Dynamic Changes in Flavor-Related Compounds and Bacterial Community Structure During Sichuan Jiangrou Ripening

Ripening time is a major determinant of quality and flavor formation in traditional Sichuan fermented Jiangrou (JR). However, the changes in physicochemical properties, flavor compounds, and bacterial communities during JR ripening remain insufficiently understood. Therefore, this study aimed to characterize the dynamic changes in physicochemical properties, flavor-related compounds, and bacterial communities during JR ripening and to identify potential markers associated with different ripening stages. JR samples collected at eight ripening stages (0-35 days) were characterized using physicochemical measurements, electronic tongue analysis, free amino acid profiling, GC-MS, and 16S rRNA amplicon sequencing. The data were further analyzed using Spearman correlation analysis and interpretable machine learning. The results indicated that moisture content decreased from 74.60 to 45.87 g/100 g, whereas salt content increased to 3.67 g/100 g. Lipid oxidation progressively intensified, while superoxide dismutase activity and total free amino acids reached their highest levels around day 25. Total free amino acids increased from 31.85 to 313.98 mg/100 g before declining during late ripening. These temporal patterns suggest that days 20-25 represent a transition period under the conditions tested. Electronic tongue and volatile-profile analyses revealed pronounced stage-dependent changes in taste and aroma. Aldehydes accumulated prominently at day 25, whereas esters became predominant during late ripening. An XGBoost model built with aroma-active compounds correctly classified all samples in the current dataset. SHAP analysis identified heptanal, octanal, ethanol, methyl pentanoate, and 2-methylbutanal as the most influential candidate markers for differentiating ripening stages. Firmicutes remained the dominant bacterial phylum. At the genus level, the community shifted from the initial predominance of Brochothrix toward enrichment of Staphylococcus and Macrococcus. Spearman correlation analysis revealed that dehydration, salt accumulation, and lipid oxidation were associated with the dominant species and various volatile aldehydes, esters, and alcohols. Overall, these findings clarify the multidimensional succession of quality and flavor during JR ripening and provide a basis for monitoring the critical ripening period and standardizing production.