Three-factor approach for modulating the content of phenols and taste attributes of Oblica cv. (Olea europaea L.) virgin olive oil

Phenols are responsible for virgin olive oil (VOO) taste characteristics, and significantly determine VOO oxidative stability and shelf life, as well as its nutritive value. The content of phenols in VOO depends on many agronomic and technological factors, and olive fruit ripening degree and paste malaxation duration and temperature are among the most important. The aim of this study was to investigate the main effects and interactions of these three key factors on the content of phenols and related taste sensory characteristics of Oblica cv. (Olea europaea L.) VOO. Olives were picked at three ripening degrees as green (RD1), semi-ripe (RD2) and ripe (RD3), and processed by malaxation at 22 / 30 °C, for 30 / 60 min. The obtained oils were subjected to HPLC-DAD analysis of phenols, and sensory analysis by the official IOC method. The highest variability was observed for ripening degree, where later harvest caused the particular oleuropein and ligstroside aglycons, phenolic acids, acetoxypinoresinol, and vanillin to decrease. The amounts of the two major aglycons, 3, 4- DHPEA-EDA and p-HPEA-EDA mostly increased, but only at 30 ⁰C. The effect of higher malaxation temperature was significant for phenolic acids and flavonoids which mostly decreased, and for vanillin and the majority of secoiridoids which increased. The main effect of malaxation duration was relatively weak. For the majority of phenols the effects of the factors significantly interacted. Among many specific and unique outcomes, several clear patterns were noted. For the majority of phenols, the positive effect of higher malaxation temperature was found to intensify with ripening, peaking in RD3, most strongly for 3, 4-DHPEA-EDA and p-HDEA-EDA. Ripening degree also interacted with malaxation duration. At RD1, except for vanillin and p-HPEA-EDA, a negative effect of longer duration was observed, while at RD3 longer malaxation caused a reversed effect and all phenols increased, but exclusively at 22 ⁰C. Desirable taste sensory attributes correlated positively with particular main phenols. A decrease of bitterness and pungency, and an increase in sweetness was observed along ripening. Bitterness and pungency were enhanced by the higher malaxation temperature. This work has been supported in part by Croatian Science Foundation under the project UIP-2014-09- 1194.