Effects of Co-60 gamma-irradiation and refrigerated storage on the quality of Shatang mandarin

The effectiveness of Co-60 gamma irradiation in controlling citrus red mite (Panonychus citri McGregor) had been proved in our earlier work. However, whether it could be used as an alternative method to replace the current way of quarantine treatment against citrus red mites depends on the performances of effective doses on citrus fruits. This study was conducted to explore the effects of Co-60 gamma irradiation on the nutrient composition of citrus (Shatang mandarin); selected fruits were divided into different groups and each group was irradiated at 0.0, 0.2, 0.3, 0.4, 0.5, and 0.6, respectively. And then the treated fruits were stored at 4 ℃ and the nutrient composition was studied in the following days. The results showed that the shelf-life could be extended when fruits were irradiated in the dose range of 0.2–0.4 kGy, while most unirradiated citrus decayed by 15 d. It also turned out that the citrus irradiated at 0.5 and 0.6 kGy were fully decayed within 45 d of refrigerated storage. The content of total soluble solids (TSS), total sugar, ascorbic acid (AA), and titratable acidity had no significant differences compare to those of the control during the 15 d storage period. Nevertheless, the activities of peroxidase (POD) and superoxide dismutase (SOD) decreased after 15 d; the improvement of storage quality and shelf life may be explained by the change of the protective enzyme activity. In conclusion, the results of citrus fruit treated with irradiation at a certain dose indicated the potential use of Co-60 gamma irradiation as a safe quarantine treatment.