Achieving Lethality Performance Standards for Fully-Cooked Meat Products

To meet that goal, the specific objectives are:<ol> <li>To develop and validate a computer model (based on engineering and scientific fundamentals) that predicts pathogen inactivation in a real meat product (of geometry and composition typical to those used in the meat industry) subjected to a commercial convection cooking process (of given duration, temperature, humidity, and air velocity).
<li>To develop and distribute an oven operators' tutorial that distills the relevant basics of heat and mass transfer, thermodynamics, and predictive microbiology into appropriate-level language and format for operations personnel in the U.S. meat and poultry industry.
<li>To develop a unique graduate course entitled Engineering Methods for Food Safety (to be offered via the web-based MSU Virtual University).</ol>
<p>
Scientifically supportable means do not exist for reliable predictions of process lethality in the U.S. meat and poultry industry. The purpose of this project is to develop and distribute fundamental information and technical tools that are needed for the meat and poultry industry to meet new federal regulations that specify lethality performance standards for fully-cooked products.</p>
<p>
The overall project plan integrates research, extension, and education tasks to optimize the synergistic effects of a multi-functional project. Laboratory-scale heating trials will be conducted to develop pathogen lethality models for Salmonella in meat, based on product composition and process conditions (temperature and humidity) in convection cooking systems. Subsequently, a comprehensive cooking/lethality model will be developed by incorporating the pathogen lethality models into a coupled heat and mass transfer model for air-impingement cooking of ground and formed meat products. This tertiary model will then be validated via inoculated challenge studies in a commercial pilot-scale air-impingement oven. The validated model will then be used to develop information and exercises that will be included in an oven operators' tutorial, to be developed in collaboration with an industry partner. Additionally, educational case studies will be developed in cooperation with industry partners to form the foundation of a web-based graduate course entitled Engineering Methods for Food Safety. In this way, the research results will directly impact relevant outreach materials and state-of-the-art graduate education.</p>
<p>
A computer model for impingement cooking was developed using the finite element method. Coupled heat and mass transfer was modeled with the mass transfer portion comprised of both moisture transport and fat transport. The condensing-convective boundary conditions were modeled by treating condensation as a true mass transfer process, rather than by using "effective" convection coefficients (which is the method that has been used in all previously published studies for meat cooking). A Salmonella inactivation model was integrated into the cooking model. The heat and mass transfer model was validated using data collected from an industrial moist-air impingement oven at 121-232 deg C, 50-86% air moisture content (by volume), and 12-22 m/s gas (exit) velocities. Salmonella inactivation was validated using previously published data from a pilot-scale impingement oven. The model satisfactorily predicted the results observed in the commercial oven. Patty surface temperature increased with increasing oven steam fractions. The standard error of prediction for patty center temperature (n=54) was 5 deg C. When fat transfer was ignored, the model overestimated cooking yield (n=54) by up to 10%. These additional losses were accounted for by incorporating fat transport into the model as a second mass transfer component, so that the yield prediction error was reduced to ~6% (without bias). With respect to predicting process lethality, the standard error of prediction for the model was 1.3 and 1.1 log(CFU/g) for Salmonella and Listeria, respectively. Work on this objective in the final year of the project will focus on validation of the lethality predictions via independent, inoculated cooking trials (Salmonella in ground meat patties) in a pilot-scale impingement oven.
<p>
The second objective of this project is aimed at development of training materials for line-level oven operators in the meat and poultry industry. The needs analysis has been completed and published, and the preliminary outline of the training materials has been completed. The final year of the project will include production of the prototype training materials for testing with industrial collaborators. The last objective of this project is related to web-based graduate education. The second offering of our completely web-based graduate course, "Engineering Methods for Food Safety", occurred in Fall 2004, with the first industrial participation. To expand the impact of this activity, additional funding has been acquired to develop a completely web-based, multi-institutional graduate certificate program in "Food Safety Engineering", and the course developed in this project will be a core course in that program.</p>
<p>
The validated cooking and lethality model will enable meat and poultry processors to quantify process lethality for a complete convection cooking system, given only the product and process parameters. This will reduce the cost of product/process development and improve the tools available for ensuring the safety of ready-to-eat products. The line-level worker training materials will improve the fundamental knowledge of oven operators in the meat and poultry industry, and thereby improve the ability of food manufacturers to rely on those workers as important team members ensuring the safety of ready-to-eat products.</p>