4. Conclusions
This work provides information about the quality, chemical composition and antioxidant activity of oils produced from ‘Coratina’ and ‘Koroneiki’ cultivars of different ages. Hierarchical cluster analysis traced an overview of the samples and variables, showing evidence of their grouping according to cultivar and tree age based on the composition of oils. Cultivar is the most important factor affecting the characterization of olive oils. VOOs from Coratina showed higher concentrations of linoleic acid, γ-tocopherols and phenolic compounds while those from Koroneiki cultivar were characterized by higher concentrations of oleic acid and squalene. Moreover, the results verified that tree age had effect on chemical composition of oils, but the influence was less than cultivar except for the structure of phenolic compounds. It is very interesting that the phenolic compound structures of oils from 2-year-old trees were unique from other oils which may be related to the enzyme activities of endogenous olive polyphenol oxidase and peroxidase. In general, quality of all samples reached the specifications for EVOO. The contents of total tocopherols and total phenols were extremely positively correlated with antioxidant capacities of DPPH, FRAP, ABTS and ORAC. Among the phenolic compounds, concentrations of Hy-EDA, Hy-EA and tyrosol were extremely correlated with all kinds of antioxidant capacities determined in the study. Data generated in this study provided references for expanding the cultivation of these cultivars in China.