Performing Department
Animal Sciences
Non Technical Summary
Thermal treatments are critical for controlling foodborne pathogens in RTE meat products. Currently, U.S. processors of RTE meat and poultry products have limited science-based documentation to validate pathogen destruction during thermal processing. USDA, FSIS Appendix A is widely used as validation support for thermal processes, but its time-temperature tables and humidity requirements were originally developed and validated for only Salmonella in roast, cooked, and corned beef by Goodfellow and Brown regarding over 35 years ago. Despite the narrow focus of this research, Appendix A guidelines are routinely applied to a wide variety of processes and pathogens. Recent USDA draft guidance on food safety validation challenges the scientific appropriateness of Appendix A as support documentation for thermal processing of products not included in the original study. However, Appendix A is routinely applied to a wide array of products including hams, hot dogs, luncheon meats and jerky, to name a few. The widespread use of a procedure originally developed only for roast beef has raised question about its appropriateness for non-roast beef products or for pathogens other than Salmonella. Therefore, this proposed research will address identified shortcomings, develop new knowledge, and provide assurance thermal processing does not contribute to foodborne illnesses.
Animal Health Component
0%
Research Effort Categories
Basic
10%
Applied
90%
Developmental
0%
Goals / Objectives
This study will focus on developing newscientifically supported thermal processing criticalparameters for non-beef ready-to-eat (RTE) products and will include pathogenic Salmonella and Listeria monocytogenes frequently identified as a food safety hazard likely to occur by USDA, FSIS. The research will equip meat processors in Wisconsin, extending to those nationwide, with important scientifically supported knowledge to improve as well as ensure the safety of their thermally processed RTE products.
Project Methods
Phase 1: Impact of physicochemical properties on total lethality D- & z- value generation: The physicochemical factors, fat content, pH, and salt concentration, will be investigated in this study. Cooked beef, pork, and poultry (1/3 of each used in formulation) sausages will be manufactured with varying levels of each factor. Fat levels investigated will include 10%, 20%, and 30% (based on total formulation). pH levels will include 5.5, 5.9, 6.3. Salt concentration levels will include 1.5% and 2.5% (based on total formulation). Eighteen treatment combinations will be included in this experiment. In addition, two pathogens Salmonella and L. monocytogenes will be investigated in two separate experiments. No study has been designed for address multiple intrinsic factors in a balanced design thus this study is expected to yield valuable data to establish fundamental concepts. Although other factors such as inclusion of other non-meat ingredients could also impact thermal lethality, it is not feasible to include these factors. Multiple text batches will need to be manufactured to create formulations that achieve factor targets. Due to the magnitude of these experiments (18 treatment combinations x 2 pathogens x 2 replicates), it is expected to take 10-12 months to complete. For reach treatment combination, separate experiments will take place at 4 different temperatures with microbial sampling, in triplicate, at 4 different pull times at each temperature (a minimum of 3,456 samples assayed). This is further detailed below.Small batches (2-5 lbs) of each experimental treatment will be manufactured utilizing formulations and processing methods mimicking industry practices. Beef, pork and turkey trimmings will be selected (based on treatment needs for fat content) and ground thru a ½" grinder plate and transferred to a meat mixer. Water, salt (based on treatment requirement), dextrose, sodium phosphates, spices, sodium nitrite, and sodium erythorbate will be mixed with the meat for 5 minutes. Adjustment of the pH will be accomplished by adding sodium phosphates with different pHs (food grade phosphates range in pH from 4.0 to 11.0). The meat mixture will be re-ground though a 1/8" plate batched for experiment needs. Immediately after manufacture, the treatment batches will be transported to the Food Research Institute where they will be inoculated with either a 7-log cfu/g of a 5-strain mixture of Salmonella or a 7-strain mixture of L. monocytogene in two separate experiments. The rate of thermal inactivation of the pathogens will be determined by the "cook-in-bag" method. Briefly, 1 g samples of the inoculated meat will be flattened into a thin film (0.5-1.0 mm) in a