TRANSCRIPT LEVELS OF LOX GENE AND VOLATILE COMPOUNDS CONTENT IN OLIVE (OLEA EUROPAEA L.) PERICARPS AND OLIVE OILS: A COMPARATIVE STUDY ON TWENTY-FIVE OLIVE CULTIVARS HARVESTED AT TWO RIPENING STAGES

In olive (Olea europaea L.) fruit, the LOX pathway is responsible for the production of desirable organoleptic properties that differentiate virgin olive oil from other vegetable oils. The hexanal and (E)-2-hexenal; (E)-2-hexen-1-ol, 1-hexanol and (Z)-3-hexen-1-yl acetate are five biomarkers, produced as a consequence of lipid degradation following tissue disruption. Also they are the most important volatile compounds in olive oil aroma. Considering the importance that LOX displays in influencing the organoleptic features of olive oil, a study was carried out to characterize an olive LOX at the gene expression level and chemical analysis. In this contest, the aim of the present work was to elucidate the contribute of the LOX gene considered in elaborating the olive oil aroma during fruit development, in samples collected from the CRA-OLI farm, located in a southern Italian region.
The considered plants belong to the olive genome collection of the CRA-OLI (Centro di ricerca per l’olivicoltura e l’industria olearia), located in Mirto-Crosia (Ionian coasts, Calabria, Italy). Fruits were sampled from 25 Italian olive cultivars during two developmental stages: i- reddish-brown; and ii- black with >50% purple flesh. For each sample 5 kg of olives were picked from three trees, which were homogeneous for cultivar and health, and then milled in a laboratory scale hammer mill. After 30 min of malaxation at room temperature, the oil was separated by centrifugation. Levels of LOX gene expression were determined by quantitative qRT-PCR in fruit tissues. The analyses of the volatile components were performed in olive oil after 30 min of malaxation by a SPME-GC/Ion Trap Mass Spectrometry. The data suggest that in black olives the expression of the LOX gene considered is associated with the ripening and senescence processes.