Chemical and physical characteristics of the indigenous African olive

Abstract

Olive oil was extracted from whole ripe, green and semi-ripe wild African olive fruits and from its pulp and seed or kernel, and analysed. The kernel and seed oil yield (4.8%) was comparable to that from the European olive fruit. The ripe fruit oil content (7.0%) was only a little lower than that of the semi-ripe fruits (7.5%). The oil content of the seed (35.7%) was approximately equal to that of the European olive fruit seed (38.7%). The seed oils from trees of different provenance and their fatty acid profile were similar. The results suggest that the wild African olive and the European olive are genetically related because of the similarity of patterns of the ratios of respective fatty acid contents in the pulp oils to those in kernel and seed oils. Practically, all the fatty acids were within the limits given by the International Olive Oil Council olive oil trade standards. However, higher total poly-unsaturated fatty acids content and relatively lower non-essential oleic contents suggest superior nutritional value to European olive oils. Lower peroxide and p-anisidin value and higher content of tocopherol, avenosterol and of sitosterol also suggest a higher stability. These and low viscosity and high content of un-saponifiable matter make the oils suitable for cosmetics and pharmaceutical purposes. Similarity of the fatty acid profiles of the chemically-extracted African pulp oil from one lot of fruits and high contents of waxes, sterols, and tocopherol similar to those of oil of some unripe Spanish varieties suggest possibilities of identifying a variety similar to the European olive tree which can be commercialised. This is possible because pruning can shorten the fruiting period to between 2 and 3 years and increase the pulp oil yield.