## 2 Results and Discussion
### Antioxidant Components and Antioxidant Activity Assays  
#### 2.2.1 Antioxidant Components  
The concentrations of total flavanone glycosides (with hesperidin and narirutin being the most abundant) in untreated and PEF-treated blood orange juice are shown in Figure 3. As previously reported, blood oranges mainly accumulate the tasteless flavanones rutinoside, narirutin, and hesperidin, with hesperidin accounting for about 50-80% of the total flavanone content [2; 33]. Our findings are in accordance with these results, as hesperidin, narirutin, and total flavanone contents in UJ were equal to 40.72 \(\pm\) 0.90, 27.61 \(\pm\) 0.39, and 68.33 \(\pm\) 1.29 mg/L, respectively, wherein hesperidin content equaled 59.59% of the total flavanone content. The applied PEF treatment showed a significant (\(p\leq\) 0.05) improvement effect on the hesperidin content of PEF. Indeed, at T0, immediately after the process, the hesperidin content increased from 40.72 \(\pm\) 0.90 mg/L to 45.98 \(\pm\) 0.81 mg/L, producing an enhancement in total flavanone content, which passed from 68.33 \(\pm\) 1.29 mg/L to 73.12 \(\pm\) 1.29 mg/L. No significant differences in narirutin levels at T0 were recorded between UJ (27.61 \(\pm\) 0.39 mg/L) and PEFJ (27.15 \(\pm\) 0.47 mg/L). It has been previously reported that the PEF process induces an enhancement in the extraction of intracellular  
Figure 2: Cloud values (**A**) and pectinethylesterase activity (**B**) in PEFJ (PEF-treated juice) during further refrigerated storage at 4 °C. Data are expressed as means of three analytical replicates \(\pm\) standard errors; \(n=3\). components due to the electroporation occurring in the cell membranes, which causes an improvement in the mass transfer of bioactive constituents out of the cells [16; 23; 24; 34]. Other authors [16] also reported that bioactive compounds' concentration in the juice obtained after pressing PEF-treated orange, pomelo, and lemon fruits were higher with respect to the control untreated fruits. In particular, they found an increase in the release of polyphenols from the inner parts of the cells into the juice equal to 39%, 66%, and 135% for orange, pomelo, and lemon juices, respectively. As most of the previous studies have shown, greater effects on the enhancement of the bioactive compounds' levels are obtained by applying a higher electric field strength than with the application of low energy [21; 23]. Furthermore, it must be stressed that increased electric field strengths are associated with the critical increase in the juice temperature during the process, even to \(\sim\)60 \({}^{\circ}\)C [16; 17; 18], and this may cause detrimental effects on juice quality attributes induced by thermal damage. The PEF process herein proposed has been demonstrated to produce an increase in the total flavanone rutinoside content, thus ensuring an improvement in the blood orange juice quality attributes, while applying mild processing parameters, which allowed the temperature to never exceed 45 \({}^{\circ}\)C during the process, thus avoiding thermal damage to the juice matrix. Total ascorbic acid and anthocyanin contents found in untreated and PEF-treated blood orange juice are reported in Figure 4. Untreated blood orange juice had an ascorbic acid content equal to 59.19 \(\pm\) 0.75 mg/100 mL. This value is in accordance with the values reported for industrial, not from concentrate, blood orange juice [30], which was equal to \(\sim\)60 mg/100 mL, and for freshly squeezed Navelina orange juice [25], which was equal to 52.1 mg/100 mL. It is widely known that ascorbic acid acts as an antioxidant in the juice matrix and the recommended daily intake, as recommended by US FDA, should  
Figure 3: Hesperidin (**A**), narirutin (**B**), and total flavanone content (**C**) in UJ (untreated juice) and PEF) (PEF-treated juice) immediately after the process (T0). Data are expressed as means of three analytical replicates \(\pm\) standard errors.