## 3 Results and Discussions  
### Volatile Profile of RAPT with Various Years of Storage  
In the present work, an HS-SPME-GC-MS method was optimized and developed to profile the volatile compounds in RAPT with different storage durations (1-10 years). Based on the optimized method, qualitative and quantitative analyses of the volatile compounds were performed. As illustrated in Figure S1 (total ion chromatograms (TIC)), a large number of volatile compounds were detected in RAPT, and the profile of RAPT with different years of storage varied from each other. The data analysis was performed using a commercial software (GSMSsolution, version 4.30, labSolition, Shimadzu, Kyoto, Japan). A total of 130 volatile compounds were finally identified by matching with the NIST library and comparing the retention indexes (RIs), and the results are presented in Table S1. These compounds include alcohols (22%), aldehydes (12.1%), ketones (18.2%), alkenes (14.4%), esters (8.3%), acids (8.3%), pyrroles (3.8%), and others (12.9%), as illustrated in Figure 1B. In terms of the number of detected compounds, alcohols, ketones, and alkenes are the top three classes of compounds in RAPT. Figure 1A shows the compounds identified in each year and the years in which those compounds were present. Of them, 64 compounds (approximately 49.23%) were shared by all RAPT samples regardless the years of storage. Furthermore, from Table S1 and Figure 1A, it is worth noting that a few of the compounds, such as 1,2,3-trimethoxybenzene, hexanal, and 2-hexanal, were produced with a storage time of over two years. As illustrated in Figure 1 and Table S1, the composition and contents of volatile compounds in RAPT underwent apparent changes during storage. At the same years of storage, the difference in contents between compounds was also significant (\(p<0.05\)). As shown in Figure 1C and Table S1, alcohol compounds are the most abundant component, which is independent from the years of storage. In a previous study, most of the alcohols in tea, such as benzyl alcohol, phenylethyl alcohol, and (Z)-3,7-dimethyl-2,6-octaledien-1-ol, contribute to the rose-like and citrus-like aroma characteristics [9]. These alcohols are produced from the degradation of Strecker aldehydes or the hydrolysis of glycoside precursors [27]. In addition to alcohols, aldehydes, ketones, alkenes, and esters also showed relatively high contents in RAPT. The total concentration of volatiles generally fluctuated during storage (Figure 1C). Moreover, after 5 years of storage, the total volatile contents decreased, and although the overall content remains relatively stable, it is still lower compared with that in the samples with shorter storage durations. This distinction may be attributed to the differences between RAPT and other tea processing techniques. To investigate the variation in the volatile profile of RAPT samples stored for different durations, this work conducted a principal component analysis (PCA) and a hierarchical cluster analysis (HCA) using the semi-quantitative results of 64 volatile compounds. The PCA scoring plot (Figure 1D) demonstrates a clear differentiation of the samples based on the first two principal components, which collectively account for 65.3% of the total variance. The RAPT samples can be broadly categorized into four distinct groups, indicating significant changes in the volatile profile during storage. The results of the HCA and PCA revealed a clear classification of the samples into four categories: T0, T1, T2, and T5 formed one category; T3 and T4 formed another category; T6, T7, T8, and T9 constituted a third category; and T10 represented a separate category (Figure 1D,E). Notably, the samples with a storage duration of 10 years (T10) exhibited a distinct separation from other samples, suggesting a significant change in the volatile composition following a decade of storage. In addition, the samples with a storage duration of 1-5 years were predominantly located in the left region of the scoring plot.