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Ask Dr. Universe: What’s the purpose of baking soda and baking powder?

UPDATED: Sun., Oct. 24, 2021

Baking powder and baking soda are two of the most important ingredients on a baker’s shelf.  (Scott Suchman/For the Washington Post)
Baking powder and baking soda are two of the most important ingredients on a baker’s shelf. (Scott Suchman/For the Washington Post)
Washington State University

By Washington State University

Dr. Universe: What’s the purpose of baking soda? What’s the purpose of baking powder? What’s the difference between the two? – Kyle, 9, Florida

Dear Kyle,

When I got your question, I headed directly to my kitchen cabinet. I grabbed some baking soda and baking powder from the shelf and made some observations.

Not only did the baking soda and baking powder look similar to each other, but both contained an ingredient called sodium bicarbonate.

To find out more about this mysterious ingredient, I talked to my friend Stephanie Smith, a professor who teaches food science at Washington State University.

She reminded me that sodium bicarbonate is a chemical compound. A compound is something made up of atoms or molecules. This particular chemical compound can react with certain ingredients to create tender and fluffy textures in our baked goods.

While baking powder and baking soda may have a similar purpose, they work in slightly different ways, Smith adds.

If you’ve ever mixed baking soda and vinegar together, you know that the mixture foams up quickly. As this happens, the mixture lets off a gas called carbon dioxide.

The carbon dioxide gas is actually what helps give everything from muffins to cookies to cakes their nice, fluffy textures. The gas creates small pockets of air in your cookie mix or cake batter. It ultimately helps the final product puff up.

Baking soda is just sodium bicarbonate. It needs a couple of things to help it react with other ingredients in our mixing bowls. First, it needs an acid. There are all kinds of acids in our world. When it comes to baking, some of the acids we use include buttermilk or lemon juice.

Once you have an acid, you’ll also need a liquid such as water or milk. Finally, the carbon dioxide bubbles will be able to form.

Meanwhile, baking powder is actually just baking soda, plus some dry acid. Since it already has the acid, all you have to do is add water or another liquid to get those carbon dioxide bubbles.

There’s another ingredient we can sometimes use in the kitchen to create carbon dioxide gas, too. Perhaps you’ve heard of it before. Unlike baking soda and baking powder, this particular ingredient is a living organism.

It’s an ingredient that is also often used in making bread or pizza dough. If you are thinking of yeast, you are correct. Yeast is a kind of microbe that can eat the sugar in your dough and release carbon dioxide gas to help the bread rise.

Whether you are using yeast, baking soda or baking powder, there sure is a lot of science that goes into making baked goods rise and get fluffy. You know, the kitchen is a great place to ask big questions about how and why things work.

Maybe one day your questions will lead you even further into the fascinating worlds of baking, chemistry or food science.


Dr. Universe

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