Microbiological analyses of Merluccius merluccius hubbsi (Marini, 1933) fillets treated with Co-60 ionizing radiation

Fillets of a hake, Merluccius merluccius hubbsi, were exposed to 2 kGy, 6 kGy, and 10 kGy of ionizing radIation from a Cobalt 60 source and were subsequently stored frozen at 0 degree C. Both these irradiated samples and control samples were examined to determine their bacterial counts and organoleptic qualities (texture, elasticity odor, color, and drip loss) for a period of seven weeks following the irradiation. The irradiated fillets showed an initial marked decrease in the total number of bacteria--amounting to roughly one order of magnitude for those exposed to 2 kGy and roughly three orders of magnitude for those exposed to 6 kGy and 10 kGy as compared to the controls. The samples irradiated with 6 and 10 kGy had bacterial counts well below the minimum acceptable level of 0.8 x 10(6) bacteria per gram for the entire seven-week study period. Regarding organoleptic quality, the fillets exposed to 2 kGy and 6 kGy were found to retain acceptable qualities for an average of about six weeks, somewhat longer than the controls and other irradiated samples. Considering both bacterial counts and organoleptic qualities, the most effective of the three radiation doses employed was 6 kGy.