Baking Soda & Baking Powder

Baking soda and baking powder are staples in a baker's kitchen and are very common ingredients in cookies, cakes, and other baked goods. However, the role that they play in baking and the differences between the two ingredients can be confusing! Keep reading to learn the difference between baking soda and baking powder (plus how to know if your ingredients are fresh or if it's time to replace them).

What is the difference between baking soda and baking powder?

Both are chemical leaveners, which means that they "lighten" dough and batter. They are what make our cookies and cakes rise. But they are not the same, and they are not interchangeable.

What is baking soda?

Baking soda is sodium bicarbonate. When activated, baking soda releases a gas (carbon dioxide) into our baked goods, causing them to rise.

Baking soda is activated when it is mixed with an acid. So in baking, we activate baking soda by pairing it with an acidic ingredient (such as lemon juice, buttermilk, or yogurt) in our recipes.

Baking soda can be a little bit tricky, because you need enough acid in your recipe to activate all of the baking soda. If you have leftover baking soda that isn't activated, you could end up with a slightly metallic taste in your baked goods. Ick! This is why it's important to follow your recipe and measure your ingredients properly.

What is baking powder?

Baking powder is a mixture of sodium bicarbonate (baking soda), powdered acid, and cornstarch. Like baking soda, when activated, baking powder releases a gas (carbon dioxide) into our baked goods, causing them to rise.

Today, most baking powder is double-acting. This means that it is activated twice: first when it is mixed with a liquid, and again when it is heated. In baking, our baking powder is first activated when it's added to our batter, and it's activated again when it's heated in the oven. Since baking powder already contains an acid, it is not necessary to mix baking powder with an acidic ingredient in order to activate it. 

When should you replace your baking soda and baking powder?

Generally, it's best to replace your baking soda and baking powder three to six months after opening to ensure that they're fresh. Baking soda and baking powder that have been open for some time or that have passed their expiration date will lose their potency and will not help your baked goods to rise properly.

To test baking soda for freshness, place a spoonful of baking soda in a bowl and add a splash of vinegar or lemon juice. The mixture should become very fizzy. If there is little or no fizzing, the baking soda should be replaced.

To test baking powder for freshness, pour some warm water into a bowl and then add a spoonful of baking powder. The mixture should become fizzy. If there is no reaction, the baking powder should be replaced.