Predicting the quality changes during microwave frying of food biopolymers by solving the hybrid mixture theory-based unsaturated transport, and electromagnetics equations

The transport mechanisms involved in microwave frying are not well understood. This can make it challenging to optimize the process for commercial use. In this study, the microwave frying of deforming viscoelastic foods was modeled by solving the unsaturated transport equations and Maxwell's equations of electromagnetism. Simulations were conducted for conventional frying and microwave frying (at 2.45 and 5.8 GHz frequencies) of French fries. The sample location in the oil during microwave frying impacted the sample temperature, internal pressure, moisture content, etc., due to the non-uniform distribution of the electric field in the oil. Microwave frying caused rapid heating of the food matrix, a faster rise in pore pressure, and higher peak pressure values than conventional frying. The higher magnitude of pore pressure in the food during microwave frying is expected to impede oil penetration in the samples. This method reduced frying times by 33-76 % and the oil content of French fries by 3-33 % compared to conventional frying. Microwaves at 2.45 GHz frequency penetrated deeper into the food matrix than at 5.8 GHz frequency and caused the development of higher magnitudes of pore pressure. Consequently, microwave frying at 2.45 GHz led to samples with lower oil content than 5.8 GHz. The microwave power dissipation followed the drying front in the samples, which can lead to the thickening of the crust. Therefore, microwave frying can help the food industry reduce processing times and produce crunchy foods with lower oil content than conventional frying.