Grey oyster mushroom (Pleurotus sajor-caju) is a type of edible mushroom that suitable to be cultivated in Malaysia. There is an increasing demand in the market due to its high nutritional values. In this study, effects of different durations of ultrasonic treatment on the growth morphology, yield enhancement and quality of mushrooms were investigated. Four different durations of ultrasonic treatment had been applied on the mushroom bags which were 1.5, 3.0, 4.5 and 6.0 minutes and 0 minutes act as control. The results showed that all ultrasonic treated bags had shorter time for mycelium to fill-up the mushroom bags as compared to control. Ultrasonic treated bags was observed could promote and activate the pinhead emergence and fruiting bodies formation. Besides, all ultrasonic treated bags also showed higher yield and better quality in terms of the largest pileus diameter of mushrooms as compared to control. For the color of mushrooms, there was no significant different (P>0.05) observed in L∗ values. However, treatment of 1.5 minutes had the highest a∗ (redness) and b∗ (yellowness) values. Different durations of ultrasonic treatment did not showed any significant different in texture and moisture content of mushrooms. In summary, 1.5 minutes was the best treatment duration as it took the shortest time for different growth stages with the greatest yield of mushrooms.
