Introduction

Within modern oil palm breeding objectives, increases in the unsaturated fatty acid content of palm oil has significant importance. (Arasu et al . 1987).

Unsaturation of the fatty acids is defined as the proportion and position of the double bonds in the hydrocarbon chain of the fatty acids (Hartley 1977).

Hardon (1969) demonstrated that there are significant differences between the species Elaeis oleifera and Elaeis guineensis regarding the content and type of fatty acids present in their oils. The oil of E. oleifera presents the lowest saturation degree; in the case of the interspecific hybrid E guineensis X E. oleifera (E. g. X E. o.) intermediate values are reached; and E. guineensis presents the highest degree of saturation.

Eventhough E. oleifera is not cultivated on a commercial scale due to its low oil extraction rate, Ooi, quoted by Rajanaidu et al . (1983) found a biotype of this specie in Brazil with high oil percentage in the bunch.

Wuidart & Gascon (1975), Noiret & Wuidart (1976) and Ng et al . (1976) found that the oil from palms of La Mé origin has unsaturation percentages of 55%, while Deli and Yangambi have less than 51% and 50.4% respectively. Besides the comparison in the behavior of their descendants, it was observed that the Yangambi origin reduced the quantity of unsaturated fatty acids. Furthermore, fruit with pisifera-type have greater amounts of linoleic acid (18:2) and less palmitic acid (16:0), in their oil, than the dura and tenera types (Ng et al . (1976).

For the reasons mentioned above, hybridation pretends to improve oil quality in E. guineensis . In this study, the variation found in the saturation percentage of the fatty acids in germplasms belonging to the Chiquita International Breeding Program (Palm Research Program) will be discussed.

Materials and Method

In order to determine the characteristics of the different oils that are being studied, sampling methods which permit an adequate extraction and conservation of each type of oil have been developed (Wuidart & Gascon, 1975; Rajanaidu & Tan, 1983).

The sampling for this research was performed during 1988 in 37 oil palm progenies, at the experimental station in Coto,Costa Rica. From each one of the progenies selected, at least four plants were sampled and from each plant an average of 6 subsamples were obtained throughout the sampling period. One hundred and seventy-six individual palms of Compact material were studied (Sterling et al . 1988), plus hybrid E. g. X E. o., E. oleifera and E. guineensis palms.

From each bunch, subsamples of 100 g of mesocarp were collected and sterilized at a pressure of 1.0 kg/cm² for 15 minutes and desiccated at 105°C for three hours. The oil was extracted with 150 ml of petroleum ether and then vacuum-filtrated through N1 Watman paper.

The ether was separated by distillation at 65°C. Before storing at -10°C, a small amount of sodium sulphate was added as a dehydrating agent. At the end of the sampling period, the subsamples were homogenized by fusion of the oil at 65-70°C.

The Iodine Value (IV) was determined by the Wijs method (AOCS, 1973); the 50 samples with the highest unsaturated fatty acid content were sent to the Institut de Recherches pour les huiles et Oleagineux (IRHO Montpellier, France) in order to determine their chemical composition by gas chromatography.

Result and Discusion

Table 1 shows the average results of IV obtained from the evaluated crosses. It is interesting to point out the closed relation found between the magnitude of the IV and the origin of the genetic material. The IV's above 60% correspond to E. oleifera and the values nearest 50% to E. guineensis material. Intermediate values between 50-59% were almost totally obtained from interspecific hybrids, Compacts and backcrosses of E. guineensis and Compacts.

Wuidart & Gascon 1975, Noiret & Wuidart 1976, affirm that the main source of high levels of unsaturated fatty acids (60 to 75%) in the oil palm industry, is the germplasm of E. oleifera, this findings were in agreement with the results presented in Table 2 .

The Compact material obtained by the Palm Research Program (PRP) is being developed by recombinations of E. guineensis and interspecific hybrids (Sterling et al , 1988), which shows a greater proportion of unsaturated fatty acids.

In Table 3 , a direct relation between the total of unsaturated fatty acids and the iodine value is evident, regardless of the genetic origin of the oil palm material.

It is interesting to note the behavior of the CAM 240 and CAM 236 accessions, which present a high percentage of oleic acid (18:1), superior to the value observed in Deli x Avros and Compacts. Self-pollinated Compact and Pobè materials exhibit a greater proportion of saturated fats (16:0 and 18:0) and therefore a lower Iodine Value.

In the correlation analysis between the percentage of the different fatty acids present in the oil and the Iodine Value, a significant and positive relation was found between myristic (14:0) and palmitic (16:0) acids, as well as between the unsaturated oleic (18:1) and linolenic (18:3) acids ( Table 4 ). The Iodine value also presents a high positive correlation with the oleic acid (18:1), while its behavior is inverted in relation with the palmitic acid (16:0) ( Table 4 ).

References

AMERICAN OIL CHEMIST'S SOCIETY. 1973. Official and Tentative Methods of AOCS. 3rd. edition. Edited by W.E. Link. Illinois, V1.

ARASU, N.T.; LAURENCE, M.J. and RAJANAIDU, 1987. Prospects for the alteration of fatty acid composition in the oil palm throught Breeding. In International Oil Palm/Palm Oil Conference, Kuala Lumpur, Malaysia. 20 p.

HARDON, J.J. 1969. Interspecific hybrids in the genus Elaeis. II. Vegetative growth and yield of F1 hybrids E. guineenisis X E. oleifera . Euphytica, 18:380-388.

HARTLEY, C.W., 1977. La Palma de Aceite, Trad. de la 2a. ed. por E. Maldonado. C.E.C.S.A., México. 958 p.

NG, B. H.; CORLEY, R.H.V. and CLEAG, A.J., 1976. Variation in the fatty acid composition of palm oil. Oleagineux 31 (1):1-6.

NOIRET, J.M.; WUIDART, W., 1976. Posibilities for improving the fatty acid composition of palm oil. Oleagineux 31(11) 465-472.

LINK, W.E.,1971. Official and Tentative methods of the American oil Chemists Society Editor of Analytical Methods. Third Edition.

RAJANAIDU, N. and TAN, B.K., 1983. Variability of fatty acid composition within bunches in the oil palm Elaeis guineensis . Oleagineux 38 (11) 1-6.

__________; TAN, B.K. and RAO, V., 1983. Analysis of Fatty Acid Composition (FAC) in Elaeis guineensis , Elaeis oleifera , their hybrids and its Implication in Breeding. Malaysia. Porim Bulletin No. 7.

STERLING, F.; RICHARDSON, D. L. y CHAVEZ, C. 1988. Comportamiento de las progenies del material compacto. Boletín Técnico OPO-UB 2(1): 1-14.

WIDART, W. and GASCON, J.P., 1975. Study of composition of Elaeis guineensis oil. Possibilities for improvement. Oleagineux 30 (10): 406-409.