Comparison of Three New Drying Methods for Drying Characteristics and Quality of Shiitake Mushroom (Lentinus edodes)

This articles provides results of an experimental investigation of three hybrid drying technologies on the drying characteristics and key quality parameters of shiitake mushroom (Lentinus edodes). The drying techniques tested at the laboratory scale are mid-infrared-assisted convection drying (MIRCD), hot air coupled with radio frequency drying (HCRFD), and hot air coupled with microwave drying (HCMD). For comparison, the standard drying technique using hot air was also tested. The quality parameters include texture, color, rehydration rate, shrinkage, nutrient retention, microstructure, etc. These four drying tests were conducted at fixed air temperature (60°C), and the power level for HCRFD, MIRCD, and HCMD was fixed at 4 W/g. The results showed that hot air coupled with microwave drying gave the shortest drying time, and mid-infrared-assisted convection and hot air coupled with radio frequency drying showed better color attributes and nutrient retention. Under the conditions tested, mid-infrared-assisted convection drying yielded minimal shrinkage (maximal rehydration) and lower hardness upon rehydration. The uniform honeycomb network and less collapsed structure of MIRCD samples can be used to explain these better quality characteristics.