1a. Objectives (from AD-416):
1: Determine the prevalence, levels, types, and locations of pathogens at various points from production through to consumption of raw, further processed, and/or RTE foods. 1.1. Determine the prevalence and levels of L. monoctyogenes, STEC, and Salmonella spp. in RTE foods at retail, as well as at abattoirs/processing plants. 1.2. Determine the relatedness of L. monoctyogenes, STEC, and Salmonella spp. recovered from foods using molecular typing methods such as PFGE and MLGT. 1.3. Assess perceptions, food safety attitudes, and self-reported behaviors related to observed food safety hazards by consumers who shop at grocery stores. 2: Develop, optimize, and validate processing technologies for eliminating pathogens. 2.1 - Determine the transfer and survival of STEC and Salmonella spp. in ground and tenderized (i.e., non-intact) red meat, pork, pet, and poultry products. 2.2 - Determine cook dwell times for ground poultry products using common consumer preparation methods such as cooking on gas or electric grills at internal instantaneous temperatures ranging from 100° to 160°F for lethality towards Salmonella and STEC and for consumer acceptability. 2.3 - Determine the effectiveness of food grade antimicrobials applied via electrostatic spray and Sprayed Lethality in Container (SLIC®) methods on pork offal and on chicken necks and frames for control of Salmonella and STEC. 2.4 - Validate fermentation and cooking of dry-fermented sausages for control of STEC, Salmonella, and other pathogens. 3: Develop and/or validate strategies to deliver antimicrobials to raw and packaged foods from production through to consumption to control L. monocytogenes, STEC, Salmonella spp., and other pathogens.
1b. Approach (from AD-416):
We will exploit the tools of microbiology, molecular biology, and food science to recover, characterize, and control food borne pathogens from production through to consumption for a variety of foods, with emphasis on specialty/ethnic and higher volume, higher risk foods. We will identify where pathogens enter the food supply, determine how they persist, and investigate biological, chemical, and physical interventions to eliminate or better manage them to improve public health. The target pathogens of greatest concern for this project are Listeria monocytogenes, Salmonella spp., Shiga toxin-producing Escherichia coli, Trichinella spiralis, and Toxoplasma gondii. Targeted foods would include, but not be limited to, raw and ready-to-eat (RTE) meat, poultry, pet, and dairy foods, as well as raw and further processed non-intact meats. One focus of the proposed research is to identify sources and niches of the above mentioned pathogens in foods and food processing environments, as well as at retail and food service establishments, to gain insight on factors contributing to their survival and persistence. Multiple isolates recovered from each sample testing positive from such surveys will be retained for further characterization by phenotypic and genotypic (e.g., pulsed-field gel electrophoresis, PCR-based methods, and/or whole genome sequencing) methods to establish relatedness of isolates and their source and succession. As another focus of our research, efforts will be made to validate processes and interventions such as fermentation, high pressure processing, food grade chemicals, and heat, alone or in combination, to inhibit/remove undesirable bacteria from the food supply and to better manage their presence, populations, and/or survival during manufacture and storage of target foods/feed. The proposed research to find, characterize, and kill pathogens along the food chain continuum will expand our knowledge of the most prevalence/potent food borne pathogens and help us to elaborate better methods for controlling them in foods prior to human contact or consumption, thereby enhancing the safety of our global food supply.
