What is baking soda used for, and how much should be added?
Baking soda is used in cooking for two purposes:
- As a leavening agent, in order to make baked goods rise. It does this by reacting with acids in the batter or dough, and producing carbon dioxide gas.
- To soften beans during cooking, particularly chickpeas. The alkalinity of the soda helps the complex carbohydrates and fiber in some types of beans break down, allowing them to puree more smoothly.
I can't answer "how much is added" unless I know what you're making.
According to the King Arthur website, 1/4 teaspoon of baking soda is enough to leaven 1 cup of flour. Baking soda leavens by reacting with acidic ingredients and moisture (plus a little more when heat is added). It begins to lose its leavening effect as soon as it is mixed, so cooking soon is critical.