Aflatoxin occurrence and molecular identification of fungi isolated from staples purchased: A case study

Foods, especially those with dual purposes such as staples and cash crops, have been considered important for mycotoxin control because as they provide human nourishment, these foods also support fungal growth and the accompanying aflatoxins produced are carcinogenic in nature. Dried melon, maize and groundnut seeds that form majority of African diets are, hereby, included in this study. Representative weight of staples was purchased from commercial vendors in the New Market of Obafemi Awolowo University, and screened for contaminating fungi and aflatoxins. In the melon seeds, Rhizomucor, Rhizopus and Aspergillus niger represented majority of contaminating fungi; Aspergillus niger and Aspergillus flavus in dried maize samples, while Aspergillus niger and Aspergillus parasiticus were most abundant in the groundnut seeds. The ITS-PCR method employed to determine the genetic variability among representative Aspergillus flavus-like isolates (MaF, Ma6, GrL, GrM) revealed 99.50%, 99.09%, 99.83% and 100.00% homology with Aspergillus flavus isolate LUOHE (MT645322.1). Preliminary aflatoxin screening of selected strains was carried out on the Coconut Agar Medium agar and aflatoxin presence in the samples was confirmed using the thin-layer chromatography and densitometry methods. The groundnut and maize samples purchased from Vendor 1 contained the highest levels of aflatoxin B1 (233 and 25 μg/kg) and B2 (17 and 51 μg/kg) respectively amongst others whereas, toxin levels in melon seeds were below detectable levels. This study gave a valuable insight into the food quality of staples supplied to New Market, Obafemi Awolowo University, Ile–Ife at the time of sampling, and established the importance of continual surveillance of food consumed by populace especially within the University community.