Effect of storage on quality parameters and phenolic content of Italian extra-virgin olive oils.

The quality of extra virgin olive oils is affected mainly by hydrolytic and oxidative reactions. The present paper investigated the changes of major and minor components and oxidation indices of three monovarietal extra virgin olive oils after 18 months of storage at room temperature and in dark glass bottles conditions. After storage, the basic quality parameters such as free acidity, peroxide values, extinction coefficients, fatty acids composition, chlorophyll and carotenoid content, did not exceed the upper limits set by European Community Regulations for extra-virgin olive oils. Given the importance of the phenolic fraction, UHPLC-HESI-MS metodology was used. A decrease in 3,4-DHPEA-EDA (oleacin) and p-HPEA-EDA (oleochantal) was detected whereas, an increase of tyrosol and hydroxytyrosol was measured as a consequence of degradation of ligstroside and oleuropein derivatives. Based on the results it is possible to observe the high nutritional value of the studied oils even after 18 months of conservation.