Effect of Istarska bjelica and Oblica cvs. fruit maturity on virgin olive oil phenolic composition and related typical sensory properties

To investigate the effect of olive fruit maturity on virgin olive oil phenolic composition and related sensory properties, Istarska bjelica (IB) and Oblica (OB) olives were harvested at three dates covering the whole customary harvest period in the Croatian regions of Istria and Dalmatia, respectively. During maturation, IB olives did not change skin color significantly (which is a cultivar characteristic), while OB olives were picked as green, semi-ripe, and ripe. Olives were processed using a laboratory scale Abencor system, and the obtained oils were subjected to HPLC-DAD analysis of phenols. Sensory analysis of oils was performed by an accredited authorized panel using the official IOC method. Hydroxytyrosol, tyrosol, and hydroxytyrosol acetate increased with ripening in IB oils. In OB oils the same was observed for hydroxytyrosol acetate, while other simple phenols exhibited irregular fluctuations. Vanillic acid decreased proportionally with the maturation of IB olives, while in OB oils the same was observed also for vanillin and p-coumaric acid. Flavonoids and lignans increased with harvest date in IB, while during OB maturation acetoxypineoresinol decreased. Secoiridoids exhibited similar variation for both cultivars: the majority of oleuropein and ligstroside aglycons decreased with maturation, except for 3, 4-DHPEA-EDA and p-HPEA-EDA which surprisingly increased in OB. However, the decrease of other aglycons was much sharper in OB than in IB oils. Sensory analysis generally revealed a positive correlation between phenols amount and bitter and pungent sensory attributes of the oils, as well as their overall quality and cultivar typicity. This work has been supported in part by Croatian Science Foundation under the project UIP-2014-09-1194.