Modeling heat and mass transport during microwave heating of frozen food rotating on a turntable

Microwave heating of frozen foods involves multiple physics and food product development has been trial-and-error in the food industry. Multiphysics models can be used to understand microwave interactions and can assist in design of food that can be heated more uniformly. A comprehensive three-dimensional finite element model for describing microwave heating of a food product on a rotating turntable is developed including multiphysics of Maxwell's electromagnetic heating, energy conservation, Darcy's velocity, mass conservations of water and gas, and phase change of melting and evaporation of water. The necessity of incorporating mass transfer physics was investigated and confirmed. Twelve discrete rotational steps were used in one rotational cycle. Two approaches of updating dielectric properties at each rotational step (typical) and each cycle (simplified) were evaluated. The models using typical and simplified approaches were developed and validated for heating of a 550 g tray of frozen mashed potato for 6 min in a 1250 W microwave oven on a rotating turntable. The spatial variation of the top surface temperatures of the mashed potato acquired by an infrared camera, the transient temperatures at six locations recorded by fiber optic sensors, and the total moisture loss during heating all showed good agreement with the simulation results for both approaches. The typical and simplified approaches had similar RMSE values of transient temperatures of, respectively, 13.1 and 13.2 °C, while the RMSE values between experimental replications was 8.0 °C. The RMSE values of total moisture loss of were similar (2.2 and 2.4 g) for both approaches. With 83% reduction in computation time for the simplified approach, this method can be used to evaluate the microwave heating of food products and accelerate microwaveable food products development.