Effect of Low Dose Gamma Irradiation on Tristimulus Color and Carotenoid Stability of Seedless Kishu Mandarins (Citrus \u3cem\u3ekinokuni mukakukishu\u3c/em\u3e) During Postharvest Storage

Abstract

The following research seeks to identify the most appropriate irradiation dose at which carotenoids can be preserved in Kishu mandarins. Irradiation serves as a potential quarantine treatment for imported commodities into the U.S. California grown mandarins kinokuni mukakukishu were treated using gamma irradiation at 0, 150 Gy, 400 Gy and 1000 Gy. The carotenoids in mandarin were evaluated for 3 test days following irradiation: after two days, after 3 weeks at 6 °C and after 3 week storage at 6 °C plus 1 extra week at 20 °C. These storage conditions simulate the sea shipment conditions of imported mandarins from China to U.S. Samples were subject to extraction, separation and saponification in order to obtain a pure carotenoid solution. Carotenoid identification was done based on order of elution, UV-VIS spectral data and retention times through HPLC-DAD analysis. The major carotenoids found were β-cryptoxanthin and β-carotene. The results show that the major carotenoids were sensitive to all irradiation doses immediately upon treatment, however exposure to room temperature for a week increased their concentrations. Irradiation caused a decrease in color a* and b* values only in the third week of storage. There did not appear to be a clear correlation between changes in carotenoid content and color values