Mycotoxins and surface and internal fungi of maize from Ethiopia

Abstract

Invasion of maize grain by fungi leads to losses in quantity and quality but also to contamination by mycotoxins, fungal metabolites, which are harmful to human and animal health. The problem of mycotoxins is higher in developing countries because of poorly managed environmental factors and due to the gap in supply and demand of food that forces people to consume what they might have otherwise rejected. The objective of this study was to determine the fungi and major mycotoxins that are naturally occurring in maize from Ethiopia where little information existed so far. Maize grain samples of 2004/2005 harvest were collected from small scale farmers′ storage in Adama, Ambo and Dire Dawa representing three agroecological zones of Ethiopia. Surface and internal fungi of samples were determined employing dilution plate method on DG-18 agar. Samples were also analyzed for aflatoxins (AFT) and fumonisins (FUM) using enzyme linked immunosorbent assay (ELISA), and for deoxynivalenol (DON) and nivalenol (NIV) using high performance liquid chromatography (HPLC). Species of Aspergillus, Fusarium and Penicillium occurred in 94%, 76.5% and 64% of the samples, respectively. Fusarium verticillioides and Aspergillus glaucus were among the dominant species. A. flavus was less frequent. The mean levels of total fungal density ranged from 2.9x10 3 cfu g -1 in maize samples from Dire Dawa, 1.9x10 4 cfug -1 for samples from Adama to 3.8x10 5 cfu g -1 for samples from Ambo. Aflatoxins were detected in 88% of the samples at 27 μg kg -1 in one sample and less than 5 μg kg -1 in others. Fumonisins occurred in two samples from Dire Dawa at 700 and 2400 μg kg -1 , and at 300 μg kg -1 in one sample each from Adama and Ambo. Five samples contained DON at 50 - 700 μg kg -1 . NIV was detected at 50, 130 and 210 μg kg -1 . The mycotoxins analyzed played a minor role in the contamination of maize of 2004/05 harvest in Ethiopia. Further monitoring of mycotoxins in maize from different regions of the country is justified in order to conclusively determine the actual risks from mycotoxins and possibly low mycotoxin-risk maize production areas.