How does baking soda produce carbon dioxide in dough and batter?

Baking soda, or sodium bicarbonate, produces carbon dioxide in dough and batter through two primary mechanisms:

• Acid-Base Reaction: When combined with acidic ingredients—such as buttermilk, yogurt, lemon juice, cream of tartar, honey, or molasses—sodium bicarbonate undergoes a neutralization reaction. This chemical process releases carbon dioxide gas, water, and a salt. Because this reaction occurs rapidly upon mixing, batters and doughs using baking soda must be handled and baked quickly to prevent the gas from escaping before the structure sets.1234

• Thermal Decomposition: At higher temperatures during the baking process, sodium bicarbonate can also decompose independently into sodium carbonate, water vapor, and carbon dioxide.1

These gas bubbles expand as the mixture heats, creating the light, porous structure characteristic of breads and cakes. Without sufficient acid, baking soda may leave the product overly alkaline, leading to off-flavors, discoloration, and reduced leavening.123