Postharvest and stored corn in Brazil: mycoflora interaction, abiotic factors and mycotoxin occurrence

The mycoflora of 130 samples of postharvest and stored corn was analysed throughout one year. The sample originated from Riberirão Preto, State of São Paulo, Brazil. The influences of abiotic factors (moisture content, relative humidity, temperature, rainfall) and mycotoxin occurrence were also verified. The isolation of the fungi was performed with Potato Dextrose Agar. Fungi were identified by using standard techniques. The determination of mycotoxins (aflatoxins, ochratoxin A, sterigmatocystin, zearalenone, deoxynivalenol and fumonisin B1) was carried out by thin-layer chromatography. The Fusarium spp. was the most dominant fungi (83.8%) followed by Penicillium spp. (55.3%), Aspergillus spp. (40.7%) and 11 other filamentous fungi. All of these were isolated from grains with moisture contents of 12.3-17.8%, an average temperature of 18.4-24.1 degrees C, a relative humidity between 64.0 and 97.5% and rainfall of up to 337 mm. With regard to the number of colony forming units (cfu), Fusarium spp. was the main contaminant, varying from 545 x 10(3) to 1.5 x 10(3). The Simple linear correlation analysis showed significant positive correlation of the Fusarium genus with moisture content of grains, and a significant negative correlation in relation to the minimum and medium temperatures, rainfall and relative humidity. The linear correlation of the Penicillium and Aspergillus genera with the abiotic factors was not significant. In the samples analysed only one contained aflatoxin B1.