Microbial succession and metabolic mechanisms driving flavor evolution in Northeast Chinese dajiang: a comprehensive review integrating insights from East Asian fermented soybean pastes

This review systematically explores the spatiotemporal microbial succession and flavor evolution during the fermentation of northeast Chinese soybean paste (dajiang), with a focus on the jiangpei (solid-state starter) and jianglao (brine fermentation) stages. By integrating metagenomic, metabolomic, and sensory data, this review synthesizes evidence linking microbial community dynamics—featuring Lactobacillus spp., Zygosaccharomyces rouxii, and Aspergillus oryzae—to the biosynthesis of key flavor compounds. These include umami amino acids (e.g., glutamic acid, 1.5–2.0 g/kg), fruity esters (e.g., ethyl acetate, 124.67 μg/kg), and phenolic antioxidants. Cross-feeding interactions (e.g., yeast utilization of lactic acid for ester synthesis) and environmental stressors (12%–18% NaCl, 25 °C–30 °C) are shown to enhance flavor complexity by modulating metabolic pathways like amino acid degradation and lipid β-oxidation. Unlike prior studies focusing on fragmented fermentation stages, this review systematically addresses the full fermentation continuum, highlighting how aerobic-to-anaerobic transitions drive functional metabolite accumulation. The review concludes by outlining a roadmap to modernize dajiang production through standardized quality control, precision flavor modulation, and traditional process optimization, enabled by culturomics/MAGs, multi-omics integration, and AI-assisted fermentation monitoring and control.