Gamma irradiation improves the microbiological safety and shelf-life of kimchi seasoning mixture

Kimchi seasoning is manufactured non-thermally without any additional decontamination step, resulting in possible microbiological growth and food safety issues. This study examines the effects of gamma irradiation on the microbiological and physicochemical characteristics of kimchi seasoning mixture during storage. Foodborne pathogens, i.e., Escherichia coli O157:H7 and Salmonella Typhimurium were inoculated into the seasoning mixture and irradiated at doses ranging from 0 to 10 kGy. Regardless of the microbial species, the number of microorganisms was adversely correlated with increasing gamma irradiation. The levels of E. coli O157:H7 and S. Typhimurium were reduced to below the detection limit (1 log CFU/g) after exposure to 5 kGy of gamma irradiation. The number of total aerobic and lactic acid bacteria decreased by 3.29 and 4.78 log CFU/g, respectively, after 10 kGy of gamma irradiation exposure. Changes in pH, acidity, reducing sugar content, and headspace gas concentrations were significantly delayed in irradiated kimchi seasoning mixtures (P < 0.05), whereas no significant difference was observed in color values between the irradiated and non-irradiated kimchi seasoning mixtures (P > 0.05). These results imply that gamma irradiation can enhance the microbiological safety and shelf-life of kimchi seasoning mixture, and decrease the initial concentration of microorganisms without adverse effects on quality.