Prota 14: Vegetable oils/Oléagineux
Consp. pl. charc.: 8 (1859).
2n = 36
Sinapis juncea L. (1753).
Brown mustard, Indian mustard, leaf mustard (En). Moutarde brune, moutarde de Sarepta, moutarde de Chine, moutarde frisée (Fr). Mostarda vermelha, mostarda indiana (Po). Haradali, mastadi (Sw).
Origin and geographic distribution
Brassica juncea is an amphidiploid with Brassica nigra (L.) Koch (2n = 16) and Brassica rapa L. (2n = 20) as parents. Several regions in western and central Asia have been assumed to be the centre of origin of Brassica juncea. Brown mustard has been cultivated in Asia and Europe for thousands of years for its leaves and seeds. Presently, vegetable types of Brassica juncea are cultivated throughout southern and eastern Asia. Variation is greatest in China. Brown mustard is grown as a leafy vegetable in West and southern Africa, known as ‘laulau’ in Nigeria, ‘mpiru’ in Malawi and ‘tsunga’ in Zimbabwe. In many African countries it has been introduced and became naturalized. However, its exact distribution in Africa is difficult to indicate because of confusion with other Brassica species, especially Brassica carinata A.Braun. Oilseed types are particularly important in southern Asia, China, North America and Europe, but are not or only rarely found in Africa. Brassica juncea is important as a source of mustard in Europe and North America, and it is occasionally planted for this purpose in Africa, e.g. in Réunion and Mauritius.
Brassica juncea has many uses: it yields a seed oil, crushed seed is used in the production of mustard and it has a variety of vegetable uses. It is also used as forage and medicinally.
In Africa and many parts of Asia the leaves are eaten as a vegetable; they are often shredded, cooked and served as a side dish with the staple food. Older leaves and leaves affected by drought are very bitter. When they have to be used, consumers renew the cooking water once. Young tender leaves, called ‘mustard greens’ are used in salads, mixed with other salad greens. In Asia brown mustard leaves are used in pickles or offered as frozen or canned vegetables. Sprouted seeds are used as a garnish or to add a spicy note to salads. In East Asia a variety of vegetable types have been developed that are comparable to that of Brassica oleracea L. ‘Tai Tau Choi’ has an enlarged root and is prepared and eaten like turnips, while ‘Cha Tsoi’ has peculiar swollen stems with knobby bulges that are preserved in brine and pressed flat until most of the sap is removed.
In Asia, Europe and America, Brassica juncea is grown mainly for its seed used in the fabrication of brown mustard or for the extraction of vegetable oil. It has been introduced for this purpose locally in Africa, e.g. in the Mascarene Islands. In much of Europe Brassica juncea has replaced Brassica nigra as the main source of commercial mustard seed. Its mustard is spicier than the yellow type made from Brassica nigra. Mustard oil is one of the major edible oils in Bangladesh, India and Pakistan, appreciated for its special taste and pungency. In adjacent parts of the former Soviet Union it is used as a substitute for olive oil. In Western countries its use as edible oil is restricted because of the high erucic acid content. The oil is also used as hair oil and as lubricant. The oil of cultivars bred for extra high erucic acid content is used for industrial purposes. A peculiar use of mustard oil is to retard the fermentation process when making cider from apples. The seeds are also used in birdseed mixtures. The remaining seed meal is high in protein, but the high glucosinolate content makes it unacceptable for human or for monogastric-animal consumption.
Brown mustard is reported to have anodyne, aperient, diuretic, emetic and rubefacient properties. It is a folk remedy for arthritis, foot ache, lumbago and rheumatism. In China the seed is used as medicine against tumours. Ingestion may impart a body odour repellent to mosquitoes. Leaves applied to the forehead are said to relieve headache. The leaves are eaten in soups to treat bladder inflammation or haemorrhage. In Korea the seeds are used to treat abscesses, colds, lumbago, rheumatism and stomach disorders. Brown mustard oil is used against skin eruptions and ulcers. In Tanzania the roots have been given to cows to promote milk production.
