Effect of different drying treatments on the chemical properties of maitake (Grifola frondosa) mycelia

Maitake (Grifola frondosa) is an edible mushroom that contains high dietary and medicinal properties. In this study, maitake was cultivated using submerged fermentation in order to get their mycelia. The mycelia were susceptible to extreme environment and hence need to be preserved properly prior further process. For this purpose, drying is an important process to extending their shelf life. The aim of this study was to investigate the effect of vacuum and oven drying on the chemical properties (reducing sugar, total phenolic content, DPPH radical scavenging activity and total soluble proteins) of Grifola frondosa mycelia. Submerged culture technique was employed to grow the mycelia
using Mushroom Complete medium (MCM). The pH of medium was decreased from pH 5 to pH 4.03-4.52 during cultivation for 14 days. The harvested mycelia biomass was dried into powdery form using vacuum and oven drying. The mycelia treated by vacuum oven drying exhibited highest reducing sugar content (170.73 ± 4.86 µg/mL) as
compared to oven drying (74.81 ± 5.20 µg/mL) and fresh (25.18± 0.32 µg/mL). Vacuum drying seems to improve the total phenolic content (19.96 ± 0.37 mg GAE/g) and DPPH
radical scavenging (84.66 ± 0.14%) of maitake mycelia. A strong positive correlation was observed between total phenolic content and DPPH radical scavenging activity
(R²=0.9971). However, the maitake mycelia possessed higher total soluble protein content treated by oven drying (283.61 ± 7.14 µg/mL) as compared to vacuum oven
drying (279.80 ± 4.78 µg/mL) and fresh (274.09 ± 9.48 µg/mL). The outcomes of this study revealed that vacuum drying was a suitable approach to dry maitake mycelia
without affecting its basic chemical properties.