What is the primary role of yeast in baking?

The primary role of yeast in baking is to ferment and produce carbon dioxide for leavening. When yeast is mixed with dough and provided with warmth and moisture, it begins to ferment the sugars present in the flour and other ingredients. This fermentation process produces carbon dioxide gas, which gets trapped in the dough, causing it to rise and develop a light and airy texture. This leavening action is what distinguishes yeast-leavened products, such as bread and rolls, from those that are chemically leavened or not leavened at all.

While there are other factors involved in baking that enhance sweetness, moisture retention, and dough elasticity, the essential function of yeast centers around its ability to create gas through fermentation. This is crucial for the characteristic texture of yeast-based baked goods. As the dough bakes, the heat causes the gas bubbles to expand further, leading to the desired rise and structure.