Synergistic inactivation of Escherichia coli O157:H7 by plasma-activated water and mild heat

This study was designed to evaluate the synergistic antimicrobial effect of plasma-activated water (PAW) combined with mild heat (40, 50, and 60 °C) against Escherichia coli O157:H7. Populations of E. coli O157:H7 were reduced from about 8.28 log CFU/mL to undetectable levels following exposure to the combined treatment of PAW and mild heat (60 °C, 4 min), which was higher than that of individual treatment of PAW (0.77 log CFU/mL) or mild heat (1.78 log CFU/mL). The results demonstrated that PAW had good synergistic activity with mild heat against E. coli cells. Field emission scanning electron microscope (FE-SEM) confirmed that the combined treatment with PAW and mild heat caused marked morphological damage of E. coli cells. The N-phenyl-1-napthylamine (NPN) uptake assay and propidium iodide (PI) staining indicated that the combined treatment with PAW and mild heat synergistically enhanced the permeability of the outer and cytoplasmic membrane of E. coli cells, resulting in the leakage of intracellular components such as proteins and nucleic acids. It can be concluded that membrane damage is a key mechanism involved in the inactivation of E. coli cells by the combined treatment with PAW and mild heat. This synergistic antimicrobial treatment of PAW and mild heat may be used as a potential intervention strategy to reduce the incidence of E. coli and other pathogens entering the food chain.
Source: Food Control - Category: Food Science Source Type: research