Effect of Ripening on the Phenolic and Sugar Contents in the Meso- and Epicarp of Olive Fruits (Olea europaea L.) Cultivar ‘Leccino’

Abstract

The study was conducted during the harvest season in the year 2020 to identify and quantify primary and secondary metabolites in olive fruit of the ‘Leccino’ cultivar during ripening. Sugars, individual phenolic compounds, total phenolic content and total tannin content were measured separately for the first time in the skin and pulp. Most of the studied metabolites were higher in the skin. Five sugars were identified, the most important being glucose in both tissues, although its content decreased during ripening. The highest total phenolic content was observed in the skin at the last stage of ripening, because of the accumulation of anthocyanins. Individual phenolic compounds were measured by high performance liquid chromatography with-diode array detector (HPLC-DAD) and confirmed by mass spectrometry. Thirty phenolic compounds were characterized and quantified. The main individual phenolic compound in the skin and pulp was oleuropein, which decreased during ripening. Two previously unreported anthocyanins, cyanidin-3-O-diglucoside and cyanidin-3,5-O-sophoroside, were identified for the first time in olive skin. These results will allow us to better understand the synthesis, distribution and storage of some primary and secondary metabolites in different tissues of olive fruits during ripening.