Microbial ecology and metabolite dynamics of backslopped sourdough productions using high-arabinoxylan wheat flour

To increase the intake of dietary fibre (DF) among Western consumers, the production of fibre-rich bakery goods offers a promising option. In wheat, the main fibre fraction consists of arabinoxylans (AX), which is an obvious target for enrichment through breeding. However, increasing the concentration of AX in wheat flour may have implications for the microbial consortia that are involved in cereal processing, in particular in the case of sourdough productions and the breads thereof. Thus, the microbial ecology and associated substrate and metabolite dynamics of seven spontaneously backslopped sourdough productions based on high-AX flour from experimental wheat lines were assessed over two independent trials. For the sourdough productions of the first trial, a blend of flour of crosses of the wheat cultivars Yumai-34 and Valoris was used, whereas for those of the second trial, a blend of flour of crosses from Yumai-34 and Ukrainka were employed. Specific crosses were selected based on the highest concentrations of total AX (TOT-AX) and water-extractable AX (WE-AX). During the second trial, a control was included, replacing 5 % of the high-AX flour blend with industrially produced flour (WheatC). After ten backslopping steps, different species of lactic acid bacteria were prevalent. Lactococcus lactis was prevalent in the first trial. Limosilactobacillus fermentum was prevalent in the second trial. Pediococcus pentosaceus and the yeast Wickerhamomyces anomalus were prevalent when a industrially produced flour was used as control, showcasing the microbial quality of laboratory- vs. industrially-milled flours. Fermentation caused the concentration of WE-AX in all cases to increase as a result of the solubilization of part of the TOT-AX that earlier were water-unextractable, indicating an impact of the acidification of the flour-water mixture on enzymatic activity. The WE-AX concentration increased from 1.05 ± 0.02% to 1.34 ± 0.06% during the first trial, and from 0.72 ± 0.02% to 2.04 ± 0.08%, during the second trial. The TOT-AX remained constant, suggesting an impact of the acidification of the flour-water mixture in the WE-AX. The ratio of arabinose over xylose decreased after sourdough fermentation, pointing to the release of free arabinose and its possible consumption by sourdough microorganisms. Finally, various metabolites could be linked to the presence of specific microorganisms. The presence of Limosilactobacillus fermentum paralleled the production of mannitol, glycerol, erythritol, and ethyl lactate, among others, whereas that of W. anomalus was associated with the production of arabitol and ethyl esters.