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MUSTARD. Mustard is the world's third most important spice after salt and pepper, and in temperate regions it is the most important native spice. The term "mustard" is believed to be derived from the practice of mixing the sweet must of old wine with crushed mustard seed to form a paste, mustum ardeus (hot must), hence mustard. The condiment is made from seeds of annual plants of the family Cruciferae, so named for the flower's four yellow petals, which form a cross. The mustard family includes the cole vegetables, radishes, turnips, cress, and horseradish, as well as many important weedy species, such as wild mustard or charlock (Sinapis arvensis L.).

Black mustard (Brassica nigra [L.] Koch), although later considered a weed, was likely the first mustard species harvested as a spice as it grew in the wild or was cocultivated with cereal crops. Its use predates recorded history with seeds, ready for sowing, found in a Bronze Age lake dwelling at the Bielersee (Lake of Bienne) in Switzerland and in vessels in northwest China dating to 5000–4000 B.C. The spice was well known to the earliest Egyptian dynasties and was spread by spice traders and conquering armies throughout Europe and Asia. The Spaniards introduced mustard to the Americas, and in California, Father Junipero Serra scattered black mustard seeds along the routes from monastery to monastery to mark the way in 1768. The bright yellow spring blooms, which mark the old trail, can be seen from the main north-south highway.

The Mustard Species

Black mustard plants are tall (up to 3 meters) and sparsely branched, and they produce many short pods (sliques). As the pod matures, the highly pungent, small (1.5 grams per 1,000 seeds), round dark brown seeds are shed, necessitating frequent hand harvesting or cutting and stacking immature plants on the threshing floor.

The characteristic seed shedding and seed dormancy of black mustard made it unsuited to monoculture and mechanized agriculture, and the spice trade turned to the production of a closely related species, Brassica juncea (L.) Czern and Coss. Plants of B. juncea, when compared to black mustard, are shorter (1 to 2 meters) and have many upright, heavily podded branches with longer pods that retain their seeds when ripe. The seed is larger (3 grams per 1,000 seeds) but produces the same pungency. The seed color is either brown (brown mustard) or yellow (Oriental mustard).

The species originated from a natural cross between B. nigra and Brassica rapa L. (turnip rape) followed by chromosome doubling to produce a vigorous and productive interspecific hybrid. This interspecific cross is believed to have occurred more than once where the two species occupied the same region. Possible centers of origin are believed to be North Africa, northern India and Pakistan, and western China.

The third condiment mustard species, Sinapis alba L., is called yellow or white mustard and produces a different pungency from both B. nigra and B. juncea seeds. From its Mediterranean center of origin, it has been widely disseminated throughout the temperate regions where day lengths (hours of sunshine) were sufficient to stimulate flowering. When moistened, the ripe seed will exude a mucilage from its yellow seed coat to form a whitish coating when dry. This may explain why white mustard is the common name in Europe, while in North America it is called yellow mustard.

Plants of yellow mustard are shorter (0.6 meters) than either B. nigra or B. juncea and have deeply lobed leaves. The short, hairy pods, with flat beaks, contain and retain 5 to 6 seeds when ripe. The seed is significantly larger than the other mustard species (6 grams per 1,000 seeds), which aids in rapid seedling establishment. In Europe the crop is frequently sown and ploughed under as a green manure crop.

The Chemistry of Mustard

All three mustard species contain a significant amount of edible oil and high quality protein. Indeed on the Indian subcontinent B. juncea seeds are the second most important source of edible vegetable oil, and the residual high protein meal, after it is soaked in water, is fed to cattle. However, for the spice trade the important ingredient is the presence and concentration in the seeds of sulphur compounds called glucosinolates. Over forty such compounds are known, and their presence and quantity determines the flavor and odor of the cole vegetables as well as the taste and heat of the mustards. The glucosinolate that imparts the pungency and flavor to black and B. juncea mustards is called "sinigrin," while in Sinapis alba it is "sinalbin." When the seeds are stored whole and dry, they retain their quality for several years. However, when the cells of a mustard seed are broken and moisture is present, the enzyme myrosinase, also present in the seed, breaks down the glucosinolates to release sugar, sulphur, and the hot principles called isothiocynates. Black and B. juncea mustard seeds release the pungent, volatile, biting allyl isothiocynate found in powdered and Dijon mustards. Yellow mustard, on the other hand, releases the milder, nonvolatile para-hydroxybenzyl isothiocynate characteristic of hot dog or cream salad mustard.

