Prota 14: Vegetable oils/Oléagineux
Ann. Inst. Bot.-Géol. Colon. Marseille 5(2): 40 (1898).
2n = 22
Ricinodendron africanum Müll.Arg. (1864).
Groundnut tree, corkwood tree, African oil-nut tree (En). Essang, essessang (Fr). Menguela, munguella (Po). Muawa (Sw).
Origin and geographic distribution
Ricinodendron heudelotii occurs from southern Senegal eastwards to Kenya, and southwards to Angola and Mozambique.
The seeds of Ricinodendron heudelotii are widely used in cooking in West and Central Africa. An edible oil is extracted from the seeds and a paste made by crushing dried kernels is sometimes used as a thickening agent for soups and stews. A paste from the dried and pounded kernels is also stored for making porridge in times of food shortage. The protein-rich leaves are eaten as a cooked vegetable with dried fish and are used as forage for goats and sheep.
The wood, called ‘erimado’ or ‘essessang’ in trade, is very light, soft and perishable, but is occasionally used in carving and for making household utensils, furniture, boxes and crates. In Uganda the Semliki and Unyoro people use it for making doors for their huts, while in southern Nigeria and DR Congo well-sounding drums are carved from it. It is a potential substitute for balsa wood (Ochroma pyramydale (Cav. ex Lam.) Urb.) for making floats and lifebelts. The wood is also suitable for boat building, sporting goods, toys and novelties, hardboard, particle board, plywood, wood-wool and wood-pulp. The ash of the wood is used as vegetable salt in cooking, indigo dyeing and soap making. The seeds are used in rattles and as counters in games. In Bas Congo (DR Congo) the tree is planted to attract edible caterpillars (Imbrasia epimethea), and several other edible caterpillars are collected from it. The leaves are used as wrapping material and for mulching. In DR Congo Ricinodendron heudelotii is planted as amenity tree, as live fence and for erosion control.
Many parts of the tree are used in medicine. Bark of the root and stem is used in decoctions or lotions to treat constipation, cough, dysentery, rheumatism, rickets in children, oedema, elephantiasis, fungal infection, blennorrhoea, painful menstruation, and to prevent miscarriage, relieve pain in pregnant women, cure infertility in women, give strength to premature babies, and to mature abscesses, furuncles and buboes. The sap is instilled into the eye against filaria and ophthalmia and leaf decoctions are used as febrifuge. Leaves are also used to treat dysentery, female sterility, oedema and stomach pain. Roots are used as aphrodisiac in Côte d’Ivoire. Fruits and latex are used in West Africa to cure gonorrhoea and diarrhoea.
Production and international trade
Kernels of Ricinodendron heudelotii are traded internationally and are found in many markets in West and Central Africa; they are exported to Europe from Cameroon as ‘ndjanssang’. The humid forest zone of Cameroon appears to be the main production area. In 1995, 36,000 kg of seeds were marketed in this zone, for a total value of about US$ 79,000.
The dried seeds of Ricinodendron heudelotii contain on average per 100 g: water 6 g, energy 2200 kJ (530 kcal), protein 21 g, fat 43 g, carbohydrate 23 g, Ca 611 mg, P 926 mg, Fe 0.4 mg, thiamin 10 μg, riboflavin and niacin traces (Leung, Busson & Jardin, 1968). Some sources give a fat content of up to 60%. The fat is pale yellow and liquid but somewhat viscous at ambient temperatures. Its fatty acid composition is: palmitic acid 6–10%, stearic acid 6–7%, oleic acid 7–9%, linoleic acid 28–36%, α-eleostearic acid 30–51%. The fat also contains small amounts of β-eleostearic acid, catalpic acid, gadoleic acid and lignoceric acid. When exposed to air in a thin layer it dries to a frosted film; when the oil is heated first to 280°C it dries to a hard clear film.
The heartwood is whitish to pale yellow, and is not differentiated from the sapwood. The wood darkens on exposure to light. The grain is straight, texture coarse and even. The wood is light-weight with a density of 130–300 kg/m3, soft and brittle. It dries rapidly and with little or no degrade. The shrinkage rates are low: from green to oven dry 1.9–2.4% radial and 4.7–5.4% tangential. At 12% moisture content, the modulus of rupture is 29–46 N/mm2, modulus of elasticity 3700–4800 N/mm2, compression parallel to grain 14–21 N/mm2, shear 2.2–3.2 N/mm2, cleavage 5.0–7.3 N/mm (tangential) and Chalais-Meudon side hardness 0.2–0.6.
The wood saws and works easily, and nails without splitting, but turning and planing are difficult. The wood is liable to decay and attack by termites, powder-post beetles and marine borers. The wood is permeable to preservatives.
