Determination of thickness of microwaveable multicompartment meals using dielectric, thermal, and physical properties

• A 1-D model was developed to replace 3-D models to predict the average heating rate of microwaved food.
• The thicknesses of multicompartment meals were determined to improve heating uniformity.
• The determined thicknesses were validated in 3-D microwave heat transfer models.

Multiphysics based numerical model are promising tools to enhance understanding of microwave heating of foods. These models are specific for particular microwave oven and food configuration, which limits generalization. In addition, the models are computationally expensive limiting their utility in the food industry. In this study, we have developed a simple 1-dimensional (1-D) analytical model based on planar wave assumption to predict the average heating rate of a food product and to determine the thickness of multicompartment meals based on the dielectric, thermal, and physical properties. The model was benchmarked by comparing with earlier developed 1-D model. A numeric “vpasolve” solver in MATLAB was used to adjust the thickness of two compartments such that they would heat at the same rate and have better heating uniformity. To validate this approach of determination of thickness using the 1-D model, a 3-D multiphysics based numerical model and experimental microwave cooking were used to evaluate the average heating rate in the original equal and adjusted food designs. The validation using 3-D numerical model was also performed for three multicompartment meals, three top surface areas, three food shapes, and three microwave ovens. The meals with adjusted thicknesses showed that the average heating rates of two compartments were closer indicating improved heating uniformity. The average heating uniformity indices based on average final temperature difference and coefficient of variation of 21 scenarios are 57.6% ± 9.4% and 29.3% ± 5.3%, respectively. Therefore, the simple 1-D model can be used for preliminary design of microwaveable food products.