Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/28/2006
Publication Date: 10/1/2006
Citation: Sommers, C.H., Boyd, G. 2006. Radiation sensitivity and post-irradiation growth of foodborne pathogens on a ready-to-eat “frankfurter on a roll” in the presence of modified atmosphere and antimicrobials. Journal of Food Protection. 69(10):2436-2440. 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, modified atmosphere packaging, and antimicrobial food additives can all be used to control pathogenic bacteria on foods. However, very little information is available on the use of all three when used in combination. In this study the ability of irradiation, modified atmosphere packaging, and the antimicrobial food additives sodium diacetate and potassium lactate were used to reduce the levels of Salmonella, Listeria monocytogenes, Staphylococcus aureus, E.coli O157:H7 on a “frankfurter on a roll”. A low radiation dose of 1.5 kGy was able to inactivate 99 to 99.9% of the four foodborne pathogens on the frankfurter product. The combination of irradiation and antimicrobials was more important in controlling the pathogens, while the presence of modified atmosphere was less important. 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: Intervention technologies including ionizing radiation (IR), antimicrobials, and modified atmosphere (MA) can be used to inhibit the growth of, or inactivate, food borne pathogens on complex ready-to-eat foods such as sandwiches. However, the effect of these technologies when used in combination, the hurdle concept, on the survival of foodborne pathogens is unknown. The ability of IR to inactivate Escherichia coli O157HH7, Salmonella spp., Listeria monocytogenes, and Staphylococcus aureus inoculated onto a “frankfurter on a roll” (FOAR) containing the antimicrobials sodium diacetate (SA) and potassium lactate (PL) in the presence of MA (100% N2, 50% N2: 50% CO2, or 100% CO2) was investigated. The radiation resistances (D-10 values) of the foodborne pathogens were 0.43-0.47 kGy for E.coli O157:H7, 0.61-0.71 kGy for Salmonella spp., 0.53-0.57 for L. monocytogenes, and 0.56-0.60 for S. aureus. MA had no effect on the radiation resistance of the pathogens. During a 2 week storage period under mild temperature abuse (10 C), none of the pathogens were able to proliferate on the FOAR product, regardless of the MA used. However, application of sublethal doses of IR resulted in increased lethality of the gram-positive pathogens L. monocytogenes and S. aureus during the storage period, again regardless of MA. While the antimicrobials (SA and PL) clearly inhibited the growth of the pathogens during the storage period, application of a post-packaging intervention step was needed to actually inactivate the foodbrne pathogens. IR, when used in combination with SA and PL, resulted in additional lethality of L. monocytogenes and S. aureus, independent of MA, during the 2 week storage period.