Comparative metabolomic assessment of bioconverted traditional and black wheat via the in vitro piglet digestion model

Colored wheat is gaining significant attention in the food and feed industry due to its components’ potential health benefits. As weaning piglets experience major discomfort in their early life, the quality and bioavailability of the feed nutrients become crucial for their survival. Fermentation of the feed aims to be a cheap and efficient stage of the feed production, as it is able to overcome major shortcomings of the cereals. The aim of this study was to investigate the differences in metabolites between traditional (variety “Herkus”) and black (variety “DS8558-1”) (DS) wheat cereals (both non-pre-treated and fermented with Lactiplantibacillus plantarum strain) using an in vitro swine digestion model with weaning piglets’ faecal microbiota. The following in vitro digestion and fermentation parameters were evaluated: free and total amino acids concentration in the digesta; total amino acids in the undigested residue and bioconverted/control wheat wholemeal substrate; short-chain fatty acids (SCFAs), volatile organic compounds (VOCs), free amino acids (FAAs), biogenic amines (BAs) and other small non-volatile metabolites in the in vitro fermentation samples. The in vitro digestibility and fermentability were significantly altered by bioconversion, while the substrate factor was significant only for the in vitro fermentability. The in vitro digestion of some of the non-essential and essential (valine, phenylalanine, leucine/isoleucine, histidine) AAs was significantly affected by both factors. Lysine digestibility was affected only by bioconversion. The bioconversion significantly affected the content of SCFAs, such as 2-methylpropanoic, butanoic, 3-methylbutanoic and pentanoic acids in in vitro fermentation (IVF) samples. The substrate was significant for all the analysed SCFAs, except propanoic and hexanoic acids. Benzenacetic, dihydrocinnamic and 4-hydroxyhydrocinnamic acids were significantly upregulated in DS IVF samples. P-cresol was upregulated in the bioconverted IVF samples. Both of the factors were significant for p-cresol concentrations in the IVF samples. The γ-aminobutyric acid (GABA) production in the IVF samples was significantly affected by both factors. Lactate concentrations in the IVF samples were affected only by the substrate factor. These results highlight the significance of bioconversion for the overall digestibility of wheat wholemeal substrates as well as changes in the production of biologically relevant metabolites for piglets.