## 4 Conclusions  
In this study, we investigated the changes in known functional compounds in six different types of beer. The known functional compounds included \(\gamma\)-aminobutyric acid (GABA), glutathione (GSH), \(\beta\)-glucan, B vitamins (B1, B2, B3, B5, and B6), and phenolic acids (gallic acid, ferulic acid, catechchin, vanillic acid, and protocatechuic acid). We found that the content of functional compounds in ale was higher than that in lager except for vitamin B5. Under the same yeast and brewing conditions, the contents of functional compounds in the two types of lager with different malts and hops varied. The process of pasteurization showed no significant effect on GABA and GSH levels (\(p>0.05\)), but it can lead to the loss of B vitamins (B2, B3, B5, B6) and ferulic acid and an increase in aldehyde odor substances. Among the volatile components, farnesol and caprylic acid were present in all the types of beer. Regarding functional substances, the selection of appropriate pasteurization conditions and the application of top-refmenting yeast in ale beer could aid in the development of functional beers and the improvement of their quality.  
**Supplementary Materials:** The following supporting information can be downloaded at [[https://www.mdpi.com/article/10.3390/beverages11030063/s1](https://www.mdpi.com/article/10.3390/beverages11030063/s1)]([https://www.mdpi.com/article/10.3390/beverages11030063/s1](https://www.mdpi.com/article/10.3390/beverages11030063/s1)): Table S1: The contents of flavor substances in different types of beers. RA--relative amount, SD--standard deviation. CRB--classic ripe beer, CDB--classic draft beer, PRB--pure ripe beer, PDB--pure draft beer, ARB--alre pipe beer, ADB--ale draft beer.  
**Author Contributions:** Conceptualization, S.H., X.Z., and J.L.; methodology, J.D.; formal analysis, J.D. and X.H.; writing--original draft preparation, J.D.; writing--review and editing, X.Z. and J.D. All the authors have read and agreed to the published version of the manuscript. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This research was funded by the Foundation for Innovative Research Groups of the National Natural Science Foundation of China (32021005), the Jiangsu Basic Research Center for Synthetic Biology (BK20233003), and the National First-class Discipline Program of Light Industry Technology and Engineering (LITE2018-08).  
**Data Availability Statement:** The original contributions presented in this study are included in this article; further inquiries can be directed to the corresponding author.  
**Conflicts of Interest:** [PERSON] participated in formal analysis, and [PERSON] participated in conceptualization. Tsingtao Brewery Co., Ltd. provided all the beer samples. It is clarified that  
Figure 5: Multivariate statistical analysis of volatile components in the examined beers. (A) OPLS-DA model plots of volatile fractions in the lager and ale (R\({}^{2}\)x = 0.816, R\({}^{2}\)y = 0.989, R\({}^{2}\) > 0, Q\({}^{2}\) > 0.5). The numbers in the figure correspond to the following: 1–3: CRB, 4–6: CDB, 7–9: FRB, 10–12: PDB, 13–15: ARB, 16–18: ADB; (B) the charts of the 200 replacement tests. CRB—classic ripe beer; CDB—classic draft beer; PRB—pure ripe beer; PDB—pure draft beer; ARB—ale ripe beer; ADB—ale draft beer.  
it will not affect the fairness of the experimental results and does not involve product promotion. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.