Pattern of Quality Changes and Its Correlation with Microbial Community Succession during Spontaneous Fermentation of Chili Pepper

To investigate the pattern of quality formation and its correlation with microbial community succession during the spontaneous fermentation of chili pepper, this study combined targeted metabolomics and high-throughput sequencing to analyze the changes in key quality indicators and microbial community structure in chili pepper after 0, 3, 10, 20, and 30 days of fermentation. The results showed that as fermentation progressed, pH decreased significantly, total acid content increased, and nitrite content initially increased and subsequently decreased, which remained within the safety range throughout the process. The 10-day fermented sample had the highest sensory score, exhibiting optimal aroma complexity and taste harmony. The content of total organic acids increased, with lactic acid gradually becoming the dominant organic acid. Aspartic acid was found to be the free amino acid that contributed most to the overall flavor. A total of 19 key aroma-active compounds (odor activity value > 1) were identified, the main ones being alcohols, esters, and aldehydes. Significant microbial community succession occurred, with Weissella being the dominant bacterial genus. In the early fermentation stage, the fungal community was dominated by Debaryomyces and Hanseniaspora, which were subsequently replaced by Pichia in the mid-to-late stages. Redundancy analysis (RDA) revealed that pH and total acid were key factors driving microbial community succession, and correlation analysis showed a significant positive association between Weissella and nerol synthesis. This study reveals the intrinsic relationship between microbial community succession and quality formation in spontaneously fermented chili pepper, providing a theoretical basis for the screening of dominant fermentation strains (such as Weissella) and the precision regulation of the fermentation process.