What Does Baking Soda Do In Cookies?

Even the most amateur bakers know one thing to be true: Baking is a science. Leaving out even one ingredient (or using the right ingredients in the wrong amounts) can result in a decidedly un-delicious disaster.

But how, you ask, can baking soda be so important when it looks so unassuming? Here's what you need to know about the tiny-but-mighty leavening agent — and what the heck it's doing in your cookie recipe:

Baking Soda vs. Baking Powder

Baking soda and baking powder are both leavening agents, or ingredients that make baked goods rise. They look almost identical and they have similar purposes, but they are not the same thing and they can't always be used interchangeably.

When baking soda, also called sodium bicarbonate, is combined with an acid (like buttermilk or lemon juice) and a liquid, it produces the carbon dioxide that helps the dough or batter rise.

Baking powder, meanwhile, already contains the sodium bicarbonate and acid it needs to become activated—all it needs is a liquid to produce carbon dioxide. Most recipes that call for baking powder are referring to the double-acting varieties, which react twice in the baking process: Once when it's combined with liquid, and again when the product is heated.

What Does Baking Soda Do In Cookies?

So, if baking soda and baking powder both create carbon dioxide, are they really that different? Yes and no. Baking soda is used in recipes that include one or more acids. When the recipe doesn't include an acid, baking powder is used. A recipe that calls for both ingredients probably contains an acid, but not enough to completely leaven the batter or dough.

Baking soda also serves another important purpose when it comes to cookies: It encourages spreading by raising the mixture's pH, which slows protein coagulation. This gives the dough more time to set before the eggs set, which results in a more evenly baked cookie.

Baking Soda Substitute

Don't try to substitute baking soda in cookie recipes that are quite acidic (like snickerdoodles or lemon crinkles). Substitution works better when you're dealing with something sugar-based and dense (like peanut butter or chocolate chip).

You technically can use baking powder as a baking soda alternative, but you'll need to consider a few factors first:

• Baking soda is generally about three times stronger than baking powder, so adjust your recipe accordingly.
• Baking soda and baking powder can produce cookies with different textures. Baking soda is typically used for chewy cookies, while baking powder is generally used for light and airy cookies.
• Since baking powder is comprised of a number of ingredients (baking soda, cream of tartar, cornstarch, etc.), using it instead of pure baking soda will affect the taste of your cookies.

You can also try potassium bicarbonate, a dietary supplement that is often recommended as a baking soda alternative for people with high sodium levels, as a substitute. If you're not watching your sodium intake, you'll probably want to add a pinch of salt to get the closest flavor match.

Learn more: What's a Good Baking Soda Substitute?