Inactivation efficacy of combination treatment of blue light-emitting diodes (LEDs) and riboflavin to control E. coli O157:H7 and S. Typhimurium in apple juice

Abstract

In the present study, we assessed the bactericidal effect of a combination of blue light (BL) and riboflavin (Rb) and elucidated the bacterial inactivation mechanism. Higher Rb concentrations (0.005-50 mu M) resulted in greater inactivation of Escherichia coli O157:H7 and Salmonella Typhimurium suspended in phosphate buffer saline (PBS). In the present dose-dependent study, significant inactivation was observed following BL + Rb treatment at 30 J/cm(2) (19 min 23 s) in PBS. In apple juice (pH 3.2), BL + Rb treatment resulted in a 3-4-log reduction in the pathogens at 30 J/cm(2). As expected, ROS was the key factor for pathogen inactivation. Moreover, cell membrane damage was observed on propidium iodide (PI) uptake analysis and transmission electron microscopy (TEM). These results indicated that BL + Rb treatment can be used as a powerful intervention system to ensure microbial safety in liquid beverages, in addition to enhancing the nutritional value.