Variation of Fungal Metabolites in Sorghum Malts Used to Prepare Namibian Traditional Fermented Beverages Omalodu and Otombo

Abstract

Sorghum malts, which are important ingredients in traditional fermented beverages, are commonly infected by mycotoxigenic fungi and mycotoxins may transfer into the beverages, risking consumers' health. Liquid chromatography⁻tandem mass spectrometry was used to determine variation of fungal metabolites in 81 sorghum malts processed for brewing of Namibian beverages, <i>otombo</i> (<i>n</i> = 45) and <i>omalodu</i> (<i>n</i> = 36). Co-occurrence of European Union (EU)-regulated mycotoxins, such as patulin, aflatoxins (B₁, B₂, and G₂), and fumonisins (B₁, B₂, and B₃) was detected in both malts with a prevalence range of 2⁻84%. Aflatoxin B₁ was quantified in <i>omalodu</i> (44%) and <i>otombo</i> malts (14%), with 20% of <i>omalodu</i> malts and 40% of <i>otombo</i> malts having levels above the EU allowable limit. Fumonisin B₁ was quantified in both <i>omalodu</i> (84%) and <i>otombo</i> (42%) malts. Emerging mycotoxins, aflatoxin precursors, and ergot alkaloids were quantified in both malts. Notably, 102 metabolites were quantified in both malts, with 96% in <i>omalodu</i> malts and 93% in <i>otombo</i> malts. An average of 48 metabolites were quantified in <i>otombo</i> malts while an average of 67 metabolites were quantified in <i>omalodu</i> malts. The study accentuates the need to monitor mycotoxins in sorghum malts intended for brewing and to determine their fate in the beverages.