Title: Evaluation of chlorine dioxide gas treatment to inactivate Salmonella enterica on mungbean sprouts Authors
Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 27, 2014
Publication Date: N/A
Interpretive Summary: Mungbean sprouts have been identified as a vehicle for Salmonella infection, implicated in at least 37 out of 46 outbreaks of foodborne salmonellosis in the U.S and resulting in more than 2,500 cases between 1990 and 2010. Our laboratory has investigated a variety of treatments for sanitizing sprouts, concluding that aqueous sanitizers were only partially effective at reducing populations of Salmonella. Recently, our laboratory has focused on the use of chlorine dioxide gas as a simple intervention to inactivate surface associated human pathogens. The goal of the current research was to demonstrate the efficacy of chlorine dioxide gas surface pasteurization, with or without mechanical mixing, for the inactivation of Salmonella and compare to efficacy of chlorine wash treatment. Results confirmed that in excess of 99.999% reduction of pathogen populations could be obtained by the chlorine dioxide gas treatment with mechanical mixing. These results indicate that this treatment will enhance the microbiological safety of this commodity. These findings will assist food industry and regulatory agencies in establishing processing guidelines to guard against pathogens, thereby decreasing the incidence of illness outbreaks.
Technical Abstract: Although fresh-sprouted beans and grains are considered a good source of nutrients, they have been associated with foodborne outbreaks. Sprouts provide a good matrix for microbial localization and growth due to optimal conditions of temperature and humidity while sprouting. Also, the lack of a kill step post-sprouting is a major safety concern. The objective of this work was to evaluate the effectiveness of chlorine dioxide gas treatment to reduce surface Salmonella on mungbean sprouts. The effectiveness of gaseous chlorine dioxide (0.5 mg/l air) with or without tumbling (mechanical mixing) was compared to an aqueous chlorine (200 ppm) wash treatment at room temperature. Tumbling the inoculated sprouts during the chlorine dioxide gas application for 15, 30 and 60 min reduced Salmonella populations by 3.0, 4.0 and 5.5 log10 CFU/gram, respectively, as compared to 3.0, 3.0, and 4.0 log10 CFU/gm reductions obtained without tumbling, respectively. A 2.0-log10 CFU/gm reduction in Salmonella was achieved with aqueous chlorine wash. The difference in microbial reduction between chlorine dioxide gas vs. aqueous chlorine wash points to the important role of surface topography, pore structure, bacterial attachment to inaccessible sites, and/or biofilm formation on sprouts. These data suggested that chlorine dioxide gas was capable of penetrating and inactivating cells which are attached to inaccessible sites and/or are within biofilms on the sprout surface as compared to an aqueous chlorine wash. Consequently, scanning electron microscopy imaging indicated that chlorine dioxide gas indeed was capable of penetrating and inactivating cells attached to inaccessible sites on the sprout surfaces.