Constituent-Taste Relationship of Kuding Tea Fermented by Aspergillus neoniger and Aspergillus cristatus: Unveiling taste Characteristics through Untargeted Metabolomics

Kuding tea (KDT), known for its medicinal and edible attributes, currently faces limited application due to its unfavorable taste. Thus, we aimed to improve KDT flavor using fungal fermentation and elucidate the mechanism of flavor change through the constituent-taste relationship. In this study, an electronic tongue was utilized to assess the flavor profiles of unfermented and fermented teas by Aspergillus neoniger (AN) and Aspergillus cristatus (AC). A constituent-taste relationship method combining untargeted metabolomics and taste sensors was employed to analyze the taste-related differential metabolites. The analysis of metabolic pathways further elucidated the potential taste-altering mechanisms. Fermentation of both AN and AC led to changes in the umami and sweetness of KDT. Additionally, AN fermentation impacted bitterness and sourness, while AC fermentation influenced saltiness. Based on the strategy of constituent-taste relationship, 31 and 30 metabolites predominantly including lipids, phenolic acids, flavonoids, amino acids and phenolic glycosides were discovered to be significantly correlated with the flavor characteristics of KDT. During fermentation, AN and AC participated in 5 and 4 metabolic pathways, respectively, showing distinct regulatory mechanisms in altering KDT flavor. AN led to pronounced deglycosylation of glycosides, while AC impacted the degradation of phenolic acids and lipids. Together, this study advances the understanding of metabolic changes in fermented KDT and provides valuable insights into the enhancement of flavor characteristics.