Combined ohmic heating and krypton-chlorine excilamp treatment for the inactivation of Listeria monocytogenes, Salmonella Typhimurium, and Escherichia coli O157:H7 in apple juice

The combined effect of the 222-nm krypton-chlorine (KrCl) excilamp and ohmic heating for the inactivation of Listeria monocytogenes, Salmonella enterica serovar Typhimurium, and Escherichia coli O157:H7 in apple juice was investigated in this study. When ohmic heating and a KrCl excilamp were applied to apple juice simultaneously, the reduction level of E. coli O157:H7 following 70 s (target temperature of 65.9 degrees C) of combination treatment reaching 4.6 log CFU/ml was significantly higher than that of each treatment alone (2.7 log CFU/ml). The same trend, indicating a synergistic bactericidal effect, was observed for L. monocytogenes and S. Typhimurium. Therefore, the combination treatment of the KrCl excilamp and ohmic heating can be used effectively to control bacterial pathogens in apple juice with a reduced processing time. Practical applications Demands for energy-efficient and environmentally friendly bactericidal apparatuses have been increasing. Although the mercury UV lamp has been widely used to inactivate foodborne pathogens in water or juice products individually or combined with heat treatment, the use of this conventional lamp will be limited continuously in accordance with the Minamata Convention treaty, which restricts the use of mercury. Thus, it is of interest to identify the bactericidal effect of an alternative UV-C lamp and its combination with heat treatment. The synergistic bactericidal effect of the KrCl excilamp and ohmic heating, which are alternative nonthermal and thermal technologies, respectively, was identified in the present study. The results indicated in this study could be utilized by juice processors to achieve a 5-log reduction in foodborne pathogens.