Effect of steam cooking and particle size on the nutritional composition, phytochemicals and antioxidant activities of oyster mushroom (Pleurotus ostreatus) powder

In this study raw and steamed Pleurotus ostreatus were dried and ground and fractionated by sieving into four granulometric classes (< 200 µm, 200–250 µm, 250–355 µm and > 355 µm) and unsieved powders. The combined steam cooking and sieving improved the content of total polyphenols (+ 59.45%), flavonoids (+ 76.47%), condensed tannins (+ 68.75%) and trace elements (+ 45.51% Fe, + 63.63% Cu, + 62.42% Mn, + 121.11% Zn, and + 53.52% Se) as well as in-vitro and in-vivo antioxidant activities in the finest fraction < 200 µm compared to the raw powder. It was found that the intake at a dose of 250 mg/kg body weight of the finest fractions of raw and steamed powders by the stressed rats had more of a hepatoprotective effect marked by a reduction in the level of transaminases ALAT and ASAT. This work opens a new approach for valuing edible mushrooms in the development of new food products with high antioxidant value.