FUNGI AND AFLATOXIN DETECTION IN TWO STORED OYSTER MUSHROOMS (PLEUROTUS OSTREATUS AND PLEUROTUS PULMONARIUS) FROM NIGERIA

The detection of spoilage fungi and aflatoxin contamination in Pleurotus ostreatus and Pleurotus pulmonarius which are two edible oyster mushrooms cultivated in Nigeria were investigated. These parameters were evaluated for fresh and stored samples. (at 0, 35, 70, 105 and 140 days). Fresh samples (0 day) of P. ostreatus had 86.6% moisture content (MC) while that of dried samples of this macrofungus decreased from 14.51% to 10.91% with storage. Pleurotus pulmonarius had 88.13% MC in the fresh samples, while its stored samples decreased to 11.89% after 140days.Seven fungi were isolated from the two mushroom samples. Aspergillus niger was the most frequently encountered , followed by Fusarium oxysporum, A. tamarii, A. flavus, Penicillium chrysogenum, P. oxalicum and F. compaticum in that order. (P>0.05). The total fungal count in the fresh samples of P. ostreatus was 3.0 x 101 (cfu/g) and increased to 1.35 x 104 (cfu/g) after 105 days of storage .This value decreased to1.60 x 103 (cfu/g) after 140 days. In fresh samples of P. pulmonarius the total fungal count was 2.5 x 102 (cfu/g) and increased to 1.80 x 103 (cfu/g) in the stored samples of P. pulmonarius after 140 days. There were no aflatoxin detection in fresh samples of P. ostreatus but very low level of AFB1 (0.04^g/kg) was detected in fresh sporophores of P. pulmonarius .Stored samples (35 day old) of P. ostreatus had AFB1 of 1.12^g/kg which increased to 3.5^g/kg after 140 days. Also, AFB2 had initial value of 0.24^g/kg which also increased to 2.28^g/kg at the end of storage. AFG2 was detected at very low concentration (0.08^g/kg) in P.ostreatus after 35days.This value significantly increased to 0.23^g/kg after 140 days of storage Likewise, the stored fruitbodies of P.pulmonarius had appreciable AFB1 level increasing from 1.93^g/kg to 4.21^g/kg.Similar trends were observed for the stored carpophores of P.pulmonarius for AFB2 ,AFG1 and AFG2.The significance of these findings were discussed