Comparative study on phenolic compounds, triterpenoids, and antioxidant activity of Ganoderma lucidum affected by different drying methods

Ganoderma lucidum, a famous Chinese medicinal mushroom, is cultivated systematically, harvested seasonally and dried for preservation. In this study, the effects of sun drying, hot air drying at 50 degrees C and 70 degrees C, microwave drying at 420 W and 700 W, and freeze drying on the moisture content, rehydration capacity, the contents of total phenolics, flavonoids and triterpenoids, as well as on the antioxidant activity of G. lucidum were investigated. The results showed that the physical properties, bioactive ingredients and antioxidant activity of G. lucidum were significantly affected by the different drying techniques. Microwave drying at 700 W resulted in the lowest moisture content, whereas freeze drying resulted in the highest rehydration rate compared with the other drying methods. The content of total phenolics and flavonoids, the 2,2-diphenyl-1-picrylhydrazyl radical scavenging ability, and the ferric reducing antioxidant power were found to be the highest at the G. lucidum dried by microwave drying at 700 W. Overall, Microwave drying was of short duration and significantly retained the antioxidant activity and high content of phenolics in G. lucidum. Thus, Microwave drying could be suggested as the optimal method for preserving the fruiting body of G. lucidum.