Microbial quality and safety of X-ray irradiated fresh catfish (Ictalurus punctatus) fillets stored under CO2 atmosphere.

The effect of low-dose X-ray irradiation (0, 2, and 3 kGy) on pathogens, spoilage bacteria (psychrotrophic, anaerobic, and lactic acid bacteria), and physicochemical parameters of iced catfish fillets stored under carbon dioxide (CO(2) ) atmosphere were studied. Irradiation of 2 or 3 kGy eliminated all Listeria monocytogenes (4.8 log CFU/g) and Salmonella Typhimurium (4.7 log CFU/g) while CO(2) atmosphere alone showed less than 1 log reduction on Salmonella Typhimurium. There was no recovery of either pathogen for the experimental period. Regardless of dose, irradiation showed 2 log reduction on psychrotrophic, anaerobic, and lactic acid bacteria for 24 d. Further post-irradiation reductions of spoilage bacteria were observed. Spoilage bacteria on catfish fillets treated with 2 kGy irradiation regained their growth after 16 d of storage. However, catfish fillets exposed to 3 kGy did not show growth of spoilage bacteria throughout the experimental period (24 d). Irradiation (2 or 3 kGy) increased pH and TBARS, and decreased Hunter "b" values but produced no effect on water holding capacity and texture. Shelf life of catfish fillets exposed to 2 or 3 kGy irradiation could be extended by more than 24 d at 2 to 4 °C, with the added safety of possibly eliminating pathogens.