Synergistic bactericidal effect of simultaneous near-infrared radiant heating and UV radiation against Cronobacter sakazakii in powdered infant formula.

The aim of this study was to investigate the synergistic bactericidal effects of the simultaneous application of near-infrared (NIR) heating and UV irradiation against Cronobacter sakazakii in powdered infant formula and to determine the effect on quality by measuring color changes and performing sensory evaluation. A cocktail of C. sakazakii strains was inoculated into powdered infant formula, followed by NIR, UV, and combined NIR-UV treatments. The sum of NIR and UV inactivation was lower than that obtained by the simultaneous application of both technologies due to their synergism. Simultaneous NIR-UV combined treatment for 7 min achieved a 2.79-log-unit CFU reduction of C. sakazakii. The underlying inactivation mechanisms of the combined NIR-UV treatment were evaluated by the propidium iodide (PI) uptake test, and we confirmed that disruption of the bacterial cell membrane was the main factor contributing to the synergistic lethal effect. The color values and sensory characteristics of simultaneously NIR-UV-treated infant formula powder were not significantly (P > 0.05) different from those of the control. The results of this study suggest that a NIR-UV decontaminating system can be applied as an alternative to other interventions in powdered weaning foods.