ABSTRACT:The objective of this study was to investigate the amino acid composition and antioxidant properties of two oyster mushroom species, Pleurotus ostreatus and Pleurotus sajor-caju, commercially cultivated in NE Thailand. Proximate composition and dietary fibre of dried mushrooms were determined. Amino acid composition of fresh mushrooms was analysed by HPLC. Water and ethanol extracts were obtained from dried mushrooms and determined for total phenolic contents (TPC) by the Folin-Ciocalteu method, free radical scavenging efficacy by the DPPH method, and reducing power by the ferric reducing-antioxidant power method. Except for protein, proximate compositions of dried mushrooms were significantly different. Similar amino acid profiles in both mushrooms were obtained, with glutamic acid, aspartic acid, and arginine being the three most abundant. Water extracts contained higher TPC and possessed better antioxidant activities than did ethanol extracts for both mushrooms. Overall, P. ostreatus possessed more antioxidant than P. sajor-caju. The EC50 of P. ostreatus and P. sajor-caju water extracts were 11.56 and 13.38 mg/ml, respectively, while those of the ethanol extracts were 31.75 and 58.44 mg/ml, respectively.

Dietary fiber is one of value added products from cassava pulp, byproduct of cassava starch industry. It could be produced by enzymatic digestion in which the optimal condition was studied. The three independent variables are heating temperature (°C) after adding α-amylase concentration (%v/v) and amyloglucosidase concentration (%v/v) regarding of two responses solid percentage yield and neutral detergent fiber (NDF) in the digested sample. The experimental design was based on central composite design. The highest solid percentage yield and NDF of cassava byproduct could get from enzymatic digestion condition at heating temperature at 90 °C, α-amylase concentration of 0.3 % (v/v), and amyloglucosidase concentration of 0.5 % (v/v). For ultrasound-assisted preparation was investigated at the optimum condition of enzymatic digestion. Ultrasound condition was control power of 140% and a frequency of 40 kHz for 15 min. The ultrasound was applied at pre-treatment condition (before adding α-amylase, PU) collocated with intermediate condition (before adding amyloglucosidase, IU) higher NDF yield than optimal condition at 18.78%. In addition, this ultrasound assisted technique give the highest solid percentage.