Effects of different drying techniques on the water-soluble polysaccharides content and antioxidant activities of Ganoderma lucidum Karst

Evaluation of Ganoderma lucidum Karst. dried fruiting bodies are important since high quality of dried G. lucidum is crucial either for direct consumption or further processed into pharmaceutical products. The drying process may cause irreversible modifications to the cell wall polysaccharides and affect antioxidant activities. The aim of the present study was to investigate the influences of different drying techniques on the water-soluble polysaccharides content and antioxidant activities of G. lucidum. Fresh fruiting bodies of G. lucidum prepared in two ways: (1) the whole fruiting bodies dried then sliced, and (2) the fruiting bodies sliced previously then dried. Drying experiment were carried out using five different techniques including dried under direct sunlight (SL), dried in the sunlight-covered with black fabric (SL-BF), dried in the shade (DS), oven drying (OD) and air circulation oven drying (AC-OD). Water-soluble polysaccharides content was analyzed by phenol-sulfuric acid method and antioxidant activities were analyzed using 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical assay. The result suggested that the fruiting bodies form could retain the high content of water-soluble polysaccharides and antioxidant activities at various drying techniques (SL, SL-BF,OD, and AC-OD) but it required relatively long drying time to reach final moisture content (≤10% d.b). Slice form had a low retention of the water-soluble polysaccharides content and antioxidant activities during drying of G. lucidum at various drying techniques and it required shorter drying time. OD and AC-OD did not show asignificant difference in terms of the retention of water-soluble polysaccharides content and antioxidant activities as compared to SL, SL-BF, and DS.