This study evaluated effects of low does X-ray irradiation treatment on physicochemical properties and antioxidant activities of Navel oranges during storage at 3℃ for 45 days and 20℃ for 12 days. The samples were irradiated at doses of 0.2, 0.4, 0.6, 0.8 and 1.0 kGy and changes of their color value, hardness, Brix/acid ratio, total sugar contents, reducing sugar contents, vitamin C contents, sensory evaluation and total phenolic contents, flavonoid contents, radical scavenging activity and reducing power were investigated.
In condition at 3℃ for 45 days, there were no significant increase or decrease between the non-irradiated and irradiated samples in color value, hardness, Brix/acid ratio, total sugar contents, reducing sugar contents, vitamin C contents. For the sensory evaluation scores of 30 day, sweetness, flavor and overall acceptability of irradiated samples more than 0.6 kGy have low preference. Also, there were no significant increase or decrease between the non-irradiated and irradiated samples in total phenolic contents, flavonoid contents, radical scavenging activity and reducing power. The result suggest that X-ray irradiation under 0.6 kGy does in condition at 3℃ not affect physicochemical properties and antioxidant activities.
In condition at 20℃ for 12 days, there were no significant increase or decrease between the non-irradiated and irradiated samples in color value, hardness, Brix/acid ratio, total sugar contents, reducing sugar contents, vitamin C contents. The sensory evaluation scores of non-irradiated and irradiated were no significant differences according to storage period. Also, there were no significant increase or decrease between the non-irradiated and irradiated samples in total phenolic contents, flavonoid contents, radical scavenging activity and reducing power. The result suggest that X-ray irradiation below 1.0 kGy does in condition at 20℃ not affect physicochemical properties and antioxidant activities.
In conclusion, the influence of storage period is greater than the influence of irradiation doses and there was no tendency on the dose. Previous studies were reported that the low dose of less than 400 Gy prevents the pest. And in this study, X-ray irradiation over 0.6 kGy does in condition at 3℃ was quite bad for sensory evaluation. Therefore, the sample irradiation under 0.6 kGy is optimum dose for minimizing quality changes and preventing the pest.