Untargeted flavoromics and correlation analysis reveal microbial interactions driving flavor in LAB co-fermented...

Lactic acid bacteria (LAB) co-fermentation has been increasingly recognized as an effective approach to improve the sensory quality of food products. In this study, a novel starter composed of Lacticaseibacillus rhamnosus (L. rhamnosus), Lactiplantibacillus plantarum (L. plantarum), and Lactobacillus helveticus (L. helveticus) was innovatively applied in co-fermentation of Beita juice, imparting distinctive flavor to the final product. The dynamic changes of key flavor substances, including organic acids (OAs), free amino acids (FAAs), and volatile flavor compounds (VFCs) during fermentation were systematically elucidated. Interaction-network and redundancy analysis (RDA) clearly demonstrated the synergistic effects of the three LAB strains on shaping the flavor profile of the final product, particularly contributing to the formation of mild acidity, umami taste, and enriched fruity-floral aroma. Untargeted metabolomics revealed a prospective impact of LAB co-fermentation on the metabolic profile of Beita juice, resulting in 4 significant differential metabolites including diacetyl, malate, l- (+)-lactic acid, and dl-malic acid out of 278 differential metabolites, consistency to the results of flavor substances analysis. And pathway enrichment analysis further confirmed that pathways associated with energy metabolism (e.g., carbohydrate metabolism) and the biosynthesis of key flavor precursors (particularly amino acid and organic acid metabolism) were significantly enriched during co-fermentation. This study provides critical insights into the biochemical mechanisms by which LAB co-fermentation enhances flavor characteristics, offering a scientific basis for targeted flavor modulation in fermented foods production.