The flavor of yogurt is primarily determined by its aroma-active compounds.This study aimed to track the physicochemical, microbiological, flavor changes, and metabolomic profiles of yogurt during fermentation (0, 60, 120, 180, and 240 min).When the pH dropped to 4.54 and the acidity rose to 72.8 °T, the fermentation was terminated.Volatilomics identified 13 volatile compounds that distinguish different fermentation stages.Concurrent sensomics analysis detected 13 aroma-active compounds.Integrating both data sets yielded 7 highly variable aroma-active compounds (with OAV >1 and VIP >1).Furthermore, untargeted metabolomics coupled with multivariate statistics identified 81 highly significant differential metabolites during fermentation.KEGG enrichment analysis of these metabolites revealed 10 pathways (p < 0.05).Correlation analysis revealed that the accumulation of aroma-active compounds, including acetic acid, hexanoic acid and 2,3-pentanedione, etc. is governed by hub metabolic pathways such as glyoxylate and dicarboxylate metabolism, the citrate (TCA) cycle, and alanine, aspartate and glutamate and pyruvate metabolism.Within this network, pivotal node metabolites, pyruvate, dihydrouracil, citrate, uracil, orotate, malate and isocitrate, were identified as hub metabolites potentially involved in volatile flavor formation.This work delineates the metabolic-network basis of fermentation flavor, providing defined engineering targets for the rational design of yogurt aroma.
Han et al. (Fri,) studied this question.