Prota 14: Vegetable oils/Oléagineux
Suppl. carp.: 131, t. 205 (1807).
2n = 24
Butyrospermum niloticum Kotschy (1865), Butyrospermum parkii (G.Don) Kotschy (1865), Butyrospermum paradoxum (C.F.Gaertn.) Hepper (1962).
Shea butter tree, shea tree, bambouk butter tree, galam butter tree (En). Karité, arbre à beurre (Fr). Cárei, carité (Po).
Origin and geographic distribution
Vitellaria paradoxa is indigenous to the Guinea and Sudan savanna zone from Senegal to Sudan, and to western Ethiopia and Uganda, in a belt 500–700 km wide. It is found in the interior, separated from the Gulf of Guinea by forest; only in Ghana and Nigeria does it occur within 50 km from the coast.
The kernel of the seed (often incorrectly called ‘nut’) contains a vegetable fat known as shea butter. High quality shea butter is consumed throughout West Africa as a cooking fat. Refined fat has been marketed as margarine and baking fat. It is used for pastries and confectionery because it makes the dough pliable. It is a substitute for cocoa butter, which has similar properties. Many cosmetic products, especially moisturizers, lotions and lipsticks, have shea butter as a base because its high unsaponifiable matter content imparts excellent moisturizing characteristics. Low-quality shea butter, often mixed with other oils, is a base material for soap. It is also very suitable for making candles because of its high melting point.
Shea butter is a suitable base for topical medicines. Its application relieves rheumatic and joint pains and heals wounds, swellings, dermatitis, bruises and other skin problems. It is used traditionally to relieve inflammation of the nostrils. Shea butter is given externally and internally to horses to treat sores and galls.
As a waterproofing agent, shea butter is used as daubing for earthen walls, doors and windows. The black sticky residue, left after oil extraction, is used to fill cracks in walls and also as a waterproofing material.
Waste water from shea butter production has pesticidal properties and has been mixed with stored cowpea seeds in Burkina Faso to protect them from being eaten by the weevil Callosobruchus maculatus. The press cake is unsuitable as livestock feed because it contains anti-nutritional compounds. However, detoxified meal can be given as feed in low proportions. In Europe the cake is utilized as a non-nutritional bulk for compound cakes. The press cake and the husks are also potential fertilizers and fuels.
The flowers and fruits are important foods. The flowers are sometimes made into fritters. In spite of their slightly laxative properties, mature fresh fruits are commonly eaten in savanna regions as they ripen during the land preparation and planting season. The sweet pulp of fallen ripe fruits can also be fed to livestock.
The leaves are used to treat stomach-ache. They are also added to vapour baths to treat headache and as an eye bath. Leaves soaked in water produce a good lather for washing. Ground roots and bark are used to treat diarrhoea, jaundice and stomach-ache. Roots are used as veterinary medicine for horses.
Bark infusions have medicinal and antimicrobial properties, e.g. against dysentery. They are applied as an eyewash to counteract spitting-cobra venom. A bark decoction has been used in baths to facilitate childbirth and stimulate lactation among feeding mothers.
The reddish latex (gutta shea or red kano rubber) which exudes from deep cuts in the bark is made into glue, chewing gum and balls for children’s games. Musicians use it to repair drums.
Only unproductive and unhealthy trees are cut for timber. The wood is used for poles, house posts, rafters, flooring, domestic utensils and furniture. It is an excellent fuelwood, burning with great heat, and a source of charcoal.
Shea butter tree is an important source of honey. Beehives placed in its branches are assured a good supply of nectar and pollen. The widely collected edible and protein-rich caterpillar of Cirina butyrospermi feeds solely on its leaves.
The tree is considered sacred by many tribes. The oil is placed in ritual shrines and used for anointing. In some areas leaves are hung in doorways to protect newborn babies, and are also used in making masks.
Production and international trade
Vitellaria paradoxa is one of the most important sources of vegetable oil in rural areas of the savanna zone of West Africa. The bulk of the seed produced is for home consumption and local trading. Nigeria is the leading producer of seeds: 355,000 t in 1999, 58% of the African production, but 10,000 t lower than in 1996. Mali and Burkina Faso are other leading producers; at the end of the 1990s they produced 85,000 t/year and 70,000 t/year, respectively, followed by Ghana (55,000 t), Côte d’Ivoire (20,000 t), Benin (15,000 t) and Togo (6500 t). Up-to-date statistics on seed production are not available for most countries. Reports on Burkina Faso show a remarkable increase in production to 222,000 t in 2005. Similar trends probably take place in other West African countries.
