Microwave vacuum drying of banana slices

Vacuum drying of banana slices was studied in a domestic microwave oven. The results show that banana temperature rises uniformly and rapidly to the saturation water vapor temperature corresponding to the vacuum used then rises slowly until most of the free moisture is lost. The thermal and drying efficiencies were found to drop from almost 100% at the beginning of the drying (high moisture content) to as low as 40% and 30% respectively at the end of drying. Both efficiencies were found to increase with the use of vacuum, especially at low moisture content.