## 3 Results and Discussion
### Olive Oil Quality  
In accordance with the previous studies concerning the recent thermal and non-thermal technologies applied to the olive oil mechanical extraction process and based on the alteration of cell membrane permeability and structure [22; 26; 29; 30; 39; 40], the prototype industrial PEF model used for the treatment of Nocellara del Belice cv. olive paste did not impact values of the EVOO primary legal quality parameters, as shown in Table 2.  
The concentration of primary EVOO hydrophilic phenols was not negatively affected by the PEF system applied to the olive paste (Table 3). On the contrary, a slight increase in the amount of dialdehydic forms of decarboxymethyl elenolic acid linked to hydroxytyrosol (3,4-DHPEA-EDA or oleacein) and to tyrosol (p-HPEA-EDA or oleocanthal) was detected in the EVOO extracted with PEF technology compared to the control test. However, the total phenols data contrasted with the previous studies [30; 41], that showed a general increase of the phenolic fraction of EVOOs treated with a PEF. The positive effect on EVOO quality, mainly connected to the phenolic composition, is probably due to the position of the PEF system during the mechanical extraction process, which in this study was downstream of the crusher instead of after the malaxation phase, as described by [PERSON] et al. [41]. This statement is also confirmed by the results of [PERSON] et al. [29]; applying the PEF chamber in the same position after the crushing step did not measurably enhance the phenolic fraction due to non-thermal treatment of the olive paste. This result could be related to a limited effect on the release and solubilisation phenomena of phenolic compounds into the oily phase and to a putative, minor impact on the inhibition of the degradative enzyme (peroxidase and poliphenoloxydase) activity compared to the tests in which the PEF system operated after the malaxation step.  
The volatile fraction of the PEF EVOO (Table 4) did not show significant differences in the sum of the saturated and unsaturated C5 and C6 aldehydes and of total esters (freshly cut grass and floral), whereas the concentration of total alcohols (fruity and ripe fruits) decreased 25% compared to the control trial [42]. These results, which were not confirmed by [PERSON] et al. [41] for the other three cultivars, could be due to an impact of a different olive genetic origin and/or a different effect of PEF technology on the different enzymes of the lipoxygenase pathway when applied after the crushing phase.  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline  & **Test** & **Variety** & **Free Acidity** & **Peroxide Value** & **K232** & **K270** & **\(\Delta\)K** \\ \cline{2-7}  & **Conditions** & & **(\%)** & **(meq O2/kg)** & & & \\ \hline Legal limit EVOO & & \(<\)0.8 & \(\leq\)20 & \(\leq\)2.50 & \(\leq\)0.22 & \(\leq\)0.01 \\ \hline \multirow{4}{*}{Treatment on paste} & \multirow{2}{*}{Control} & Nocellara del Belice & 0.59 \(\pm\) 0.02 \(a\) & 6.78 \(\pm\) 0.39 \(a\) & 1.51 \(\pm\) 0.20 \(a\) & 0.17 \(\pm\) 0.01 \(a\) & 0.001 \(\pm\) 0.001 \(a\) \\  & & & & & & \\ \cline{1-1}  & & & & & & \\ \hline \hline \end{tabular}
\end{table}
Table 2: Standard virgin olive oil parameters specified by the International Olive Council (IOC, 2017). EVOO: extra virgin olive oil.