In 1998, Africa exported 56,000 t seeds, valued at US$ 10.5 million, of which 60% came from Ghana. Benin’s exports decreased from 15,000 t in 1995 to 5600 t in 1998, Togo had only a slight decrease from 6500 t in 1994 to 5100 t in 1998, whereas exports from Burkina Faso increased from 5000 t in 1994 to 7600 t in 1997 and then to 26,600 in 2003. No export data have been reported for Nigeria since 1995. Processed shea butter exports in 1998 for the whole of Africa totalled 1200 t, worth US$ 571,000. Benin was top exporter (1000 t, valued at US$ 400,000), followed by Côte d’Ivoire (200 t) and Burkina Faso (30 t). African exports of shea butter have increased to 3200 t in year 2000.
Major seed importers in recent years were Belgium, Denmark, Japan, the Netherlands, Sweden and the United Kingdom.
Shea butter from fresh seeds is white, odourless and of high quality, while that from stale seeds is dark, and tastes bitter. The approximate chemical composition of the kernel per 100 g dry matter is: fat 31–62 g, protein 7–9 g, carbohydrate 31–38 g, unsaponifiable matter 2.5–12 g. The fatty acid composition of shea butter is approximately: lauric acid trace, myristic acid trace, palmitic acid 4–8%, stearic acid 31–45%, oleic acid 43–56%, linoleic acid 4–8%, linolenic acid trace and arachidic acid 1–2%. The chemical properties of shea butter vary across its distribution range, Burkina Faso and Uganda representing the two extremes. The highest oleic acid content was found in Uganda (57%), the lowest in Burkina Faso (45%), while shea butter from the Mossi plateau in Burkina Faso has the highest proportion of stearic acid (45%) and that from Uganda the lowest (31%).
Shea butter is a useful cocoa butter substitute because it has a similar melting point (32–45°C) and high amounts of di-stearin (30%) and some stearo-palmitine (6.5%) which make it blend with cocoa butter without altering flow properties.
The high proportion of unsaponifiable matter, consisting of 60–70% triterpene alcohols, gives shea butter creams good penetrative properties that are particularly useful in cosmetics. Allantoin, another unsaponifiable compound, is responsible for the anti-inflammatory and healing effect on the skin. It is used in toothpastes and other oral hygiene products, in shampoos, lipsticks, cosmetic lotions and creams, and other cosmetic and pharmaceutical products. Clinical tests with patients suffering from rhinitis, and having moderate to severe nasal congestion, showed that shea butter may relieve nasal congestion better than conventional nasal drops.
The seed cake is a potential source of feed for livestock. Per 100 g dry matter it contains: protein 8–25 g, fat 2–20 g, carbohydrate 48–67.5 g, fibre 5–12 g. However, it has low digestibility and toxic properties attributed to saponins or tannins. Mouldy seeds contain relatively low quantities of aflatoxin, while commercial samples have a maximum of 20 μg aflatoxin B1 per kg.
The fruit pulp contains per 100 g: glucose 1–2 g, fructose 1–2 g, sucrose 1–2 g, ascorbic acid 200 mg, Ca 36 mg, Mg 26 mg, Fe 2 mg, and trace amounts of Zn, Mn and Cu. Sweetness of the pulp is the main quality criterion.
The wood of Vitellaria paradoxa is moderately heavy (density about 720 kg/m³ at 12% moisture content) and hard. It is liable to crack on drying and needs to be seasoned slowly. It is difficult to work and tends to split on sawing, but it polishes well. It glues, nails and screws well, but pre-boring is recommended to avoid splitting. It is durable and resistant to termites. Both sapwood and heartwood are resistant to impregnation with preservatives.
