Investigation of Superoxide Dismutase (SOD) Enzyme Activity, β-carotene, Total Phenol and Antioxidant Capacity in Fruit Peel of Five Citrus Cultivars under Low Temperature

Regarding the sensitivity of citrus fruit to low temperatures and the conjunction of the fruit harvest season with cold days of the year necessisates more research on physiological effects of cold-stress damages. In this study, five citrus cultivars including Sanguinelli blood orange, Local lemon, Valencia orange, Unshiu mandarin and Local orange were stored under various cold treatments (3, 0, -3 and -6 °C) at two stages of before fruit ripening and ripening. Control treatment had temperature of 15 °C. Variations of activity of superoxide dismutase (SOD), β-carotene and total phenol of fruit peel at two stages of before fruit ripening and ripening, as well as antioxidant capacity at ripening stage were examined. Results showed that under low temperature and control treatment, the SOD acivity, β–carotene and total phenol in fruit peel of the studied cultivars at ripening stage are higher than before ripening stage. In all the cultivars, except Local lemon, there was an increasing trend in the antioxidant capacity until 0 °C treatment and then became stable. The increasing trend of enzymetic and non-enzymetic antioxidants in fruit peel at ripening stage as compared with before ripening stage, was probably due to cold tolerance of fruits at this stage