Metagenomics and volatile metabolomics reveal microbial succession and its correlations with fruity flavor volatile compounds during Mianhua industrial processing

Mianhua, a traditional fermentation-type staple food popular in northern China, undergoes dynamic microbial and volatile compound changes during industrial processing. 848 volatile compounds were identified using volatile metabolomics dominated by esters (18.51 %), notably hexanoic acid ethyl ester and octanoic acid ethyl ester, which confer fruity flavors. Metagenomics analysis revealed <i>Proteus</i> (25.93 %), <i>Fructilactobacillus</i> (16.63 %), <i>Lactobacillus</i> (10.16 %) and <i>Companilactobacillus</i> (7.14 %) as dominant genera. Mixing with traditional starters was critical for flavor development, driven by microbial succession and synergistic interactions between <i>Lactobacillaceae</i> (e.g., <i>Fructilactobacillus sanfranciscensis</i> and <i>Lactobacillus helveticus</i>) and <i>Kazachstania</i> during fermentation. Notably, <i>F. sanfranciscensis</i> and <i>L. helveticus</i> were significantly correlated with the formation of key esters with fruity characteristics, elucidating their roles in substrate conversion via carbohydrate metabolism and the esterification pathways. This study clarifies the microbial contributions to fruity flavor and provides insights into volatile-microbiota correlations, laying a foundation for future flavor-oriented research and industrial applications of microbiota regulation in Mianhua production.