What is the purpose of yeast in bread making?

Yeast plays a crucial role in bread making primarily by fermenting sugars present in the dough. During this fermentation process, yeast converts these sugars into carbon dioxide and alcohol. The carbon dioxide produced is what causes the bread to rise, creating the characteristic airy texture. As the dough ferments and expands, it develops its volume and creates a light, fluffy crumb.

The fermentation process also contributes to the bread’s flavor and aroma. However, the defining purpose in the context of yeast's function is its ability to produce carbon dioxide through fermentation. This makes it essential for leavening bread, distinguishing it as a primary ingredient that affects the structure and texture of the final product.