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.