Changes in flavor quality of raw Liupao tea during the piling process

Piling is a critical process for the formation of raw Liupao tea (RLT) flavor quality. However, given the unclear changes in the flavor quality of RLT during the piling process, and the key substances of taste-contributing and aroma components that affecting the flavor quality of RLT was lacking. Herein, the present study aimed at evaluating the changes in flavor quality and its key substances of RLT during the piling process.

Sensory evaluation was conducted on RLT samples collected at 11 time points during the piling process. The biochemical and aroma components of these samples were detected using UV spectrophotometer, high-performance liquid chromatography (HPLC), and headspace solid-phase microextraction gas chromatography-mass spectrometer (HS-SPME-GC-MS), respectively. Multivariate analysis was performed to investigate the effects of piling time on the flavor quality of RLT.

The sensory quality of RLT increased and then decreased during the piling process. The changes in flavor quality of RLT during the piling process could be divided into four stages: 0-6, 9-15, 18-24, and 27-30 h. The flavor quality of RLT changed significantly with the variations in biochemical and volatile compounds. The key contributors to taste changes included significant decreases in (-)-epigallocatechin gallate, (-)-epicatechin gallate, (-)-epigallocatechin, (-)-catechin gallate, and theobromine content and significant increases in gallic acid, gallocatechin, and theaflavin content. Additionally, alterations in the content of 19 characteristic aroma compounds, such as cedrol, methyl salicylate, methyl palmitate, trans-nerolidol, decanal, 6,10-Dimethyl-2-undecanone, neryl alcohol, α-cedrene, and (E, E)-2,4-heptadienal, significantly influenced the aroma of the tea infusion. This study provides insights into the formation of flavor quality in RLT at different piling stages, which also provide a scientific foundation for optimizing the piling and production processes of RLT.