Production and international trade
Statistics on the production and trade of seed oil and mustard of Brassica juncea are difficult to find as they are often combined or confused with those of rape seed (Brassica napus L. or Brassica rapa L.). Brassica oil is the third-most important vegetable oil after only soya bean and oil palm. Brown mustard as a vegetable is only marketed locally even in those parts of Asia where it is an important vegetable. In Africa it is mainly encountered in southern Africa and is quite rare elsewhere. In Zambia and Zimbabwe, where it is referred to as ‘rape’, it is very popular, but no reliable statistics are available on the area under cultivation, production or produce traded.
Brown mustard leaves contain per 100 g edible portion: water 90.8 g, energy 109 kJ (26 kcal), protein 2.7 g, fat 0.2 g, carbohydrate 4.9 g, total dietary fibre 3.3 g, Ca 103 mg, Mg 32 mg, P 43 mg, Fe 1.46 mg, Zn 0.2 mg, vitamin A 10,500 IU, thiamin 0.08 mg, riboflavin 0.11 mg, niacin 0.80 mg, folate 187 μg, ascorbic acid 70 mg. Dry mustard seed contains per 100 g edible portion: water 6.9 g, energy 1964 kJ (469 kcal), protein 24.9 g, fat 28.8 g, carbohydrate 34.9 g, Ca 521 mg, Mg 298 mg, P 841 mg, Fe 10.0 mg, vitamin A 62 IU, thiamin 0.54 mg, riboflavin 0.38 mg, niacin 7.9 mg, ascorbic acid 3 mg (USDA, 2003).
The seeds and leaves contain the glucosinolate sinigrin. Their pungency develops when cells are damaged and sinigrin is hydrolyzed by the enzyme myrosinase to form allyl isothiocyanate. The seed also contains sterols of which the most important ones are brassicasterol, campesterol and sitosterol. The oil content of the seed is 28–45% with an average of about 35%. The oil is similar to that of other Brassica species and is made up of erucic acid 25–55%, oleic acid 8–33%, linoleic acid 12–21%, linolenic acid 8–14%, eicosenoic acid 6–12%, palmitic acid 2–4%, stearic acid 0.8–1.5%, arachidic acid 0.5–1.2%, palmitoleic acid 0.2–0.5%, nervonic acid 0–2%, behenic acid 0–1% and lignoceric acid 0–1%. Eicosenoic acid and erucic acid are long-chain fatty acids that have antinutritional and toxic properties. Cultivars yielding oil low in eicosenoic acid and erucic acid have been developed. Their fatty acid composition is: palmitic acid 56%, stearic acid 25%, arachic acid 10%, behenic acid 6% and lignoceric acid 3% (USDA 2002). They are generally recognized as safe for human consumption. Together with cultivars of Brassica napus and Brassica rapa, yielding similar oil, they are known in Canada as ‘canola’. The seed cake remaining after oil extraction contains about 37% crude protein.
Experiments with rats suggest that brown mustard might be beneficial in attenuating the damage caused by oxidative stress involved in diabetes and its complications.
Adulterations and substitutes
Mustard leaves are often erroneously called ‘rape leaves’, but rape (Brassica napus) is a distinct vegetable and oil crop. Brown mustard as leafy vegetable can easily be replaced by leaf cabbages (special cultivars of Brassica oleracea, Brassica carinata and Brassica napus), although these lack the typical taste of brown mustard.
Erect, annual to biennial herb up to 160 cm tall, often unbranched, sometimes with long ascending branches in upper part, almost glabrous to scattered hairy, slightly glaucous; taproot sometimes enlarged (root mustard). Leaves alternate, pinnately lobed but upper ones often simple; stipules absent; all leaves with short petiole; blade ovate to lanceolate or with up to 2 side lobes on each side and a large end lobe, up to 30 cm × 10 cm, margin irregularly toothed. Inflorescence initially an umbel-like raceme but soon strongly elongating, up to 60 cm long. Flowers bisexual, regular, 4-merous; pedicel ascending, 5–12 mm long; sepals oblong, 4–6 mm long, green; petals obovate, 6–10 mm long, clawed, bright yellow; stamens 6; ovary superior, cylindrical, 2-celled, stigma globose. Fruit a linear silique 2.5–7.5 cm × 2–3.5 mm, often constricted between the seeds, with a conical beak usually longer than 6 mm, dehiscent, up to 20-seeded. Seeds globose, 1–1.5 mm in diameter, finely reticulate, pale to dark brown.
