Which ingredient is primarily responsible for leavening in many baked goods?

Yeast is primarily responsible for leavening in many baked goods due to its fermentation process. When yeast is combined with warm water and sugar, it metabolizes the sugars and produces carbon dioxide gas as a byproduct. This gas forms bubbles that cause the dough to rise, creating a light and airy texture in breads and other baked goods.

This leavening action not only contributes to the volume of the final product but also enhances the flavor and texture. The presence of yeast is particularly critical in recipes that require a significant rise, such as bread and some pastries, where it develops the structure and crumb of the product through fermentation.

While water, sugar, and salt all play significant roles in baking, they do not act as leaveners. Water is essential for activating yeast and dissolving ingredients, sugar provides food for yeast and contributes sweetness, and salt enhances flavor and controls fermentation speed, but none of these ingredients serve the primary purpose of leavening like yeast does.