How does single-acting baking powder differ from double-acting baking powder?

The primary difference between single-acting and double-acting baking powder lies in their reaction time and the release of carbon dioxide gas during the baking process.12

• Single-acting baking powder: These contain acids such as tartaric acid or cream of tartar. They release carbon dioxide immediately upon contact with moisture at room temperature. Because the gas is released quickly, mixtures using this type must be baked immediately to prevent the loss of leavening power.13
• Double-acting baking powder: This is the most common type used in commercial and domestic baking. It typically contains a combination of sodium aluminum sulfate and calcium acid phosphate. It releases a small amount of carbon dioxide during the initial mixing and makeup stages, but remains relatively inert until the batter is heated in the oven. This delayed reaction helps prevent the excessive loss of gas, making it more stable for batters that may sit for longer periods before baking.123