Multi-Omics Analysis Elucidates Flavor Evolution and Bioformation Mechanisms of Key Aroma Compounds in Malty-Aroma Yogurt

Flavor enrichment in commercial yogurts commonly relies on exogenous flavoring agents, failing to meet consumer demand for clean-label products with natural ingredients. This study developed a starter culture for malty-aroma yogurt by combining Lactococcus lactis BL-19 with a commercial yogurt starter culture. Evaluation by eleven trained sensory assessors indicated that malty-aroma yogurt exhibited a distinctive sensory profile compared with four commercially available plain yogurts. Time-series flavoromics identified 13 key aroma compounds and revealed the 3 h as the key time node of flavor evolution during fermentation. Furthermore, time-series metabolomics analysis revealed metabolic transitions from nutrient adaptation to active biosynthesis at 3 h, significantly increasing the odor-active values of the key aroma compounds. Moreover, correlation network analyses revealed potential metabolic precursors and metabolic bypass associated with the production of key aroma compounds and highlighted the valine, leucine and isoleucine biosynthesis pathway as central to malty-aroma formation. This study elucidates the evolution of flavor compounds and the underlying bioformation mechanisms of malty-aroma yogurts, offering insights for the precise flavor modulation of fermented dairy products.