Enhancing drying efficiency and temperature uniformity during microwave-assisted freeze drying: A weight-dependent microwave power approach

Microwave-assisted freeze-drying (MWFD) presents a promising time- and energy-saving alternative to conventional, costly freeze drying. However, achieving temperature uniformity during the drying process remains a significant challenge. This study introduces a novel process control strategy designed to enhance temperature uniformity without compromising time- and energy-efficiency. Traditional MWFD methods employ a constant microwave power input, often resulting in uneven processing and potential quality loss. In contrast, our newly developed strategy adjusts the power input according to the drying progress of the sample by a weight-based approach, with increased initial microwave power input compensating for reduced power at the end of drying. Our approach demonstrated for a wide range of tested microwave input power levels significant advantages over the traditional constant power input approach. This included faster drying times, lower overall energy consumption and lower total microwave energy use. A consequent reduction in temperature non-uniformity compared to the constant power counterpart was achieved at substantially lower final product temperatures. The findings suggest that this strategy can significantly improve MWFD processes, making it a valuable alternative to traditional MWFD. This advancement is particularly relevant in the context of growing efforts towards energy and time efficiency in the food industry.