Leavening agents include steam, air, yeast, baking soda and baking powder. They have various ways of causing dough to rise.
Leavening agents help the dough rise by releasing gases into the mixtures. When using air to cause a dough to rise, the mixture is stirred quickly to incorporate air bubbles. Egg whites are generally used for creating the fluffy texture of these doughs. Yeast releases carbon dioxide. This is how most breads are formed, such as sour dough or rye. Baking soda and baking powder are used to create a chemical reaction when mixed with batters that contain an acid. These doughs must be baked quickly after being mixed.