Synergistic effects of combined X-ray and aqueous chlorine dioxide treatments against Salmonella Typhimurium biofilm on quail egg shells

The current study investigated the synergistic effect of combined X-ray irradiation (0.5, 1.0, 1.5, and 2.0 kGy) and aqueous chlorine dioxide (ClO2) treatment (10, 20, 30, and 50 ppm) on Salmonella enterica serovar Typhimurium biofilms on the surfaces of quail egg shells. The synergistic effect was not dependent on the X-ray irradiation dose or ClO2 concentration. The synergistic reductions of biofilms after X-ray/ClO2 treatment on the egg shells were - 0.1-1.1 log CFU/egg. The largest reduction was 1.1 log CFU/cm(2) after a 2.0 kGy X-ray and a 20 ppm ClO2 treatment. No significant change (P > 0.05) was observed in the Hunter colors (L*, a*, and b*) and shear force (shell thickness) of the egg shell surfaces after single or combined treatments. Similarly, no significant changes (P > 0.05) were observed in the same parameters on the egg shell surfaces when a combination treatment of minimum X-ray doses/ClO2 concentrations and a combination treatment of maximum Xray doses/ClO2 concentrations were applied separately. The results indicated that the combination treatment of 2.0 kGy X-ray/20 ppm ClO2 could be used in the egg production, processing, and distribution processes to enhance food safety without causing changes to the egg shell surface color and shell thickness.