## 3 Results and Discussion  
### Extra Virgin Olive Oil Quality Indices and Lovibond Color Parameters  
Table 1 presents the quality indices, the oxidation induction time and the Lovibond color parameters of the flavored EVOO samples. All the analyses were performed in duplicate and the mean values, along with the standard deviation, were reported. The free fatty acids (FFAs), peroxide value (PV) and coefficients of extinction (K\({}_{232}\) and K\({}_{270}\)) are critical parameters used to evaluate the quality of flavored EVOO, mainly in terms of the chemical changes and oil stability. In all the olive oil samples, the FFAs content was much lower than the limit of 0.8% _w/w_ (expressed as oleic acid) set by EU Regulation 2568/91 for the quality of extra virgin olive oil [39]. The extinction coefficients K\({}_{232}\) and K\({}_{270}\) varied significantly between the oil samples flavored with marjoram, at different addition levels and at different storage time. The K\({}_{232}\) and K\({}_{270}\) values are indicative of the presence of conjugated dienes and trienes or unsaturated carbonyl compounds, respectively. The slight increase observed in the K\({}_{232}\) and K\({}_{270}\) values of the flavored EVOO samples compared to the unflavored EVOO could possibly be attributed to the presence of oxygen in contact with the samples during the ultrasound application, in accordance with [PERSON] et al. (2016) [40]. The peroxide value (PV) denotes the content of hydroperoxides produced at the early stages of lipid oxidation. The unflavored EVOO had a higher value for the PV (although not significantly different) compared to the respective ones for the flavored EVOO samples, suggesting that oxidation proceeds at a lower rate in flavored olive oil samples, possibly due to the presence of antioxidant compounds of marjoram [41]. In all cases, all the flavored EVOO samples presented K\({}_{232}\), K\({}_{270}\) and PV values below the maximum permitted for virgin olive oil, concerning the quality characteristics of olive oils according to the European legislation (K\({}_{232}\)\(\leq\) 2.50, K\({}_{270}\)\(\leq\) 0.22 and PV \(\leq\) 20 meq O\({}_{2}\)/kg) [39]. In line with the above findings, [PERSON] et al. (2009) [42] carried out a study of the quality indices during the storage of flavored olive oils and found that olive oils flavored with garlic maintained their indices below the maximum level permitted for extra virgin olive oils. Regarding the oxidative stability measured by [PERSON], the flavoring of EVOO with _Origanum majorana_ L. significantly increased the oxidation induction time in comparison to the unflavored oil. In a similar vein, [PERSON] et al. (2007) [43] observed that the addition of various concentrations of garlic, hot pepper, oregano and rosmary improved the long-term stability of olive oils. A number of researchers analyzed the changes in the oxidative status of flavored olive oils to confirm the efficacy of the flavorings' bioactive properties and the role they played in promoting olive oils' stability. [PERSON] et al. (2009) [11] found that aromatics such as rosmary and thymme protected the olive oil from thermal oxidation.