Abstract: This study aimed to explore the key chemical components that can affect the brightness of Congou black tea infusions. Firstly, 26 Congou black tea infusions were classified into three groups (high-brightness, mid-brightness and dark) based on the brightness evaluated by a professional sensory panel. Then, 24 components in tea infusions were quantitatively analyzed, and the small molecular compounds significantly related to the brightness of tea infusions were selected by means of statistical analysis. Finally, the tea infusions were fractionated by ultrafiltration and the macromolecular fractions affecting the brightness of tea infusions were determined and further validated by reconstitution and addition experiments. The results of multivariate analysis and one-way analysis of variance (ANOVA) showed that theaflavin-3-gallate (TF-3-G), gallocatechingallate (GCG) and caffeine (CAF) were significantly increased in tea infusions with high brightness, while gallocatechin (GC) was significantly decreased. Moreover, it was found that the macromolecular fraction greater than molecular mass cut-off (MMCO) of 100 kDa negatively affected the formation of bright tea infusions. The results of this study will be of theoretical significance for guiding the quality control and directional processing of Congou black tea in the future.

Key words: Congou black tea; brightness of tea infusions; factors; molecular mass cut-off