Baking Powder vs. Baking Soda: What’s the Difference?

Baking soda, also known as bicarbonate of soda or sodium bicarbonate, is a chemical leavening agent commonly used in baked goods. Baking soda is a base alkaline compound, which means it is not acidic. When baking soda is combined with an acid, it creates carbon dioxide gas (think: baking soda and vinegar volcanoes from elementary school).

Baking soda reacts with acids in a recipe, neutralizing them and, in the process, creating carbon dioxide. Examples of acids include: buttermilk, brown sugar, lemon juice, or yogurt. The bubbles from the carbon dioxide cause the batter to rise. Without baking soda, cookies would be dense pucks and cakes would be flat.

Be careful not to use too much baking soda, as more baking soda doesn’t mean more rise. Too much baking soda and not enough acid results in leftover, unreacted baking soda, which creates a metallic, soapy, or bitter taste in the final product.

Baking powder is comprised of baking soda and a dry acid, like cream of tartar or sodium aluminum sulfate. Since the acid in baking powder is dry, the baking soda does not react until combined with a liquid.

There are two different kinds of baking powder:

• Double acting baking powder is the most common form of baking powder and the one most widely available in supermarkets. In double acting baking powder, the first rise occurs when baking powder gets wet at room temperature. The second rise happens when the baking powder is heated.
• Single-acting baking powder foregoes the first rise of double acting baking powder and only reacts once it reaches a high temperature. This type of baking powder is almost exclusively used by professional pastry chefs.

Baking powder is used in recipes that do not call for the addition of acidic ingredients. For example, in a simple biscuit recipe that only calls for baking powder, eggs, milk, and flour, the baking powder reacts with the liquids and acts as the rising agent. If you are experimenting in the kitchen, a good rule of thumb is to use one teaspoon of baking powder per one cup of flour.

The primary difference between baking soda and baking powder is that baking powder already contains an acid in the chemical mixture, whereas baking soda needs an acidic ingredient to create the rising reaction. Use baking soda in recipes that have acidic ingredients like buttermilk, lemon juice, or vinegar; use baking powder in recipes that do not have acidic ingredients, like biscuits, corn bread, or pancakes.

There are three general instances in which a recipe will call for both baking soda and baking powder:

• If the baking soda successfully neutralizes the acid but doesn’t create enough carbon dioxide to leaven the batter completely, then baking powder is used for extra lift.
• If the recipe calls for acidic ingredients specifically for their flavor (like lemon juice or buttermilk), too much baking soda would completely neutralize that flavor. Using both baking soda and baking powder will leave enough acid to give the final product a tangy flavor, while providing a nice lift.
• Baked goods brown better in highly alkaline environments. In order to better brown, baking soda is added to recipes where baking powder is the main leavening agent, to create a more alkaline environment.

If you don’t have baking soda on hand, you can substitute with baking powder—just use three times as much baking powder as baking soda in the recipe. For example, if a recipe calls for one teaspoon of baking soda, use three teaspoons of baking powder.

However, this substitute can backfire in one of the following ways:

• The final product is too acidic and bitter. This would be a result of too much baking powder.
  
• The final product is dense and hard. This would be a result of not enough baking powder.
• The final product is too salty. Baking powder contains more sodium than baking soda (so watch for the additional salt in the recipe!).

If you don’t have baking powder on hand, you can try these substitution methods:

1. 1. Make your own. Mix two parts cream of tartar with one part baking soda to make a homemade “baking powder.” If storing long-term, add a teaspoon of cornstarch to keep the cream of tartar and baking soda dry and separate. Store in an airtight container.
2. 2. Use whipped egg whites. Whipped egg whites are filled tiny air bubbles that are a good stand-in for the bubbles created by carbon dioxide gas. Try substituting whipped egg whites in pancakes, soufflés, and cakes. Whip the egg whites using a hand mixer or electric mixer until they resemble foam. Increase the speed on the mixer until soft peaks begin to form. Gently fold the egg whites into the batter.
3. 3. Replace the liquids in a recipe with club soda. Club soda is carbonated water with added baking powder, which will help batter rise. Club soda can be used in lieu of another liquid like milk but will require some trial and error and will water a recipe down.

If your recipe calls for both baking soda and baking powder and you don’t have either, use self-rising flour instead. Self-rising flour contains flour, salt, and baking powder. Self-rising flour substitutes the all-purpose flour in a recipe one for one.

Baking soda has an infinite shelf life, which means that it’s always safe to eat. However, baking soda loses its efficacy over time. An unopened container of baking soda will remain potent for two years, while an opened container should be replaced every six months.

To test your baking soda for freshness, stir 1/4 teaspoon of baking soda into three tablespoons of vinegar or lemon juice. If it the mixture bubbles, the baking soda is still good.

Baking powder is also always safe to eat, but baking powder loses strength as a leavener over time. An unopened can of baking powder will last up to 18 months. An opened container of baking powder should be replaced every three to six months, depending on how much it was exposed to air and humidity. Since baking powder contains an acid and a base, it is reactive to moisture in a way baking soda is not.

To test your baking powder for freshness, stir 1/2 teaspoon baking powder in a bowl with a tablespoon of hot water. If the mixture bubbles, the baking powder is still good.

Baking powder and baking soda should be stored in a dry cupboard away from the stove, dishwasher, sink, or other areas of moisture. Any moisture or humidity will cause baking powder to react in the can and, if there is any acidity in the water, it will do the same to baking soda.