During the fermentation the process where yeast converts sugar to carbon dioxide and alcohol in the absence of oxygen, causing dough to rise. Leavening agents make bread and other baked good rise by causing a foaming action that traps air bubbles in the food as it cooks. The trapped air gives the final product a light and fluffy texture Related Theory Many breads containing yeast not only are leavened by yeast-produced carbon dioxide but also owe their distinctive flavor to the metabolic products of yeast.