Making Mustard

English powdered mustard is made from brown or Oriental (yellow seeded) B. juncea seeds using a dry milling process in which the seeds are passed through a series of rollers and sieves to produce a fine flour. The seed coats, which are cracked off by the first roller, may be used in food preparation or sent to an oil extraction mill. The pure mustard flour is then blended with some yellow mustard flour, prepared separately in the same way, plus a certain amount of wheat flour to give the desired level of heat when mixed with water.

French or Dijon-style mustard is made with only brown mustard seeds using a wet milling process in which whole seeds are ground to a fine paste and the hulls or seed coats are separated with centrifuges. Some of the hulls may be added back to the paste along with vinegar, herbs, and spices. Since the hot principle allyl isothiocynate is volatile, much of the heat is lost in the process, resulting in less pungency than might be expected from B. juncea seeds.

Hot dog or cream salad mustard is made from yellow mustard seeds using a wet milling process that creates a fine paste. However, the hulls are usually separated from the embryos by passing the seeds through a set of break rollers prior to grinding. The paste is then mixed with cereal flours, spices, and vinegar according to the recipe being followed.

Mustard seeds and leaves have also been harvested as a food and for medicinal purposes. The medical applications, such as mustard plasters, baths, and treatments for chilblains, are largely a thing of the past, but mustard greens and mustard seed oil are still household staples in parts of China and on the Indian subcontinent.

Modern Mustard

Mustard was a common spice in ancient Greek and Egyptian civilizations, where it was often eaten raw, chewed with meat to mask off flavors, to aid digestion, and for its antimicrobial properties. However, the Romans recognized mustard's potential by grinding and mixing mustard flours with unfermented grape juice, vinegar, and honey. They introduced mustard manufacture into Dijon and other regions of France and later into England. They recorded its application as a preservative and its use in sauces with meat, fish, and vegetables. In medieval times mustard making was primarily done by the monasteries, but by the thirteenth century French family firms supplied quality mustard to French royalty. In England large-scale mustard manufacture did not flourish until the sixteenth century, when large dried balls of mustard infused with horseradish were manufactured in Tewkesbury and were sold by peddlers throughout the country. Later Mrs. Clements in Durham began to mill and distribute mustard flour, a product later made famous by the competing firms of Keen's and Colman's. In the United States, R. T. French, seeking a milder mustard in the 1800s, introduced cream salad and hot dog mustard, thereby adding a new dimension to the mustard industry.

In the second half of the twentieth century, world usage of mustard more than doubled, from 75,000 tons to over 170,000 tons. Originally most countries grew their own supplies, but by the twenty-first century the predominant supplier was Canada. The United States and central Europe also are important producers. Yellow mustard has become more important with the popularity of fast-food outlets. In addition, a strong demand developed for deheated yellow mustard because of its high protein content and excellent emulsifying, water-holding, and stabilizing characteristics. It is also widely used as a meat extender in prepared meats. The hulls of yellow mustard are also in demand for the unique properties of the mucilage (vegetable gum) they contain.

Specialty mustards, which include almost every possible blend of added flavors and range of textures, have grown dramatically. Popular formulations include ingredients such as honey, beer, wines, whiskey, garlic, horse-radish, lemon peel, ginger, onion, peppers, tarragon, and so forth (see Man and Weir for a more extensive list).The Mount Horeb Mustard Museum in Wisconsin boasts a collection of 3,341 different prepared mustards. The use of mustard in restaurants and in home cooking has expanded and become more subtle and more adventurous.

R. Keith Downey