## 4 Conclusions  
In this work, non-volatile compounds endowed the taste and volatile compounds responsible for the aroma in XYMJ green tea harvested during the spring and autumn season were determined. The changes of the flavor compounds in XYMJ green teas are  
\begin{table}
\begin{tabular}{c c} \hline
**Green Teas** & **Top 10 Key Odorants Identified in Green Teas** \\ \hline \multirow{3}{*}{Chestnut-like green tea} & trans-\(\beta\)-ionone (1617) , 3-methylbutanal (105.2) 3 , nonanal (99.79) 4 , benzeneacetaldehydehyde (77.28) 5 , decanal (60.80) 6 , linalool (41.64) 7 , (E)-3-penten-2-one (22.34) 8 , heptanal (17.22) 9 , octanal (15.16) 10  \\ \hline \multirow{3}{*}{Fangping green tea} & dimethyl sulfide (1195.21) 6 , linalool (80.27) 7 , octanal (36.36) 8 , 1-nonanal (27.91) 9 , \(\beta\)-ionoine (20.24) 8 , pentanal (15.58) 11 , 2-methylbutyaldehyde (12.87) 12 , benzaldehyde (11.98) 13 , ethyl \\  & acetate (10.98) 14 , \(\alpha\)-ionone (6.72) 8  \\ \hline \multirow{3}{*}{Longing tea} & \(\beta\)-ionone (20,406) 1 , 1-methyllnphthalene (7275) 15 , naphthalene (2347) 16 , 2,4-nonadien (2022) 17 , (E)-2-monen (1354) 17 , decanal (1100)  18 , 1-octen-3-ol (507) 18 , hexanal (417) 19 , (E,E)-3-octadien-2-one (397) 19 , 2-methylbutanal (390) 19  \\ \hline \multirow{3}{*}{Jingshan green tea} & dimethyl sulfide (458) 1 , (E,E)-2,4-heptradien (46) 10 , 1-hexen-3-one (19) 11 , geranol (17) 11 , methanethiol (14) 12 , (E,E)-2,6-nonadien (13) 13 , 3-methyllnonane-2,4-dione (13) 14 , 3-methyllnonane-2,4-dione (13) 14 , (Z)-1,5-octadien-3-one (21) 15 , 2-4-heptrenal (11) 1 , methanethiol (11) 14 , \\ \hline \multirow{3}{*}{Longing tea} & dimethyl sulfide (440) 1 , (E,E)-2,4-Heptadien (50) 14 , methylpropanal (32) 15 , 3-methylbutanal (28) 16 , 3-methyllnonane-2,4-dione (27) 17 , 1-hexen-3-one (22) 18 , (Z)-1,5-octadien-3-one (21) 19 , 2-ionnone (16) 17 , (Z)-4-heptrenal (15) 19 , methanethiol (12) 19  \\ \hline \multirow{3}{*}{XYMJ green tea} & trans-\(\beta\)-ionone (2195.05) 1 , decanal (57.94) 19 , nonanal (30.96) 19 , dimethyl sulfide (19.53) 19 , linalool (15.0) 15 , genanol (14.37) 19 , naphthalene (10.34) 19 , (Z)-3-hexenyl hexanoate (26.2) 16 , 1-octen-3-ol (20.0) 19 , 2-octanolanalyzed and discussed. It is found that the flavor compounds differ between the spring and autumn tea samples and they showed various change trends. The average contents of FAA were significantly higher and gradually declined in the spring teas, whereas the caffeine was significantly lower and gradually increased in the spring teas. A total of 39 volatile compounds were determined by the HS-SPME combined GC-MS. The contents and types of volatile compounds displayed various change trends during the spring and autumn season, which confirms that the XYMJ green tea aroma formation is dynamic. There were 15 volatile compounds identified as the key odorants based on OAV, including trans-\(\beta\)-ionone, nonanal, dimethyl sulfide,linal, gerniol, naphthalene, (Z)-3-hexenyl hexanoate, 1-octen-3-ol, benzaldehyde, cis-nerolidol, heptanal, hexanal, \(\beta\)-cyclocitral and 2,3-octanedione. The OAVs of gerniol, (Z)-3-hexenyl hexanoate, heptanal, benzaldehyde and hexanal in XYMJ spring teas were higher than XYMJ autumn teas. The XYMJ green teas harvested during the spring and autumn seasons have their key odorants and corresponding precursors, which were mainly derived from fatty acids, amino acids, glycosides and carotenoids. The types and OVAs of volatile compounds are different from the other green teas, which endow the unique aroma quality of the XYMJ green tea. The non-volatile and volatile compounds were chosen as the variables, respectively, to perform the hierarchical clustering analysis, and the results indicated that harvest season had important effects on the flavor quality of XYMJ green teas.