Most baking powders are made up of an alkaline ( usually baking soda ) , one or two acid salts , and a starch ( cornstarch or sometimes potato starch ) . Most commercially-available baking powders are made up of an alkaline component ( typically baking soda , also known as sodium bicarbonate ) , one or more acid salts , and an inert starch ( cornstarch in most cases , though potato starch may also be used ) .