There are three main kinds of mustard plants and seed, each with its own character.
- Black mustard, Brassica nigra, is a Eurasian native, small and darkhulled, with a high content of the defensive storage compound sinigrin and therefore a high pungency potential. It was long important in Europe and still is in India, but is an inconvenient crop and in many countries has been replaced by brown mustard.
- Brown mustard, B. juncea, is a hybrid of black mustard and the turnip (B. rapa) that is easier to cultivate and harvest. It has large, brown seeds that contain somewhat less sinigrin than black mustard and therefore less potential pungency. Most European prepared mustards are made with brown mustard.
- White or yellow mustard, Sinapis alba (or Brassica hirta), is a European native with large pale seeds and a different defensive storage compound, sinalbin. The irritating portion of sinalbin is much less volatile than the irritant in sinigrin, so little of white mustard’s pungency rises into the nose. It mostly affects the mouth, and generally seems milder than black or brown mustard. White mustard is used mainly in the United States, in prepared mustards as well as whole in pickle mixes.