plays a starring role: orange and buttermilk pancakes, anyone? The basic baking soda reacts with the acidic liquids to make fluffy, flavorful pancakes that take breakfast to new heights.