Pathogen reduction on mung bean reduction of Escherichia coli O157:H7, Salmonella enterica and Listeria monocytogenes on mung bean using combined thermal and chemical treatments with acetic acid and hydrogen peroxide

Abstract

Mung bean sprouts were implicated in several foodborne outbreaks worldwide in recent years. The objectives of this study were to (i) assess the efficacy of individual (mild heat) and combined treatments (mild heat followed by acetic acid or/and hydrogen peroxide) for the inactivation of enteric bacterial pathogens on mung bean intended for sprout production and (ii) determine the impact of the treatments and storage conditions on germination. Mung bean was co-inoculated with Escherichia coli O157:H7, Salmonella enterica and Listeria monocytogenes to achieve initial populations of approximately 5-6 log CFU of each species/g bean. The inoculated bean was then subjected to eight different treatments immediately after inoculation and after four weeks of storage at 22 °C. Selective media were used to estimate residual populations of each pathogen after treatment and subsequent to germination. The results showed that all combined treatments achieved a minimum 3-log CFU/g reduction in E. coli O157:H7, S. enterica and L. monocytogenes on freshly inoculated bean. The combined treatment with hot water followed by exposure to H₂O₂ and acetic acid resulted in a > 3-log reduction on mung bean stored for four weeks. The bactericidal effect of the combined treatments was significantly (P < 0.05) impacted by the duration of treatment and bean storage time. These data suggest that the combined use of mild heat, acetic acid and H₂O₂ may serve as a choice for organic sprouts industry in the disinfection of mung bean.

Keywords: E. coli; Listeria monocytogenes; Mung bean; Salmonella.