Microbial succession and flavor compound dynamics during the spontaneous fermentation of baby mustard (Brassica juncea var. gemmifera).

Abstract

Baby mustard (Brassica juncea var. gemmifera) is a popular cruciferous vegetable in Southwest China, yet little information is available on its spontaneous fermentation. At the end of fermentation, titratable acidity and lactic acid bacteria counts reached 4.26 g/kg and 1.4 × 108 CFU/mL. Lactic, oxalic, malic and acetic acids dominated taste-active components. A total of 68 volatile constituents were characterized, including 13 nitrides, 11 heterocyclics, 8 sulfides, 8 isothiocyanates, 5 ketones, 3 esters, 3 alcohols, 3 aldehydes, 2 unsaturated hydrocarbons, 1 phenolic compound, and 11 others. Among them, 28 volatiles were differential compounds, with butane, 2-isothiocyanato- and dimethyl trisulfide as key aroma-active markers. Microbial community structure changed markedly across fermentation stages. Leuconostoc citreum functioned as a core-hub microorganism within the microbial co-occurrence network, while Lactiplantibacillus argentoratensis and Latilactobacillus sakei represented core microbes driving flavor formation. These findings provide a theoretical reference for optimizing fermented-vegetable production and improving product quality.