Multidimensional correlation analysis based on PCA/PLS-DA revealed the dual role of Lacticaseibacillus helveticus KLDS1.8701 in flavor synthesis and microbiota construction in Dongbei Suancai

• Flavoring substances in the fermentation process of Dongbei Suancai; • Correlation of flavor substances with bacterial diversity; • Improvement of flavor by inoculation with L. helveticus KLDS 1.8701 fermentation. Suancai is a traditional fermented cabbage popular in the Dongbei region of China. This study investigated flavor enhancement and modulation of microbial communities in Dongbei Suancai through the synergistic application of Lacticaseibacillus helveticus KLDS1.8701 and conventional direct-pitch fermentation. Electronic tongue analysis and free amino acid profiling revealed that the fermentation supplemented with L. helveticus significantly enhanced sensory richness and fresh sweetness compared to natural fermentation and traditional starter methods. Gas Chromatography-Ion Mobility Spectrometry (GC-IMS) and Gas Chromatography-Mass Spectrometry (GC-MS) detected 106 volatile compounds across three fermentation techniques: natural fermentation, fermentation with the addition of a direct-pitch fermenter, and co-fermentation with a direct-pitch fermenter and L.helveticus KLDS1.8701. Fermentation with L. helveticus and the direct-pitch fermenter produced the most complex flavor profile, increasing the diversity of esters, ketones, aldehydes, alcohols, olefins, and acids. Based on statistical analysis, it was shown that this fermentation was significantly different from the other fermentation groups, in which the esters that contributed most critically to flavor were not only all screened as key markers (VIP >1), but also their relative concentrations were significantly higher than those of the control group. High-throughput sequencing revealed that the dominant phyla across all three fermentation approaches were Firmicutes (61.2%-77.3%) and Proteobacteria (20.3%-36.8%). Notably, L. helveticus optimized microbial diversity, reducing the abundance of Proteobacteria to the lowest levels in fermented samples (20.3%), as this phylum is often associated with food spoilage. Strong positive correlations were observed between Lactobacillus proliferation and the biosynthesis of critical flavor compounds, particularly esters and acids ( p <0.05). These findings demonstrate the dual functionality of L. helveticus KLDS1.8701 in flavor modulation through directed synthesis of volatile substances and microbiome engineering via competitive exclusion. The introduction of this strain has opened up an innovative path for the improvement of the quality and functional development of the traditional Dongbei Suancai.