Master of Science / Food Science / Kelly J.K. Getty / Listeria monocytogenes has the potential to contaminate ready-to-eat (RTE) meat and poultry products. Listeria monocytogenes contamination is a hazard that can potentially occur after post-lethality treatment in a processing environment during slicing or packaging of RTE meat products. United States Department of Agriculture’s Food Safety and Inspection Service (USDA/FSIS) requires facilities to have intervention strategies to demonstrate control of this pathogen in RTE meat and poultry products. FSIS categorizes different intervention strategies into Alternative 1, 2, or 3. If an establishment chooses Alternative 1, it must use a post-lethality treatment that reduces or eliminates microorganisms on the product and an antimicrobial agent or process that suppresses or limits the growth of L. monocytogenes. If an establishment chooses Alternative 2, it can either use a post-lethality treatment or an antimicrobial agent or process that suppresses or limits growth of L. monocytogenes. Under Alternative 3, the establishment must have a detailed sanitation program as its intervention strategy. As establishments increase the number of interventions or change from Alternative 3 to 2 to 1, the frequency of FSIS sampling of RTE meat and poultry products for safety and wholesomeness decreases. The effectiveness of post-package decontamination technologies such as high-pressure processing, ultraviolet C light, and pre/post-package surface pasteurization have been researched for controlling L. monocytogenes in RTE products. Formulating meat products with antimicrobial additives such as lactates, sodium lactate and sodium diacetate, potassium lactate and sodium diacetate, sodium levulinate, lauric arginate, glucono-delta-lactone, or organic acids is another common approach to control L. monocytogenes in RTE meat products. Also, a combination of sodium lactate and sodium diacetate in a formulation is an acceptable antimicrobial strategy to provide Alternative 2 status. Bacteriocins such as nisin can also be added to the formulation of RTE meat and poultry products for controlling L. monocytogenes. In addition nisin can be applied as packaging film coating. Another approach for controlling L. monocytogenes in products such as jerky, kippered steaks, snack sticks and turkey tenders is the use of packaging environments and holding times prior to shipping. In conclusion, there are various approaches for controlling L. monocytogenes in RTE meat and poultry products post-lethality and processors should consider these options rather than relying on sanitation alone.

Understanding potential cross contamination pathways is essential to reducing the risk of food product contamination. The use of a fluorescing abiotic surrogate (GloGermTM) to visualize the potential spread of bacteria may be beneficial to researchers. To quantify cross contamination during experimental trials in a mock retail deli, a rating method for visualization of fluorescence levels using a trained sensory panel was developed. Panelists feedback led to a pre-defined strategy allowing for characterization of contamination seen in photographs and reduced variability within responses. Following validation, GloGermTM was used to visually represent how bacteria may spread through a deli environment. Six origination sites (slicer blade, meat chub, floor drain, preparation table, employee's glove, employee's hands) were evaluated separately and spread was photographed throughout the mock deli. The trained sensory panel then analyzed the photographs. Five of the six contamination origination sites transferred GloGermTM to surfaces throughout the mock deli. Contamination from the floor drain did not spread to any food contact surfaces. To determine the potential of using a GloGermTM/ bacteria mixture to simultaneously track and sample contamination spread; surfaces were co-inoculated with GloGermTM and bacteria to determine if co-inoculation would affect the recoverability of microorganisms from these surfaces. Three common foodborne bacteria (E. coli O157:H7,Salmonella enterica ser. Enteritidis, Listeria monocytogenes, Listeria innocua) were inoculated on 2 by 2 stainless steel coupons alone and with GloGermTM . There was no significant difference found (p > 0.05) between the recovery of bacteria alone and the mixture for all bacteria. Finally, the use of co-inoculation was further explored by inoculating two contamination origination sites with either bacteria alone (L. monocytogenes and L. innocua) or a GloGermTM/bacteria cocktail. Nine recipient sites were sampled after a series of deli procedures were performed. Generally, no significant differences (p>0.05) were seen between the transfer of bacteria inoculated alone and the transfer of bacteria inoculated with GloGermTM to the selected recipient sites, regardless of contamination source or bacteria. These results suggest there may be potential in using L. innocua in combination with GloGermTM to visually track and sample contamination from a known source throughout a retail deli environment. / Ph. D.