The effect of temperature-controlled pile-fermentation on the flavor quality of primary dark tea

The pile-fermentation temperature significantly influences the quality of dark tea. The study compared traditional pile-fermentation of dark tea with temperature-controlled pile-fermentation at 45 °C to improve quality. Sensory evaluation , untargeted metabolomics , and Illumina MiSeq sequencing were employed to assess the effects. Results indicated that temperature-controlled fermentation at 45 °C produced a mellower taste and enhanced overall flavor, while also altering the abundance of key microorganisms and accelerating the formation of flavor compounds. Compared with traditional pile-fermentation, the total amount of tea polyphenols and flavonoids decreased faster, and phenolic acids and organic acids showed a decreasing trend. In particular, 4-p-coumaroylquinic acid decreased significantly in the late stage of temperature-controlled pile-fermentation. A variety of factors combine to improve the dark tea flavor. The predominant bacterial genus identified was Klebsiella , while the primary fungal genera included Cladosporium , Wallemia , and Aspergillus . These results suggest that temperature-controlled pile-fermentation not only improves the quality of primary dark tea but also increases the efficiency of the fermentation process.