A Study on the Analysis of Microbial Community Characteristics and the Regulation of Safety and Flavor Composition in Homemade Fermented Chili Peppers via Ultrasound-Assisted Fermentation.

To address inconsistent quality, monotonous flavor, and nitrite residues in fermented chili, this study established an integrated quality-improvement system. High-throughput sequencing showed significant differences in the microbial community structure of peppers from different origins, yet common functional microorganisms (e.g., Lactobacillus plantarum and Pediococcus pentosaceus) could be screened. The optimal initial starter ratio (L. plantarum: L. pentosus: P. pentosaceus = 3:2:1) and fermentation parameters (salt 6.30%, glucose 1.5%, inoculum 5%, and 31.5°C) were determined by combinatorial screening and response surface methodology. Ultrasound-assisted fermentation was introduced to improve process efficiency; 60 W ultrasound significantly increased total acidity (29.61% higher than the control) and reduced nitrite by 10.42% (p < 0.05). Headspace gas chromatography-ion mobility spectrometry analysis identified 72 volatile compounds, including 12 esters, 9 alcohols, 8 terpenes, and 8 heterocyclic compounds. In addition, core characteristic volatile aroma compounds with Variability Importance in Projections values greater than 1 were screened; among them, 3-octanol, 4-methyl pentanol, and dipropyl disulfide were identified as key biomarkers for distinguishing between different treatment groups. Ultrasound treatment promoted the acid-catalyzed esterification by disrupting pepper cell walls to release precursors and activate metabolic enzymes, thereby enriching key flavor compounds such as methyl octanoate and 2,3-dimethylpyrazine. This study provides a theoretical basis and technical support for the industrialization of high-quality fermented chili peppers.