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The overall goal of this proposal is to integrate heat transfer and thermal destruction models in a risk assessment model to assess risks of microwave cooking with a goal of improving the uniformity of heating of a Prepared, but not-ready-to-eat (NRTE) food in a domestic microwave oven. <P>
The specific objectives are to: <OL> <LI> Develop a holistic microwave cooking model to understand how microwaves interact with NRTE food components and resulting heating patterns. a) Determine the temperature dependent dielectric and thermal properties. b) Unify and extend existing microwave heating models to produce a holistic microwave cooking model to simulate relevant scenarios associated with consumption of NRTE food products. c) Develop recommendations for packaging design, layout and sizing of various food components in the package based on their dielectric properties. <LI> Develop and validate microbial destruction model for Salmonella spp. and integrate it with the heat transfer model a) Develop a database of the lethality parameters for Salmonella spp. in individual components and validate the values in composite NRTE foods. b) Validate the integrated model by conducting microbial challenge studies. <LI> Conduct risk analysis of microwave cooking of frozen food products. a) Develop a risk assessment model for microwave cooking by incorporating the holistic heat transfer and microbial destruction models and dose-response curve to estimate risk. b) Conduct sensitivity analysis to identify critical factors that can contribute significant risks to consumers of frozen microwaveable food products. c) Estimate the risks of specific behaviors and pre- and post-cooking regimes associated with consuming frozen ready to eat scenarios. <LI> Develop and deliver traditional and non-traditional programs of microwave cooking safety of NRTE food products for academia, industry and consumers a) Develop and deliver course materials related to heat transfer, microbial destruction, and risk assessment models to undergraduate and graduate students in engineering and food science. b) Develop and deliver easy to understand extension tools (fact sheets and bulletins) on assuring safety of microwavable foods through selection of microwave ovens, translation and adoption of cooking instructions, and safe cooking instructions. c) Deliver the integrated heat transfer and microbial destruction model and the risk assessment tool for processors on designing and developing safe microwavable foods and appropriate cooking instructions to assure safety of frozen ready to eat foods. </ol>
Expected Outcomes: We expect to have a holistic heat transfer, microbial destruction , and risk assessment models for microwave cooking. These models will be used to develop recommendations and guidelines for processors to develop safe microwavable foods. We expect to come up with several recommendations for consumers to analyze the performance of microwave oven and recommendations for processors to prepare clear cooking instructions for microwave ovens of various performance levels. This will significantly reduce the risk of NRTE foods.
NON-TECHNICAL SUMMARY: Prepared, but not ready-to-eat (NRTE) microwaveable foods are convenience foods that comprise a considerable portion of foods consumed in the U.S. NRTE foods are partially cooked or contain partially cooked or raw ingredients and some of these products may appear ready-to-eat. These foods rely on proper heating or cooking before consumption for achieving food safety. However, most NRTE foods are cooked in microwave oven that provides uneven heating. The problem of uneven heating is severe when the product is frozen, because ice absorbs microwave energy to a lesser extent than liquid water, leading to defrosted sections of food warming faster while frozen sections remain cold. Most NRTE food packages provide cooking instruction without regard for the size, power, or condition of the microwave. Improper cooking and uneven heating in microwave ovens resulted in recent outbreaks and recalls of packaged frozen foods. The overall goal of this proposal is to improve the safety of NRTE microwaveable foods through heat transfer, pathogen destruction, and risk assessment modeling. The overall outcome of this study is to develop educational and outreach materials for a. processors by providing recommendations and guidelines to modify package and product parameters to improve the uniformity of heating and to develop clear cooking instructions b. consumers to understand the performance of their microwave ovens and to interpret the cooking instructions c. students to understand and apply modeling techniques for food safety applications. <P>
APPROACH: <BR> Objective I. Develop heat transfer model: Dielectric, thermal, and physical properties of complex food products will be determined and used in the heat transfer model. We will unify and extend a model that couples Maxwell's equation with thermal equations to model the cooking of frozen NRTE foods with active packages in a domestic microwave oven. The models will be validated by monitoring the temperature real-time during microwave cooking using fiber optic temperature measurement system. <BR><BR>Objective 2. Develop microbial model: A five strain cocktail of Salmonella spp. will be used. The D and z-values values for Salmonella spp. will be determined. The integrated heat transfer and thermal destruction model will be evaluated by inoculating the five strain mixed cocktail of Salmonella spp. using in each food product. The product with then be heated in the microwave for various times and Salmonella spp. populations will be enumerated. <BR><BR>Objective III. Develop risk assessment model: The risk assessment model will include the food, the microwave oven, the microwave cooking and heat transfer models, consumer practices, pathogen destruction model, and dose response curves. A fully developed model will be implemented using a Monte Carlo simulation of the entire food-oven-cooking-microbial-consumption-dose/response system. We will conduct sensitivity analysis will help in identifying the importance of uncertainties in the model which will in turn identify data gaps and needs to further improve the model. Simulations will be conducted to evaluate the mitigation efforts on reduction of final risk. <BR><BR>Objective IV. Educational and instructional materials: Course materials in the areas of heat transfer, microbial destruction, and risk assessment models will be developed and delivered to undergraduate and graduate students in engineering and food science. Easy to understand extension tools (fact sheets and bulletins) will be developed on assuring safety of microwavable foods through selection of microwave ovens, translation and adoption of cooking instructions, and safe cooking instructions. For the processors of the NRTE microwavable foods, the fact sheets will be developed to provide information on design of foods for microwave heating, design of packaging to maximize the uniformity of microwave heating to assure microbiological safety and developing proper cooking instructions for the consumer. <BR><BR>Analysis of Results: Both our heat transfer and microbial destruction models will be validated by extensive experimental observation of temperature distribution and microbial enumeration. Risk assessment model can be validated by comparing the estimated risk to foodborne illness outbreaks in the United States compiled by CDC and FSIS. <BR><BR>Evaluation methods: For evaluating educational materials, appropriate pre/post-course assessment tools will be developed and implemented. Evaluation of the extension intervention video modules and traditional class room modules will be done using a newly developed evaluation system similar to TEVAL, an evaluation method in use at the University of Nebraska.