Small to medium-sized deciduous tree up to 15(–25) m tall; taproot up to 1(–2) m long, lateral roots shallow, concentrated at a depth of 10 cm and extending up to 20 m outward from the tree, secondary lateral roots growing downwards to the same depth as the tap root; bole short, usually 3–4 m long, up to 100 cm in diameter; bark blackish, greyish or reddish, rough, deeply fissured and splitting regularly into corky square or rectangular scales, producing white latex when cut; crown round to spindle-, umbrella- or broom-shaped; young branches initially pubescent and reddish but becoming glabrous, flowering branches stout, up to 1.5 cm in diameter, with numerous leaf scars. Leaves arranged spirally, mostly in dense clusters at the tips of branches, simple; stipules small and caducous; petiole 3–10 cm long; blade lanceolate to ovate-oblong, 10–25 cm × 4–14 cm, base cuneate to rounded or slightly cordate, apex rounded to acute, margins entire to wavy, leathery, glabrescent to slightly hairy at both surfaces, pinnately veined with regularly and closely spaced veins. Inflorescence a dense fascicle at the end of a twig, (8–)30–40(–100)-flowered. Flowers bisexual, regular, white or creamy white, fragrant; pedicel up to 3 cm long; sepals free, in 2 whorls of (3–)4, 1–1.5 cm long, pubescent; corolla with short tube and (6–)8 lobes about as long as sepals, contorted in bud; stamens (6–)8, inserted at top of corolla tube, free, staminodes (6–)8, alternating with the stamens, petal-like, with a filiform point; ovary superior, globose to ovoid, pubescent, (5–)6–8(–10)-celled, style long and slender. Fruit a globose to ellipsoid berry 4–5(–8) cm × 2.5–5 cm, weight (10–)20–30(–57) g, initially green but turning yellowish green or brown on maturity, 1(–2)-seeded. Seed globose or broadly ellipsoid, 3–5 cm × 2–3.5 cm, weight (5–)8–10(–16) g; seed coat rather thin, shining, with broad scar; kernel consisting of two thick, fleshy, closely adpressed cotyledons and not-exserted radicle. Seedling with hypogeal germination with cotyledons remaining in the seed; epicotyl 3–4 cm long, bearing stipulate rudimentary leaves.
Other botanical information
Vitellaria comprises a single species. Two subspecies are recognized in Vitellaria paradoxa: subsp. paradoxa (synonym: Butyrospermum parkii (G.Don) Kotschy) and subsp. nilotica (Kotschy) A.N.Henry, Chithra & N.C.Nair (synonym: Butyrospermum niloticum Kotschy). Subsp. paradoxa has a less dense and shorter indumentum, and slightly smaller flowers than subsp. nilotica. The former occurs from Senegal to the Central African Republic, the latter is found in Sudan and Uganda with small populations in Ethiopia and DR Congo. The ranges of the two subspecies do not overlap, although they come to within 175 km of each other at the divide between the drainage basins of Lake Chad and the Congo River to the west, and the Nile to the east and north-east.
Growth and development
Seeds of Vitellaria paradoxa are recalcitrant. After water absorption, the seed coat breaks and 2 days later a structure (sometimes called a ‘pseudo-radicle’, but anatomically the fused petioles of the cotyledons) emerges and grows downwards into the soil. When it is 7–8 cm long a shoot with rudimentary leaves arises from it and grows upwards to the soil surface. The structure itself continues to grow downwards, forming the taproot with a corky surface and lateral roots. When the shoot pushes through the soil surface it starts developing normal leaves. The taproot and secondary root system strongly develop during the first few years of growth. This enables the seedling to produce new shoots when the original ones are damaged by drought or fire. Early stem growth is slow; branching occurs after 4–7 years. Vitellaria paradoxa begins flowering at 10–25 years. Early flowers may be sterile. Maturity is reached at 20–45 years. The lifespan is 200–300 years.
Growth occurs in flushes, and according to Aubréville’s model. A flush starts with the formation of a short, thick shoot on which a tuft of leaves develops. Branches owe their characteristic appearance to sympodial growth, producing twigs with alternating long, thin sections and short, compact ones. Leaves and flowers develop on the short, thick terminal section characterized by very short internodes and prominent leaf scars. When leaf development stops, growth of the branch continues from an axillary bud.
Leaf fall, flowering, flushing and the onset of fruiting occur during the dry season. Leaves drop mostly at the beginning of the dry season. Trees are rarely completely leafless, or only for relatively short periods. Flowering occurs from the beginning to the middle of the dry season (between November and January depending on latitude). In Uganda, where rainfall is bi-modal, there is also a single flowering season, which peaks in February. Fire may cause defoliation followed by earlier flowering. Flowers attain full size about 3 weeks after their appearance. They are protogynous; styles are exserted from the unopened flowers before the pollen matures. Pollination is by insects (e.g. bees) or by wind. About 25% of the flowers set fruit. Fruits develop in 4–6 months; maturation peaks in the rainy season. Fruiting cycles are variable, 2–5 years long.
