Effects of microwave power control on enzyme activity, drying kinetics, and typical nutrients of Pleurotus Eryngii: Exploring the blanching mechanism by microstructural and ultrastructural evaluation

A Penetrating Microwave Infrared Hot-Air Rolling-Bed Dryer (PMIHRBD) was developed for penetrating microwave blanching (PMB) of pleurotus eryngii. The effects of PMB pretreatment on enzyme activity, drying kinetics and typical nutrients constituents were investigated at different power levels (1-3 W/g) and pretreatment times (7-12 min). The quality changes of pleurotus eryngii were further elucidated by microstructural and ultrastructural evaluations. The results showed that PMB effectively inhibited polyphenol oxidase (PPO) and peroxidase (POD) activities and affected the contents of total polysaccharides, total phenols, total acids, and malondialdehyde (MDA) of pleurotus eryngii, in which the drying time was shortened by 25.09%- 49.44%. In addition, scanning electron microscopy (SEM) observations revealed that cell wall damage was correlated with drying time, water-holding capacity and water-binding capacity. Transmission electron microscopy (TEM) revealed the relationship between cell membrane damage and MDA content. Observations of both SEM and TEM revealed the mechanism behind the changes in the quality of pleurotus eryngii.