Species of flowering plant
Jute mallow or Nalita jute (Corchorus olitorius, also known as "Jew's mallow",[2] "Tossa jute", "Bush okra", and "West African sorrel") is a species of shrub in the family Malvaceae. Together with C. capsularis it is the primary source of jute fiber.[3][4] The leaves and young fruits are used as a vegetable, the dried leaves are used for tea and as a soup thickener, and the seeds are edible.[3]
Origin and history
It is unclear whether Corchorus olitorius originated in Africa or in Asia. Some authorities consider that it comes from the Indo-Burmese area or from India, along with several other related species. Others point out that there is a greater genetic variation in Africa and a larger number of wild species in the genus Corchorus. Wherever it originated, it has been under cultivation for a very long time in both continents and probably grows, wild or as a crop, in every country in tropical Africa.[5]
In classical antiquity, Pliny recorded that jute plants were used as food in ancient Egypt.[6] It may have also been cultivated by the Jews in the Near East, which gives the plant its name.[6]
Botany
Corchorus olitorius is an erect herbaceous plant, fairly branched and grows about 1.5 m high. However, if grown for fibre production, it can reach heights up to 4 m. The taproot leads to a sturdy and hairless stem, which is green with a faint red-brownish hue and sometimes turns a little woody on ground level. The serrate acute leaves alternate, are 6 to 10 cm long and 2 to 4 cm wide. The plant carries the flowers solitary or in two-flowered cymes opposite of the leaf. The flowers sit on the end of a short stem, count 5 sepals, 5 petals and 10 free and yellow stamina. The fruit is spindle-shaped, dehiscent and divided into transversal sections through five valves. The fruit measures 2 to 8 cm in length and colors vary from greyish-blue to green or brownish-black. Every seed chamber contains 25 to 40 seeds, which sum up to 125 to 200 seeds per fruit.[4][7]
Cultivation
Corchorus olitorius is an annual crop. The plant grows well in the lowland tropics, ranging from warm temperate zones through tropical desert to wet forest life zones. It can tolerate an annual precipitation between 400 and 4290 mm (optimum 1000 mm per year[8]). Some cultivars are sensitive to waterlogging, especially when they are young.[9] Temperatures between 16.8 and 27.5 °C are optimal for the plant growth.[2][10] For the soil a pH of 4.5 to 8.2 is needed.[2][10] The plant prefers a fertile, humus-rich, well-drained alluvial soil but also grows well in suboptimal soil conditions.[11] Before sowing, the soil is prepared carefully by plowing and the seeds are broadcast or dribbled behind the plow in the wet season. Twenty-four hours before seeding, the seeds must be pre-soaked for ten seconds in hot water (around 93 °C[12]) to overcome dormancy.[13] If the small seeds are mixed with sand, it makes it easier to sow them.[8] And if the soil is wet, germination takes place two to three days after sowing. In some systems, the seedlings are transplanted at a height of 10 cm.[8] The plants are grown in rows with a spacing of 20–50 cm. When the plant achieves a height of 8–25 cm, the seedlings are harrowed with a rake three to four times and weeded two to three times.[9] Cow dung, wood ashes or rotted water hyacinth (Eichhornia crassipes) or its ashes are used as manure.[9] The yield of the crop responds more to water availability and soil organic matter than to high mineral nutrient status.[13]
Plant protection
The most serious pests are nematodes from the genus Meloidogyne, leaf-eating beetles and caterpillars. If it is dry, eight to ten weeks after planting, yield losses can occur due to leaf bugs and spider mites attacks resulting in terminal shoot wilt. Damage by nematodes can be minimized by crop rotation. Application of insecticides is also possible, but agent and application time should be chosen carefully since the leaves are harvested for consumption.[14] Attacks were also observed by weevils species (Myllocerus spp.), semilooper (Anomis sabulifera), and yellow mites (Polyphagotarsonemus latus).[9] Diseases (bacterial and viruses infections) are not as serious as pests (insect and nematode attacks). Seedling damp-off occurs but can be reduced by good drainage and cultivation in humus-rich soils with adequate water holding capacity. Attacks by Sclerotium rolfsii in dry weather of the late season can lead to wilts at the stem collar.[14] Anthracnose spots caused by Colletotrichum gloeosporioides may infect the crop but can be easily controlled by spraying copper oxychloride.[15]
Harvest and yield performance
