Effect of Drying Method on the Bioactive Properties of Oyster Mushroom (Pleurotus ostreatus)

Pleurotus ostreatus is a source of natural antioxidants. Evaluation of Pleurotus ostreatus dried fruiting bodies is paramount since the high quality of dried P. ostreatus is critical for food processing. The drying procedure may cause irreversible alterations to the cell wall polysaccharides and affect antioxidant activities. Consequences of the drying method (direct sun-drying, sun drying- with black fabric cover, and air circulation-oven) on P. ostreatus quality was studied. The aim of the study was to investigate the impacts of different drying techniques on the bioactive properties of P. ostreatus. The surface morphology of sundried mushroom by Scanning Electron Microscopy (SEM) was more rigid and smoother compared to air circulation-oven dried mushroom. Air circulation-oven dried mushroom surface had cellular porous structures. Color analysis showed that pretreatments and drying methods affected the color of dried P.ostreatus. Fourier transform infrared (FTIR) spectroscopy analysis has been utilized to compare the spectroscopic characteristics of molecules contained in P. ostreatus with different drying techniques. FTIR spectra profile showed the functional groups of molecules contained in P. ostreatus. All samples of different drying techniques presented a similar FTIR spectra pattern. Air circulation-oven dried samples of slice form had the highest total phenol content (2.95 ± 0.05 %w/w DW), terpenoids content (4.47 ± 0.36 %w/w DW), and DPPH free radical scavenging activity (0.120 ± 5.24 %w/w DW). The drying method affects oyster mushroom quality as proved in this study.