Other botanical information
Brassica juncea is a highly variable species which has been cultivated for centuries as a vegetable and oil plant, and is also a widespread weed. Brassica juncea cultivars have only slightly glaucous, often dark green and more or less hairy leaves, distinct from the bluish green, glabrous leaves of the other leaf brassicas. In Africa it has been much confused with Brassica carinata, but the lower leaves of the latter species are simple or have up to 1 side lobe on each side, and its fruit beak is shorter (usually < 6 mm).
Several authors have proposed cultivar classifications for Brassica juncea. These have little relevance for Africa, where farmers use mostly local cultivars. Only occasionally is seed imported from Western seed companies, e.g. ‘Florida Broad Leaf’.
Growth and development
Seed germinates within 5 days after sowing at 20–25°C. Under good conditions plants grow rapidly and leaves are harvestable after 3 weeks when plants have developed 6–8 fully expanded leaves, but harvesting will start later when larger leaves are demanded for sale. Under tropical African conditions, flowering occurs early as low temperatures are not required for flower induction. Water stress or low soil fertility promote early flowering. Brassica juncea is self-fertile, but bees may effect cross-pollination. Fruits develop rapidly and the seeds can be ready for harvesting within 4 weeks from flowering.
Brown mustard is reported to tolerate annual precipitation of 500–4000 mm and temperatures of 6–37°C and is therefore suited to the tropical lowlands as well as relatively cool conditions. It grows best on fertile, well-drained loamy soils with a pH of 5.5–6.8, rich in organic matter. At high temperatures it will quickly flower and yields are lower, but production is still possible. For seed production, brown mustard is tolerant of adverse conditions including moisture stress, high or low pH, salt and insect damage.
Propagation and planting
Brown mustard can be sown directly or transplanted. Direct sowing is mainly used when time is a limiting factor and where there is a market that will accept smaller leaves. This system is frequently used in Zambia in wet areas called ‘dambos’. The weight of 1000 seeds is 1.7–2 g. The seeds need to be mixed with sand and broadcast thinly to avoid the need for removing too many seedlings later on. The first harvest can be in the form of thinned-out seedlings, collected after about 35 days from sowing. Transplanting is common and seedlings are raised in 1 m wide nursery beds with fertile finely-tilled soil. Seed beds should be prepared by loosening the soil and incorporating up to 50 kg of well-fermented manure per 10 m2. Seed is sown in drills 25–30 cm apart and seedlings are thinned to a spacing of 5–10 cm. Seedlings need to be adequately watered. They are ready for transplanting after 20–30 days when they have 3–4 true leaves, and are planted at a spacing of 30–50 cm between rows and 20–40 cm in the row, depending on the size of the plant required. When grown as an oil crop, seeding is at a rate of 4–6 kg/ha. Plant density may vary as brown mustard has a considerable capacity to compensate for an irregular plant stand.
The uptake of minerals by brown mustard is high and manure application to the field at a rate of 30 t/ha is recommended. When no manure is available, it can be replaced by a fertilizer gift of about 500 kg/ha NPK 18–12–12, depending on soil fertility. Top dressing of N-fertilizer is practised a few weeks after transplanting. For seed production fertilizer applications may be lower. Weeding is required during the early growth stages of leaf mustard and ample watering is necessary to promote rapid growth. Early flowering can occur during hot weather with high temperatures. In several parts of the United States Brassica juncea is considered a noxious and invasive weed
Diseases and pests
A devastating disease of brown mustard during the rainy season is bacterial soft rot (Erwinia carotovora), for which there is no adequate control. Another bacterial problem is black rot caused by Xanthomonas campestris, a disease that is both soilborne and seedborne. Amongst the fungal diseases, the most important is Alternaria black spot (Alternaria brassicae and Alternaria brassicicola). Turnip mosaic virus (TuMV) is also noticed quite frequently on brown mustard.
The most destructive pest is diamondback moth (Plutella xylostella), especially during the dry season. Other pests are cabbage web worm (Hellula undalis), caterpillars of the mustard leaf webber (Crocidolomia binotalis), aphids and flea beetles (Phyllotreta spp.) and several nematodes. In cold weather brown mustard has few pests, but warmer weather will bring on aphids and other insects.
Field sanitation, rotation with unrelated crops and the use of pathogen-free seeds considerably reduce the impact of pests and diseases. However, under conditions of subsistence production little is done to control pests and diseases.
