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

Abstract

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.