Mustard seeds are the small round seeds of various mustard plants. The seeds are usually about 1 or 2 mm in diameter. Mustard seeds may be colored from yellowish white to black. They are important spices in many regional foods. The seeds can come from three different plants: black mustard (Brassica nigra), brown Indian mustard (B. juncea), and white mustard. Mustard grows well in temperate regions. Major producers of mustard seeds include Canada (90%), Hungary, Great Britain, India, Pakistan and the United States. Brown and black mustard seeds return higher yields than their yellow counterparts. Mustard seed is a rich source of oil and protein. The seed has oil as high as 46-48 percent, whole seed meal has 43.6 percent protein.
Yellow mustard seeds are commonly used in European and American cooking. This is the type called for in most pickling and canning recipes, or in making corned beef or boiled vegetables.