Physico-chemical Stability of Blood Orange Juice during Frozen Storage

Blood orange juice from Citrus sinensis (L) Osbek cv Moro was compared to a concentrated blood orange juice and both juices were studied during frozen storage at -20 °C. Analyses were conducted on pH (3.33 - 3.81) and titratable acidity as citric acid (11.14 - 13.16 g/L). The formol number decreased in both blood orange juice and concentrated blood orange juice during frozen storage, while vitamin C showed a very slight decrease. Scavenging abilities of the juices for the DPPH∙ radical ranged from 53.39% to 42.55% in blood orange juice and from 39.16% to 33.75% in concentrated blood orange juice during frozen storage. Although anthocyanins showed a diminution during storage in both the concentrated and non-concentrated blood orange juice, they were always higher in the non-concentrated juice fruit. Four phenolic acids were detected: gallic, chlorogenic (the highest quantity, 13-27 mg/L), caffeic and ferulic, the latter showed the lowest content. Ten flavonoids were identified, 2 flavonols (rutin and quercetin) and 8 flavanones: narirutin (the second highest flavonoid), naringin, hesperidin (the highest quantity), neoeriocitrin, didymin, eriocitrin, neohesperidin, and hesperitin. Concentration and duration of frozen storage were found to influence the physicochemical properties of blood orange juice in different ways.