# Characterization of the Key Aroma Compounds of Shandong Matcha Using HS-SPME-GC/MS and SAFE-GC/MS
## 5 Conclusions  
In this study, the combined application of HS-SPME-GC/MS and SAFE-GC/MS obtained a more comprehensive volatile composition of Shandong matcha. Distinctions between the three grades of Shandong Matcha were observed on the PCA score plots, especially for high versus low-medium grades. The aroma of matcha is mainly composed of the odors common to every grade, while a small number of odorants are unique to each grade. A higher proportion of heterocyclic compounds in Shandong matcha is the key to its strong roasted aroma, which can meet the demands of consumers in Northern China, especially in Shandong tea areas. In this study, 10 key aroma components were screened from the unique components of high-grade Shandong matcha tea, including 3-methyl-2-butene-1-thiol, 3-ethyl-phenol, 2-thiophenemethanethiol, (E,E)-2,4-undecadienal and (E,Z)-2,6-nonadienal, all presenting pleasant aromas. In addition, the aroma components that are common to each grade but differ in content also affect the aroma characteristics of different grades of Shandong matcha. The volatile components of seaweed aroma were dominant in high-grade matcha, while the volatile components of high-fired aroma and crude green gas were dominant in medium and low-grade matcha. The grinding process can increase the content of volatile components of matcha, effectively increasing the concentration of matcha aroma. In this study, the number of volatile components in the matcha showed an increasing trend, far more than the volatile components that showed a decrease after the three grades of tencha were made into matcha. In conclusion, the findings of this study contribute to a deeper understanding of the flavor of Shandong matcha tea. Based on the powder's physical properties and aroma characteristics, studying the interaction between matcha and food ingredients and developing novel tea drinks and matcha products will be the focus of future research on Shandong matcha.  
The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/foods11192964/s1](https://www.mdpi.com/article/10.3390/foods11192964/s1)]([https://www.mdpi.com/article/10.3390/foods11192964/s1](https://www.mdpi.com/article/10.3390/foods11192964/s1)), Figure S1. OPLS-DA results of Shandong matcha and tencha; Table S1. Comparison of volatile components extracted from Shandong matcha and tencha with different methods; Table S2. Differential compounds of different grades of Shandong matcha; Table S3. Different aroma components of tencha ground into matcha; Table S4. The 53 volatile components with higher content in M-CS.  
Conceptualization, Y.L. and J.H.; methodology, Y.Z.; software, F.Q.; validation, P.W., J.G. and X.Z.; formal analysis, Y.L.; investigation, Y.L.; resources, J.G.; data curation, J.H.; writing--original draft preparation, Y.L.; writing--review and editing, J.H. and F.Q.; visualization, Y.Z.; supervision, X.Z.; project administration, J.H.; funding acquisition, J.H. and X.Z. All authors have read and agreed to the published version of the manuscript.  
Funding: This research was funded by the Natural Science Fund of Shandong Province (ZR2019 MC039), the Youth Innovation and Science Technology Support Program of Shandong Province (2021 KJ103) and the project of Laoshan District Tea Innovation Group (LSCG2022000017). Data Availability Statement: Data is contained within the article or Supplementary Material.  
We are grateful for the support from Qingdao Hongyu Matcha Technology Development Co., Ltd. (Qingdao, China) on the use of matcha processing equipment.  
[PERSON] is from Qingdao Hongyu Matcha Technology Development Co., and the company only gives the support of matcha processing equipment in this study, it will not influence the ob-jectivity of the experimental results and conclusions and have no conflict of interest.