## 3 Results and Discussion
### Analysis of OAV, Odor Characteristic and Key Compounds in Tea with Different Types
In terms of aroma compounds in green tea, 3-octanone was the first and dominant contributor for green odor; \(\beta\)-cyclocitral was the first contributor for fruity odor, secondary by 3-octanone; 3-octanone was the first contributor for woody odor, secondary by \(\beta\)-ionone and \(\beta\)-cyclocitral; and valeraldehyde was the first and dominant contributor for fatty odor. There were 10 compounds with OAVi \(>\) 1 in oolong tea and the OAVt was 302.74 (Table 3). They were \(\beta\)-cyclocitral (120.00) \(>>\) valeraldehyde (66.67) \(>\)\(\beta\)-ionone (45.71) \(>\) 6-methyl-5-hepten-2-one (30.80) \(>\) (_E,E_)-2,4-heptadienal (14.49), as well as five compounds (<7.4). The OAVi of the first four compounds was much higher than that of other compounds, accounting for 86.93% of the OAVt. In terms of odor characteristics, the OAVt (302.74) of oolong tea was composed of 111.04 for fruity, 66.74 for fatty, 35.55 for woody, 35.27 for floral, 34.73 for green, and 19.40 for burnt. The fruity odor (accounting for 36.68%) was the first feature of oolong tea, complemented by fatty (accounting for 22.05%), as well as woody (accounting for 11.74%), floral (accounting for 11.65%), and green (accounting for 11.48%). These five odors (accounting for 93.60% of OAVt) formed the strong and the most abundant fragrance of oolong tea with fruity odor as the dominant one and fatty odor as complementary, consisting of aromas of flowers, wood, and green. \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{5-10}  & & & & & **Woody** & & **Floral** & **Burnt** & **Green** & **Fruity** & **Fatty** \\ \hline
3-Octanone & 0.23 \(\pm\) 0.01 & 230.00 & 46.74 & 34.50 & 0 & 0 & 172.50 & 23.00 & 0 \\ \(\beta\)-Cyclocitral & 0.30 \(\pm\) 0.05 & 100.00 & 20.32 & 10.00 & 0 & 0 & 20.00 & 70.00 & 0 \\ Valeraldehyde & 0.67 \(\pm\) 0.08 & 55.83 & 11.35 & 0 & 0 & 0 & 5.58 & 11.17 & 39.08 \\ \(\beta\)-Ionone & 0.19 \(\pm\) 0.00 & 27.14 & 5.52 & 13.57 & 8.14 & 5.43 & 0 & 0 & 0 \\ (_E_)-3-Hexen-1-ol & 1.54 \(\pm\) 0.07 & 22.00 & 4.47 & 0 & 0 & 0 & 19.80 & 2.20 & 0 \\
6-Methyl-5-hepten-2-one & 0.71 \(\pm\) 0.06 & 14.20 & 2.89 & 0 & 9.94 & 0 & 0 & 4.26 & 0 \\
1-Penten-3-ol & 5.04 \(\pm\) 0.25 & 14.07 & 2.86 & 0 & 0 & 5.63 & 2.81 & 5.63 & 0 \\
1-Octen-3-ol & 0.52 \(\pm\) 0.04 & 13.00 & 2.64 & 0 & 0 & 10.40 & 1.30 & 0 & 1.30 \\
1-Pentanol & 0.79 \(\pm\) 0.01 & 5.26 & 1.07 & 0 & 0 & 0 & 0 & 0 & 5.26 \\ (_E,E_)-2,4-Hepdienal & 0.25 \(\pm\) 0.00 & 5.10 & 1.04 & 0 & 0 & 0 & 0 & 0 & 5.10 \\ Hexanal & 1.39 \(\pm\) 0.02 & 2.90 & 0.59 & 0.29 & 0 & 0 & 0.29 & 0.58 & 1.74 \\
2-Hexen-1-ol & 0.31 \(\pm\) 0.01 & 1.34 & 0.27 & 0 & 0 & 0 & 1.34 & 0 & 0 \\
1-Octanol & 0.13 \(\pm\) 0.02 & 1.18 & 0.24 & 0 & 0.24 & 0 & 0.47 & 0 & 0.47 \\ Total & 12.07 & 492.02 * & & 58.36 & 18.32 & 21.46 & 224.09 & 116.84 & 52.95 \\ \% ** & & & & 11.86 & 3.72 & 4.36 & 45.55 & 23.75 & 10.76 \\ \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 2: The content, OAVi and OAV-splitting of key aroma compounds in green tea. In terms of aroma compounds in oolong tea, \(\beta\)-cyclocitral was the first and dominant contributor for fruity odor; valeraldehyde was the first contributor for fatty odor, secondary by (\(E\),\(E\))-2,4-heptadien; \(\beta\)-ionone and \(\beta\)-cyclocitral were the main contributors for woody odor; 6-methyl-5-hepten-2-one and \(\beta\)-ionone were the main contributors for floral odor; and \(\beta\)-cyclocitral was the first and dominant contributor for green odor. There were 13 compounds with OAVi > 1 in red tea, and the OAVt was 471.88 (Table 4).