Effects of postharvest gamma irradiation on quality maintenance of Cara Cara navel orange (Citrus sinensis L. Osbeck) during storage

Gamma irradiation is a non-thermal treatment to effectively eliminate pathogenic microorganisms in citrus production. Here, Cara Cara fruit samples were treated with gamma irradiation (0.3, 0.6, and 0.9 kGy), then their physicochemical quality and antioxidant ability were evaluated for a period of 70 days (d). The irradiated fruit exhibited increases in respiration rate with irradiation dose in the storage period of 0-56 d. During early shelf life (0-42 d), the decay rate of irradiated fruit (0-22%) was higher than that of the control (0-6%) in a dosedependent manner; while in later shelf life, 0.3 and 0.6 kGy irradiation resulted in lower decay rates. The irradiation showed no significant effect on titratable acidity and total organic acids during storage. Irradiation at 0.6 kGy reduced free sugar content and TSS value, while increased the total phenolic content, DPPH and ABTS values of the fruit at most sampling time points. Considering the reduction of decay rate, respiratory intensity, and weight loss of the fruit under 0.6 kGy irradiation during 56-70 d of storage, 0.6 kGy may be an appropriate radiation dose to maintain the shelf-life quality of Cara Cara fruit, particularly for prolonged postharvest storage.