Indian Mustard

Indian mustard is an annual herb, usually one to two meters tall, with lobed lower leaves, many branches and clusters of small four-petaled yellow flowers typical of the cabbage family. After flowering it forms slender pods that hold a row of round seeds roughly one to two millimeters across.

The seeds range from yellow-brown to dark reddish brown and are harder and more pungent than the pale seeds of white mustard. Whole seeds have almost no smell, but when crushed and moistened they release a sharp, hot, nose-clearing aroma that comes from sulfur compounds.

The seed is sold whole for tempering in oil, ground into powder, made into brown and Dijon-type mustards, and pressed for mustard oil. Leaves are sold fresh as mustard greens.

Brassica juncea arose as a natural cross between two other species in its genus, field mustard (Brassica rapa) and black mustard (Brassica nigra), followed by a doubling of chromosomes, which created a new fertile species. The hybridization is thought to have taken place in the region between Central Asia, the Middle East and northern India, although the exact site is uncertain.

Several distinct forms were later selected in different regions, including oilseed types in India, leafy types in China and Japan, and root and stem types in Asia. The species name juncea comes from Latin and refers to rush-like, slender stems. The English word mustard itself comes from Old French, derived from a Latin phrase for burning must, because the crushed seeds were once mixed with unfermented grape juice.

Mustard seed has been used by humans for thousands of years, and brown mustard in particular has been cultivated across the Indian subcontinent for a very long time as both an oilseed and a condiment. It spread to China, where leafy forms became part of the regional vegetable cuisines, and later to Europe, where the seed was used in prepared mustards.

In India, mustard oil became the characteristic cooking fat of the north and east, including Punjab, Bengal and Bihar, and it also appears in pickling traditions. The seeds are among the first things to crackle in hot oil when a tarka is started in many Indian kitchens, and whole and ground mustard seed features in Bengali fish dishes and Kashmiri cooking.

The crop later became important in North America and Australia, where it is grown for oil, condiment seed and as a break crop in cereal rotations. Plant breeders have developed canola-quality lines with low erucic acid and low glucosinolates in some regions. The plant also has a recorded history of use in phytoremediation research because it can take up heavy metals from soil.

In the kitchen, whole seeds are fried briefly in hot oil or ghee to release a nutty flavor before other ingredients are added, and they are ground into pastes with chili and spices for fish and vegetable dishes. The seeds are the main ingredient of brown and spicy mustards and are used in pickle masalas and spice mixes.

Pressed mustard oil is used for cooking, pickling and massage in South Asia, and in some countries the oil is sold only for external use because of its erucic acid content. Leaves, called sarson ka saag in Punjab, are cooked as a green.

Outside the kitchen, mustard meal is used as a biofumigant and soil amendment, and the oil has been tested as a biodiesel feedstock.

Mustard seed provides fat, protein, fiber, selenium and magnesium, along with glucosinolates, which the plant converts to isothiocyanates when the seed is crushed. Laboratory work on these compounds is active, but human evidence for disease prevention is still limited. Traditional uses include warm poultices and mustard foot baths for colds, which rest on tradition rather than strong trial data. As with most spices, the amounts eaten in cooking are small and are best viewed as flavoring rather than a therapy.