Microwave vacuum drying of foods with temperature control by power modulation

Microwave power modulation during drying was evaluated to guarantee mild temperatures, reducing burning spots when producing sweet potatoes snacks. Samples were peeled, sliced, blanched, and microwave vacuum dried with (MWVDc) and without (MWVD) controlling the temperature (60 degrees C) with a PID system. MWVD used constant power, while MWVDc adjusted the power input based on samples' temperature target. Moisture content was reduced from 4.5 g g(-1) (db) to 0.4 g g(-1) (db), resulting in water activity lower than 0.55. MWVD processing time was about 80, 15, and 10 min at 300, 1500, and 2700 W, respectively, resulting in dried samples with dark areas due to hot spots. The power modulation in MWVDc resulted in intermediary drying time (50 min) and uniform color products without burnings. This study demonstrated that automated temperature control leads to high-quality sweet potato chips by microwave processing.