Seasonal and processing-driven succession of microbial communities and quality formation in black tea

This study integrated 16S rRNA/ITS amplicon sequencing, HS-SPME-GC-MS, physicochemical assays, electronic sensory analysis and PICRUSt2 functional prediction to systematically investigate microbial succession, quality dynamics and their interactions during summer and autumn black tea processing. Microbial richness was significantly enhanced by processing, with seasonal variation exerting a stronger impact on community structure than processing. Thirty key aroma compounds with odor activity values (OAV) ≥ 1 were identified, including phenylacetaldehyde and methyl salicylate. Catechins and tea polyphenols decreased markedly during fermentation, and seasonal differences affected amino acids and polyphenol contents. Electronic tongue data indicated that black tea processing increased sourness and reduced umami, and autumn teas exhibited higher sourness than summer teas. Acidovorax (bacterium) and Hannaella (fungus) were identified as the most significant season-discriminating biomarkers. Hannaella showed significant positive correlations with floral compounds (phenylacetaldehyde, geraniol). Variovorax exhibited strong positive correlations with multiple beneficial aromas, whereas Pantoea was negatively correlated with undesirable odorants. Functional enzyme prediction indicated greater intervention potential of bacteria than fungi. From a microbe–metabolite linkage perspective, this study elucidates how seasonal variation drives quality differences in summer and autumn black teas, offering a theoretical basis for targeted process control and screening of functional microbes.