Effects of tangerine peel flavonoids on flavor compounds and microbial communities in cigar tobacco fermentation: insights from ion migration chromatography and microbiomics

IntroductionIt is reported that addition of tangerine peel extract (flavonoids) can significantly improve the quality and flavor of tobacco leaves during fermentation. Nobiletin, tangeretin and hesperidin are the predominant flavonoids present in tangerine peel. However, their effects on the fermentation process of cigar tobacco leaves (CTL) have not yet been elucidated.MethodsThree major tangerine peel flavonoids, hesperidin (CPG), nobiletin (CCPS) and tangeretin (JPS), were applied during the fermentation of CTL) to evaluate their effects on fermentation outcomes. Gas chromatography–ion mobility spectrometry (GC-IMS) and microbiome analysis based on 16S rRNA and internal transcribed spacer sequencing were employed to characterize volatile flavor compounds and microbial community dynamics during the 30 days of fermentation.ResultsA total of 157 volatile compounds were identified in CTL in this study. All tangerine peel flavonoid treatments improved the flavor quality of tobacco leaves by modulating the microbial community. The CPG group was enriched in esters and acids (e.g., n-amyl formate and propyl acetate), contributing to fruity aroma, with high relative abundances of Firmicutes and Staphylococcus, and a slight increase in Bacillus. The CCPS group accumulated abundant ketones (e.g., 3-methyl-2-cyclopenten-1-one, 3-pentanone, and 2-hydroxy-2-methyl-4-pentanone), providing caramel-like sweetness and enhancing the smoke body, while the enrichment of Sphingomonas, Rhizobium and other genera elevated bacterial diversity. The JPS group formed characteristic volatile compounds showed the highest fungal richness among all treatments. The mixed flavonoid (HHHT) group exhibited the highest abundance of Firmicutes and Staphylococcus, the lowest proportion of Proteobacteria, nearly undetectable harmful microorganisms, and the lowest microbial diversity. All treatment groups shared certain microbial trends, but distinct microbial profiles were observed among the CPG, CCPS, JPS, and HHHT groups, with significant correlations between key microorganisms and volatile flavor compoundsDiscussionIn this study, the influence of tangerine peel flavonoids on CTL flavor quality and microbial community was systematically analyzed. These findings demonstrated that tangerine peel flavonoids enhanced flavor of CTL by modulating microbial communities during fermentation, and this provides new insights into CTL processing.