## 3 Results and Discussions
### Fatty Acids Composition  
The fatty acid composition of the oils extracted from fruits of different oleaster populations are shown in Table 2. Oleic acid (C\({}_{18:1}\)) was the major fatty acid, varying from 68.9% to 70.6%, with highly homogeneous contents between the three populations studied, in opposition to the ranges reported from other geographical regions, like Tunisia, which varied from 47% to 72%, [5] and 48.4% to 71.1% [28], or Algeria, with values ranging from 64.7% to 76.1% [7]. Additionally, the oleic acid contents were within the regulated values for virgin olive oil according to Commission Regulation (EEC 2568/91). Palmitic acid (C\({}_{16:0}\)), ranging from 14.2% to 15.2%, and linoleic acid (C\({}_{18:2}\)), varying from 7.9% to 9.9%, were the second and third major fatty acids, also with similar values in the different locations. Once again the content ranges are more homogeneous that those observed by the previously mentioned authors. Nevertheless, some minor fatty acids showed significant differences between the three population: stearic acid (C\({}_{18:0}\)) was more abundant in the VNFC population than in Alijo and Moncorvo (\(p\)-value = 0.0102). In opposition, the amounts of linolenic acid (C\({}_{18:3}\)) were significantly higher in the Alijo population (\(p\)-value = 0.0098), as was eicosenic acid (C\({}_{20:1}\)). The oleaster oils from Moncorvo were significantly richer in heptadecanoic (C\({}_{17:0}\)) and heptadecenoic (C\({}_{17:1}\)) acids, while VNFC showed the highest amounts of arachidonic acid (C\({}_{20:0}\)) (Table 2).  
The sum of saturated fatty acids (SFA), monounsaturated fatty acids (MUFA) and polyunsaturated fatty acids (PUFA) had no significant differences between the different populations (Table 2). The highest fraction as expected were the MUFA, varying from 71.9% (Alijo population) to 73.0% (Moncorvo population), followed by SFA (16.9-18.2%) and PUFA (8.8-10.9%). When comparing these results with the fatty acid composition of Portuguese traditional cultivars (cvs. Cobrancosa, Madural and Verdeal Transmontana) [29], similar profiles could be found. Additionally, all the values are in agreement with the legal maximum values established by the Commission Regulation (EEC 2568/91) for olive oil. As mentioned before, in the present work the variation in fatty acid profile showed high homogeneity between samples within and between locations, in disagreement with the literature for oleaster oils [5, 7, 28]. This fact could probably be related with genetic factors, with more stable and homogeneous populations in the present study, and also imposed by more similar environmental conditions observed in the studied locations. It has been shown that the fatty acids composition varies slightly from region to region, related to the environmental condition, particularly with the lowest mean temperature observed during fruit growth [30, 31].  
Lower temperatures increase the amount of oleic acid with an increase of 1 \({}^{\circ}\)C causing up to 2% decrease on oleic amounts [32]. The geographical region under study (Northeastern Portugal) is colder than North Africa, probably contributing for the higher oleic acid and MUFA contents. Nevertheless, the climacter conditions of the three locations of our work are very similar, the observed differences between populations probably being due to genetic factors.