Baking powder is a common chemical leavening agent used to create a light, fluffy texture in many baked goods. Baking powder consists of an alkaline powder, an acid salt, and a neutral starch. The alkaline and acid components combine to give baking powder leavening action, while the starch (usually corn or potato starch) serves to absorb moisture and prolong the powder’s potency during storage.
Baking powder is most often used to leaven muffins, pancakes, quick breads or other mixtures that use a loose batter. Batters are not strong enough to hold in gases for long periods of time so they need quick acting leavening action like that created with baking powder or baking soda.
How Does Baking Powder Work?
When acids and bases combine, they often release gas as a byproduct of the reaction. To prevent baking powder from reacting as soon as it is made, an acid salt is used, which will not react with the base until water is added.
When moisture is added to baking powder, the acid and base react and produce carbon dioxide gas. As the gas is released, it becomes trapped in the batter, which causes it to inflate and expand.
The neutral starch added to baking powder absorbs moisture in the ambient air, thus preventing it from catalyzing the reaction during storage.
Single Acting vs Double Acting Baking Powder
Single acting baking powder reacts upon hydration at room temperature. This means the bulk of the leavening action occurs as soon as the batter is mixed. If there is a delay between mixing an baking, some of the gas may escape and cause deflation. Double acting baking powder releases a second burst of gas upon exposure to heat. This second burst of gas makes up for any loss of gas between the initial hydration of the batter and when the batter solidifies in the oven. This is especially useful for products like pancakes that may not be cooked immediately after mixing.
The type of acid salt used in the baking powder will determine whether it is a single acting or double acting powder. For convenience and reliability, most baking powders sold in stores today are double acting.
Baking Powder vs Baking Soda
Baking powder contains both an acid and a base component and relies on moisture and heat to react. Baking soda is an alkaline only powder that requires the addition of an acid ingredient (vinegar, lemon juice, buttermilk, etc.) to react.
Baking powder can be made at home by combining baking soda (base), cream of tartar (acid) and cornstarch. If the mixture is going to be used immediately, the cornstarch is not necessary. Cream of tartar is a room temperature reacting acid so this mixture would be considered a single acting baking powder.
Whether baking soda or baking powder will be used in a recipe usually depends on the relative acidity of the other ingredients in the batter. Batters that include acidic ingredients will use mostly, if not all, baking soda because the addition of too much baking powder will result in an acidic batter and the flavor will be affected. Likewise, if a batter does not include acidic ingredients and baking soda is used, there will not be enough acid to cause the leavening reaction and the end product may taste bitter due to the abundance of alkaline ingredients.
How to Test Baking Powder
Because baking powder only requires moisture to react, exposure to ambient air can cause a slow loss of potency over time. To test your baking powder, simple place a small amount in a dish and add water. Vigorous bubbles should appear within 10-15 seconds. If the powder does not react with water, it no longer holds its leavening power.