Quantification of multi-mycotoxin in cereals (maize, maize porridge, sorghum and wheat) from Limpopo province of South Africa

ABSTRACT

Mycotoxins are secondary metabolites that are produced by filamentous mycotoxigenic fungi belonging to the Alternaria, Aspergillus, Fusarium and Penicillium genera amongst others. Multi-class mycotoxins were extracted from 55 cereal samples and analysed using liquid chromatography-tandem mass spectrometry. The adopted extraction method for maize, maize porridge, sorghum and wheat was comprehensively validated. This method was further tested to determine the natural occurrence of mycotoxins in foodstuffs. Twelve (12) out of 22 mycotoxins were detected in maize, maize porridge, sorghum and wheat, including α-zearalenol (α-ZEL) (89%), fumonisin B₃ (FB₃) (84%), fumonisin B₁ (FB₁) (80%), tenuazonic acid (TeA) (78%), ochratoxin B (42%), deoxynivalenol (DON) (12%), ochratoxin A (11%), 3-acetyldeoxynivalenol (7%), sterigmatocystin (STG) (6%), 15-acetyldeoxynivalenol (2%), cyclopiazonic acid (CPA) (2%) and aflatoxin B₂ (2%). The data revealed high incidence rate of α-ZEL (range: 6.5–70.5 µg kg⁻¹) in all matrices. Maize samples had high mycotoxin co-occurrence compared to other matrices. All recovered mycotoxins in food commodities were within the maximum regulatory limits, with the exception of fumonisins (FB₁ and FB₃) exceeded the South African and European Commission regulation, and the highest concentration was 2153 µg kg⁻¹ in maize. It is essential to monitor the level of emerging mycotoxins in food commodities from rural areas as trace amount of CPA (< limit of quantification), STG (range: 0.30–0.74 µg kg⁻¹) were detected and high concentration of TeA (292.7 µg kg⁻¹) was detected in sorghum. The occurrence of these mycotoxins further encourages frequent analyses, their co-occurrence in the samples poses a significant threat to public health and more emphasis should thus be placed on reducing the contamination levels of these toxins in staples.

KEYWORDS:

• Mycotoxins
• liquid chromatography- mass spectroscopy
• method validation
• Limpopo Province
• cereals

Acknowledgments

The authors express their gratitude to all participants in Mohlarekoma village in Limpopo Province who assisted with samples for analysis and the Faculty of Science of the University of Johannesburg for funding this study. Thanks to Department of Biotechnology and Food Technology for support and utilization of resources. We are thankful to Sharon Maphala, Uche-Okereafor Godwin and Orphelie Lootens for their assistance during sampling. Greatest gratitude to National Research Foundation (NRF) for sponsoring this study and Ms Shandry Tebele received DST-NRF Innovation Master’s Scholarship (Ref: SFH180515330219). Special thanks to Riaan Meyer and Darryl Harris from Shimadzu, South Africa for their technical assistance with the LC-MS/MS instrument used. We are also thankful for technical support from all colleagues in our team and reviewers of this paper.

Declaration of interest statement

The authors declare that there is no conflict of interest.