The role of microorganisms in the conversion of color class aroma precursors to aroma during air-curing of cigar tobacco leaves.

Introduction: Air-curing is a key process shaping cigar flavor quality. The mechanism underlying microbial-mediated color-class aroma precursor conversion remains unclear. This study explores their dynamic correlations during air-curing. Methods: Water content, color class aroma precursors (CCAP, e.g., chlorophyll a, chlorophyll b, β-carotene, etc.) and CCAP-derived aroma components in cigar tobacco leaves were determined during air-curing (AC). To explore the microbial drivers of these dynamic changes, high-throughput sequencing was used to analyze microbial communities across different AC stages. Furthermore, β-carotene-degrading microorganisms were isolated from the leaves using β-carotene-containing solid medium (β-CSM), and their degradation capacity was verified. Results: Most CCAP contents presented an overall downward trend, while amino acid levels increased initially before declining, and aroma components also changed. Moreover, the structures of bacterial and fungal communities varied in each key phase during the AC process. Partial least squares discriminant analysis identified four core functional microorganisms. Discussion: The future utilization of microorganisms for the targeted processing of cigar tobacco during production holds significant potential. These findings provide a strong theoretical and practical foundation for the development of high-quality raw materials for manufacturing cigars.