Occurrence of mycoflora, their association and production of aflatoxin B1 in groundnuts

Abstract

Groundnut (Arachis hypogaea L.) is an important food crop in Africa which is a source of nutrients and income in rural areas of Zimbabwe. It is considered to be a crop highly susceptible to aflatoxin contamination. Accordingly, the objectives of this study were to understand the presence of mycoflora, their association and the level of ontamination by aflatoxins of groundnut from various markets in Zimbabwe. Thirty groundnut samples were purchased randomly from Bulawayo (Shashe and Main market), Gweru (Kudzanayi and Kombayi markets) and Harare (Mbare and Highfield markets). Identification of various fungi was determined using the cultural method on Czapek Dox Agar. Fungi belonging to genera Aspergillus, Mucor, Penicillium and Rhizopus were isolated and characterised from six groundnut markets. Rhizopus species was the most dominant and negatively associated with other fungi species which is attributed to differences in environmental requirements or competition. pergillus flavus, Aspergillus fumigatus, Aspergillus niger and Aspergillus parasiticus were identified in groundnut samples with A. flavus being the dominant and found in all markets. The range of AFB1 in groundnut samples analysed using a semi-quantitative immunochromatographic technique was within the safe limits for human consumption according to existing Zimbabwe (5 ppb) regulation. The presence of aflatoxigenic fungi (A. flavus and A. parasiticus) in groundnuts, however, means there is potential for aflatoxin production and fungal proliferation when conditions are favourable.