Numerical investigation of coupled heat-mass transfer and expansion in wheat starch-gluten systems during microwave processing: Role of power and initial moisture.

Microwave heating is favored in wheat-based food processing for its rapid and selective heating, high efficiency, and environmental benefits, yet it often suffers from non-uniform temperature distribution. The underlying coupled heat transfer, mass transfer, and deformation mechanisms remain insufficiently understood, limiting the optimization of moisture content and microwave parameters. This study developed a multiphysics model to simulate heat and mass transfer in hydrated wheat starch-gluten systems under microwave irradiation. The model was experimentally validated and applied to analyze the effects of microwave power and moisture content on temperature, moisture, and stress-strain distributions. Results indicated that higher power and moisture levels accelerated heating and drying without altering distribution patterns, while also increasing internal stress and promoting volumetric expansion. Moisture content enhanced microwave absorption and intensified coupled gradients of temperature, pressure, and moisture, facilitating expansion. A feasible heating scheme of 440 W for 120 s was identified as optimal for achieving high expansion and low weight loss across various samples. These findings provide valuable insights for designing efficient microwave processes in wheat-based food production.