Postharvest Quality and Physiology of ‘Fuji’ Apples Subjected to Phytosanitary Irradiation

Irradiation is an effective treatment to sterilize and destroy insect pests on fresh fruit. It serves as an alternative to cold treatment and to fumigation which are time consuming and ozone depleting, respectively. In this study, the postharvest quality of Fuji apples was evaluated after irradiation at 400 Gy and 800 Gy. The quality of the apples which were stored at 1˚C for 7 days to mimic ground transportation and distribution and then at ambient temperature for another 7 days to mimic retail storage and consumer use, was assessed. Irradiation caused an immediate decrease in firmness by 12% at 400 Gy and by 38% at 800 Gy; this difference remained throughout storage. Electrolyte leakage was higher (P\u3c0.05) in the 800 Gy apples as compared to control and 400 Gy and malondialdehyde content was higher at the end of day 15 for 800 Gy. Irradiation initially elevated respiration rate by 27% at 800 Gy and 15% at 400 Gy. During storage at cold temperature there was no significant difference between control and 400 Gy while 800 Gy continued to be significantly higher. In contrast, ethylene decreased by 29% at 800 Gy and 18% at 400 Gy one day after treatment. During storage at room temperature, ethylene levels increased significantly in the control and 400 Gy, and remained constant and significantly lower at 800 Gy. The increase in respiration rate was not reflected in quality parameters such as internal color, browning index, total soluble solids, sugar content, organic acids, titratable acidity, polyphenol oxidase, and total phenolics, none of which were affected by irradiation. Irradiation at 400 and 800 Gy did not affect postharvest quality of the Fuji apples and could be used as an alternative to fumigation or cold treatment