VARIATIONS IN THE RADIATION SENSITIVITY OF FOODBORNE PATHOGENS ASSOCIATED WITH COMPLEX READY-TO-EAT FOODS

Authors: Sommers, Christopher; Boyd, Glenn

Submitted to: Radiation Physics and Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/19/2005
Publication Date: 4/1/2006
Citation: Sommers, C.H., Boyd, G. 2006. Variations in the radiation sensitivity of foodborne pathogens associated with complex ready-to-eat foods. Journal of Radiation Physics and Chemistry. 75:773-778.

Interpretive Summary: Ready-to-eat food products such as sandwiches commonly sold in retail food outlets and vending machines can occasionally become contaminated with foodborne pathogens that cause illness. Ionizing radiation is a safe and effective method for inactivating pathogenic bacteria in foods. In this study the ability of irradiation to reduce levels of Salmonella, Listeria monocytogenes, Staphylococcus aureus, E.coli O157:H7, and Yersinia enterocolitica from a "hot dog on a roll", a "beef cheeseburger" and a "vegetarian cheeseburger" was investigated. A low radiation dose of 2.5 kGy was able to inactivate greater than 99.99% of the five foodborne pathogens on each of the three products. Regulatory agencies will be able to use these results to evaluate a petition currently under review to allow irradiation of ready-to-eat food products, and food processors will be able to use irradiation to provide safer ready-to-eat foods to consumers.

Technical Abstract: Foodborne illness outbreaks and product recalls are occasionally associated with ready to-eat (RTE) sandwiches and other "heat and eat" multi-component RTE products. Ionizing radiation can inactivate foodborne pathogens on meat and poultry, fruits and vegetables, seafood, and RTE meat products. However, less data is available on the ability of low dose ionizing radiation, doses under 5 kGy typically used for pasteurization purposes, to inactivate pathogenic bacteria on complex multi-component food products. In this study the efficacy of ionizing radiation to inactivate Salmonella spp., Listeria monocytogenes, Staphylococcus aureus, Escherichia coli O157:H7, and Yersinia enterocolitica on RTE foods including a "frankfurter on a roll", a "beef cheeseburger on a bun" and a "vegetarian cheeseburger on a bun" was investigated. The average D-10 values, the radiation dose needed to inactivate one log10 of pathogen, by bacterium species, were 0.61, 0.54, 0.47, 0.36 and 0.15 kGy for Salmonella spp., S. aureus, L. monocytogenes, E. coli O157:H7, and Y. enterocolitica, respectively when inoculated onto the three product types. A low radiation dose of 1.25 kGy was able to inactivate >2 log10 of Salmonella, the most radiation resistant of the pathogens tested, on the three products tested, while a radiation dose of 2.5 kGy was able to inactivate > 4 log10 of Salmonella. These results indicate that irradiation may be an effective means for inactivating common foodborne pathogens including Salmonella spp, S. aureus, L. monocytogenes, E. coli O157:H7 and Y. enterocolitica in complex RTE food products such as 'heat and eat' sandwich products.