Vitellaria paradoxa is characteristic of West African savanna, but is also present in the southern Sahel. Subsp. paradoxa grows mostly at 100–600 m altitude (mean annual temperatures 25–29°C), although it also occurs up to 1300 m; subsp. nilotica occurs at 450–1600 m. Subsp. paradoxa grows in areas with mean annual rainfall of 600–1400 mm and 5–8 months dry season (precipitation less than 50 mm); subsp. nilotica grows in areas with mean annual rainfall of 900–1400 mm, with 3–5 dry months.
Vitellaria paradoxa grows on a variety of soils, such as clay, sandy clay, sand, stony soil and laterites. It prefers colluvial slopes with moderately moist, deep soils, rich in organic matter.
Propagation and planting
Vitellaria paradoxa is propagated by seed. Seeds should not be dried, but sown as soon as possible because their viability is very short. When fresh seed is used, germination is 90–97% at 25–30°C. Storing seed at 25°C for 70 days and 140 days resulted in 96% and 88% germination, respectively. Seed can be planted directly in the field or in the nursery. Seed-beds are made of a mixture of organic compost and sand. Seeds are planted at 1–5 cm depth and 20 cm × 15 cm spacing or in polythene bags. After 1 year, seedlings are transplanted in the nursery or planted directly in the field. Those grown in polythene bags are transplanted after 1–2 years.
Vegetative propagation has only been successful in experiments. Grafting can accelerate the fruiting of Vitellaria paradoxa. In experiments in Burkina Faso, some grafted seedlings started to bear fruit one year after grafting. Latex exudation interferes with rooting of cuttings and with grafting. A 25% success rate can be achieved in grafting if the scion is soaked in water for a few hours to allow the latex to drain. Marcotting has been tried with some success; growth hormones improved the success rate.
Field spacing depends on the cropping system; recommendations vary from 25 trees per ha (20 m × 20 m) to 100 trees per ha (10 m × 10 m). Mulching and weeding encourage seedling growth. Young plants should be protected from livestock and fires. Slow growth and late maturation have discouraged the planting of Vitellaria paradoxa in plantations.
Shea butter tree has been protected by farmers for many centuries in the West African savanna, particularly where cattle are scarce. Productive shea butter trees are retained when new fields are cleared, giving rise to the so-called ‘ Vitellaria parkland’ in Sudan, in which more than 40% of the trees are Vitellaria paradoxa. Natural regeneration is favoured by fallow of at least 5 years. Shortening the fallow period leads to insufficient regeneration. In areas of cultivation, shea butter tree is found in association with annual crops, such as pearl millet, sorghum, groundnut, cotton, cassava, yams and vegetables.
Pruning, weeding, applying manure or fertilizer, and removing dead and diseased trees can markedly increase productivity. Recommended fertilizer applications are 2.5 kg ammonium sulphate, 1.5 kg calcium phosphate and 1.5 kg potassium chloride for 10 trees. Although Vitellaria paradoxa is fire tolerant, its growth and fruiting are affected by fire, so trees must be protected by ring weeding. Overgrazing by livestock should be prevented.
Diseases and pests
Two fungal diseases are potentially important: Pestalotia heterospora causes leaf spot, while Fusicladium butyrospermi causes dark patches on branches. In Ghana Botryodiplodia spp. also causes leaf spot.
There are numerous insect pests, the most important being Curimosphena senegalensis (synonym: Himatismus senegalensis) which attacks young shoots, Xyloctonus scolytoides which tunnels through the bark of twigs impeding growth of leaves and flower buds, Nephopteryx sp. which damages fruits, and Cirina butyrospermi which causes defoliation. Fruits are attacked by maize cob borer Mussidia nigrivenella and the fruit fly Ceratitis silvestrii, which feeds on the pulp of maturing fruits. Shea butter tree is a host of the nematode Aphasmatylenchus straturatus, which also affects intercropped legumes. Trees are often hosts to strangler figs (Ficus spp.) and hemiparasitic plants (Tapinanthus spp.). In Burkina Faso and Mali, up to 95% of the trees are infested. Unless controlled by removing and burning affected branches, infestation will eventually kill the trees.
Fruits are gathered in the wet season, usually in June–August depending on latitude. Harvesting continues for about 2.5 months, and is done mostly by women and children. Fallen fruits are collected from the ground because it is difficult to distinguish between ripening and fully mature fruit. Harvesting rights depend on tenure. A woman collects 20–45 kg of fruits per day, depending on ethnic group, proximity of trees to the village, and distance between trees. Fruits are brought back to the village in head-loads of about 25 kg.
