Integration of cross-correlation analysis and untargeted flavoromics reveals unique flavor formation of lactic acid bacteria co-fermented oat beverage

Lactic acid bacteria (LAB) fermentation has the potential to be an effective way to improve the flavor of foods. In this study, Lactococcus lactis (L. lactis), Lactobacillus plantarum (L. plantarum) and Lactobacillus rhamnosus (L. rhamnosus) co-fermented oat beverage was prepared and both the molecular and biochemical basis for its unique flavor formation were investigated by using cross-correlation analysis combined with untargeted flavoromics. Results showed that via co-fermentation main flavor substances like organic acids, free amino acids (FAAs) and volatile flavor compounds (VFCs) could be regulated dynamically. Interaction network analysis and redundancy analysis (RDA) convinced the crucial roles of three bacteria in shaping the overall flavor profile of co-fermented beverage, especially for the formation of soft sourness, sweetness, and freshness. According to untargeted metabolomics, it could be concluded that co-fermentation regulated significant differential metabolites (56 in total) unique to LAB co-fermented oat beverage such as benzoic acid, DL-arginine, uridine, and citrate. KEGG pathway enrichment analysis further predicted the viable formation pathways of key flavor compounds obtained by RDA such as organic acids (malate, citrate, et al.), FAAs (aspartate, glutamate, et al.) and VFCs (2,3-butanedione, 1-nonanol, et al.). This work demonstrates the positive flavor contribution of LAB co-fermentation, providing valuable reference for subsequent multi-omics studies on fermented oat products.