Impact of fermentation regime and metabolically defined LAB consortia on sourdough bread nutritional and volatile composition

This study investigated whether a metabolically characterized lactic acid bacteria consortium could be effectively applied in a propagated Type IV sourdough system and how it compared with conventional sourdough starters under different fermentation regimes. Six breads produced by Type II and propagated sourdough processes, with or without bacterial protease, were compared with baker's yeast bread. Despite the shorter fermentation time, breads made with the defined consortium showed in vitro protein digestibility, predicted glycemic index, amino acid composition, and protein quality indices within the range of conventional sourdough breads. Volatile profiling revealed a shared sourdough-associated pattern dominated by organic acids and unsaturated alcohols, while also indicating a distinct Type IV profile linked to relatively greater contributions of acetic acid, (E)-2-hexenol, (E,E)-2,4-decadien-1-ol, and 1-octen-3-ol. Multivariate integration further showed that the defined consortium promoted a more acidification-associated and compositionally differentiated bread phenotype. • Defined LAB consortium applied in propagated Type IV sourdough. • Consortium-based fermentation enhanced protein digestibility. • Protein quality indices improved in consortium-fermented breads. • Nutritional indices preserved under propagated fermentation. • Integrated profiling resolved fermentation-driven volatilome patterns.