## 2 Results and Discussion  
### Characterization of Fresh VOOs  
Four VOOs were selected from three different cultivars (Hojiblanca, Picual and two from Arbequina) for this study. These cultivars were selected to cover different chemical composition and for their genuine sensory characteristics [27; 28]. The quality parameters were determined for the fresh four VOOs before starting the storage (\"time zero\") with the aim of characterizing their actual quality at the moment of bottling. Free acidity, extinction coefficients (K\({}_{270}\) and K\({}_{232}\)), peroxide value (PV), fatty acid composition, total phenol content, and results from Rancimat and sensory assessment (medians of the defect and the fruity attribute) are shown in Table 1, together with date of extraction and cultivar of each VOO. According to the results obtained for PV, K\({}_{270}\) and K\({}_{232}\), all the values were below the limits stated in EC regulation [13] for the classification as \"extra virgin olive oil\" category. However, the sample VOO2 was pointed out as the most oxidized sample before starting the experiment despite all the samples were collected from the vertical centrifuge and the storage experiment started shortly after. Thus, in all these parameters, VOO2 showed the highest values, although far from the maximum limits for the \"extra virgin olive oil\" category. However, the sensory quality parameters (medians of defect and the fruity attribute showed in Table 1) revealed that VOO4 was initially categorized within the \"virgin olive oil\" category instead of \"extra virgin olive oil\" category. In this sample, panelists detected a winey-vinegary defect (median of defect = 2.1) before starting the storage. The organoleptic assessment before the storage experiment reported the sensory differences associated to the cultivars [27; 28]. Thus, assessors identified an intense fruity and green odor in the fresh sample of VOO1 (VOO1-0m), which explained the highest median value for the fruity attribute (Table 1). VOO3-0m was characterized by a high median of the fruity attribute and the panelists described it as a fruity, bitter and pungent oil with some fig and wood notes, typical from Picual cultivar [29]. Whereas, VOO2-0m and VOO4-0m, from Arbequina cultivar, showed a delicate fruitiness with slight bitter and pungent notes, showing the lowest median of the fruity attribute. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Chemical Parameters**} & \multicolumn{5}{c}{**Virgin Olive Oil Codes**} & \multirow{2}{*}{**Quality Criteria**} \\ \cline{2-2} \cline{4-6}  & **VOO1** & & **VOO2** & **VOO3** & **VOO4** & **(EVOO)** \\ \hline
**Cultivar** & **Hoigblanca** & **Arbequina** & **Pical** & **Arbequina** & **Arbequina** \\ \cline{2-6}
**Extraction Date (dd/mm/yy)** & **3/1/01/5** & **3/12/2015** & **12/11/2015** & **2/11/2015** & \\ \hline Organopileptic & Mf \({}^{\circ}\) & 4.7 & 3. In order to assess the oil susceptibility to oxidation, the content of total phenols and the fatty acids composition were determined (Table 1). Furthermore, the oil stability index (OSI) was determined by Rancimat method, which values are shown in Table 1. The results show the following stability order of the oils (from more to less stable): VOO3, VOO4, VOO1, VOO2. Thus, VOO3 showed the highest oxidative stability (82.80 h), which can be explained by its high concentration of phenols (534.82 mg/kg) and monounsaturated fatty acids (81.82%). VOO2 and VOO4, which were characterized by a medium phenol content and the highest percentage of polyunsaturated fatty acids (Table 1), showed totally different oxidative stability values between them. Thus, VOO4 showed better stability (53.60 h) than VOO2 (22.95 h), the former showing a higher phenol concentration (468.10 mg/kg) than the latter (338.90 mg/kg). Sample VOO1 showed an intermediate situation because its oxidative stability value was 38.71 h. Although this sample had a high monounsaturated fatty acid percentage, it showed the lowest total phenol content (226.71 mg/kg).