## 3 Results and Discussion
### Analysis of OAV, Odor Characteristic and Key Compounds in Tea with Different Types  
There were eight compounds with OAVi \(>\) 1 in white tea and the OAVt was 68.10 (Table 1). They were \(\beta\)-ionone (22.86) \(>>\) (_E_)-3-hexen-1-ol (10.43) \(>\) 6-methyl-5-hepten-2-one (9.40) \(>\) methyl salicate (6.75) \(\approx\) linalool (6.58) \(>\) Epoxydihydrolinalool (5.82) \(>\) phenethyl alcohol (4.51) \(>\) hexanal (1.75). The OAVi of the first three compounds was much higher than that of other compounds, accounting for 62.69% of the OAVt. In terms of odor characteristics, the OAVt (68.10) of white tea was composed of 28.36 for floral, 17.71 for woody, 10.01 for green, 6.59 for burnt, 4.21 for fruity, and 1.22 for fatty. The floral odor (accounting for 41.64%) was the first feature of white tea, complemented by woody (accounting for 26.01%), as well as green (accounting for 14.70%). These three odors (accounting for 82.35% of OAVt) formed the weak fragrance of white tea with floral odor as dominance, hierarchically mixing odors of floral, wood, and green. In terms of aroma compounds in white tea, \(\beta\)-ionone, 6-methyl-5-hepten-2-one and linalool were the main and even contributors for floral odor; \(\beta\)-ionone was the first contributor for woody odor, secondary by epoxydihydrolinalool; and (_E_)-3-hexen-1-ol was the first and dominant contributor for green odor. \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Compound**} & \multicolumn{2}{c}{**Ci**} & \multirow{2}{*}{**OAVi**} & \multirow{2}{*}{**\%**} & \multicolumn{6}{c}{**OAV-Splitting of Odor Characteristic**} \\ \cline{4-9}  & & & & & **Woody** & & **Floral** & **Burnt** & **Green** & **Fruity** & **Fatty** \\ \hline \(\beta\)-Ionone & 0.16 \(\pm\) 0.02 & 22.86 & 33.57 & 11.43 & 6.86 & 4.57 & 0 & 0 & 0 \\ (_E_)-3-Hexen-1-ol & 0.73 \(\pm\) 0.01 & 10.43 & 15.32 & 0 & 0 & 0 & 9.39 & 1.04 & 0 \\
6-Methyl-5-hepten-2-one & 0.47 \(\pm\) 0.01 & 9.40 & 13.80 & 0 & 6.58 & 0 & 0 & 2.82 & 0 \\ Methyl salicate & 0.27 \(\pm\) 0.02 & 6.75 & 9.91 & 0 & 4.73 & 2.02 & 0 & 0 & 0 \\ Linalool & 3.29 \(\pm\) 0.08 & 6.58 & 9.66 & 0 & 6.58 & 0 & 0 & 0 & 0 \\ Epoxydihydrolinalool & 2.91 \(\pm\) 0.26 & 5.82 & 8.55 & 5.65 & 0 & 0 & 0 & 0 & 0.17 \\ Phenethyl alcohol & 3.38 \(\pm\) 0.56 & 4.51 & 6.62 & 0.45 & 3.61 & 0 & 0.45 & 0 & 0 \\ Hexanal & 0.84 \(\pm\) 0.01 & 1.75 & 2.57 & 0.18 & 0 & 0 & 0.17 & 0.35 & 1.05 \\ Total & 12.05 & 68.10 \({}^{*}\) & & 17.71 & 28.36 & 6.59 & 10.01 & 4.21 & 1.22 \\ \% ** & & & & 26.01 & 41.64 & 9.68 & 14.70 & 6.18 & 1.79 \\ \hline \hline \end{tabular} Note: OAVi = Ci/Ti, where Ci is the content of compound i (ug kg\({}^{-1}\)), and Ti is the threshold value of compound i (ug kg\({}^{-1}\)). \({}^{*}\)OAVt = \(\sum\)OAVi. * % is proportion of the each odor OAV accounting for OAVt.  
\end{table} 
Table 1: The content, OAVi and OAV-splitting of key aroma compounds in white tea. There were 13 compounds with OAVi \(>\) 1 in green tea and the OAVt was 492.02 (Table 2). They were 3-octanone (230.00) \(>>\)\(\beta\)-cyclocitral (100.00) \(>>\) valeraldehyde (55.83) \(>>\)\(\beta\)-ionone (27.14) \(>\) (E)-3-hexen-1-ol (22.00) \(>\) 6-methyl-5-hepten-2-one (14.20) \(\approx\) 1-penten-3-ol (14.07) \(>\) 1-octen-3-ol (13.00), as well as five compounds (<5.3). The OAVi of the first three compounds was much higher than that of other compounds, accounting for 78.41% of the OAVt. In terms of odor characteristics, the OAVt (492.02) of green tea was composed of 224.09 for green, 116.84 for fruity, 58.36 for woody, 52.95 for fatty, 21.46 for burnt, and 18.32 for floral. The green odor (accounting for 45.55%) was the first feature of green tea, complemented by fruity (accounting for 23.75%), as well as woody (accounting for 11.86%) and fatty (accounting for 10.76%). These four odors (accounting for 91.92% of OAVt) formed the strong fragrance of green tea with green odor stand out, fruity odor obvious, accompanied by odors of softly woody and fatty.