Determination of Aflatoxin Concentrations in Cereals and Legumes Marketed in Zaria Metropolis, Kaduna State, Nigeria

Abstract

Aflatoxins are group of secondary fungal metabolites produced by Aspergillus species, such as Aspergillus flavus and Aspergillus parasiticus. The aflatoxin producing moulds can grow on cereals and legumes in the field, poorly dried harvested crops in storage, processed food, and feed products. The study was carried out with the aim to determine the level of aflatoxin contamination of cereals grain and legumes in Zaria metropolis, Kaduna State, Nigeria. Ninety (90) samples were collected, which comprises of 18 samples each of millet, sorghum, maize, beans, and groundnuts respectively. The samples were subjected to proximate analysis. The grains were further subjected to cultural isolation and microscopic identification. The isolates were then screened for aflatoxin production ability with neutral red desiccated coconut agar and viewed under UV light (365nm). The remaining portions of the samples was grounded and extracted with 80% (v/v) methanol. The enzyme-linked Immunosorbent Assay (ELISA) technique was used in quantifying the total aflatoxin content of the samples. The results revealed that all the cereals and legumes analysed contain organic and inorganic nutrients that can support the growth of aflatoxigenic moulds and production of aflatoxins. Some major parameters such as carbohydrate content, crude protein, crude lipid, and ash contents were statistically significant (p < 0.05). Thirty-one (31) isolates from the 90 samples were confirmed to be A. flavus and seventeen (17) were A. Parasiticus, with percentage occurrence of 34.4% and 18.9% respectively. All the isolates were screened and demonstrated ability for aflatoxin production under UltraViolent light (390nm). The results also revealed a high concentration of aflatoxin (11.04 µg/kg) in millet and a low concentration in sorghum (1.07 µg/kg). The contamination levels within the grains were found to be statistically significant (p < 0.05). Aflatoxin contaminations also occurred in 48 samples out of the 90 samples analysed. The grains samples analysed were found to be contaminated with varying amounts of aflatoxins, which is harmful to humans and animals. Therefore, steps should be taken to ensure that grains are properly dried prior to storage. Keywords: aflatoxin, A. flavus, A. parasiticus, cereals, Enzyme-linked Immunosorbent Assay, legumes