If you listened to “America’s Test Kitchen” tonight, you heard Chris Kimball and Bridget Lancaster struggle with a listener’s question about mustard oil: Why is it labeled “for external use only,” and is the stuff safe to cook with? Bridget figured, rightly, that the oil was labeled that way to get around “some government regulation,” and that it was probably safe to use in small amounts. At this point I imagined readers of The Joy of Pickling waving their arms and shouting at their radios in their eagerness to supply a fuller answer.
For those of you who haven’t read The Joy of Pickling—or at least not cover to cover, yet—here’s the lowdown on mustard oil: In 1989 the U.S. Food and Drug Administration banned its sale for culinary use because some laboratory studies performed in the 1950s associated the oil with nutritional deficiencies and cardiac lesions in rats. Subsequent studies have shown that the results for rats don’t apply to people, and that mustard oil in human diets is in fact associated with a lowered risk of heart disease. In addition, a 1999 U.S. Department of Agriculture report says that mustard oil, like horseradish, contains the pungent antimicrobial chemical allyl isothiocyanate, and that for this reason mustard oil and horseradish “pack a punch against Listeria monocytogenes, E. coli, Staphylococcus aureus and other food pathogens you definitely don’t want in your sandwich.”
Throughout much of India, people have for centuries favored mustard oil for frying and for making oil-based pickles. The unrefined oil has a unique, strong flavor. Use something else—such as raw sesame oil—if you don’t like the taste, but don’t avoid mustard oil out of fear that it will hurt you. Remember that the oil is all in mustard seeds and prepared mustard, which you’ve probably been eating all your life.
You can buy mustard oil at any Indian grocery. Today it’s often combined with cheaper refined oil, so look for the pure stuff. If it’s too strong for you, you can cut it with other oil at home.
Because mustard oil is rich in antioxidants, it will keep for months in a tightly closed container at room temperature.