## 5 Conclusions  
In this study, we employed a combination of tea flavor sensory evaluation, GC-MS, and UPLC-MS techniques coupled with multivariate statistical analysis to quantitatively analyze major flavor metabolites and identify key components distinguishing different grades of TSH standard samples. Furthermore, we investigated the biochemical basis underlying the formation of TSH's flavor quality. The main conclusions are as follows:  
1. TSH samples generally exhibit linear correlations with the contents of non-volatile compounds (including amino acids and ester-type catechins). Thea, Arg, and GABA show significant differences across grades and serve as potential biomarker components for MKH. 2. Methyl salicylate and linalool were the most abundant volatile compounds in higher-grade TSH, contributing to the formation of delicate sweetness and floral notes. These compounds not only showed significant correlations with tea grades but also played crucial roles in developing the persistent sweet aroma with floral characteristics in premium-grade TSH. 3. The cultivar, harvesting season, and maturity of fresh tea leaves were closely associated with TSH grades and flavor profiles, which may represent the primary factors contributing to the differential accumulation of flavor metabolites across various grades. **Supplementary Materials:** The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/beverages11040111/s1](https://www.mdpi.com/article/10.3390/beverages11040111/s1)]([https://www.mdpi.com/article/10.3390/beverages11040111/s1](https://www.mdpi.com/article/10.3390/beverages11040111/s1)), Figure S1: Cluster analysis ANOVA of 19 amino acids in different grades of Tianshanhong; Table S1: Key compounds by comparing fold change (FC) values of different grades of Tianshanhong (TSH). **Author Contributions:** S.-T.X. and X.-Z.H. : investigation; writing--original draft; formal analysis; writing--review and editing. J.-F.H. : investigation; Q.-Y.W. : methodology. Y.W. : formal analysis, T.-T.D. : validation, X.-X.X. : formal analysis, H.-X.L. : supervision. X.-H.C.: resources. S.-Z.Z. : data curation. Z.-W.Z. : conceptualization; writing--review and editing; and funding acquisition supervision. All authors have read and agreed to the published version of the manuscript. **Funding:** This research was funded by Spark Technology Project of Fujian Province (2023S0061); the Fujian Provincial Natural Science Foundation of China (2022J05271); Educational and Scientific Research Project for Young and Middle-aged Teachers in Fujian Province (JAT220756); Professional Group of Tea Production and Processing Technology of the Provincial-level Teaching Innovation Team for Vocational College Teachers in Fujian Province (Document No. Minjiaobanshi [2023] No. 16); Huang Xianzhou Skilled Master Studio in Ningde City (024/3232301). **Institutional Review Board Statement:** Tea is universally recognized as a safe food material that does not typically require special ethical review for analytical studies. Our methodology strictly follows established protocols for tea evaluation (GB/T 23776-2018) and utilizes standard analytical procedures with certified reagents. **Informed Consent Statement:** The five authors ([PERSON], [PERSON], [PERSON], [PERSON], [PERSON]) are all national senior teaasters. We voluntarily participated in the sensory evaluation test of Tienshanhong (TSH) black tea at different grades, adhering to an objective and fair attitude and a rigorous and meticulous professional spirit. Moreover, no ethical tests were involved in the tea evaluation process. **Data Availability Statement:** The original contributions presented in this study are included in this article/Supplementary Materials. Further inquiries can be directed to the corresponding author. **Conflicts of Interest:** Author [PERSON] was employed by the company Fujian Hongjun Agricultural Development Co., Ltd. He participated in investigation in the study. The role of the company was general manager.