 In yeast doughnuts, a flour with a higher protein content of about 9 to 12 percent is used, resulting in a doughnut that is lighter and more airy.In addition, yeast doughnuts utilize yeast as a leavening agent.Specifically, "Yeast cells are thoroughly distributed throughout the dough and begin to feed on the sugar that is present ... carbon dioxide gas is generated, which raises the dough, making it light and porous."