Table 1 shows the determined amount of oil in the seeds and the chemical properties of the fruit oils extracted from P. lentiscus and Quercus. The crude fat content of the P. lentiscus fruit varied from 32.8% for black fruits to 11.70% red fruits (w/w). The amount extracted from the acorn was 9% (w/w) from the two species of Quercus, which is consistent with previous findings that reported an oil content of 7–10% [11, 14]. These results indicated that the black fruit of P. lentiscus can be considered as an oleaginous seed as in peanut, olive, sunflower and cotton seeds which possess (30–45% oil content) . Although the acorn cannot be considered as an oil-bearing seed, its oil content was in the range of other vegetable materials that are used for their health components or their industrial or pharmaceutical applications, as in the case of wheat germs (less than 10% fat content).
The acid value was high in the four oils and specifically in the red P. lentiscus fruit (24.0 mg KOH/g) which indicates that the oils contain a huge amount of free fatty acids. High values of the acidity in the oils are perhaps due to the bad conservation of the fruits before extraction and analysis or to the incomplete ripeness of the seeds. The relatively high iodine value in the four oils may be indicative of the presence of many unsaturated bonds and would certainly contain more unsaturated fatty acids and can thus be grouped as drying oils. Saponification values varied among in the oils and were highest in the Quercus (160.3–166.7 mg KOH/g); the lowest value was in red seeds oil of P. lentiscus (130.5 mg KOH/g). Because there is an inverse relationship between saponification value and weight of fatty acids in the oils, it can be assumed that the oils hold fatty acids with 16–18 carbon atoms with a significant amount of saturated fatty acids in the case of the P. lentiscus oil.
Except for the acid value, the chemical examinations of the oils as used in this study were in agreement with the other vegetables oils reported in the literature .
The FAME composition of the oils of the species is shown in Table 2. Seven fatty acids were identified in the seed oils. Individual percentages of each fatty acid are given in Table 2. The saturated fatty acids in the oils or triglycerides are palmitic and stearic; however palmitic acid was the major saturated fatty acid constituent, ranging from 16.3 to 19.5% in the oils and from 13.00 to 22.1% in the triglycerides of the oils. Stearic acid was detected in lower amount in the fruit oil of P. lentiscus only (0.7–1.7%).
Concerning the unsaturated acids, C18:1 and C18:2 were detected in all oils. C18:1 acid was determined to be the dominant fatty acids in the oils and TAG with 55.3–64.9% in the oils and 49.9–70.1% in the TAG. For the C18:2 acid the content was from 17.6–28.4% in the oils and 16.1–32.5% in the TAG. C18:2 acid was found only in the acorns seeds in very tiny amount that did not exceed 0.93% in the two oils. C16:1 acid was found only in two oils of P. lentiscus fruit with 1.0% in the red seed and 2.1% in the black one. However C20:1 acid was detected in the oil and TAG of Quercus suber species only. The content was ranged from 0.5–1.11% respectively.
The unsaturated fatty acids were predominant in all oils as confirmed by the iodine value test (78.6 and 109.0). However, the oleic acid was the main fatty acid in the present study. Oleic and linoleic acids are the major fatty acids reported in Spanish acorn oil (Quercus ssp) . Also, our results for P. lentiscus fruit oil agree well with the data recorded by Ucciani in his dictionary .
Our study of the fatty acid composition in the acorn showed identical values for oleic acid in the olive oil. The monounsaturated fatty acids such as oleic acid have great importance because of their nutritional implication and effect on oxidative stability of oils .
The profile of fatty acids confirms the similarity between Quercus and P. lentiscus oils and other edible vegetable oils such as sunflower, peanut, cotton, olive and avocado. The unsaturated/saturated ratio (ratio of the sum of unsaturated FA to the sum of saturated FA) was generally high, and this high value gives these oils a good prevention of oxidation.
Based on our study, the seeds of P. lentiscus and Quercus are good sources of oil. The oils have similar but not identical fatty acid composition and contain a many amount of unsaturated fatty acids. Better knowledge on the composition properties of the seeds would assist in efforts to achieve industrial application of these plants. The data on chemical composition of the fruits should be useful for educational purposes and for compiling local food composition tables.
Further studies are needed for the valorisation of unsaponifiable matters in the oils of P. lentiscus and Quercus and also to determine composition of the amino acid and phenolic compounds.