Productivity of shea butter trees is variable. In a sample taken in Burkina Faso, the best 25% of the trees produced 60% of the yield, while the poorest 30% of trees produced little fruit. A good tree can bear on average 15–30 kg fruits per year. In a good year this may be as much as 50 kg, but then only about 15 kg in the next two years. Although a clear production cycle is not confirmed, observations show a tendency for Vitellaria paradoxa to give only 1 good harvest per 3–4 years.
Handling after harvest
In rural areas, seeds are traditionally processed by hot water extraction, usually the job of women. The fruit pulp is first removed for food, or by fermentation or boiling. The seeds are then boiled and later sun- or kiln-dried. Sun-drying may take 5–10 days. Seeds are cracked using mortar and pestle, or stones; the kernels are removed by trampling and redried before being crushed, ground and kneaded to form a paste; the paste is put in water, heated or boiled and the boiling mass is churned until a grey, oily fat separates from the emulsion. The fat is skimmed off from the surface and washed to remove impurities. The congealed fat may subsequently undergo further refining before being moulded in to various forms. This traditional method of processing is inefficient and labour intensive. Mechanization of the various operations, in particular the use of hydraulic or continuous screw expellers or application of solvent extraction, will improve oil extraction efficiency considerably. Pretreatment of the kernel paste with enzymes (e.g. proteases and cellulases) may also result in higher extraction rates.
There are indications that genetic variation in Vitellaria paradoxa is higher within populations than between them and selection of many individual trees from a limited number of populations would probably adequately capture the genetic variability, especially for fruit traits. However, differences between populations have also been found, e.g. in the fatty acid composition. The genetic diversity is gradually being lost because of bush fires and overgrazing. Vitellaria paradoxa is designated as one of the African forest genetic resource priorities. It is the subject of in situ conservation and germplasm exploration. Local and regional germplasm collections have been made by the Institut National de l’Environnement et de Recherches Agricoles (INERA) and the Centre National de Semences Forestières (CNSF) in Burkina Faso, the Cooperative Office for Voluntary Organisations of Uganda and the World Agroforestry Centre (ICRAF) in Mali. There are also local collections; those of Ghana’s Cocoa Research Institute were analyzed for fruit and seed size and fat content.
The Cocoa Research Institute of Ghana has started a breeding programme to select and breed cultivars that establish easily in the field and have seeds with high fat content. The long juvenile phase and the difficulty of vegetative propagation of Vitellaria paradoxa make breeding a long-term process.
Shea butter tree is of great economic importance in the Guinea and Sudan savanna zones. It grows over a wide area, regenerates well, is traditionally managed and protected by farmers. However, natural regeneration and sustainability of seed production are threatened by agricultural intensification in the area. Progress made on grafting techniques suggest that selected vegetative material with specific fruit or butter qualities can be multiplied for small scale clonal plantations to meet market demand for high quality fruit or butter production. Vitellaria paradoxa has a niche in the international markets as a cocoa butter substitute in the food, cosmetic and pharmaceutical industries. Recent studies on the variation in fat composition across the species distribution range indicate that the soft shea butter from Uganda is preferred for cosmetic purposes, while shea butter with a higher stearic acid content as found in Burkina Faso is more suitable for the chocolate industry. Shea butter is increasingly popular as an ingredient in cosmetics and soaps, especially in European countries and the United States. Now that the European Union allows the use of 5% cocoa butter substitutes in chocolate, chocolate and confectionery products account for 95% of the shea butter demand, with only 5 percent currently used for cosmetic and pharmaceutic products. It is likely that the overall demand for shea butter will continue to rise in the world market as a result of progress made in better knowledge of its various properties.
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Sources of illustration
• Aubréville, A., 1964. Sapotacées. Flore du Cameroun. Volume 2. Muséum National d’Histoire Naturelle, Paris, France. 143 pp.
Correct citation of this article:
Nikiema, A. & Umali, B.E., 2007. Vitellaria paradoxa C.F.Gaertn. In: van der Vossen, H.A.M. & Mkamilo, G.S. (Editors). PROTA 14: Vegetable oils/Oléagineux. [CD-Rom]. PROTA, Wageningen, Netherlands.
wild and planted
1, tip of branch with leaves and fruit; 2, tip of branch with inflorescence; 3, flower; 4, part of corolla with staminode and 2 stamens; 5, seed in front view; 6, seed in side view.
Redrawn and adapted by M.M. Spitteler
branch with flowers and young fruits
bark of savanna tree, ‘pyrophyte’