## 3 Results and Discussion  
### Variation of Non-Volatile Compounds in XYMJ Green Teas  
The non-volatile compounds endowed the taste of XYMJ green teas, which varied with the season (Table S1). The average contents of free amino acids (FAA), gallic acid (GA) and epicatechin gallate (ECG) were significantly higher in spring teas, while the average contents of caffeine (CAF) and catechin (C) were significantly lower in spring teas (Table 1). As for epicatechin (EC), epigallocatechin (EGC) and epigallocatechin gallate (EGCG), there were no significant differences between XYMJ spring teas and autumn teas. The XYMJ spring teas has higher content of non-galloylated catechins, including EGC and EC, a finding consistent with the previous report [5]. During the spring season, FAA responsible for the umami taste gradually declined from 2.007% to 1.658%, the bitter caffeine and astrtingent EGCG increased from 3.317% to 3.738% and 4.527% to 6.790%, respectively (Table S1). The degrees of catechin galloylation were designed as ECG/(EC + ECG) and ECGC/(EGC + EGCG), which were found to be inversely correlated to the cultivation altitude for oolong tea [22]. Although the degrees of catechin galloylation varied in XYMJ spring teas or autumn teas, there were no significant differences in XYMJ leas between spring and autumn season. Sweet afterate is a positive term to describe tea infusions and is often observed after XYMJ green tea drinking, which is attributed to the hydrolysis of gallbladder catechins [3]. The non-volatile compounds were chosen as variables to perform the principal coordinate analysis (PCoA, Figure 1A) and hierarchical clustering analysis (HCA, Figure 1C). The clustering results of PCoA were evaluated by PERMANOVA in vegan and the results showed that the 8 XYMJ green teas were divided into three clusters (PERMANOVA \(R^{2}\) = 71.0%, \(p\) < 0.001). Cluster-1 consisted of the earlier spring teas XYMJ01 and XYMJ02, and Cluster-2 consisted of the later spring teas XYMJ03 and XYMJ04. The four XYMJ spring teas were clearly discriminated, while the four XYMJ autumn teas consisted of Cluster-3, indicating that the quality of XYMJ spring teas changed greatly within a single spring season.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Compounds**} & \multicolumn{2}{c}{**XYMJ Spring Teas**} & \multicolumn{2}{c}{**XYMJ Autumn Teas**} \\ \cline{2-5}  & **Range** & **Average** & **Range** & **Average** \\ \hline FAA & 1.658–2.007 & 1.826 \(\pm\) 0.147 \({}^{\text{a}}\) & 1.619–1.750 & 1.691 \(\pm\) 0.060 \({}^{\text{b}}\) \\ CAF & 3.317–3.738 & 3.477 \(\pm\) 0.197 \({}^{\text{b}}\) & 3.559–3.694 & 3.608 \(\pm\) 0.062 \({}^{\text{a}}\) \\ GA & 0.055–0.060 & 0.057 \(\pm\) 0.003 \({}^{\text{a}}\) & 0.044–0.053 & 0.047 \(\pm\) 0.004 \({}^{\text{b}}\) \\ EGC & 1.979–2.466 & 2.178 \(\pm\) 0.284 & 1.748–2.362 & 1.991 \(\pm\) 0.274 \\ C & 0.077–0.104 & 0.090 \(\pm\) 0.011 \({}^{\text{b}}\) & 0.091–0.126 & 0.104 \(\pm\) 0.015 \({}^{\text{a}}\) \\ EGCG & 4.527–6.790 & 5.712 \(\pm\) 1.107 & 5.724–5.871 & 5.820 \(\pm\) 0.065 \\ EC & 0.517–0.703 & 0.623 \(\pm\) 0.093 & 0.531–0.696 & 0.604 \(\pm\) 0.076 \\ ECG & 1.681–1.893 & 1.793 \(\pm\) 0.110 \({}^{\text{a}}\) & 1.620–1.770 & 1.703 \(\pm\) 0.072 \({}^{\text{b}}\) \\ \hline \hline \end{tabular} Note: All data are expressed as mean \(\pm\) S.D. (\(n=3\)). Different letters in the same row indicate significant differences between mean values (\(p<0.05\), ANOVA, Duncan test).  
\end{table}
Table 1: Contents of non-volatile compounds in XYMJ green teas (%).