Location: Characterization and Interventions for Foodborne Pathogens
2025 Annual Report
Objectives
Objective 1: Determine the recovery rate, population levels, relatedness, persistence, and harborage sites of target pathogens in raw, further processed, and/or ready-to-eat foods from production through to consumption to assist in risk assessments and communication. [C1, PS1]
Sub-Objective 1.A: Determine the prevalence and levels of Lm, STEC, and Salmonella in RTE foods at retail, raw organ meats from abattoirs, and frozen bakery products containing meat and vegetables from food retailers.
Sub-Objective 1.B: Determine the relatedness of Lm, STEC, and Salmonella recovered from foods using molecular typing methods such as PFGE and WGS.
Sub-Objective 1.C: Assess perceptions, food safety attitudes, and self-reported behaviors related to observed food safety hazards by consumers who shop at grocery stores.
Objective 2: Validate lethality (heating) and stabilization (cooling) processes for ready-to-eat (RTE) and not ready-to-eat (NRTE) meat and poultry products. [C1, PS5]
Sub-objective 2.A: Validate lethality and stabilization processes to control of Salmonella, Lm, and Cperf in non-intact and specialty/ethnic pork and beef products.
Sub-objective 2.B: Validate consumer-relevant cooking times, temperatures, and appliances to control target pathogens in (multi-species) bakery products containing meat and vegetables.
Sub-objective 2.C: Validation of cooking and cooling profiles for large mass meat products to achieve stabilization performance standards that prevent growth of Cperf.
Objective 3: Develop, optimize, and validate biological, physical, and chemical interventions and processes to control target pathogens in raw, RTE, and specialty/ethnic foods. [C1, PS5]
Sub-objective 3.A: Apply interventions to control target pathogens in RTE meats and multi-component meat-based salads and salsas.
Sub-objective 3.B: Validate food-relevant interventions to control target pathogens in plant-sourced meat alternatives.
Sub-objective 3.C: Evaluation of the impact of processing parameters of dry-cured fermented meat on lethality towards STEC, Salmonella, and Lm.
Sub-objective 3.D: Develop and/or validate strategies to control pathogens in forcemeats.
Approach
The overarching theme of this research plan is to identify where pathogens enter the food supply, where, how, and why they persist in foods, and/or what can be done to reduce their levels or to eliminate them along the farm to fork continuum. Target pathogens will include Listeria monocytogenes (Lm), Salmonella, Clostridium perfringens (Cperf), and Shiga toxin-producing cells of Escherichia coli (STEC). Target foods will include raw and ready-to-eat meats, dairy, baked foods, and vegetables, as well as simulated meats and specialty/ethnic foods, targeted for human and animal consumption. A primary focus will be to identify entry points, sources, and levels of target pathogens in foods or within food processing, food service, and retail environments, and to elucidate factors contributing to their survival and persistence. Phenotypic and molecular methods, including pulsed-field gel electrophoresis (PFGE) and whole genome sequencing (WGS), will be used to identify and differentiate isolates from the farm through distribution and at retail to determine pathogen relatedness, niche, persistence, and succession. Another focus will be to validate processes and interventions such as fermentation, drying, high pressure, biopreservatives, food grade chemicals, and heat (e.g., grilling and sous vide), alone or in combination, to inhibit/remove undesirable bacteria and better manage pathogen presence, populations, and/or survival during manufacture and/or subsequent storage of target foods. We will also develop and optimize methods to deliver antimicrobials to food systems, including electrostatic spraying and various strategies to introduce interventions into/onto foods or food containers/packaging (e.g., SLIC®). Our findings will assist numerous producers and processors with meeting current regulatory guidelines and assist regulators such as the DHHS FDA and the USDA FSIS with making science-based policy decisions, thereby enhancing the safety of the Nation’s food supply.
Progress Report
In collaboration with federal, industry, and academic partners we continued to address our programmatic goals to recover, characterize, and control target pathogens in various foods. These efforts included validation of processes and interventions to reduce pathogen levels, persistence, and proliferation in raw, further processed, and ready-to- eat (RTE) foods. Target bacterial pathogens included Salmonella (Sal), Shiga toxin-producing Escherichia coli (STEC), Clostridium perfringens (Cperf), Listeria monocytogenes (Lm), and low pathogenic avian influenza virus (LPAIV). Target foods included further processed, RTE, and/or fermented beef, chicken, or pork products, as well as raw milk, raw beef, and raw poultry products inclusive of large mass meat products. In addition to physical interventions (e.g., cooking) and biological interventions (e.g., heterofermentative lactic acid bacteria), we also evaluated chemical interventions (e.g., food grade lactates, acetate, and diacetate) for pathogen control and threat mitigation. The latter delivered significant antilisterial activity in various RTE products formulated by an industry partner. For example, inclusion of salts of organic acids as ingredients for RTE cooked sausage, ham, head cheese, and/or meat-based salads lowered levels of Lm (e.g., reductions of 3.5 to 100 cells per package) or precluded outgrowth (i.e., less than an increase of 100 cells per package) during extended refrigerated storage compared to otherwise similar foods without antimicrobials (e.g., an increase of greater than 100,000 cells per package). A series of experiments was also conducted to validate USDA Food Safety and Inspection Service recommended cooking parameters, as listed in Appendix A, to inactivate target pathogens in large mass meats. These data showed that cooking parameters prescribed in Appendix A were sufficient to deliver reductions of about 10 to 100 million cells of Sal in/on turkey hams. Lastly, via our collaborations with other ARS scientists and academic partners we expanded our efforts to confirm that existing processing technologies were sufficient to eliminate the potential threat of LPAIV in raw dairy and beef products. In brief, food relevant conditions (e.g., pH 4.4, pH 5.0, or pH 5.8 maintained at 23°or 37°) reduced levels of AIV in beef slurries (10% slurry prepared from raw ground beef 85:15 percent lean:fat) by about 90-99.9% in about 7-15 hours. Also, we validated that fermentation was sufficient to inactivate LPAIV in yogurt prepared from raw milk: a reduction of ca. 99.999% was achieved by the end of fermentation. Collectively, our data are used by industry to validate their processes and by regulators to make science-based policy decisions. Our unique ability to work with real pathogens using pilot-scale equipment ensures that our data can be used directly by our various partners. These data ensure product safety and save processing times/monies, while maintaining product quality and nutritional attributes.