3. Progress Report:
Progress was made possible by our many and valued collaborations with CRADA partners and food safety professionals from academia, government, industry, and consumer groups. The primary focus of our research has and continues to be the development and validation of biological, chemical, and physical interventions to control Listeria monocytogenes (Lm), Shiga toxin-producing Escherichia coli (STEC), and Salmonella spp. (Sal) in a variety of foods. These efforts included validating high pressure processing and cooking to reduce the levels of Sal in/on poultry livers and pate. These efforts also included the use of buffered vinegar, a “clean label” food grade chemical, to reduce levels and/or prevent outgrowth of Lm during extended refrigerated storage of ready-to-eat (RTE), fully-cooked, uncured pork breakfast patties. In the absence of antimicrobials, pathogen numbers increased by ca. 630,000 cells per gram after 90 days at 4 deg C. When 1.5% or 2.0% BV were added to the formulation, pathogen numbers decreased by only ca. 4 cells per gram after 90 days at 4 deg C, whereas Lm numbers remained relatively unchanged during of 180 days at -20 deg C. In the event of post-process contamination, inclusion of 1.5% of BV would be effective as a clean label ingredient for inhibiting outgrowth of Lm on fully-cooked, uncured pork patties during extended refrigerated storage. We also expanded our efforts to deliver antimicrobials into/onto foods via the Spray Lethality in Container (SLIC) and air assisted electrostatic spray (ESS) technologies. These delivery strategies save time and money, as well as increase efficiency. At the suggestion of USDA-FSIS, we conducted surveys of raw and RTE foods, including ground pork, beef and poultry, frozen vegetables, marinades, and salads, purchased at retail grocery stores to assess the “true” prevalence of Sal, STEC, and Lm, as well as to gain insight on their levels and types present in samples testing positive. Studies are ongoing to conduct proximate analyses of representative food samples. Considerable efforts and resources were also directed to establish time and temperature parameters to maximize thermal inactivation of STEC and Sal in raw and further processed red meat and poultry products such as dry-fermented sausage, ground poultry, and livers/pate. Parameters tested included cooking appliance, volume and type of cooking oil, product formulation, and various cooking times and temperatures. As expected, the higher the temperature and the longer the time for application of heat, the greater the reduction in pathogen levels. Of note, since we engage both regulators and the industry as part of the planning, conduct, and data analyses, and since we utilize pathogenic strains and pilot-scale processing equipment, our data are of immediate use to academicians, policy makers, and the food industry for enhancing the wholesomeness of our food supply and improving public health in general.
1. Interventions to improve food safety at retail stores. Food safety hazards at retail food stores as identified by experts are often quite different from what consumers perceive as a hazard/risk. Past research to change consumer perspectives about such risks relied primarily on surveys, interviews, and focus groups to assess attitude, aptitude, and self-reported behavior data; however, past efforts did not measure consumer perceptions and action in real time at retail food stores. In collaboration with scientists at North Carolina State University, ARS researchers at Wyndmoor, Pennsylvania, developed and field tested a series of videos to help consumers identify potential food safety risks while shopping. Among the 66 citizen scientists who collected data while shopping, both before and after viewing the training videos, more hazards were identified in agreement with the assessment of a food safety professional/expert after seeing the video (n = 9, 82%) compared to the baseline (n=2, 18%). Also, participants who viewed the videos agreed with the expert assessment 17% of the time compared to 12% (n=4) for the control group. These findings confirm that videos about food safety hazard identification at retail food stores may improve the ability of consumers to identify potential food safety hazards while grocery shopping.
2. Recovery of pathogenic Escherichia coli from retail ground meats. Shiga toxin-producing Escherichia coli (STEC) pose a serious threat to public health. Cells of STEC are somewhat frequently found on raw meat and have been the cause of numerous recalls and several illnesses over the last 35 years due to undercooked and/or improperly prepared or mishandled beef and veal products. Based on a very limited sampling set, the USDA-FSIS reported a higher risk associated with raw ground beef components (RGBC) derived from veal compared to beef. Thus, ARS researchers in Wyndmoor, Pennsylvania, collected 555 samples of raw ground veal and 540 of beef at retail stores over a 2-year period from across the mid-Atlantic region of the U.S. to establish the comparative “true” prevalence of the 7 regulated serotypes of STEC in veal and beef. Similar to data reported by USDA-FSIS based on a limited number of samples, the recovery rate for non-O157 STEC in retail ground veal was appreciably higher than in ground beef and, thus, systematic interventions should be implemented across the food chain continuum to reduce the risk of STEC cells associated with veal products.
3. Interventions for poultry liver and pate. Chicken livers may harbor pathogens such as Salmonella both on the outside surface and within the organ itself. Poultry liver is frequently used in the preparation of pate, but based on consumer preferences for taste and texture, it may be undercooked. ARS researchers in Wyndmoor, Pennsylvania, evaluated high pressure processing (HPP) and cooking as interventions for Salmonella on/in liver or pate. Raw chicken liver or pate (i.e., livers, eggs, sautéed onion, salt, pepper, and butter) were inoculated with a multi-strain cocktail of cells of Salmonella to a target level of 6.5 million cells per gram and treated with high pressure for 5 minutes. Reductions in the number of cells for Salmonella were observed in both liver and pate. Also, cooking pate to 60 to 73.8 deg C in a thermostatically-controlled, circulating water bath delivered reductions in the number of cells per gram of Salmonella. Results confirmed that longer times along with higher temperatures or higher pressure delivered greater reductions of the pathogen. Thus, both HPP and heat can appreciably reduce the levels of Salmonella inoculated on/in chicken liver or pate and, in turn, lower the risk of salmonellosis associated with consumption of undercooked chicken liver and/or pate prepared therefrom.
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