Lactic acid bacteria-mediated transformation of black tea extract: Insights into metabolite profile and sensory characteristics

To improve the nutritional and sensory qualities of black tea extract, this study explores the potential of lactic acid bacteria (LAB) fermentation to enhance flavor and bioactive polyphenols through microbial metabolism and enzymatic transformation.Twenty-four LAB strains were screened for their growth, acid production, sugar consumption, and phenol metabolism. Three strains (LPL048, LPL043, LPL007) were identified as optimal for fermentation. These strains significantly increased the content and variety of volatile substances and enriched polyphenol content, with catechin, epicatechin, and epigallocatechin levels rising by 33%–73%, and phenolic acids (ferulic, caffeic, sinapic acids) increasing by 16%–75%. Quercetin levels rose by 9%–18%, and indole-3-lactic acid increased by 50%–119% post-fermentation. Fermentation enhanced the aftertaste of bitterness and astringency, enriched the flavor profile, and improved sensory complexity. This research provides a foundation for developing specialized LAB strains for black tea fermentation, potentially enhancing the health benefits and sensory experience of fermented tea products.