Dynamic changes of volatile and phenolic components during the whole manufacturing process of Wuyi Rock tea (Rougui)

Abstract

Wuyi Rock tea (WRT), a top-ranking oolong tea, possesses characteristic woody, floral, nutty flavor. WRT flavor is mainly formed during the manufacturing process. However, details regarding its formation process are not fully understood yet. In this study, the dynamics of volatile and phenolic components over the whole manufacturing process of WRT were investigated. During withering, despite minor changes in volatile and phenolic components, the central vacuole shrunk remarkably, which reduced the cell mechanical performance and facilitated the subsequent enzymatic fermentation. During fermentation, approximately 78% of flavan-3-ols in fresh tea leaves were oxidized and converted to a diverse mixture of highly heterogeneous oxidation products, such as theaflavins, whereas flavonols, phenolic acids, and xanthine alkaloids remained stable throughout the manufacturing process. Aldehydes, ketones, and heterocyclic compounds, imparting woody, floral, and nutty scent, were mainly formed during the roasting steps. This detailed information can expand our understanding on the formation of WRT flavor.

Keywords: Dynamic changes; Manufacturing process; Morphology; Phenolic compounds; Volatile compounds; Wuyi Rock tea.