The Influence of Growing Region on Fatty Acids and Sterol Composition of Iranian Olive Oils by Unsupervised Clustering Methods

Twenty seven Iranian olive oil samples were collected from different provinces to evaluate fatty acids and sterol compositions. The samples were collected from different geographical locations that varied in altitude, temperature, humidity and rain fall. The sample collected from the northern part of Iran by the Caspian Sea had higher oleic acid [G2 sample (75.98%)] and lower linoleic acid [Go5 sample (6.5%)] and palmitic acid [G2 sample (10.78%)] concentrations than samples from the southern part of the country such as F1 whose contents of C16:0, C18:1 and C18:2 were 15.27, 62.73 and 16.09%, respectively, in the southern part, the climate is dry and the temperature variation is wider and the elevation is 1,488 m. The results indicated that oleic acid was the predominant fatty acid with 62.7% for F1 sample in the warmer climate at the south of Iran to 76.0% for G2 sample in the cooler climate in the north of Iran. According to the results, the highest content of β-sitosterol was 87% related to samples G9 and Z3 from the north of Iran and the lowest content was 69.95% related to sample F1–24 from the south of Iran. Clustering techniques such as principal component analysis and hierarchical cluster analysis were carried out on olive composition data to show similarities and discrimination between samples as a function of the cultivation zone. The two methods applied clearly showed the effect of growing regions on the distribution of the olive oil samples in the high dimensional space created by fatty acid and sterol compositions.