Radiation Preservation of Citrus Unshiu

Part I. Effect of gamma-1rradiation on organoleptic properties and reduction of spoilage during storage

Abstract

To elucidate the feasibility of using gamma-irradiation for the extension of shelf life of Citrus Unshiu ("Satsuma" orange), organoleptic properties, browning of peel and rotting by fungi of irradiated fruits during storage were investigated.
When the fruits were irradiated with 50 krad and tested immediately after irradiation, off-flavor was detected in flesh of fruits. However, after 7 days' storage at 4°C, there were no statistical differences in the qualities as judged by the taste panel members. Off-flavor of fruits irradiated with 200 krad also decreased during storage at low temperature.
Radiation dose of 50 krad was not sufficient to prevent development of microorganisms causing spoilage of fruits, but 150 to 200 krad were effective to control the rate of development of blue and green mold. The fruits irradiated with 200 krad exhibited the browning of peel during storage. There were no effects of dose rate in a range of 5-500 krad/hr on the peel browning and rotting during storage at 3°C for 3 months. No growth of fungi was detected in the fruits which were irradiated with 200 krad followed by storage at 3°C for 3 months. However, when the irradiated fruits were stored at room temperature for one week after storage at 3°C for 3 months, rotting by fungi and browning of peel increased, and in addition, extreme softening and shrinking of peel were observed.