Mucuna pruriens (L.) D.C.

Leguminosae

Synonyms

Mucuna utilis Wall.

Common names

velvet bean, banana stock pea (Aust.), ojo de venado, poroto aterciopelado (Arg.), frijol terciopelo (Mex.), haba de terciopelo (P.R.), pois a gratter, haricot veloute, pois mascate, dolique de Floride, alkusi, makhmali sem, alkushi, cigu, kaocho, taingilotra, stizolobia, fluweelboontjie

Description

Velvet beans are annual, or perennial, herbaceous, vigorous climbing vines, which can reach 18m in length when grown on supports and even on the ground can attain a length of 5.5m but 2-3m is normal, although bushy forms also exist. 

Roots: The roots are fleshy, usually well nodulated and produced near the soil surface. 

Stems: The long trailing stems are rather slender and sparsely pubescent. 

Leaves: The stems bear numerous, alternate, trifoliolate leaves on short, hairy, fleshy
petioles, with large, ovate leaflets; they are glabrous and leaflets are about 10cm long x 8
cm wide. 

Flowers: The inflorescence is axillary and the flowers, usually 5-30, are showy, and purple, red or greenish-yellow in colour. Fruits: Pods are 9-14 cm long, hard, curved, slightly ridged and covered with soft black, white or grey hairs which give them a velvety appearance.

Seeds: The pods contain 4-6 seeds, globular, approximately 1.2 x 1.2 cm, often a mottled
brown or black colour, sometimes with a pale-grey background; a few cultivars produce
pure grey, white or black seed. The funicular hilum is about 4 mm long and is surrounded
by a distinctive white aril. The seed coat is hard, thick and glossy. One hundred seeds
weigh approximately 109 g.

Habitat

They are now cultivated in many tropical and subtropical areas, and through breeding,
certain cultivars tolerant of more temperate conditions have been developed.

Temperature

A warm equable temperature of 20-30°C throughout the growing period is preferred; night temperatures of 21°C are reported to stimulate flowering. Velvet beans are susceptible to frost and require a frost-free period of 180 to 240 days. Exposure to temperatures below 5°C for periods as short as 24 or 36 hours is reported to be fatal to young Florida velvet bean plants.

Water

Velvet beans are often grown in the tropics and subtropics in areas with an average rainfall of between 1200-1500 mm/yr., or more.

Soil

Physical: A wide range of soil types are suitable, including heavy clays, provided that they
are well drained, since velvet beans cannot stand waterlogging.

Chemical: They are tolerant of fairly acid soils, but for optimum yields light sandy loams,
with a pH of between 5-6.5, are required.

Distribution

Velvet beans are thought to have originated in Asia (India) and to have been introduced
into the western hemisphere via Mauritius.

Crop management

Velvet bean is a minor leguminous crop, many cultivars of which are suitable for the more humid regions of the tropics, while others, e.g. the Mauritius velvet bean, are suitable for dryland farming. They can be grown successfully on soils unsuitable for cowpeas, but have the disadvantage of a longer growth period and are more difficult to thresh. Moreover, the seed is not highly valued for human or animal feeding, because of the prolonged soaking and, or, boiling required before it can be consumed safely. The leaves and vines make an excellent fodder. 

System: Velvet beans are frequently grown mixed with other vigorous growing crops such as sugarcane or maize. They are also grown as a green manure or cover crop and are
particularly valuable as an anti-erosion crop. In India the wild species is often used as a cover crop in coconut plantations. When grown as a mixed crop with cereals, such as maize or millet, it is usual to plant every alternate or third row with velvet beans. 

Land: For optimum results the seedbed should be well prepared to a depth of at least 15 cm and completely free from weeds. 

Fertility: Little is known of the crop's precise requirements, but it responds to applications of phosphate, and in the USA the application of superphosphate at 112-225 kg/ha has been recommended.

Harvest: When grown for seed in the tropics many cultivars are normally ready for harvesting approximately 180 to 270 days after planting. In the USA, Florida velvet beans take about 240-270 days to reach maturity. The Yokohama velvet bean normally matures within 110-120 days. When grown for forage, the plants are usually harvested between 90 and 120 days after sowing. The pods should be thoroughly ripe before being harvested. As they are liable to shatter, they are often hand-picked and are usually left to dry for several days before being threshed. Threshing can be carried out by hand or machine, but whichever method is used only fully mature, dry pods can be threshed without difficulty.

Propagation

Multiplication: Seed is used, germination is hypogeal and usually occurs within 5-7 days, with a rate of between 90-95%. Inoculation of the seed is not usually necessary if velvet beans are grown in areas where the cowpea has been cultivated, otherwise inoculation with a commercial cowpea inoculum may be necessary.

Planting: When grown for the production of seed, planting is usually in rows, but when grown as a fodder or green manure crop, the seeds are often broadcast. Adapted maize planters with thick plates and enlarged holes are sometimes used for planting in countries such as the USA, S. Africa and Australia. In Asia the crop normally receives little attention, but the suppression of weeds during the early stages of growth and the provision of supports for the vines to climb is beneficial. When grown for seed, velvet beans are frequently planted in rows 90-180 cm apart, with 15-90 cm between the plants. In India the average seed-rate is reported to vary between 28-50 kg/ha, in most other countries it normally varies from 11-22 kg/ha, when the crop is planted in rows, and from 45-90 kg/ha when broadcast.

