Revealing the influence of top-brewing and bottom-brewing methods on the flavor of green tea based on the interaction between EGCG and aroma compounds

The brewing process is a crucial step in determining the flavor profile of green tea infusions. However, the flavor differences arising from top-brewing and bottom-brewing methods remain poorly understood, and the underlying mechanisms are largely unexplored. In this study, GC-MS and sensory analysis were employed to investigate the flavor differences in Shucheng Little Cymbidium tea infusions under varying water temperatures and brewing methods. Subsequently, the variations in major polyphenolic compounds were analyzed, and the potential causes of flavor differences were explained from the perspective of the interactions between EGCG and key aroma compounds. Multivariate statistical analysis revealed that compounds such as geraniol, nonanal, and methyl salicylate serve as important markers for discriminating between different brewing conditions. Moreover, EGCG exhibited a significant binding effect with compounds such as geraniol and nonanal, driven by hydrogen bonding and hydrophobic interactions. This binding may regulate the transfer of aroma compounds from tea leaves to the infusion during brewing, thereby shaping distinct sensory characteristics. These findings provide a molecular-level rationale for empirical techniques in traditional tea art. More importantly, it inspires researchers to pay attention to the crucial role of the tea infusion matrix in determining flavor. • The flavor and polyphenols in tea infusion were different due to the top-brewing and bottom-brewing. • Compounds such as geraniol, nonanal, and methyl salicylate were important markers for distinguishing different brewing methods. • The combination and interaction of polyphenolic substances and aroma compounds affected the volatilization and release of aroma. • The interaction between aromas and polyphenols were influenced by the functional groups of aroma molecules.