Harvesting of leaves starts about 4 weeks after transplanting. Leaves may be cut once weekly during the vegetative phase until the crop loses its tenderness and leaves become stiff. When the crop starts developing inflorescences, it becomes more economical to replant. In some cases young plants are harvested whole with their roots attached, especially when grown under closer spacing. In Africa leaves of 15–30 cm long are preferred for marketing.
For seed production, plants should be harvested before fruits are fully ripe to reduce shattering of the seeds. Harvesting is usually done early in the morning. Plants are tied into bundles and dried in the sun for 4–10 days.
The leaf yield of Brassica juncea ranges from 8–35 t/ha, with 20 t/ha as average on better farms. In Zimbabwe, this crop performs better during the winter, with average yields of 20–30 t/ha. Seed yields of brown mustard in India range from 900–1200 kg/ha with an oil content of 30–38% and in the United States seed yields are about 1100–1500 kg/ha.
Handling after harvest
Under hot conditions, leaves wilt soon after harvest and are therefore sold as soon as possible. Where facilities are available, it is recommended that the product be cooled to near 0°C immediately after cutting, and that it be kept as cool as possible during transport and marketing. This can be done by placing ice between the leaves, which will also keep the humidity high. The humidity can also be kept high by packing the leaves in polythene bags or plastic film.
In Zimbabwe farmers dry the leaves in the sun for use during the off-season. Dried leaves offered as broken pieces and packed in polythene bags are frequently encountered at markets in Harare and elsewhere in Zimbabwe. Extraction of oil from the seed is by rotary mill, expeller or hydraulic processes. Mustard is made by mixing ground seeds with water, spices and vinegar.
Large germplasm collections of Brassica juncea are maintained at the Australian Temperate Field Crops Collection, Horsham Victoria, Australia, the Institute of Crop Germplasm Resources (CAAS), Beijing, China, the All India Coordinated Research Project on Rape & Mustard, Haryana University, Hisar, Haryana, India and the N.I. Vavilov All-Russian Scientific Research Institute of Plant Industry, St Petersburg, Russian Federation. Smaller working collections are held in many other countries. A working collection of brown mustard with African landraces is present at the Horticultural Research Centre, Marondera, Zimbabwe. The diversity found in farmers’ fields in Africa is considerable and there is a need to collect and evaluate this material before this potentially valuable resource disappears with the introduction of improved varieties.
Many African farmers use their own landraces of farm-saved seed. Brassica juncea can be reproduced by means of self-pollination, allowing for a rapid purification of new selections. East-West Seed Company in Thailand has developed cultivars especially for tropical conditions, e.g. ‘Mayur’ harvestable 30–35 days after sowing or 21–25 days after transplanting, and ‘Laguna’ with bolting tolerance at high temperatures and harvestable 40–45 days after sowing. ‘Suehlihung No.2’ is a cultivar from Taiwan that is resistant to soft rot and viruses. It can be grown year-round in Taiwan and be harvested 20 days after transplanting. The cultivar ‘King Mustard’ produces large and tender green-purple leaves.
There is a good potential for improving current landraces of this excellent vegetable which can be grown in humid hot lowland areas like the coastal regions of West Africa and the cooler regions of southern Africa. Many people prefer brown mustard and other loose-leaved Brassica types over white cabbage and when healthy seed of improved cultivars becomes available, the demand for this crop will increase. Prospects for Brassica juncea as an oil crop or for mustard production in tropical Africa are limited.
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Sources of illustration
• Toxopeus, H., 2001. Brassica L. (oilseed crops). In: van der Vossen, H.A.M. & Umali, B.E. (Editors). Plant Resources of South-East Asia No 14. Vegetable oils and fats. Backhuys Publishers, Leiden, Netherlands. pp. 65–70.
Correct citation of this article:
Schippers, R.R. & Mnzava, N.A., 2007. Brassica juncea (L.) Czern. In: van der Vossen, H.A.M. & Mkamilo, G.S. (Editors). PROTA 14: Vegetable oils/Oléagineux. [CD-Rom]. PROTA, Wageningen, Netherlands.
planted and naturalized
1, flowering branch; 2, flowering and fruiting branch; 3, seed.
field with one flowering plant
plants ready for harvesting
plant ready for transplantation