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 first is the kernel of the Strephonema, a tree or shrub confined to Tropical West Africa, and particularly abundant in the Belgian Congo.
The sample consisted of very dark brown kernels, roughly hemispherical in shape, and measuring from 1 to 1 1/2 inches in diameter. Internally the kernels were hard, and of purplish-brown colour. They were found to yield 38.6 per cent, of a bright yellow, rather soft fat, equivalent to a yield of 41.8 per cent, from the dry kernels. The fat was free from unpleasant smell or taste.
The report states that the low saponification value is unusual for a fat of this character. This feature is probably due to the presence of a considerable amount of fatty acid having a low saponification value, and not to the presence of di-glycerides. The yield of glycerine is somewhat low, and would be much higher if di-glycerides were present.
The residual meal left after the extraction of the oil was of chocolate colour, and had an unpleasant astringent taste. It was analysed with the following results :-
Crude proteins, ....
Consisting of-True proteins,
Other nitrogenous substances,
Starch, tannin, etc. (by difference),
No alkaloids or cyanogenetic glucosides were present. A considerable quantity of tannin is present, as the following result3 show, and the astringent taste of the meal is no doubt due to this :-
Matter insoluble in water, ....
Extractive matter (non-tannin),
Tinometer readings for a 0.5 per cent. Red
tannin solution in a 1 cm. cell, Yellow,
The meal thus contained a fairly large amount of tannin, but the extract was of a dark purplish-red colour, and would yield a dark coloured leather, so it seems unlikely that the meal would be of commercial value either as a tanning material or for the manufacture of tanning extract.
This investigation indicates that the yield of fat from these kernels is sufficient to make them of commercial value. For oil seeds, however, to sell readily, especially in the United Kingdom, it is necessary that they should yield a good feeding cake, and the presence in the meal of a considerable amount of dark coloured tannin would prevent its use for feeding purposes without special preliminary treatment for removal of the tannin.
The N'gore Nut.-The next is the N'gore nut, almost-spherical-shaped, bluntly pointed at one end, and measuring from 3/4 to 1 inch in diameter. The kernels are brown externally, mostly of pale cream colour within, and of soft consistence. They yielded 66.2 per cent, of a reddish-yellow viscous oil, equivalent to a yield of 70.7 per cent, from the dry kernels.
The oil, which has an unpleasant odour, possesses an unusually high specific gravity. It is partially soluble in alcohol and completely so in ether, but is not soluble In light petroleum, although it absorbs this solvent to some extent. In respect of its high specific gravity, viscosity, and behaviour with solvents, it is somewhat similar to castor oil, and the acetyl value shows that, like castor oil, it contains hydroxylated acid. Although the oil has a high iodine value it does not dry on exposure to air in a thin film.
The unpleasant smell and viscous nature of the oil, together with its dark colour, would prevent its use for edible purposes. It yields a dark-coloured soap, but could no doubt be used for making certain kinds of soap. It might also prove useful as a lubricating oil, and could probably be utilised for several purposes to which castor oil is applied.
The residue after extraction of the oil consisted of a cream-coloured meal, having a faint but somewhat unpleasant garlic-like taste. The meal was submitted to chemical examination with the following results :-
Crude proteins, .......
Consisting of True proteins, ......
Other nitrogenous substances,
Starch, etc. (by difference), .....
Nutrient ratio, .......
Food units, .......
No alkaloids or cyanogenetic glucosides were present in the meal.
The report adds that the above results indicate that this N'gore meal has a high nutritive value, but owing to its peculiar character further examination and feeding trials would be necessary in order to ascertain whether it could be used safely as a feeding stuff for animals.
The N'gore kernels furnish a large yield of oil which is of unusual type, but may prove to be of considerable technical value.
The N'kamba Nut, called the Kamba Nut.-This sample consisted of pale brown nuts, measuring 1 1/4 inches in length and 1 inch in diameter. The kernels yielded 14.5 per cent, of a yellow liquid oil, equivalent to a yield of 16.3 per cent, from the dry kernels. The oil is of a non-drying character, and could no doubt be used for various industrial purposes. The yield from the kernels is, however, so small that the latter would be of little value as a commercial source of oil.
The residue after the extraction of the oil from the kernels consisted of a cream-coloured meal having a pleasant and rather sweetish taste. It was submitted to chemical examination, with the following results, which are shown in comparison with those recorded for a sample of palm-kernel meal :-
Crude proteins, .....
True proteins, ....
Other nitrogenous substances,
Starch, etc., (by difference),
Nutrient ratio, .....
Food units, .....
No alkaloids or cyanogenetic glucosides were present in the N'kamba meal.
The above results indicate that N'kamba meal should have a nutritive value about equal to that of palm-kernel meal. The meal appears, however, to contain saponin, as it causes frothing when shaken with water, and an attempt to gain further evidence on this point will be made. There appears to be no record of the use of Heisteria meal as a feeding stuff, and as it may contain saponin, which is an undesirable constituent, it cannot be recommended for this purpose.
A further sample of these kernels received in July, 1917, was found to contain 18.1 per cent, of oil, calculated on the dry kernels, as compared with 16.3 per cent, in the case of the first sample. Two specimens of nuts from the Belgian Congo, which were very similar in appearance to N'kamba nuts, have also been received at the Imperial Institute; they contained 15.6 and 13.2 per cent, of oil respectively, expressed on the dry kernels. In view of the low yield of oil and the doubtful quality of the meal it is improbable that these kernels would be of value in this country, at any rate under present conditions.