Abstract
In this study, the physicochemical quality and antioxidant activities of fruits peel from 6 citrus varieties which commonly consumed in the North of Iran were determined. Some parameters were measurement such fruit size, peel thickness, residue percentage, peel color indices, total phenolics, total flavonoid, total anthocyanins, total carotenoids, total chlorophyll, ascorbic acid content and antioxidant capacity by DPPH● assay and ABTS +● scavenging activity. Results showed that there were a positive relationship between fruit size, peel thickness and residue percentage. Thamson variety was largest among all varieties. Generally, all varieties had standard peel color at harvesting time. The total content of phenolic was superior in peel of ‘Siavaraz’ (0.49 mg/ml) and ‘Page’ (0.43 mg/g) varieties. The peel of ‘Moro’ with 7.68 mg/g and 13.29 mg/l had highest total flavonoid and anthocyanin respectively. The highest of total carotenoid and chlorophyll accumulation with 0.84 and 3.5 mg/ml were observed in ‘Tarocco’. Perfectly, peel carotenoid concentration ranged from 0.12 to 0.84 and also from 0.87 to 3.5 mg/g to total chlorophyll. The quantity of ascorbic acid content ranged from 18.17 (Siavaraz) to 23.56 mg/100g FW (Thamson). Also, results showed ‘Sanguinello’ peel had the lowest IC50 values (0.2 mg) of DPPH radical scavenging activities. Base of AE results, significant differences only observed between ‘Sanguinello’ and other varieties. According to the ABTS assay, the antioxidant activity was at least 68.58% in ‘page’ variety. Finally, this peel of citrus varieties possessed relatively high antioxidant activity and might be rich sources of natural antioxidants.

Keywords: Citrus, Peel, Color, Antioxidant activity, Carotenoid, Flavonoid, Ascorbic acid