Effect of combined treatments between gamma irradiation, spices and/or thermal treatment on the viability and enterotoxicity of Staphylococcus aureus

ABSTRACT

Heat-irradiation combination sequence decreased the thermal resistance of S. Aureus. The synergistic effect increased by increasing either the pre-irradiation thermal exposure time or by increasing the radiation dose. The complete inhibition of bacterial cell was recorded by pre-irradiation thermal treatment at 65, 60 and 55C for 5, 15 and 25 minutes, respectively, at the irradiation dose 0.5 kGy. Combination treatment between irradiation and species decreased the lethal species concentration from 2% to 1% at irradiation dose 0.25 kGy for all examined species and to 0.5% concentration with the irradiation dose 0.5 kGy. The combination treatments between species, temperature and radiation had a great synergistic effect on S. Aureus cells comparable with the individual treatment or with the combination treatment between two factors. There was no variation in the amounts of enterotoxin produced by the organism after treated by the sublethal doses of the combined three factors except in case of mint, which recorded 200% increase for untreated cells