Variability

There has long been some uncertainty as to whether the velvet beans should be segregated from Mucuna as the genus Stizolobium, and although not currentlyc fashionable, the latter name has been used in much of the literature, especially in the USA. Only two species are commonly grown, the true velvet bean M. pruriens var. utilis, which has medium-sized seeds, and the horse bean, M. sloatiei Fawcett & Rendle (syn. M. urens auctt.), which has larger seeds with an extremely hard seed-coat. There are, however, numerous cultivars of M. pruriens, some of which were formerly treated as separate species. The principal ones are:

(i) Deering, Florida or Georgia velvet bean, frequently designated as Stizolobium deeringianum or Muncuna deeringiana. It is of some importance as a cattle fodder, particularly in the USA and parts of S. America.
(ii) Bengal velvet bean, frequently designated as M. utilis or S. utile, and grown in India.
(iii) Mauritius velvet bean, often designated as M. aterrima or S. aterrimum, and grown in Mauritius, Australia, Brazil and the W.I., often as a rotating crop with sugar cane or as a drought resistant cover crop.
(iv) Yokohama velvet bean, usually designated as S. hassjoo. This is an early-maturing type and is a less vigorous grower than the other velvet beans, it is thought to have originated in Japan, where it is known under the names 'Osharuka-mame' and 'Hasshomame'.
(v) Lyon bean, designated M. nivea, S. niveum, M. cochinchinensis or Carpogon niveum, which is sometimes cultivated as a vegetable for its immature pods in the Philippines and SE.Asia.

Products & uses

Nutrition: Velvet beans can be used as a human foodstuff but require considerable care in their preparation, because of the toxic principle they contain. In many parts of Africa and Asia they are regarded as a famine food. The toxic principle can be removed by boiling and soaking the seeds in several changes of water. In parts of Asia, the seeds are sometimes roasted before being eaten. In other parts of Asia, notably Java, the seeds are sometimes boiled, the seed-coat removed, and the decorticated seeds soaked in water, after which they are chopped, steamed, and left to ferment to produce a bean cake, 'tempe benguk', which resembles tempe produced from soybeans. The immature pods and leaves are occasionally boiled and eaten as a vegetable.
Medicine: The possibility of utilizing velvet beans as a commercial source of L-dopa (which is relatively expensive to produce synthetically), used in the treatment of Parkinson's' disease, has received attention in recent years. Yields of around 4.8% are reported to be attainable from the decorticated seed meal. Details of Mucuna's traditional medicinal uses, chemical constituents, pharmacological activities and clinical trials have been reported in 'Medicinal Plants of the World' by Ross I.A. 1999.
Secondary: The possibility of utilizing the seed as a source of industrial starch has been investigated in Brazil and results indicate that a starch with a high viscosity, similar to that obtained from cowpeas, and suitable as a thickening agent for food products, or as an adhesive in the paper and textile industries, could be obtained.

Nutritional Quality and Animal Production

Velvet beans are a nutritious animal feed and are used mainly for grazing, although the mature seeds are also used in the manufacture of compound feeds, or fed direct to the animals, when they are often soaked in water for 24 hours, or ground into a meal. They are used mainly for feeding cattle or sheep and can only be fed to pigs if they constitute less than 25% of the diet. They are considered unsuitable for poultry. The residual cake has a protein content of 15-20%.

Characteristics: The approximate composition of the green forage of velvet beans, on a dry weight basis, has been given as: protein 15.1%; fat 2.1; N-free extract 48.6; fibre 19.3 and ash 14.9. Digestible protein 10.7%; digestible carbohydrate 49.6; total digestible nutrients 63.4; nutritive ratio 4:9. The composition of the whole, dry pods has been reported as: moisture 10.0$; protein 18.1; fat 4.4; N-free extract; fibre 13.0 and ash 4.2. The approximate composition of the mature seeds is: moisture 10.0%; protein 23.4; fat 5.7; N-free extract 51.5; fibre 6.4; ash 3.0; calcium 0.18; phosphorus 0.99; potassium 1.36; vitamin A 50 iu/100 g; thiamine 0.50mg/100g; riboflavin 0.20 mg/100g; niacin 1.7 mg/100g. The amino acids present (mg/gN) are: isoleucine 300; leucine 475; lysine 388; methionine 75; cystine 56; phenylalanine 300; tyrosine 319; threonine 250; valine 344; arginine 494; histidine 131; alanine 219; aspartic acid 794; glutamic acid 763; glycine 288; proline 369; serine 306.
The oil present in the seeds has been found to be highly unsaturated with 47.2% linoleic acid; 14.2 oleic acid; 3.8 linolenic and 0.5 palmitoleic acid. The saturated fatty acids are: palmitic 19.5%; stearic 12.6; arachidic 2.2. In feeding trials with rats it was shown that the toxic principle occurs in the protein fraction of the seed and not in the oil. The toxic principle L-dopa, 3-(3, 4-dihydroxyphenyl)-Lalanine, is present mainly in the seed embryo and has been isolated in amounts equivalent to 1.5% of the whole seed weight. It has been suggested that the presence of free L-dopa is the reason that velvet beans are relatively immune to attack from insects and small mammals. (Rehr S. 1973). In addition to L-dopa, a new amino acid (-)-1-methyl-3-carboxy-6, 7-dihydroxy-l, 2, 3, 4-tetrahydroisoquinoline, has been isolated recently from velvet beans.

References

Rehr S.S. et al. 1973,  Ross I.A. 1999, Westphal E. 1974 and Whyte R.O. et al.1953