Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 24, 2008
Publication Date: January 3, 2009
Citation: Jin, Z.T., Liu, L.S., Sommers, C.H., Boyd, G., Zhang, H.Q. 2009. Radiation resistance and post-irradiation proliferation of Listeria monocytogenes on ready-to-eat deli meat in the presence of pectin/nisin films. Journal of Food Protection. 72(3):644-649. Interpretive Summary: Post-processing contamination of ready-to-eat (RTE) delicatessen products by foodborne pathogens is currently of considerable concern. Listeria monocytogenes has been particularly problematic to the processed meat industry. Four major listeriosis outbreaks involving 130 cases of illness have been linked to RTE delicatessen meats since 1998. More than 45 Listeria-related recalls involving over 45 million pounds of RTE delicatessen meats have been issued since 2000. The application of antimicrobial packaging in combination with low dose irradiation is a potential food safety strategy for reducing the costs and risks of bacterial contamination of RTE meats. In this study, the ability of pectin/nisin films in combination with ionizing radiation to eliminate Listeria monocytogenes and inhibit its post-irradiation proliferation was evaluated. Irradiation at 1 or 2 KiloGray (kGy), pectin/nisin film and their combination can significantly reduce Listeria cells on RTE meat. The pectin/nisin film used in this study could replace 1 kGy treatment, or could be combined with irradiation to achieve additional reduction in Listeria. The combined treatment of 2 kGy + pectin/nisin film resulted in the greatest reduction of Listeria cells and significantly reduced the growth of this pathogen at 10C during the 8-week storage period. Data from this study suggest the potential use of ionizing radiation in combination with pectin/nisin antimicrobial packaging in preventing listeriosis in RTE meats.
Technical Abstract: In this study, the ability of pectin/nisin films in combination with ionizing radiation to eliminate Listeria monocytogenes and inhibit its post-irradiation proliferation was evaluated. Pectin films containing 0.025% nisin were made by extrusion. The surface of a read-to-eat (RTE) turkey meat sample was inoculated with L. monocytogenes and covered with a piece of pectin/nisin film. The samples were vacuum-packaged and treated at 0, 1 and 2 kGy. The treated samples were stored at 10C and withdrawn at 0, 1, 2, 4, and 8 weeks for microbial analysis. The cell reductions of 1.42, 1.56, 2.85, 3.78 and 5.36 log CFU per square cm were achieved for the treatments of 1 kGy, pectin/nisin film, 2 kGy, 1 kGy + pectin/nisin film and 2 kGy + pectin/nisin film, respectively. The greatest microbial reduction was observed after 1 week storage in samples treated with 2 kGy + pectin/nisin film, suggesting that nisin was further released from the film to the surface of meat samples. Pectin/nisin films used in this study did not prevent but did significantly reduce the proliferation of L. monocytogenes surviving irradiation. These data indicate the potential use of nisin/pectin films alone or in combination with ionizing radiation in preventing listeriosis in RTE meat products.