Nonuniform microwave heating causes localized over-heating in frozen food products, lowering the quality of the thawed products. The solid-state microwave system has the potential to enhance heating performance as it provides flexible control over microwave parameters, e.g., frequency and power. The real-time collected microwave power reflection enables dynamic parameter control. This study developed two dynamic solid-state defrosting strategies: 1) selective frequency shifting strategy that only selectively shifted frequencies with high efficiency, 2) adaptive power control strategy that adapted power input with simultaneously orderly shifted frequencies. Results showed that the adaptive power control strategy had a better defrosting performance on frozen mashed potato and pork chop samples. Besides, with the adaptive power control strategy, the rotation of the turntable did not pose a significant improvement on the standard deviation of the temperature distribution in the defrosted products when compared to the stationary heating, which might be due to the minimized movement of samples at the center of the. The absolute changes in temperature profiles contributed by the rotation were considerable, indicating the importance of turntable.

This study developed novel microwave control strategies for defrosting processes, taking the advantage of the flexible control over the microwave parameters provided by the solid-state technique. With the proposed strategy, the microwave defrosting performance can be significantly improved in comparison with the magnetron-based microwave oven performance. The implemented dynamic strategy is promising to be embedded in the algorithm for use by the future smart microwave ovens.