## 4 Conclusions  
The results of sensory evaluation indicated that fermentation by _M. purpureus_ improved the quality of Liupao tea. When following traditional technology, the inoculation of  
Figure 6: Pathways for the formation of key characteristic aromatic compounds. _M. purpureus_ fermentation resulted in a sample with a more reddish-brown appearance and infusion color, a sweeter and more mellow taste, and a more abundant aroma. Among the four Liupao teas with different fermentation methods, the DMI group exhibited the best sensory quality. Using HS-SPME-GC-Q-TOF/MS, a total of 156 volatile aroma substances across 13 categories were identified. E-nose detection results revealed distinct odor fingerprints for Liupao tea under various fermentation methods, with the sensors W1S (methyl group), W1W (inorganic sulfide), and W2S (alcohols and ketones) showing larger response contributions. PCA and OPLS-DA analyses demonstrated a significant separation of volatile components among the four groups of Liupao tea with different fermentation methods. Through differential aroma compounds screening based on VIP \(>\) 1 and \(p\) < 0.05, potential key aroma compounds were identified. These results, combined with OAV analysis and aroma flavor wheel construction, indicated that the Cl, CMI, DI, and DMI groups contained 10, 12, 9, and 11 key odorants, respectively. By further screening for characteristic aroma compounds with OAV \(>\) 10, it was observed that 1,2,3-trimethoxybenzene with stale aroma and nonanal with floral and fruity aromas were shared by all fermentation modes of Liupao tea. In the DMI group, which had the highest total aroma amount, key characteristic aroma compounds included 1,2,3-trimethoxybenzene, nonanal, and cedrol. The OAV of 1,2,3-trimethoxybenzene was significantly higher in the DMI group, contributing the most to its characteristic flavor. These findings can provide guidance for the development of Liupao tea products and the optimization of processes, providing a comprehensive understanding of Liupao tea. In the future, GC-O-MS, aroma recombination experiments and omission tests can be used to further determine the actual aroma contribution of the key aroma components of Liupao tea fermented by different fermentation methods, and to further study the synergistic effect of each aroma component. **Supplementary Materials:** The following supporting information can be downloaded at [[https://www.mdpi.com/article/10.3390/foods13162595/s1](https://www.mdpi.com/article/10.3390/foods13162595/s1)]([https://www.mdpi.com/article/10.3390/foods13162595/s1](https://www.mdpi.com/article/10.3390/foods13162595/s1)), Table S1: Sensors used in PEN3 system and their main applications. Table S2: Mean relative contents of aroma components of Liupao tea with different fermentation methods. Table S3. Odor activity values (OAVs) of key volatile substances and their aroma characteristics. Figure S1. Production of Monascus purpureus liquid. Figure S2. Processing of tea samples. Figure S3. (A) Differential Aroma Compounds Sankey Diagram (Cl vs. CMI); (B) Differential Aroma Compounds Sankey Diagram (Cl vs. DI); (C) Differential Aroma Compounds Sankey Diagram (CMI vs. DMI); (D) Differential Aroma Compounds Sankey Diagram (DI vs. DMI); The screening criteria were VIP \(>\) 1, \(p\) < 0.05. **Author Contributions:** X.Z. Data curation, formal analysis, methodology, software, investigation, writing--original draft; D.T. formal analysis, methodology, visualization, writing--original draft; H.Z. Figure creation and manuscript revision; R.D. Liupao Tea processing; C.M. Supervision; L.R. Supervision; X.Y. Software; Q.W. Software; N.C. Experimentation. L.Y. Experimentation. X.T. Experimentation. Y.B. Fermentation liquid production. Y.L. ([PERSON]) Fermentation liquid production. X.D. Fermentation liquid production. B.W. Funding and study supervision; Y.L. ([PERSON]) Study design and supervision and critical evaluation of the manuscript. All authors have read and agreed to the published version of the manuscript.