Comparative metabolomics investigation of white maize mahewu: Understanding biochemical transformations induced by traditional cereal-based starters

This study employs a mass spectrometry-based untargeted metabolomics approach to explore the biochemical changes in white maize-based fermented mahewu using diverse inocula. Fermentation was conducted with wheat, sorghum malt, millet malt, and malted white maize (MWM) inocula, and analysed using gas chromatography time of flight high-resolution mass spectrometry (GC-TOF-HRMS)-based untargeted metabolomics method. Mahewu samples prepared with the different inocula contained metabolites such as phenols, cyclic compounds, amines, vitamins, amides, esters, ketones, benzenes, fatty acid ethyl esters, and fatty acid methyl esters, which were distinct from those found in raw white maize flour. Principal component (PC) analysis revealed clear differentiation of mahewu and its inocula along PC1 and PC2. Additionally, orthogonal partial least squares discriminant analysis highlighted significant (p ≤ .05) metabolites that contributed to variations amongst the samples. White maize mahewu produced using millet malt (WMMM), and malted white maize (WMWM) contained significant levels of phenols, esters, FAME and potential health-promoting metabolites such as squalene, γ-sitosterol, α-tocopherol, and γ-tocopherol. The findings suggest that the choice of inoculum significantly influences the nutritional and biochemical characteristics of fermented mahewu, making it a functional food with potential health benefits for communities with limited dietary diversity.