So back to exciting stuff. Guys, I never knew the difference between baking soda and powder for years. I just added what the recipe said and didn't ask questions. Who am I to question a recipe? I'm nothing if not diligent in following directions. But as I've begun to tinker with developing my own recipes or even just tweaking recipes that I find on the Interwebs or in a cookbook, I've realized how important it is to understand what role each ingredient plays. First on my list was discovering the difference between baking powder and baking soda and learning what exactly they do in a recipe. So let's start with the basics:
Baking Soda: Also called "bi-carb" if you're Nigella Lawson (and who doesn't want to be Nigella Lawson?), it's a chemical leavening agent that reacts when it comes in contact with acidic ingredients (like sour cream, vinegar, or buttermilk). Basically, the alkaline baking soda reacts with the acid and forms little bubbles that lift your batter or dough.
Baking Powder: Ok here's the shocker. Baking powder is just baking soda with two additional acidic ingredients. It's a self-contained leavener! How sneaky. So in this case, both alkaline and acid are present in the powder itself and they produce the "lift" in the presence of liquid and heat.
A note about baking powder: Unlike baking soda, baking powder actually has a somewhat limited shelf life. If stored in a cool dry place, it generally lasts about 12-18 months. But the real indicator is how your baked goods look. If cakes or muffins start to look a bit sunken or just don't have the rise you want, try getting some new baking powder.
But it gets so much more exciting (I will keep exaggerating until you get excited). Baking soda also assists in browning. A perfect example of this is the Cinnamon Sugar Donuts I made. Notice how pale they are? That recipe didn't have baking soda, only baking powder. So in a recipe WITH baking soda, it creates an alkaline environment which is ripe for browning! In science talk, amino acids react with sugar in an alkaline environment to create browning. And browning means flavaahhhh.
I know, you are now astounded by these ingredients. I've amazed you. But don't thank me, thank science.