What role does baking soda play in baked goods?
Beyond fairground volcanoes and household cleaning, baking soda explains how a flat, unleavened dough becomes fluffy in the oven.
Sodium bicarbonate, also called baking soda, is a chemical compound found in nature and also manufactured industrially. It is obtained by adding carbon dioxide to the processed mineral trona, a sodium carbonate compound. When combined with an acid and a liquid, such as vinegar, it releases carbon dioxide. In baking, this acid typically comes from ingredients like yogurt, buttermilk, cocoa powder, vinegar, or cream of tartar. This gas creates and expands air bubbles in the batter, causing cookies, cakes, or banana bread to rise.
Baking soda isn't the only leavening agent. Baking powder contains sodium bicarbonate combined with a dry acid, such as cream of tartar. Because baking soda needs both an acid and a liquid to activate, the mixture remains dormant until it's added to the dough. Dual-action baking powder, the most common type found in stores, is activated first by adding liquid and then again by the heat of the oven.
Substituting one for the other is possible, but with caution. Baking soda is three to four times stronger than baking powder, and too much can leave a soapy taste. If used instead of the baking powder called for in the recipe, you'll need to add more acid to compensate for the dry acid provided by the baking powder.
Each has its time and place. The dual action of baking powder makes it ideal for cookies, whose dough may need refrigeration before baking. Bicarbonate of soda is mainly used in doughs that bake quickly, because the reaction begins as soon as the acid and liquid are added; if the dough rests, the reaction completes before baking, and the dough won't rise properly.
Some recipes use both baking powder and baking soda. When you add an acid to baking soda, it neutralizes it, which is ideal in most cases, but not when you're looking for a tangy flavor, like in buttermilk pancakes or lemon bread. That's why a small amount of baking powder, which contains dry acid, is added so that some residual acidity remains after the reaction is complete, ensuring the flavor is retained.
