Development and validation of analytical charts for microwave assisted thermal pasteurization of selected food products

For process development using an industrial Microwave Assisted Thermal Pasteurization System (MAPS), it is desirable to have effective tools that allow accurate prediction of heating rates in pre-packaged foods. This research aimed to develop engineering charts that illustrate the relationships among the dielectric properties of foods, preheating temperature, product thickness, and heating rate in the microwave heating section of MAPS. We selected three different foods, namely mashed potatoes, peas, and rice, in this study. Three complementary G-T (Gezahegn-Tang) charts were developed using MATLAB software by applying Maxwell's and heat transfer equations with measured physical properties of the selected foods. Experiments were conducted with mashed potato samples using a pilot-scale MAPS unit to validate the charts. The temperature profiles measured at the cold spots of the food samples in the microwave heating section of MAPS were positively correlated with predicted temperatures from the chart (R2 > 0.96); more than 95% of the standardized residuals were in the range of −2 to 2 °C. The charts are able to estimate microwave heating rate at the cold spots in food packages based on food dielectric properties and package thickness. They can also be used to help select an optimal preheating temperature for the maximum heating rate. This research demonstrated the possibility of using validated G-T charts to assist food companies in developing pasteurization schedules based on MAPS for the commercial production of different packaged ready-to-eat (RTE) meals.