Composition of health-promoting phenolic compounds in two extra-virgin olive oils and diversity of associated yeasts

Extra virgin olive oil (EVOO), a basic component of the Mediterranean diet, is an important functional food, for its content in health-promoting compounds, showing antioxidant, antiinflammatory and antiproliferative activities. Here, two Tuscan EVOOs were analyzed for the occurrence and concentrations of health-promoting phenols, such as tyrosol and hydroxytyrosol and the secoiridoid derivatives, oleocanthal and oleacein. Independently of the milling period, the two EVOOs showed different contents of oleocanthal and oleacein. During storage, the contents of oleocanthal and oleacein decreased, while those of simple phenols increased. In all oil samples oleacein displayed a higher rate of reduction than oleocanthal. Multivariate analyses of the polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) profiles, revealed the occurrence and diversity of oil-borne yeast communities, which differed in the two EVOOs. Sequences of excised DGGE bands identified Candida adriatica, Eremothecium coryli and Lachancea fermentati as the main components of the oil-borne yeast community. Our work detected, for the first time, differences in the content of tyrosol, hydroxytyrosol, oleocanthal and oleacein between the two Tuscan EVOOs analyzed, consistent with the differences found in yeast community composition. Further studies could confirm whether oil-borne yeasts may affect the composition of health-promoting oil phenolic compounds.