Detection of Aflatoxigenic Moulds and Aflatoxins in Maize and Millet's Grains Marketed in Zaria Metropolis

Abstract

Aims: The present study was aimed at detecting of aflatoxigenic moulds and aflatoxins in maize and millet grains commonly marketed in Zaria Metropolis. Study Design: The study was a laboratory-based research aimed at Detecting aflatoxigenic moulds and aflatoxins in the grains samples marketed in Zaria Metropolis Place and Duration of Study: The samples were purchased from six different markets in Zaria metropolis between July and August 2016. Methodology: Representative samples were subjected to proximate analysis and cultural isolation by grounding of each sample of (maize and millet) and separately added to 90 ml of sterile distilled water to form a stock suspension. An aliquot of 0.5 ml was spread on already prepared sweet potato yeast extract agar plate and the inoculated plates were incubated at room temperature. The suspected aflatoxigenic moulds were sub cultured and incubated at room temperature to obtain a pure culture and subjected to slide culture technique for microscopic identification of the moulds from the entire samples.  The main objective of this study was to detect aflatoxin-producing moulds in maize and millet grains commonly sold in Zaria metropolis markets. The isolates were then screened for aflatoxin production using desiccated coconut agar and viewed under UV light (365 nm). Enzyme-linked Immunosorbent Assay (ELISA) technique was used to determine total aflatoxin concentration of the samples. Results: The results revealed that the maize (Zea) and millet samples analyzed contain organic and inorganic nutrients that can support the growth of aflatoxigenic moulds and production of aflatoxin. Sixteen (25) isolates from the 60 samples were contaminated which account for 41.7%. The percentage of   A. flavus isolates in maize was 26.7% and that of A. parasiticus was 15%.In maize, the occurrence of A. flavus was 23.3% and A. parasiticus 13.3% and the millet had 30% A. flavus and 16.7% A. parasiticus. The isolates demonstrated ability in aflatoxin production by emitting very bright fluorescent colouration under UV light (365nm). Total aflatoxin concentration in maize sample obtained from Samaru Market was found to be 18.10 µg/Kg while millets obtained from Zaria recorded 52.0 µg/Kg. The contamination levels within the grains were found to be statistically significant (p value< 0.05) using analysis of variance (ANOVA) Conclusion: This study, therefore, revealed that the contamination level in millet samples analyzed calls for concern as it exceeded the standard limit set by NAFDAC and SON.