EFFECT OF GAMMA-IRRADIATION ON THE KEEPING QUALITY AND NUTRIENTS OF TILAPIA (OREOCHROMIS-MOSSAMBICUS) AND SILVER CARP (HYPOPHTHALMICHTHYS-MOLITRIX) STORED AT 1-DEGREES-C

Fillets (skin on) obtained from freshly killed tilapia (Oreochromis mossambicus Peters) and silver carp (Hypophthalmichythys molitrix Cuvier & Valenciennes) were gamma irradiated at 1.0 kGy at 2-4-degrees-C. The chemical composition and thiamin and riboflavin contents of irradiated fish fillets were analysed and compared with those of the non-irradiated fish. Loss of thiamin content of silver carp fillets was significant whereas the thiamin content of tilapia and other constituents of tilapia and silver carp were unaffected. Irradiation at 1.0 kGy markedly reduced the bacterial level of tilapia and silver carp. No significant increase in total counts in both irradiated and non-irradiated samples was found during 5 days' storage at 1-degrees-C. The pattern of nucleotide changes in tilapia and silver carp was different. Irradiation had little effect on the concentrations of nucleotide catabolites in both species. Sensory evaluation of flesh colour and flavour was conducted after 5 days' refrigerated storage. Except that the colour of irradiated carp was more reddish, there were no significant differences in other qualities.