## 2 Results and Discussion  
### Physicochemical Analysis  
The physicochemical properties of citrus juices are relevant quality attributes for the processing industries as they have a relevant influence on consumers' choices and preference [24]. The results of the physicochemical analyses performed on UJ (untreated juice) and PEFJ (PEF-treated juice) immediately after the process and during further refrigerated storage at 4 \({}^{\circ}\)C are reported in Table 1.  
At T0, immediately after the process, the PEF treatment produced no significant variation in pH and total acidity (TA), while total soluble solids (TSS) showed significantly higher values in the PEFJ samples, probably because of electroporation phenomena, which produced a release of bonded sugars from the juice pulp cells. These results are in accordance with what was previously reported by some authors [14], who recorded no significant changes in TA and pH, and significantly higher TSS values in PEF-treated orange juice with respect to a freshly squeezed orange juice, used as control. At time 0, CIE L*, a*, b*, C*, h* color parameter values showed no differences between UJ and PEFJ, except for L* values, which showed higher values in the PEFJ samples. Furthermore, consistent with our results, other authors [25] reported lower L* values in untreated orange juice with respect to PEF-treated orange juice, highlighting the great potentiality of this stabilizing technology for the preservation of the natural orange juice color. Additionally, other authors [13] reported brighter (L*) values in PEF-treated orange juice with respect to thermally pasteurized orange juice, providing evidence of how this treatment could be conveniently used to preserve the bright color of freshly squeezed citrus juices. As far as the refrigerated storage is concerned, an increasing trend was recorded for TSS and TA during the storage period, with TSS and TA values equal to 13.24 \(\pm\) 0.02 (\({}^{\circ}\)Brix) and 1.76 \(\pm\) 0.02 (\({}^{\circ}\) citric acid) after 20 days of refrigerated storage. No significant differences were noted in pH values from T0 to T20, probably linked to the buffering capacity of orange juice which can balance small TA variations such as those reported in this study. The \({}^{\circ}\)Brix degree represents the soluble solids percentage, and it is commonly and widely used to grade the overall quality of fruit juices [26]. At the same time, TA represents the free organic acids percentage in the fruit juice and provides a relevant indication of the juice stability. Our results showed that during the refrigerated storage, an increase in TSS and TA occurred. An increase in TSS during cold storage of orange fruit has been previously reported [27]. The authors explained this behavior as a consequence of hydrolytic scission phenomena of various glycosylated components of juice, which can occur in response to the need of free monosaccharides as a substrate for the onset of several metabolic processes during cold storage [28]. Furthermore, an increase in TA of orange juice during refrigerated storage has been previously reported by other authors [25], who opened that this behavior is probably linked to the spoilage of the juice caused by the gradual increase in the microbial load. Indeed, microorganisms, which are responsible for fruit juice spoilage, can induce an increase in acidity due to fermentation phenomena [18]. The CIE L*, a*, b*, C*, h* values remained constant throughout the whole storage, showing a relevant stability of the PEF-stabilized blood orange juice. Indeed, in accordance with our results, other authors have previously reported a lower browning index in PEF-treated orange juice with respect to thermally pasteurized ones, showing that the color of the PEF-treated orange juice remained stable during the storage at both 4 \({}^{\circ}\)C and 22 \({}^{\circ}\)C [13; 18]. The color of fruit juice is an important quality attribute, and negative changes in its coordinates may undesirably