## 4 Conclusions  
In the current study, a method to improve the quality of summer tea using stuck fermentation was proposed, and we investigated the tea quality, metabolic profile, and microbial community of summer black tea after stuck fermentation in detail, and explored the relationship between tea quality and metabolic profile and microbial community. Stuck fermentation significantly improved the quality of summer black tea by reducing the bitterness, astringency, sourness, and freshness, enhancing the sweetness, mellowness, and smoothness, and altering the aroma from sweet and floral to fungal. Flavonoids, phenolic acids, amino acids, and their derivatives that lend a bitter and asrtingent taste were down-regulated. In addition, organic acids, alkaloids with a sour and bitter taste, and glycoconjugates of amino acids and flavonoids that release glycosides were also significantly reduced after stuck fermentation. In contrast, sweet flavor saccharides and lipid precursors of aroma substances increased significantly. Stuck fermentation also led to the downregulation of floral and sweet aroma-related metabolites and increased the levels of acetophenone and isophorone, which contribute to fungal aroma. Furthermore, the richness of fungal and bacterial communities in summer black tea increased significantly after stuck fermentation, and _Aspergillus_, _Pullull  
strains that contribute to the improvement of summer tea quality and functional validation of these strains need further study. **Supplementary Materials:** The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/foods12183414/s1](https://www.mdpi.com/article/10.3390/foods12183414/s1)]([https://www.mdpi.com/article/10.3390/foods12183414/s1](https://www.mdpi.com/article/10.3390/foods12183414/s1)), Figure S1: Diagram of tea preparation; Figure S2: Sample quality control analysis; Figure S3: Permutation tests of the OPLS-DA models in LC-MS/MS; Figure S4: Sample quality control analysis. Figure S5: Permutation tests of the OPLS-DA models in GC-MS/MS. Figure S6: Alpha diversity of microbial community. Table S1: Results of sensory evaluation of YH and FHYH; Table S2: All non-volatile metabolites of UPLC-MS/MS; Table S3: 551 non-volatile differential metabolites; Table S4: All volatile metabolites of GC-MS/MS; Table S5: 345 differential volatile metabolites; Table S6: The sequence quality of 16S rRNA sequencing; Table S7: The sequence quality of ITS sequencing. **Author Contributions:** Methodology, R.C. ; Validation, Q.L. ([PERSON]); Formal analysis, L.W. and L.S. ; Investigation, J.C.; Data curation, L.W. and L.S. ; Writing--original draft, L.W. and L.S. ; Writing--review & editing, S.S. and F.C. ; Visualization, X.L., Z.L. and Z.Z. ; Supervision, Q.L. ([PERSON]) and G.S. ; Funding acquisition, S.S. and F.C. All authors have read and agreed to the published version of the manuscript. **Funding:** This study was funded by Food nutrition and health Collaborative Innovation Center of GDAAS [Grant No. XT202229]; Agricultural competitive industry discipline team building project of Guangdong Academy of Agricultural Sciences [Grant No. 202126 TD]; the open Project of Guangdong Provincial Key Laboratory of Tea Plant Resources Innovation and Utilization [Grant No. 2020 KFC9]; Guangdong Basic and Applied Basic Research Foundation [Grant No. 2021A1515010958, 2022A1515110190, 2023A1515010264]; Guangzhou Science and Technology Plan Projects [Grant Nos. 20212100005, 202201011455, 2023E04J0781]; Key-Area Research and Development Program of Guangdong Province [Grant No. 2020B0202080003]; Qingyuan Science and Technology Plan Projects, [Grant Nos. 2021 ZDZX002]; Innovation Fund projects of Guangdong Academy of Agricultural Sciences [Grant Nos. 202115, 202135]; Special fund for scientific innovation strategy-construction of high level Academy of Agriculture Science [Grant Nos. R2019 PY-JX004, R2022 PY-QY010]; the Innovation Fund projects of Guangdong Key Laboratory of Tea Plant Resources Innovation and Utilization [Grant No.