Listeria monocytogenes growth can be controlled on ready-to-eat meats through the incorporation of antimicrobial ingredients into the formulation or by postlethality kill steps. However, alternate approaches are needed to provide options that reduce sodium content but maintain protection against pathogen growth in meats after slicing. The objective of this study was to determine the inhibition of L. monocytogenes by propionic acid-based ingredients in high-moisture, cured turkey stored at 4 or 7°C. Six formulations of sliced, cured (120 ppm of NaNO2 ), deli-style turkey were tested, including control without antimicrobials, 3.2% lactate-diacetate blend (LD), 0.4% of a liquid propionate-benzoate-containing ingredient, or 0.3, 0.4, and 0.5% of a liquid propionate-containing ingredient. Products were inoculated with 5 log CFU L. monocytogenes per 100-g package (3 log CFU/ml rinsate), vacuum-sealed, and stored at 4 or 7°C for up to 12 weeks; and populations were enumerated by plating on modified Oxford agar. As expected, the control without antimicrobials supported rapid growth, with >2 log average per ml rinsate increase within 4 weeks of storage at 4°C, whereas growth was observed at 6 weeks for the LD treatment. For both replicate trials, all treatments that contained liquid propionate or propionate-benzoate limited L. monocytogenes growth to an increase of <1 log through 9 weeks storage at 4°C. Sporadic growth (>1-log increase) was observed in individual samples for all propionate-containing treatments at weeks 10, 11, and 12. As expected, L. monocytogenes grew more rapidly when products were stored at 7°C, but trends in relative inhibition were similar to those observed at 4°C. These results verify that propionate-based ingredients inhibit growth of L. monocytogenes on sliced, high-moisture, cured turkey and can be considered as an alternative to reduce sodium-based salts while maintaining food safety.

Chapter 1: Introduction Thesis Organization This thesis is organized into three chapters: the literature review, a manuscript and concluding remarks. The literature review cover information on bioaerosols and Listeria monocytogenes. The bioaerosols sections including: sources in food-production facilities, control measures, recovery and analysis, and challenges of bioaerosol research. The L. monocytogenes section covers: listeriosis, L. monocytogenes in ready-to-eat (RTE) foods, and bioaerosols. This review is designed to provide an explanation of the problem of L, monocytogenes bioaerosols and why more research is needed. The manuscript is for a research project design to assess the risk airborne L. monocytogenes to RTE meats. The risk to the RTE products was assessed using two qualitative methods and direct plating onto a chromogenic media selective and differential for L. monocytogenes. The research was designed to see if the risk was dose dependent, differed based on product type and if it changed after 28 days of cold storage. The final chapter is concluding remarks in regard to research and the recommendations for future work.