Effect of Low-dose Gamma Irradiation on the Quality of Tilapia Fish Muscle with Storage at 0°C

Abstract

The effect of gamma irradiation, followed by storage in ice, on Tilapia (Oreochromis sp.) fillets was investigated by monitoring microbiological and chemical changes after low-dose irradiation (1 and 3 kGy). Control and irradiated samples were stored in ice, and were analyzed at 7-day intervals. Bacterial counts showed that the shelf-life of 3 kGy irradiated Tilapia was extended to 70 days, and 1 kGy irradiated Tilapia had a shelf-life of 56 days. By comparison, control samples had a shelf-life of 7 days. Coliform bacteria was eliminated by 1 kGy irradiation, and was not detected again during the study. Peroxide and thiobarbituric acid levels increased up to the 28th day of storage, and then underwent reductions. The percentage of free fatty acid increased with the duration of storage in each treatment. Saturated fatty acids were significantly reduced with 1 kGy irradiation, whereas 3 kGy and control samples didn’t fluctuate. Levels of monounsaturated fatty acids were significantly increased in irradiated Tilapia, whereas control samples showed reductions with storage. Polyunsaturated fatty acids in Tilapia muscle treated with 1 kGy irradiation showed significant increases over time; however, with a 3 kGy irradiation dose, significant reductions were observed with storage. Palmitic acid (C 16:0), linoleic acid (C 18:2), and docosahexaenoic acid (C 22:6) showed significant reductions with storage. The present study indicates that 1 kGy is the safest irradiation dose for the preservation of Tilapia muscle stored in ice.