## 3 Results and Discussion
### Physicochemical Characteristics  
One of the main criteria used for the differentiation among the various varieties of olive oil is acidity, which assesses the free fatty acid (FFA) content. Extra virgin olive oil (EVOO), the most expensive grade of olive oil, is required by Commission Implementing Regulation (EU) No 299/2013 [26] and Commission Delegated Regulation (EU) No 2022/2104 [62] to contain no more than 0.8% FFA. However, all the olive oil characteristics laid down by the Regulation for each category must be met. Three requirements must also be met for olive oil to be certified as EVOO, in addition to the FFA content; it must be manufactured using mechanical extraction techniques without the use of chemicals or hot water, come from first-cold pressing, and have the best flavor possible [63]. In addition, another quality control analysis is the measurement of conjugated dienes and trienes. According to Regulations (EU) No 299/2013 [26] and No 2022/2104 [62], EVOO must not contain more than 2.50 conjugated dienes (K\({}_{232}\)), no more than 0.22 conjugated trienes (K\({}_{270}\)) and the variation of the specific extinction (\(\Delta\)K) must not be more than 0.01. Taking into account the regulations, it was observed (Table 3) that the oil produced from the control sample is out of specification, shows advanced oxidation and is, therefore, of poor quality. The oil produced from CO\({}_{2}\)-processed olives and the commercial oil sample appears to be of good quality and within the legislation requirements for the EVOO category. Regarding the color measurement, the lightness (\(L^{*}\)) of the oil produced from the CO\({}_{2}\)-processed olives was darker than the other samples. Moreover, the oil produced from the control sample had a very light color. In addition, determining the Chroma \((C_{ab}^{*})\), i.e., color density, showed that the oil produced from CO\({}_{2}\)-processed olives was less colorful than the other samples. Determination of hue angle (\(h_{ab}^{o}\)) showed that all samples had a hue of yellow color. In conclusion, the oil produced from CO\({}_{2}\)-processed olives and commercial oil samples appeared to be slightly reddish. Moreover, the concentration of total carotenoids and total chlorophylls was evaluated for the determination of pigments. In olive oils, these bioactive substances are responsible \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Physicochemical Parameters** & **Olive Oil (Commercial)** & **Olive Oil (Control)** & **Olive Oil (CO\({}_{2}\))** \\ \hline \multicolumn{4}{c}{_Acidity_} \\ FFAs (\%) & 0.68 (0.08) \({}^{*}\) & 0.59 (0.04) & 0.51 (0.04) \\ \multicolumn{4}{c}{_Spectrophotometric investigation in the ultraviolet_} \\ K\({}_{232}\) & 2.388 (0.042) & 2.870 (0.098) & 2.320 (0.038) \\ K\({}_{270}\) & 0.171 (0.008) & 1.227 (0.065) & 0.156 (0.012) \\ \(\Delta\)K & 0.004 (0.001) & 0.133 (0.028) & 0.000 (0.000) \\ \multicolumn{4}{c}{_Colorimetry_} \\ \(L^{*}\) & 56.9 (0.1) & 75.7 (0.6) & 37.5 (0.8) \\ \(C_{ab}^{*}\) & 47.87 (2.76) & 48.49 (2.80) & 16.85 (1.06) \\ \(h_{ab}^{o}\) & 88.56 (0.08) & 99.32 (0.05) & 88.64 (0.09) \\ \multicolumn{4}{c}{_Pigments_} \\ \(C_{\text{cartenotends (mg/Kg of oil)}}\) & 2.613 (0.074) & 0.383 (0.004) & 3.125 (0.021) \\ \(C_{\text{chlorophylls (mg/Kg of oil)}}\) & 0.881 (0.023) & 0.400 (0.012) & 2.896 (0.035) \\ \(R_{\text{chl/car}}\) & 0.337 (0.001) & 1.045 (0.020) & 0.927 (0.005) \\ Total & 3.493 (0.097) & 0.782 (0.015) & 6.021 (0.056) \\ \multicolumn{4}{c}{_Total polyphenols content_} \\ TPC (mg GAE/Kg of oil) & 132.20 (8.68) & 44.52 (18.36) & 209.09 (18.86) \\ \multicolumn{4}{c}{_\(\alpha\)-Tocopherol content_} \\ \(\alpha\)-TC (mg \(\alpha\)-tocopherol/Kg of oil) & 102.04 (12.26) & 32.12 (5.17) & 180.89 (22.91) \\ \multicolumn{4}{c}{_Rancimat method_} \\ Induction time (h) & 6.35 (0.21) & 3.50 (0.14) & 13.70 (0.14) \\ \hline \hline \end{tabular} \({}^{*}\) Values are the mean of triplicate determinations. The standard deviation is given in parentheses.  
\end{table} 
Table 3: Physicochemical composition of olive oils.