Baking soda and baking powder are both leavening agents that cause baked goods to rise, but they are chemically different and should be used differently.
• Baking Soda
- one ingredient: sodium bicarbonate
- contains only base
- requires addition of an acid (lemon juice, buttermilk, cream of tartar, brown sugar) to activate bubbling and rising (like the volcano experiment you did in school...nothing happened until you added vinegar)
• Baking Powder
- mixture of baking soda, cream of tartar, and cornstarch
- contains acid and base
- only requires addition of moisture to start reacting
- has a second reaction when heated in the oven
• Why do some recipes call for both?
- Sometimes additional lift is needed and you want to balance flavors differently where the taste from the acidic ingredients still comes through.
• Can you substitute one for the other?
- Technically, yes. But it can be tricky and the taste can be thrown off by requiring an increase in the amount of powder or acid for the leavening to happen.
• Don’t forget that they expire!
- Either one can lose their ability to make things rise if past the expiration date. The leavening reaction won’t be as strong and your results could literally fall flat.