Accomplishments
1. Inactivation of avian influenza virus (AIV) in yogurt. The emergence of highly pathogenic avian influenza virus (HPAIV) H5N1 in U.S. dairy cattle in March 2024 raised significant concerns about the safety of raw milk and beef products. Although both infectious HPAIV and its viral RNA have been detected in raw milk, pasteurization effectively eliminates the virus; however, limited research exists on AIV inactivation in dairy products made from raw milk, such as yogurt. ARS scientists in Wyndmoor, Pennsylvania, in collaboration with ARS scientists in Athens, Georgia, inoculated raw unpasteurized milk (ca. 2.5 % fat) with high levels of AIV and a commercial yogurt starter culture. Fermentation at 42°C for about 7 hours to an endpoint pH of ca. pH 4.4 achieved reductions of about 10,000 to 100,000 AIV per ml of milk. Although limited in both scope and in numbers and volume of yogurt analyzed, our findings suggest that the current risk for humans becoming infected with AIV from yogurt prepared from (contaminated) raw milk is de minimis when raw milk is fermented to less than or equal to pH 4.4 using a starter culture.
2. Thermal inactivation of Salmonella in a large mass ready-to-eat (RTE) poultry product. USDA Food Safety and Inspection Service (FSIS) performance guidelines (Appendix A) for cooking large mass products may not achieve the recommended lethality for some products/processes, thus allowing for pathogen survival during cooking and/or outgrowth during cooling and storage. In collaboration with an industry partner, ARS scientists in Wyndmoor, Pennsylvania, validated processing conditions for a cured, restructured, smoked boneless turkey ham. Following inoculation with a multi-strain cocktail of Salmonella (about 80 to 100 million cells/product), turkey hams were cooked within a commercial smokehouse using time and temperature parameters and relative humidity (RH) cycles listed in Appendix A. Levels of Salmonella were reduced to below the detection limit following cooking. These data will be used to populate data gaps related to time, temperature, and RH parameters in Appendix A. This ground-truthed data on thermal inactivation of Salmonella in turkey hams will also enable processors to meet current regulatory guidelines for lethality of pathogens in large meat products.
3. Validation of a commercial blend of organic acids to control Listeria monocytogenes (Lm) in a ready-to-eat (RTE) ham product. Although cooking effectively eliminates pathogens in ready-to-eat (RTE) red meat and poultry products, pathogens such as Listeria monocytogenes (Lm) have caused recalls and illnesses due to post-processing, surface contamination of RTE meats. Thus, ARS scientists in Wyndmoor, Pennsylvania, in collaboration with an industry partner validated the efficacy of a blend of organic acids salts, namely sodium lactate (NaL) and potassium diacetate (KDia), to control outgrowth of Lm on a delicatessen-style RTE sliced ham product during refrigerated storage. Hams were commercially formulated with either 0, 3.1%, or 3.55% of proprietary blend of NaL/KDia, inoculated with a multi-strain cocktail of Lm to a target level of about 3,000 cells per package, and then stored at 4°C for up to 120 days. In the absence of organic acids, pathogen levels increased to about a million cells per package within 28 days and to over a billion within 90 days. In contrast, inclusion of these antimicrobial as ingredients allowed for only an increase of about 100 cells of Lm per package over 120 days (3.1%) or precluded outgrowth of Lm over 120 days (3.55%). These data will allow processors to meet regulatory requirements and will assist them in producing a safer product.
Review Publications
Porto Fett, A.C., Shane, L.E., Shoyer, B.A., Osoria, M., Beczkiewicz, A., Barlow, K., Webb, B., Merrill, B., Vinyard, B.T., Luchansky, J.B. 2024. Thermal inactivation of cells of Salmonella spp. in pot pies prepared with a beef, chicken, or meat alternative filling, with and without gravy, during cooking in a convection oven. Journal of Food Protection. 87. https://doi.org/10.1016/j.jfp.2024.100381.
Luchansky, J.B., Porto Fett, A.C., Suarez, D.L., Spackman, E. 2024. Inactivation of avian influenza virus inoculated into ground beef patties cooked on a commercial open-flame gas grill. Journal of Food Protection. 87. https://doi.org/10.1016/j.jfp.2024.100325.