Effect of thermal treatments on antioxidant and antiradical activity of blood orange juice

Blood orange juice is noted for its antioxidant properties, due to its rich phenolic profile. Orange segments were subjected to brief thermal treatments before transformation into juice, and changes in antioxidant and chemical composition were evaluated. Thermal treatment generally induced an increase in the main phenolic substances of orange juice, such as anthocyanins and total cinnamates, while ascorbic acid underwent a decrease. Antioxidant properties, evaluated in a lipoxygenase–linoleic acid system, were higher in thermally-treated samples, while free radical scavenging activity, evaluated by ESR spin trapping of hydroxyl radical and DPPH· quenching, were enhanced in untreated juices. A possible relationship between the changes in composition and the changes in antioxidant and antiradical properties is suggested.