Shiitake mushroom drying using belt-conveyor combined microwave-hot air and hot air techniques: Drying kinetics, energy consumption, and quality characteristics

This study developed dried shiitake mushrooms through belt-conveyor combined microwave-hot air (MWHAB) drying, comparing it with hot air (HA) drying. MWHAB drying, with microwave powers ranging from 300 W to 600 W at 65 °C, was contrasted with HA drying at the same temperature. Both blanched and unblanched samples were dried to a final moisture content of 11.1% (d.b.). The research evaluated drying kinetics, specific energy consumption (SEC), and various quality aspects, including color, shrinkage, rehydration, texture, and microstructure. Results showed that blanched samples dried with MWHAB at 600 W significantly reduced drying times and SEC by 76.9% and 77.3%, respectively, compared to HA drying. Dried MWHAB products exhibited lower shrinkage and hardness but higher rehydration, larger pore sizes, and void area fraction than HA. Although no significant color differences were observed, MWHAB drying at 600 W yielded lower values for shrinkage and hardness, and higher values for rehydration, void area fraction, and larger pore sizes than other cases. Additionally, unblanched dried samples displayed reduced shrinkage and hardness but increased color values, rehydration, larger pore sizes, and void area fraction compared to blanched samples. Optimal shiitake mushroom production is recommended using unblanched samples dried with MWHAB at 600 W microwave power.