Effects of different drying treatments on the microstructure, free amino acids, volatile compounds and antioxidant activity of Flammulina velutipes root

Drying treatments are an effective method of preserving the beneficial properties of postharvest mushrooms. The effects of natural-air drying (ND), hot-air drying (HD), vacuum-freeze drying (FD), heat pump drying (HPD) and microwave-vacuum drying (MVD) on the microstructure, flavor- and health-related compounds of F. velutipes root were investigated. The results showed that FD had the least impact on the microstructure of F. velutipes root and its original porous fiber structure appeared complete. It also possessed the highest content of volatile compounds. MVD gave the highest contents of umami amino acids, total phenolics and total flavonoids, and its extract exhibited high antioxidant activity. In addition, different drying treatments had significant effect on the chemical components of F. velutipes root, with FD and MVD may be the potent drying strategies for preservation of flavor and nutraceuticals respectively. Therefore, our results provided essential data support for F. velutipes root processing and functional product development.