Change in quality during ripening of olive fruits and related oils extracted from three minor autochthonous Sardinian cultivars
Ripening stage is one of the key factors in determining quality of olive fruits and related oils. This research, thus, was aimed to study the influence of three different harvesting times on the quality parameters of olives and related oils of three autochthonous Sardinian cultivars, Sivigliana da olio, Semidana, and Corsicana da olio. We evaluated several parameters in olive fruits (dry matter, oil content, total soluble solids, total polyphenol and antioxidant activity) and oils (legal indices, total chlorophylls and tocopherols, single polyphenols and volatile compounds, antioxidant activity). The results obtained in olive fruits showed that all the parameters changed significantly during ripening and seem to confirm that the best harvesting time is that selected by the growers, that is when 70% of olives has just turned dark-colored and the rest is green. Results on oil evidenced that all the samples fulfilled the requirements of the European community for extra-virgin olive oils and showed a decrease in total chlorophylls and tocopherols, simple phenols and antioxidant activity during ripening, except for Sivigliana da olio oils, which evidenced an increase in simple polyphenols at the last sampling. A total of 17 volatile compounds were found on oils and those responsible for the green notes of the oils increased during ripening. PCA analysis well distinguished Sivigliana da olio olives from the other two cultivars and, in general, the genetic factor better explained variability, with respect to the ripening degree.