This section is from the book "The Planting, Cultivation And Expression Of Coconuts, Kernels, Cacao And Edible Vegetable Oils And Seeds Of Commerce", by H. Osman Newland. Also available from Amazon: The Planting, Cultivation And Expression Of Coconuts, Kernels, Cacao And Edible Vegetable Oils And Seeds Of Commerce.
The shea-butter tree was originally brought to our notice by Mungo Park, and named after him, Butyrospermum parkii. The shea-butter grows everywhere in West and West-Central Africa, where the oil palm does not. In Northern Nigeria especially, it flourishes over large areas. Vast and unexploited supplies exist also in the North of Ashanti beyond the evergreen forest. It is content with less rain than the oil palm requires. The vegetable fat from the nut of this tree is used by the West African natives as a food, and has been employed in this country in the manufacture of candles, and mixed with other oils, in soap-making. It is now within the scope of modern chemistry to find some means of preparing and preserving this vegetable fat so that it is an exportable form of butter. It is far nicer in taste, and far more wholesome than some of the present substitutes for the fat derived from cow's milk.
The shea tree grows to a height of 45 to 60 feet or even more. The trunk reaches a diameter of 9 feet or over, and is covered with rough greyish bark. The reddish-coloured wood is hard, heavy, and difficult to work, but is used by the natives for making pestles, mortars, and other implements. The leaves are elongated, grab-rous when fully developed, but downy when quite young, and measure from 4 to 10 inches in length and 1 1/4 to 2| inches in width, each leaf being borne on a petiole from 11/4 to 61/2 inches in length. The flowers appear from January to March, according to the climate and the situation of the tree. The white scented flowers are borne in globular corymbs at the extremities of the branches. The fruit ripens from May to September, but principally in the latter part of July. It is spherical or ellipsoidal in shape, somewhat resembling a plum, and measures from 1 1/2 to 2 inches in length and from 1 1/4 to If inches in diameter. The fruit consists of an outer succulent pulp, of a yellowish or blackish-green colour when ripe, enclosing usually one, or sometimes two or three nuts. The pulp has a pleasant flavour, and is largely eaten by the natives as a fruit. When ripe the fruit falls to the ground, the pulp being then often consumed by sheep and swine. The nuts generally measure rather less than 1 1/2 inches in length and 1 inch in diameter. The shell is usually of a light brown colour, and resembles the shell of a Spanish chestnut ; on drying it becomes hard and brittle, and can then be easily removed. The kernel is soft and yellowish when fresh, but when dry it becomes firm and turns a dark chocolate-brown colour. The dry kernels vary in size and weight; large kernels generally have an average weight of 4 1/2 to 5 grains, whilst small kernels may weigh only 2f grains each. The fresh fruit is composed of from 40 to 65 per cent, of pulp, and 35 to 60 per cent, of fresh nuts, the average being about 49 per cent, of nuts. The fresh nuts yield on drying 57 per cent, of sun-dried nuts, or 39 per cent, of sun-dried kernels, containing 5 to 6 per cent, of moisture, and in a condition suitable for export. A native must gather and work up nearly 5 1/4 tons of fruit in order to prepare 1 ton of kernels for export.
The shea tree requires a deep soil rich in humus, and is particularly abundant on soils composed of sandy-clay or of lateritic detritus.
It does not grow in marshy land, or in land liable to be flooded, or on heavy clay soils, but prefers the slopes of hills, and rocky or sandy plains. Although the tree is found in the forest or in the bush, it does not reach its maximum growth under these conditions, since it is often stunted owing to bush fires and the shading effect of more rapidly growing plants and trees. The tree flourishes best in open situations, such as the clearings round villages, and attempts are being made in Northern Nigeria and elsewhere to induce the natives to clear away the bush around the trees with a view to prevent damage by fire. Laws have also been made in the Upper Senegal and Niger region to prevent the cutting down of this valuable tree when land is being cleared for the planting of crops. Although the tree does not appear to be cultivated in the full sense of the word in any district, it is usual for the natives to leave the mature trees when clearing land. The tree is easy to propagate from seed, but grows comparatively slowly, taking about thirty years to reach maturity, whilst it does not bear fruit until from twelve to fifteen years of age. It is evident, therefore, that the establishment of plantations would be a tedious operation, and in view of the irregular yield of nuts, it might also be unprofitable.
Such considerations would, of course, be most important in the event of attempts being made to establish oil mills on the spot in West Africa. A native is able to gather 100 lbs. of fruit per day of nine hours in a good season ; but any estimate must, of course, depend largely on the nature of the district and the productivity of the trees.
The fruit, when ripe, drops to the ground and is collected ; the succulent pulp is then removed by washing or by allowing the fruit to rot in pits dug in the ground. The nuts are dried in the sun, or in a rough kiln or oven built of earth. The shells are then removed by crushing in a mortar and vanning. A native is able to shell 250 lbs. of nuts per day. Although nuts in the shell have been exported, it is better to shell the nuts on the spot, as the shells are valueless, and comprise about 30 per cent, by weight of the dried nuts.
Probably sun-dried kernels will be found best, as the native process of drying in ovens is rather liable to cause damage to the kernels, with consequent deterioration of the fat.
Generally speaking, the collection and preparation of nuts and of shea butter is carried out by women, the men being employed in transporting the kernels or butter to the local markets.
The question as to whether it be better for the natives to sell the kernels, or to prepare and sell shea butter, depends almost entirely on local conditions of labour and transport. In districts remote from railways or navigable rivers it appears that the preparation and sale of shea butter will give the greater profit ; but, in view of the fact that the native methods for the preparation of the butter are inefficient, it appears better on the whole that the native should be encouraged to sell the dried kernels. The transport of the butter on a large scale is also a matter of some difficulty, as it must be packed in casks before being placed on board ship.
A French firm tried the experiment of sending out to West Africa thin tinned sheet-iron which could be folded into boxes. In this case the cost of material for packing 1 ton of butter is said to have been only 13s.
The fact that the residual oil-cake from shea kernels does not fetch a high price in European markets renders it possible that it may ultimately be found more profitable to prepare the fat in West Africa. The preparation of the fat or butter from the kernels as practised by the natives is a tedious and wasteful process : one native can prepare about 8 lbs. in one day, but more than half the fat is not extracted from the kernels, and is thus altogether wasted. After the removal of the nut shells the kernels are roasted in a kind of oven built of earth, in which the kernels are placed upon grids of sticks. This roasting appears to serve two purposes- that of rendering the kernels easier to grind, and also of coagulating the latex and preventing it from being extracted with the fat, which it would contaminate. The roasted kernels are then crushed in a mortar or between two flat stones, and the crushed mass is boiled with water, the fat being skimmed off as it rises to the top and purified by treatment with water and by straining. The methods employed in different localities are the same in principle, but vary in detail. The prepared butter is generally stored in large empty gourds, in which it is allowed to solidify. When required for transport it is removed from the gourds and wrapped in leaves, forming a spherical or ovoid mass usually weighing 40 lbs. and upwards.
A Cacao Nursery in West Africa.