Mustard

Mustards are annual herbs with bright yellow four-petalled flowers, reaching one to two metres. After flowering they produce slim pods holding many small round seeds. White or yellow mustard (Sinapis alba) has larger, pale straw seeds with a mild flavour, brown mustard (Brassica juncea) has reddish-brown seeds that are noticeably hotter, and black mustard (Brassica nigra) has the smallest, darkest and most pungent seeds. Heat develops only when crushed seeds meet water, forming volatile pungent compounds. Seeds are sold whole, cracked, as powder, as prepared pastes and mustards, and as pressed oil used for cooking in parts of South Asia.

Mustard species originated in the Mediterranean region and in Asia, and were domesticated several thousand years ago. White mustard is native to the Mediterranean, black mustard to Europe, North Africa and western Asia, and brown or Indian mustard likely arose from a natural cross between a turnip-type and black mustard in Central Asia. The English word mustard comes from Old French moustarde, derived from the Latin mustum ardens, meaning burning must, because the Romans prepared the condiment by mixing ground seed with unfermented grape juice.

Mustard has been used for thousands of years. Sanskrit texts and Greek and Roman writers mention the seed, and the Romans spread it across Europe with their armies. Medieval monasteries in France grew mustard, and the city of Dijon became famous for it, with regulations in the thirteenth and fourteenth centuries governing how it could be made. In England, Durham became known for its mustard flour in the eighteenth century, and in the nineteenth century commercial companies produced it in quantity.

In the Gospel parables, the mustard seed is a symbol of something tiny that grows large, and the image has appeared in religious writing across cultures. In India, brown mustard seeds are a common tempering spice and mustard oil is a traditional cooking fat, particularly in the north and east. In North America, the bright yellow ballpark mustard made from white mustard became a standard condiment. Today Canada is among the largest producers of mustard seed, with important crops also grown in Nepal, India, Russia and Ukraine.

Whole seeds are tempered in hot oil in Indian cooking, pickled with vegetables and added to curries and chutneys. Ground seeds are mixed with water, vinegar, wine, beer or verjuice to make mustard condiments, from smooth Dijon to coarse grain mustards and English hot mustard. The seed is used in spice rubs, sausages, brines and pickling spice, and mustard flour is used as an emulsifier in dressings. Mustard oil is used for cooking and massage in South Asia. Young mustard plants are eaten as greens, and the plant is also grown as a green manure and cover crop.

Mustard seeds supply fat, fibre, protein, selenium, magnesium and glucosinolates, sulphur compounds that produce pungent isothiocyanates when seeds are crushed and moistened. These compounds are studied for anti-microbial and potential anti-cancer properties, but most evidence comes from laboratory and animal work. Because mustard is used in small quantities, it contributes little to energy or nutrient intake. Traditional uses include mustard plasters for chest congestion, which can irritate or burn the skin and are not recommended.