Harvest can begin after about six weeks:[8] The whole plant can be directly harvested (for jute production) or leaves are harvested by pruning several times during the vegetation period (for food production). The shoot regeneration highly depends on variety, soil fertility, adequate water supply and control of weeds and pests. Amount of pruned shoots and quality reduces with each harvest. Under farming conditions the yield usually reaches around 2.5 t per hectare of edible leaves. Under experimental conditions and with very high fertility application, yields of about 28 t per hectare have been reported.[13]
Post harvest and propagation
For fresh consumption the leaves should be stored above 8 °C (46 °F) and below 15 °C (59 °F). Low temperatures from 1 to 8 °C (34 to 46 °F) lead to browning of the leaves and too high storage temperatures are manifested in leaf yellowing.[16] To produce seeds, the fruits can be harvested six weeks after flowering. The dried capsules are threshed and can be stored for eight to twelve months in well sealed jars.[8][13] For storage, the moisture should be around nine percent.[13]
Biochemistry
Leaves
Leaves of Corchorus olitorius are mainly known to have rich sources of many chemical compounds. There are 17 active nutrients compounds in Jute leaves including protein, fat, carbohydrate, fiber, ash, calcium, potassium, iron, sodium, phosphorus, beta-carotene, thiamine, riboflavin, niacin and ascorbic acid.[17]
Seeds
According to a comparative analysis of major nutrients of Corchorus olitorius seeds showed that the protein content of the Corchorus olitorius has significantly increased after seed germination process where the sugar level has decreased in the studied seeds.[18] It can be seen from this study that the level of nutrients in the Corchorus olitorius seed changes during the germination process.
Future prospects
C. olitorius could be grown in a floating system with nutrient solution and could produce baby leaves, which would be interesting for the fresh cut leafy vegetable industry in Europe.[19]
Uses
Fibre and textile use
Jute fibre is made from the bark tissue of C. olitorius and C. capsularis, especially in South Asian countries, though fibre made from C. olitorius is considered to be of lesser quality. Finished fibres appear golden and silky with a length of up to 3 metres and with a diameter of 2.4 µm.[20] The plant stalk is cut and then processed by pulling up, rippling, partial retting, breaking, spinning and combing to obtain fine fibres that are well separated from unwanted woody material. Afterwards the fibres are cured and dried.
Many textiles are made of jute, such as yarn, twine, sacking, carpet backing cloth and other blended textiles. It is also used as raw material for cords and strings.[21]
In Africa and the Middle East, a different type is grown with the leaves and shoots being used for food while the fibre is considered of little importance.[5]
Culinary use
C. olitorius is cultivated in Syria, Lebanon and Egypt as a potherb and its culinary use goes back at least as far as the Ancient Egyptians.[6] It is an important leafy vegetable in Côte d'Ivoire, Benin, Liberia, Nigeria, Ghana, Cameroon, Sudan, Uganda, Kenya, Zambia and Zimbabwe. It is also cultivated and eaten in the Caribbean and Brazil, in the Middle East and in India, Bangladesh, Japan and China. Its leaves are a special favourite of the Boros of northeast India, who make a mucilaginous preparation with its dried leaves mixed with fatty pork and lye called narji.
In Nigeria and Zambia, the leaves are boiled to make a sticky, mucilaginous sauce which is served with balls of cassava (served with nshima in Zambia) which are otherwise rather dry.[5] In Vietnamese cuisine, it known as rau đay and made into a soup with shrimp. In Egypt and Palestine, mulukhiyah is a dish made from the boiled leaves
Nutrition
The edible part of jute is its leaves. Richness in potassium, vitamin B6, iron, vitamin A and vitamin C make this crop particularly important, where people cover a high share of their energy requirement by micronutrient-poor staple crops. This vegetable is predominantly eaten in Africa and Asia. A traditional Syrian, Lebanese, Tunisian, Turkish Cypriot, Jordanian, Palestinian and Egyptian dish made of C. olitorius leaves is mulukhiyah.
Medicinal aspects
Consumption of the leaves is reported to be demulcent, deobstruent, diuretic, lactagogue, purgative, and tonic. It is also a folk remedy for aches and pains, dysentery, enteritis, fever, pectoral pains, and tumors.[22][23] Ayurvedics use the leaves for ascites, pain, piles, and tumors. Elsewhere the leaves are used for cystitis, dysuria, fever, and gonorrhea. The cold infusion is said to restore the appetite and strength.[24] It can act as an anti-inflammatory,[25] and it has gastroprotective properties.[25]
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