Ground mustard is also called powdered mustard, mustard powder or mustard flour. It is made by grinding mustard seeds and then sifting the seed coat out to leave a fine powder behind. This powder is not as pungent or potent as whole mustard seeds. The flavor of ground mustard develops when soaked in liquid to bring out the pungent compounds. It is commonly used in spice rubs, salad dressings, soups, and to add an acidic component to cut through rich sauces like for macaroni and cheese.