CO2-modified atmosphere improves the flavor quality of low-salt Xuecai by regulating microbial communities and metabolic functions.

Low-salt pickled vegetables are often limited by their poor flavor and the accumulation of biogenic amines (BAs). In the present study, the effects of CO2-modified atmosphere (CMA) technology on the dynamics of flavor compounds, microbial communities, and metabolic functions in low-salt Xuecai during pickling were investigated. In comparison with low-salt pickling under natural air conditions, a CMA effectively prevented excessive acidification, enriched volatile metabolites (e.g., isothiocyanates, alcohols, and esters), and minimized the accumulation of bitter-tasting amino acids, resulting in pickled vegetables with excellent flavor quality. Moreover, a CMA significantly inhibited the formation of BAs compared to low-salt natural pickling (P < 0.05; 46.71 vs. 114.29 mg/kg after 90 days of pickling), thereby enhancing the safety of low-salt Xuecai. In addition, metagenomic analysis showed that using a CMA for low-salt Xuecai production inhibited halophilic and spoilage microorganisms while enriching Lactobacillus-related populations. Metabolic pathway analysis revealed that the expression levels of the tricarboxylic acid cycle, amino acid metabolism, and genes encoding enzymes (i.e., amino acid decarboxylases, amine deiminases, and amine synthases) related to BA production were lower under a CMA. This, in turn, improved the flavor quality and inhibited the generation of BAs in low-salt Xuecai. Our study offers an alternative method for developing low-salt fermented foods.