Which ingredient is commonly used for leavening in quick breads?

Baking powder is commonly used for leavening in quick breads because it is a chemical leavener that releases carbon dioxide gas when mixed with liquid and an acid. This process creates air bubbles in the dough, which expand during baking and cause the bread to rise, giving it a light and airy texture. Quick breads, such as muffins and pancakes, are prepared using a mixing method that requires immediate baking after combining the ingredients. This is why a fast-acting leavening agent like baking powder is ideal, as it provides a reliable and rapid rise without the need for fermentation time, which is necessary when using yeast.

While eggs do contribute some leavening properties and add structure and richness to quick breads, they are not primarily responsible for the leavening effect. Yeast is traditionally used in yeast breads, requiring fermentation time to develop the leavening action, and milk serves more as a liquid ingredient to hydrate the mixture rather than as a leavening agent. Thus, baking powder stands out as the best choice for leavening in quick breads due to its effectiveness and the quick preparation time characteristic of these recipes.