## 3 Results and Discussion
### Quality Parameters  
The evolution of quality parameters, including free fatty acids, PV, K232, and K270 measured in Arbequina variety virgin olive oil, issued from fresh and frozen olives at different ripening stages, are reported in Figure 1. All the values of the four parameters measured remained within the limits established by the International Oil Council (IOC) trade standards in the extra virgin olive oil category [8]. When comparing oils obtained from fresh olives with oils obtained from frozen olives, some differences were observed. Free acidity was slightly higher in oils from fresh olives, with significant differences being observed in the month of June. In both types of oils, a significant increase in acidity is observed with fruit ripening or harvesting time, especially in June and September. This difference would be due to the increase in the activity of lipolytic enzymes in the fruit when ripening [43]. The lower acidity value for oils from frozen olives compared with oils from fresh olives is due to the decrease in lipase activity during malaxation, which is caused by freezing of the fruit [43]. Thus, [PERSON] et al. [43] reported an increase in acidity level with the ripening of Manzanilla and Picual extra virgin olive oils. Figure 1: Physicochemical characterization of virgin olive oils extracted from fresh and frozen olives harvested between May and September. Values from (**a**) free fatty acid, (**b**) peroxide value, (**c**) K232, and (**d**) K270 are plotted. In relation to the peroxide value (PV), a different behavior was observed. Thus, VOOs between May and July showed higher a PV, reaching 2.84 meq O\({}_{2}\)/kg of oil, with no increase in the remaining months. Meanwhile, oils from fresh olives showed a sustained increase in PV with harvest time, reaching a PV of 3.44 meq O\({}_{2}\)/kg oil in September. During the ripening of olives, different metabolic pathways are in motion, prompting several changes in composition that could also affect quality parameters of olive oil [43]. The higher PVs in oils from frozen olives, for the months of May to July, would be related to the green pigmentation of the olives, which decreases as the fruit ripens. Thus, the damage produced in the olives by freezing would affect the chloroplasts of the fruit, leaving the chlorophyll compounds more exposed to light, thus promoting early photodoxidation reactions. The light-activated chlorophyll compounds would activate the fundamental oxygen to the singlet state, which would act on the unsaturated fatty acids in the oil, thus producing unstable hydroperoxides [33; 44]. The decrease in chlorophyll pigments at advanced stages of fruit ripening would explain the slight, although not significant, decrease in the PVs in oils from frozen olives. Regarding the changes in the PVs when the olives are ripening, there are contradictory results depending on the variety. Whereas for Gemlik, Halhalh, and Picual, PVs in olive varieties were found to increase during ripening, although for the Manzanilla variety, such an index did not change significantly [43; 45]. [PERSON] et al. [25] also found a slight rise in PV when the olives were affected by frost. The K232 absorbance values showed a similar trend to the PV values, with higher K232 values in oils from frozen olives up to July, reversing this behavior in September, with K232 values of 2.15 in oils from fresh olives. Absorbance at 232 nm measures the hydroperoxides of conjugated fatty acids formed in the autoxidation of lipids, and is indicative of primary oil oxidation [46]. The decomposition of the hydroperoxides originates from the secondary oxidation compounds, which are measured at 270 nm [33]. In general, K270 values were low for all the oils evaluated, indicating a raw material in a good state of preservation, despite the effects produced by the freezing of the olives. A greater decomposition of hydroperoxides was observed in oils from fresh olives, giving significantly higher K270 values for the months of July and September.