Fresh mushrooms contain a wide variety of minerals including copper, iron, magnesium, phosphorus, potassium and zinc which are essential for good health. The mineral composition of mushrooms largely depends on the type of nutrients available in their growth media. The objective of this study was to determine the mineral composition of oyster mushrooms, Pleurotus spp., grown on maize straw and rice bran substrates. In this study, 200 oyster mushroom tubes were grown under the same conditions of temperature and humidity on each substrate, and harvested one week after incubation. Mushroom samples from each substrate were sun dried to constant mass, ashed and acid digested before determination of P, K, Na, Mg, Na, Fe, Zn, Cu, Cr, Cd and Mn levels by Microwave Plasma Absorption Emission Spectrophotometer. Mushrooms grown on maize substrate had higher calcium, phosphorus, iron, zinc and copper levels of 1887, 649, 32, 12 and 22 mg/100 g, respectively compared to 353, 420, 12, 10 and 0.5 mg/100 g on the other substrate. Also, mushrooms grown on rice bran substrate had higher contents of magnesium, potassium, and sodium; 1587, 560 and 180 mg/100 g, respectively compared to 1199, 379 and 140 mg/100 g for mushrooms from the maize straw substrate. Manganese, chromium and cadmium were below detection limit in all the mushrooms. Conclusively, mineral content in mushrooms varies with the type of substrate where they are grown; and that mushrooms are potential valuable sources of essential mineral elements for human health. Therefore, mushroom husbandry should be encouraged to supplement the available nutrients resources.

Keywords: Oyster, mushrooms, mineral, content, substrates.