Influence of microwave hot-air flow rolling dry-blanching on microstructure, water migration and quality of pleurotus eryngii during hot-air drying

摘要

Effects of microwave hot-air flow rolling dry-blanching (MARDB) on drying characteristics and quality of pleurotus eryngii were investigated. The pleurotus eryngii were dry-blanched under microwave power of 3 W/g for blanching times ranging from 0 to 12 min. Polyphenol oxidase (PPO) and peroxidase (POD) activities, temperature and humidity change, water migration, and microstructure were analyzed to optimize the drying process. Optimal pretreatment (9 min) resulted in the increase of polysaccharide, formaldehyde and phenolic content, and full inactivation of PPO and POD, which is closely related to product deterioration by increasing the sample temperature and ambient humidity during storage. The T-2 relaxation spectrum and microstructure showed that the decrease of migration resistance of free water and pore structure at the optimal MARDB time would be the main reason to improve the drying efficiency. However, over-blanching (12 min) prolonged drying time and induced the decrease of brightness, polysaccharide, and phenolic contents. Therefore, appropriate MARDB pretreatment time can significantly improve drying characteristics and the quality of pleurotus eryngii.