|Small Scale Processing of Oilfruits and Oilseeds (GTZ, 1989, 100 p.)|
|1. Oil Plants and their Potential Use|
|1.2 The major oil plants|
Figure 2: Oil palm a) bunch, b) fruit of tenera (t), aura (d) and pisifera (p), Me = mesocarp, En = endocarp, Esp = endosperm.
Source: S. Rehm, G. Espig, 1984, p. 83
Botanically, oil palms are groups in the genus Elaeis, of which the major varieties are the African oilpalm (E. guineesis) and the American oilpalm (E. oleifera). Both can easily be crossed and give fertile hybrids.
Oil palms need an even temperature of between 24° C and 28° C; a reason why the cultivation is limited to the wet tropics about 10° north and south of the equator and below altitudes of 50° metres above sea level. Favourable conditions are annual rainfalls of 1500 to 3000 mm with dry seasons not exceeding three months.
Apart from tropical West-Africa, oil palms are mainly cultivated in South-East Asia and, as a later development, in Central and South America. Due to the introduction of new varieties, world production of oil palm fruit has at least doubled in the last decade as indicated by the growth in the production of kernels to 2.7 million tons in 1985 (see Table 1). Major producing countries of palm kernels are Malaysia (1.2 million tons), Nigeria (0.4 million tons) and Brazil (0.3 million tons). The world market for palm oil is dominated by Malaysia, Singapore and Indonesia, which have taken a market share of over 90 %; Africa as a whole only contributes 2 %.
Oil palms in a good growing condition carry in each leaf axil a flower from which a bunch (see Figure 2) with 1000 to 4000 egg-like, 3 to 5 cm long fruits can develop.
The majority of the oil is contained in the flesh of the fruit (mesocarp), about 12 % is in the inner nut (endosperm). According to the thickness of the nut shell (endocarp), three types are distinguished: aura with a shell thickness of 2 to 8 mm, tenera with 0.5 to 3 mm and pisifera without shell.
The selection of high-yielding types and the breeding of hybrid seeds (tenera is a cross between aura and pisifera) have increased the average yields of oil palms enormously. Wild growing bush palms in Africa used to give O.6 tons/ha of oil; current yields are more than 6 tons/ha and make the oil palm the highest-yielding oil plant. Hybrid seeds for tenera varieties, however, have to be produced in specialized seed centres. Aims of the breeders are, apart from a thin endocarp and and a thick mesocarp, to further shorten the unproductive growing period, to slow down and limit the height growth and to increase the fruit content.
The fruitpulp contains 56 % oil on average. As the ratio fruitpulp to nuts depends mainly on climate and variety, the oil content of the fruit (as a whole) varies widely in the range of:
- 14 % for aura fruit in a dry region,
- 20 to 27 % for wild or semi-wild aura fruit, and
- 36 % for tenera fruit.
Processing of the fruit is done as soon as possible after the harvest, because enzymes in the fruit react within 24 hours to form free fatty acids from the oil which substantially reduce the commercial value. The crude (red) palm oil contains a high level of 13-carotene and is an important source of vitamin A in the areas where it grows, preventing the disease xerophtalmia, that can cause blindness.
Palm oil for the world market is usually refined and used for the production of margarine or for other direct cooking purposes. Palm kernels contain 46 % to 48 % oil which is chemically quite similar to coconut oil, the use of which is described further below.