Deciduous, dioecious, medium-sized tree up to 30(–45) m tall; bole straight and cylindrical, up to 120(–150) cm in diameter, base with short, thick buttresses often extending into heavy superficial roots; outer bark smooth at first, becoming rough and fissured, grey; inner bark pink to red, densely mottled and granular; crown candelabra-shaped, commonly with many broken branches; twigs with few lenticels, densely brown stellate hairy but soon glabrescent, with thick pith. Leaves alternate, palmately compound with (3–)5–7(–8) leaflets; stipules fan-shaped, 1–5 cm × 1.5–4 cm, with gland-tipped teeth, persistent; petiole up to 5–30(–40) cm long; leaflets obovate to elliptical-lanceolate, median leaflet 10–30 cm × 5–15 cm, lateral ones smaller, base cuneate, apex long-acuminate, margin almost entire to shallowly glandular-toothed, thinly papery, glabrous above, glabrous to densely stellate hairy below. Inflorescence a terminal panicle, densely stellate hairy but glabrescent; bracts awl-shaped to linear, 3–7 mm long; male inflorescence up to 40 cm long; female one up to 20 cm long. Flowers unisexual, regular, (4–)5-merous, pedicellate; sepals fused at base, c. 4 mm long, densely stellate hairy; petals laterally coherent, oblong, c. 6 mm long, greenish white to pale yellow; disk lobes yellowish; male flowers with 6–14 stamens c. 6 mm long; female flowers with superior, globose ovary, 2–3-celled, stellate hairy, styles 2–3, bifid. Fruit a 2–3-lobed drupe 2.5–3.5 cm × 4–5 cm, green when young, black when ripe, each lobe containing one 1-seeded stone. Seeds globose, c. 1.5 cm in diameter, reddish brown to black. Seedling with epigeal germination; hypocotyl up to 20 cm long, epicotyl short; cotyledons with petiole 1.5–2.5 cm long, blade leafy, 6–7 cm × 5–6 cm, glandular at margins, palmately veined; first leaf 3-lobed.
Other botanical information
Ricinodendron comprises a single species. It is closely related to Schinziophyton. In Ricinodendron heudelotii 2 subspecies are recognized: subsp. heudelotii occurring from Senegal to Benin, and subsp. africanum (Müll.Arg.) J.Léonard from Nigeria eastwards and southwards. The former has mostly 3-lobed fruits, in the latter 2-lobed fruits are more common.
Growth and development
The roots of Ricinodendron heudelotii reach deep and cause little competition for nutrients and water in the upper soil layers with adjacent crops. The tree starts bearing fruits at 8–10 years of age. In Sierra Leone flowering takes place in April–May, and fruits are produced in September–October; trees are leafless for a few weeks when the fruits fall. In central Cameroon fruits are collected in July–September. Bats, hornbills and rodents are believed to contribute to the dispersal of the seed. Fruits also break open and scatter their seed when they fall on the ground.
Ricinodendron heudelotii occurs in clearings in rainforest; it is characteristic of humid secondary forest and common in abandoned farmland at 200–500 m altitude. The minimum annual rainfall required is about 1000 mm, but annual rainfall may be as high as 10,000 mm/year as in Dibunscha, Cameroon. It is a fast-growing and light-demanding tree, requiring mean annual temperatures of 18–32°C. Ricinodendron heudelotii prefers medium-textured and freely draining acidic soils.
Propagation and planting
Seeds start germinating 3–6 weeks after sowing. Scarification before sowing accelerates germination. Vegetative propagation is possible by rooting of leafy stem cuttings, layering and side grafting.
There is still little experience with management of planted Ricinodendron heudelotii. Trials are in progress at ICRAF, Cameroon. In DR Congo stakes are sometimes planted to create a live fence as they easily strike root. Although the species loses its leaves during the dry season, some farmers in Cameroon use it to shade cash crops such as cocoa. Coppicing is possible, but reports on regrowth are contradictory.
Diseases and pests
Some caterpillars have been reported to defoliate Ricinodendron heudelotii in DR Congo, such as Lobobunaea phaedusa, Imbrasia spp. and one identified locally as ‘mimpemba’. However, these caterpillars also constitute a considerable protein supply for local people. In Cameroon, a psyllid (Diclidophlebia xuani), and aphids have been reported to cause serious damage to young plants.
Fallen fruits are collected from the ground.
Handling after harvest
After collection, the fruits are left to rot in big piles. Once the fruit pulp is rotten, the stones are extracted by washing and boiling the fruits vigorously. Then the stones are removed from the hot water, put in cold water and left overnight. They are boiled vigorously once more until the shells crack. Shells are then removed using a knife. After extraction, seeds are dried.
Logs felled for timber should be extracted from the forest and converted rapidly because they are prone to staining.
Ricinodendron heudelotii is very widespread in tropical Africa and genetic variation is large. Within a sample of 47 accessions, considerable variation was found in fruit size, seed size and oil content of the seed (49–63%). Because of its wide distribution and prevalence in secondary forest and on farmland there is no risk of genetic erosion. No germplasm collections are known to exist.
Domestication of Ricinodendron heudelotii has started recently under the Tree Domestication Program of the World Agroforestry Centre (ICRAF) in Cameroon. Selection work is still in its infancy. Plant characters preferred by farmers have been identified. They include high yield, long fruiting season, stable yield, thin shell, self-cracking stones and good taste. It appears that fruit size is only weakly correlated with seed size. The self-cracking shell character is not related to shell thickness.
Continuing intensification of agriculture in humid tropical Africa will increasingly rely on domesticated, fast-growing, multipurpose tree species that fit well in agroforestry systems. If selections can be made that meet farmers’ requirements and if appropriate packages of management practices can be developed, Ricinodendron heudelotii is likely to become a more important component of such systems and contribute to the regional demand for edible and industrial oil.
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Correct citation of this article:
Tchoundjeu, Z. & Atangana, A.R., 2007. Ricinodendron heudelotii (Baill.) Pierre ex Heckel In: van der Vossen, H.A.M. & Mkamilo, G.S. (Editors). PROTA 14: Vegetable oils/Oléagineux. [CD-Rom]. PROTA, Wageningen, Netherlands.
1, base of bole; 2, part of branch with young fruits; 3, male flower; 4, fruit; 5, seed.
Redrawn and adapted by Iskak Syamsudin
bole and crown
leaves and inflorescences
leafy branch with fruits