Multidimensional Profiling of Chinese Sweet Tea (Lithocarpus litseifolius): Processing Methods Modulate Sensory Properties, Bioaccessibility and Prebiotic Potential via Gut Microbiota Regulation

This study systematically examines the effects of processing methods (green vs. black tea) and preparation techniques (brewing vs. decoction) on the flavor and functional composition of Chinese sweet tea ( Lithocarpus litseifolius ). Fermentation degree and extraction temperature were found to significantly influence polyphenol bioavailability, with green tea exhibiting the highest polyphenol and flavonoid contents (144.51 mg/g and 88.97 mg/g, respectively), while black tea showed an approximately 40% reduction in catechin levels due to oxidative polymerization. During in vitro simulated digestion, green tea maintained strong antioxidant activity despite its stronger bitter–astringent taste. Notably, in vitro fecal fermentation experiments demonstrated that sweet tea significantly promoted short-chain fatty acid (SCFA) production and modulated gut microbiota composition (with a 3.2-fold increase in acetate content in the black-tea decoction group). Black tea particularly enhanced beneficial genera (Roseburia and Coprococcus) after 24 h fermentation ( p < 0.05) and exhibited superior prebiotic properties. Principal coordinate analysis confirmed there were significant structural differences in microbial communities among the treatment groups. This study is the first to reveal that processing methods regulate the prebiotic efficacy of sweet tea by modulating the bioaccessibility of active compounds, providing a theoretical foundation for the development of functional sweet tea products.