Preparation of Palm Oil.—When the ripe head has been cut from the tree, it is left upon the ground for a few days in order that a shrinkage in the fruits may occur, which renders them more easily dislodged from their husk-lined places. The fruit also becomes slightly dull in colour. The heads bearing the fruit are often beaten to remove the latter, or they are individually broken out by hand. In order to facilitate the extraction of the fruit kernels, the fruits are usually buried in the ground in a pit lined with plantain leaves. Here they remain for from three weeks to a month, during which time decomposition is set up. The subsequent quality of the oil is dependent upon the degree to which this is allowed to proceed, rancid and thick oils resulting when it has been overdone. On the other hand, the higher the state of decomposition the greater is the facility for separating the fibrous pulp from the stones. On removing the fruits from the ground they are placed in an open vat ([Fig. 15]) and pounded by a number of people using long poles, after which they are covered up for several hours in order that the oil may drain into the small well shown at the side. Several consecutive poundings are applied, until the fibrous pulp is quite separated and most of the oil has drained out, after which the stones are combed out with the fingers, and the pulp is placed in a bag and pressed on a horizontal bar until the oil flows from it into a pit below. The oils from these extractions are boiled and cleared, and the residual pulp is often placed in the boiling pot so as to extract as much oil as possible. This is the method employed at the Krobo Plantations, but the operation varies slightly in different districts.
Kernel Oil—The value of the kernel for the extraction of oil was recognised at a much later date than the pericarp, although, in a few places in the Gold Coast, oil had probably been expressed from kernels for local consumption for some time. Among the Krobos the medicine-men prevented the trade in kernels from becoming established for several years, but they were finally overruled by the chiefs. A large and increasing trade in kernels continued for a number of years, but this has fallen off to a small extent more recently. The shell of the variety of kernel which appears to be the most common in this country is usually thick, and the laborious work of cracking each stone individually between two stones, in such a manner that the kernel is extracted in an unbroken state, prevents a larger quantity being prepared for sale, and results in much waste. Nut-cracking machines have been brought into the country, and are said to prove successful to some extent, but the native is not in a position to use machinery, and most of the material shipped is extracted in the primitive method mentioned. Cf. Bulletin of the Imperial Institute, vols. vii., viii. and xv. (1909-17). Before the cracking can be accomplished without breaking the interior, the kernel requires to be exposed to the sun and thoroughly dried. Kernel oil prepared in a native way is of two kinds, one which expressed without heat being white, whilst that made from the roasted kernels is dark brown. Both are made by pounding and grinding the kernel into fine meal, the extraction of the one being effected by cold and the other by boiling water.
In 1916 a Special Committee was appointed to consider the position of the palm-kernel trade, chiefly with reference to the protection of the newly-established British oil-crushing industry against German competition; and it was considered advisable to recommend the imposition of a differential export duty of £2 per ton on all palm kernels from British West African ports. The Colonies concerned imposed the duty at the rate mentioned and in some instances have since supplemented it by a direct revenue-producing tax.
Commercial Uses.—The chief commercial uses of the oils are for the manufacture of soap, candles, and glycerine, some qualities of palm oil being made use of in the manufacture of tin plates. With improved methods the supply of palm oil and kernels could be largely increased.
Varieties of Oil Palms.—In 1907 information was obtained from the Imperial Institute that a variety of oil palm was being propagated in the Kameruns the fruit of which contained a thin-shelled kernel and was called “Lisombe.” Further investigation in the British West African countries led to the discovery that a number of well-marked varieties of Elæis guineensis were distinguished by the natives, and were called by distinct names. Among these one possessed a thin-shelled kernel, and, together with about eight others, has been under investigation at the Imperial Institute, with the object of ascertaining their respective merits. The thin-shelled “Lisombe” and the “Gamopale” varieties from the Kameruns have recently been tried experimentally in the Gold Coast, and the advantages they possess over the other kinds have been clearly established. From the descriptions given below of the more important varieties found on the Gold Coast, it will be seen that particulars of the comparative weight of the fruit crop and the quality of the oil yielded are required to determine the relative values. In addition the proportions of fruit- and kernel-oil of each as well as the facilities for extracting the kernel must be considered.
A reference is given below to six varieties, which have been fully examined at the Imperial Institute. The native names are given, and the percentages have been calculated for comparison, from the more elaborate figures which have been published (Bulletin Imperial Institute, vol. vii. [1909], p. 366; cf. also vol. xi. [1913], p. 208).
The characteristic variations of each variety are as follows:—
1. “Abe-pa.” Fruit large, orange-red, with or without black tip, pericarp thin, nut large with thick shell. This is the commonest form in the country, and is probably identical with the variety found in Sierra Leone.
2. “Abe-dam.” Fruit of irregular shape, fairly large, bright red, pericarp slightly thicker than the last, nut large with a thick shell. This is not uncommon.
3. “Abe-tuntum.” Fruit moderately large, dark purplish-black, pericarp very thin, and nut with thick shell. Uncommon.