Absorbing Moisture

Recall that flour is a drier because it contains starch, gums, and proteins. All starches and gums, in fact, are driers, because they absorb moisture and often fats and oils.

Cornstarch in particular is added to dry powdered products to absorb moisture. This prevents caking and keeps the dry powder free flowing. For example, cornstarch is added to finely pulverized powdered confectioners’ sugar. Cornstarch is also commonly added to baking powder. Besides keeping baking powder free-flowing, cornstarch serves as a bulking agent to standardize baking powders. It also prevents losses in activity. As cornstarch absorbs moisture, it prevents the reaction of acid and baking soda and the release of carbon dioxide, an important leavening gas.