Baking Powder and Baking Soda
When a recipe calls for baking soda, it will also call for some type of acid like buttermilk, brown sugar, yogurt, lemon juice, vinegar, cream of tartar, molasses, applesauce, and natural cocoa powder or honey.
You need this additional ingredient in the recipe to react with the baking soda, creating carbon dioxide and allowing your baked good to rise. This is called a leavening agent.
Baking soda is 3-4 times stronger than baking powder. Do not overuse this ingredient. Too much baking soda means leftover baking soda in the recipe, creating a metallic taste in the baked good.
Rule of thumb: 1/4 teaspoon of baking soda per 1 cup of flour in a recipe is usually sufficient.
Baking powder contains baking soda. Baking powder is made of a mixture of baking soda, cream of tartar, and on occasion, cornstarch.
Most baking powder sold is double-acting.
The first leavening occurs when baking powder gets wet, for example, when you combine the dry and wet ingredients in the recipe.
The second leavening occurs when the baking powder is heated in the oven.
Rule of thumb: Use one teaspoon of baking powder per 1 cup of flour in a recipe.
But what if the recipe calls for both - baking powder and baking soda?
Recipes like yogurt, brown sugar, etc., that call for baking powder and soda contain some acid. However, the carbon dioxide from the acid and baking soda is not enough to leaven the volume of batter in the recipe.
For this reason, baking powder is also used to add the necessary lift. When you need more leavening than acid available in the recipe, this keeps it balanced.
Another reason to use baking powder and baking soda is that they affect both browning and flavor. Baking powder and baking soda can settle in their containers over time. Shaking it up or stirring it, then using a measuring spoon to scoop it out of the container lightly, is recommended. Use a knife (or the container with a leveler) to level it off.
Testing for freshness:
Add 3 Tablespoons of warm water into a bowl to test the baking powder. Add 1/2 teaspoon of baking powder, and give it a gentle stir.
The mixture will moderately fizz if the powder is fresh. If there is no reaction, discard the baking powder and buy a new package.
Testing Baking Soda
To test baking soda, pour 3 Tablespoons of white distilled vinegar into a small bowl. Add 1/2 teaspoon of baking soda, and give it a light stir.
The mixture should rapidly bubble if the soda is fresh. If there is no reaction, throw out the baking soda and buy a new package.