Mustard oil is mainly derived from the seeds of a strain of mustard plant found in India. (Most commonly used mustard seeds come from the Mediterranean). In its raw form, this oil has therapeutic uses such as an ointment for arthritis. Its culinary application is different from other cooking oils, because achieving the smoking point is desirable. (Most oils begin to break down and elicit unpleasant taste changes when their smoking point is achieved. See smoking point) Mustard oil is always brought to the smoking point before use because a favorable taste change occurs resulting in a smoother mustard flavor. In Indian cuisine, it is used in vegetable stir-fry as well as a medium to deep-fry certain wafers and crackers. Available in Indian and Mid-Eastern grocery stores, mustard oil, once opened, should be stored in the refrigerator to slow the oxidation process. It may keep for several months up to a year.