Dynamic changes in the metabolite profile and taste characteristics of loose-leaf dark tea during solid-state fermentation by Eurotium cristatum
Mengxue Chen, Zhongqi Zu, Shanshan Shen, Tingting An, Haiwei Zhang, Hengqian Lu, Maoyin Fu, Yu Wen, Qi Chen, Xueling Gao, Xueling Gao
Abstract
Loose-leaf dark tea fermented by Eurotium cristatum has increasingly gained favor in the market due to its unique fungal aroma and soft mouthfeel . In this study, the dynamic changes in the metabolite profile and taste characteristics of loose-leaf dark tea were investigated. Ninety-two critical metabolites were identified during fermentation by ultraperformance liquid chromatography coupled with Q-Exactive Orbitrap tandem mass spectrometry (UPLC-Q-Exactive Orbitrap/MS). Among these metabolites, catechin derivatives were converted to numerous other metabolites, such as fuzhuanin A and teadenol A, by the metabolic activity of E. cristatum , which were significantly increased in the later stages of fermentation. Taste evaluation and targeted metabolomics demonstrated that the intensities of astringency , bitterness, umami and sourness of the tea infusions gradually weakened with declines in the contents of ester-catechins and amino acids , while the intensities of color, sweetness and stale taste gradually developed during fermentation with increases in the contents of theabrownins and tea polysaccharides . These results revealed the important contribution of E. cristatum to the formation of the compounds that impart the unique taste of loose-leaf dark tea and provide a chemical basis for quality control during dark tea processing.