## 2 Results and Discussion
### Antioxidant Components and Antioxidant Activity Assays
#### 2.2.1 Antioxidant Components
Concerning the behavior of the antioxidant components during the refrigerated storage at 4 \({}^{\circ}\)C of PEFJ, the results of hesperidin, narirutin, total flavanone, ascorbic acid, and total anthocyanin contents are reported in Table 2. Total flavanones showed an increasing trend during refrigerated storage, with significantly higher values (\(p\leq\) 0.05) after 15 days for hesperidin and after 20 days for narirutin and total flavanones. Our results are in accordance with what was stated by other authors [16], who noted an increase in hesperidin and other flavanones during refrigerated storage of orange juice treated by PEF at electric field strengths ranging from 13.82 to 21.50 kV/cm and treatment time ranging from 1033.9 to 1206.2. It has been previously demonstrated that flavanones tend to precipitate at low pH, from the soluble fraction of orange juice to its cloud, and this leads to an increase in the flavancon concentration in the cloud, especially at low temperatures [41]. Considering that the cloud fraction of PEFJ was enhanced and also preserved during refrigerated storage (Figures 1 and 2), it can be postulated that flavanone components accumulated in the cloud fraction of the PEFJ were well protected during refrigerated storage and their concentration tended to increase in response to this phenomenon. Ascorbic acid content showed a decreasing trend, even though its variation from T0 to T20 was not significant. These changes are not so drastic to determine a relevant alteration of the preserving and antioxidant action exerted in blood orange juice by ascorbic acid. Indeed, ascorbic acid acts as an oxygen scavenger and its destruction provides reactive carbonyl groups, which can be precursors to non-enzymatic browning of the juice. Therefore, the preservation of this component guaranteed by our PEF process is of high relevance for the preservation of the overall quality of the stabilized blood orange juice. Regarding total anthocyanin content, a decreasing trend was observed with significantly (\(p\leq\) 0.01) lower values recorded at T20. As previously reported [24], anthocyanin degradation in thermally stabilized orange juices is presumably due to the formation of furfurals and other carbonyl compounds, which can form condensation products with anthocyanins [42]. In this way, it may be hypothesized that our PEF process prevents furfural formation, as reported by other authors [31] in blended orange-carrot juice, both after PEF treatment and with the storage, thus preventing anthocyanin degradation. Moreover, it must be pointed out that, at T20, total anthocyanin concentration was equal to 53.25 \(\pm\) 0.04, a value that is lower than that of PEFJ at T0 but still higher than that of UJ before the PEF process, which was equal to 52.35 \(\pm\) 0.04 mg CGE/L. Therefore, it can be concluded that anthocyanin components were increased by the PEF treatment so that their levels remained preserved during the 20 days of refrigerated storage. \begin{table}
\begin{tabular}{c c c c c c} \hline  & **Hesperidin** & **Narirutin** & **Total Flavanones** & **Ascorbic Acid** & **Total** \\  & **(mg/L)** & **(mg/L)** & **(mg/L)** & **(mg/100 mL)** & **Anthocyanins** \\  & & & & & **(mg CGE \textasci{}/L)** \\ \hline PEFJ-0 days & 45.98 \(\pm\) 0.81 ab & 27.15 \(\pm\) 0.47 b & 73.12 \(\pm\) 1.29 bc & 62.92 \(\pm\) 4.82 & 55.59 \(\pm\) 0.11 A \\ PEFJ-5 days & 44.18 \(\pm\) 1.14 b & 27.17 \(\pm\) 0.48 b & 71.36 \(\pm\) 1.63 c & 58.65 \(\pm\) 2.42 & 55.19 \(\pm\) 0.07 AB \\ PEFJ-10 days & 44.63 \(\pm\) 1.23 b & 27.52 \(\pm\) 0.81 b & 72.15 \(\pm\) 2.04 bc & 61.21 \(\pm\) 1.32 & 53.92 \(\pm\) 0.02 AB \\ PEFJ-15 days & 51.35 \(\pm\) 1.74 a & 27.15 \(\pm\) 0.58 b & 78.50 \(\pm\) 2.32 ab & 53.22 \(\pm\) 2.42 & 53.65 \(\pm\) 0.54 AB \\ PEFJ-20 days & 50.60 \(\pm\) 0.62 ab & 30.31 \(\pm\) 0.48 a & 80.91 \(\pm\) 1.09 a & 53.62 \(\pm\)2.79 & 53.25 \(\pm\) 0.04 B \\ \hline \end{tabular}
\end{table}