Abstract:Aiming to explore the effect of wetthermal characteristics and morphology of hotairflow on the microwave vibrating fluidized bed drying, the drying kinetics,thermal image changes,water distribution,color and microstructure of fresh bitter gourd slices under four microwave-hotairflow drying modes were studied by microwave-hotairflow vibrating dryer. The results showed that the hotairflow temperature had a significant effect on microwave-hotairflow vibrating fluidized bed drying. The drying time of hotairflow drying was slower, and the drying time of microwave drying alone, microwave power 0.6W/g+hotairflow 60℃+ airspeed 3m/s, microwave power 0.6W/g+hotairflow 70℃+ airspeed 6m/s was 56.4%,70.5% and 75.6% shorter than that of the hotairflow drying with hot air 70℃+airspeed 3m/s. The color of dehydrated product by hotairflow was closest to fresh balsam pear slices, the color of dehydrated product by microwave-hotairflow combination drying was better than that of microwave drying alone. The temperature uniformity of microwave-hotairflow combination drying was significantly better than that of microwave drying alone and hotairflow drying alone. The moisture signal was gradually decreased and the main peak was moved to the left under NMR spectrum by four drying modes. The MRI signal showed that hotairflow had a significant effect on the uniformity of water distribution during microwave drying. Scanning electron microscopy observation showed that the hotairflow drying was the most obvious to maintain the cell integrity of dehydrated product, and the cell integrity of microwave-hotairflow drying was better than that of microwave alone. The study provided a theoretical basis for the processing technology selection of dehydrated product.