Development of combined dry heat and chlorine dioxide gas treatment with mechanical mixing for inactivation of Salmonella enterica serovar Montevideo on mungbean seeds

Authors: Annous, Bassam; Burke, Angela - Mattrazzo

Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/23/2015
Publication Date: 5/1/2015
Citation: Annous, B.A., Burke, A.M. 2015. Development of combined dry heat and chlorine dioxide gas treatment with mechanical mixing for inactivation of Salmonella enterica serovar Montevideo on mungbean seeds. Journal of Food Protection. 78(5):868-872.

Interpretive Summary: Foodborne outbreaks have been associated with the consumption of fresh sprouted beans. The sprouting conditions of mungbean seeds provide optimal conditions for any potential pathogenic contaminant on the seeds to grow. The lack of kill step post-sprouting is a major safety concern. Thus, the use of a kill step on the seeds prior to sprouting step would enhance the safety of fresh sprouts. Variety of aqueous sanitizing seed treatments was only partially effective at reducing populations of Salmonella. Recently, this work has focused on dry heat and chlorine dioxide gas treatments as a simple intervention to inactivate human pathogens on seed surfaces. The objective of this work was to demonstrate the efficacy of the combined dry heat and chlorine dioxide gas treatment with mechanical mixing on inactivation of Salmonella on mungbean seeds. Combining dry heat treatment and chlorine dioxide gas treatment with mechanical mixing reduced the pathogenic populations on the seeds in excess of 99.999%. These results indicate that this treatment could be a viable process to eliminate human pathogenic cells on mungbean seeds. Thus, enhancing the microbial safety of fresh sprouts prepared from such treated seeds. These findings will assist the sprout industry in utilizing a viable process to eliminate pathogens, thereby decreasing the incidence of illness outbreaks.

Technical Abstract: Foodborne outbreaks have been associated with the consumption of fresh sprouted beans. The sprouting conditions of mungbean seeds provide optimal conditions of temperature and humidity for any potential pathogenic contaminant on the seeds to grow. The lack of a kill step post-sprouting is a major safety concern. Thus, the use of a kill step on the seeds prior to sprouting step would enhance the safety of fresh sprouts. The objective of this work was to evaluate the effectiveness of the combined dry heat and chlorine dioxide gas (3.5 mg/liter air) treatment with mechanical mixing (tumbling) to eliminate Salmonella on artificially inoculated mungbean seeds. Dry heat treatments (55, 60, or 70 deg C) for up to 8 h reduced Salmonella populations in excess of 3 log CFU/gm. The use of tumbling while treating the seeds resulted in up to 1.6 log CFU/gm reduction in Salmonella populations as compared to no tumbling. Dry heat treatment at 65 deg C for 18 h with tumbling resulted in a complete inactivation of Salmonella populations on seeds and with low inoculum levels as compared to high inoculum. The increased reductions in pathogenic populations on the seeds with the use of tumbling could be attributed to increased uniformity of heat transfer and exposure to chlorine dioxide gas. All treated seeds were capable of germinating as well as the non-treated controls. These data suggest that this combined treatment would be a viable process for enhancing the safety of fresh sprouts.