moisture-impermeable pouch, vacuum-packaged, heated at one of four temperatures (130, 140, 150, and 160°F) in a water bath in 4 separate experiments. Triplicate samples will be removed at predetermined time points based on expected results at each temperature (such as 0, 5, 15, 30 and 60 minutes at 130°F or 0, 20, 40, 60, 80 and 100 seconds at 160°F) and samples will be immediately chilled to <40°F by placing in ice. Samples will then be enumerated for the survival of Salmonella, or L. monocytogenes using XLD or Modified Oxford agar, respectively, with thin layer overlay of nonselective media to enhance recovery of injured cells. Initial times and temperatures were selected based upon review of work by Goodfellow and Brown (7) where a 7-log reduction at 135oF was achieved in 30 minutes of elapsed time. Finished products will be analyzed for moisture, salt, pH, aw, protein and fat, and nitrite, as appropriate. The study will be replicated twice to determine D- and z-values for each product type and pathogen.Phase 2: Impact of physicochemical properties and extrinsic factors on total lethality: validation of D- and z-values in commercial products and exploration of surface lethality: Phase 2 will be designed to elicit "worst-case" parameters for the factors investigated in Phase 1 and validate the findings in commercial product systems as well as incorporate surface lethality exploration. This will be important as to validate D- values using a system approach where the results generated in a 1 g system can be scaled up to commercial products in a commercial processing environment. To validate the results found in Phase 1, at least three treatment combinations with the highest D-value for each physicochemical factor explored above (n=3) will be again manufactured using the same formulations and procedures outlined in Phase 1. It is likely more than 3 will be need to be included in this phase since multiple combinations of the investigated factors could result in pathogen lethality resistance. In addition, the impact extrinsic factors have on surface lethality will also be explored in this research phase by first measuring environmental (wet bulb, dry bulb, and relative humidity) and product surface (water activity) conditions during a commonly used meat industry thermal process. Based upon the results, up to 2 additional thermal processes will be developed for each treatment combination tested (n=3) that focus on surface temperature and dwell time to determine the feasibility and approaches to achieving product surface lethality. This experiment is expected to add additional 6-10 product treatments. It is important to validate D and z values otherwise their application value is negated. Careful review of Phase 1 data will need to take place to ensure the most appropriate treatment combinations are used for validation. Consultation with the meat industry will also need to occur to ensure experimental practices and procedures mimic those used in the meat industry. There is potential that not all D values will be successfully validated (as we determined was the case in previous research noted in Table 1) and will require additional experiments address and understand this occurrence. Due to the complexity of the proposed work, 7-8 months are expected for validation work while an additional 3-4 months are expected for surface lethality experiments.Cooked sausage meat batter will be inoculated with Salmonella or L. monocytogenes, stuffed into 4-5" diameter casings to represent an average product size, and thermally processed using a combi-oven (Alto Shaam) or smokehouse using cooking schedules similar to those commonly used in the meat industry. Temperature mapping of the product will take at the surface, mid-point, and the geometric center of the product to establish thermal lethality/location specific data and for use in integrated lethality calculations while environmental conditions of the oven will also be recorded. Inactivation of pathogens will be validated at one to three internal temperatures (depending on experimental findings) by enumerating, with the same techniques previously described, at appropriate time intervals. The three internal temperatures utilized will be chosen based upon results of Phase 1. All experiments in this phase will be replicated at least twice. These experiments will include a minimum of 3 treatments (from validation) x 2 replicates x 3 sample locations x 3 temperatures x 4 pull times x triplicate samples=648 samples plus a minimum of 6 treatments to investigate surface lethality (6 treatments x 2 replicates x 6 surface temperature/dwell points x triplicate samples=216 samples. Finished products will be analyzed for moisture, salt, pH, aw, and nitrite, as appropriate.