## 3 Results and Discussion
### Volatile Compounds Identified by GC-IMS
#### 3.1.2 Differences of Volatile Compounds in Teas by GC-IMS
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**No.**} & \multirow{2}{*}{**Volatile Compounds**} & \multirow{2}{*}{**RI**} & \multicolumn{4}{c}{**Relative Content (\%)**} & \multirow{2}{*}{**Odor Description \#**} \\  & & & **FTL** & **BT** & **GT** & \\ \hline
**sum** & & & **36.12** & **38.27** & **45.26** & \\
**Alcohols** & & & & & & \\  1 & Linalool & 1105.1 & 0.69 & 1.67 & 0.92 &
\begin{tabular}{c} floral, fruit, green, \\ orange-like \\ Sweet, floral, creamy \\ \end{tabular} \\
2 & Linalool oxide & 1085.9 & 0.26 & 0.75 & 0.30 & Sweet, floral, creamy \\
3 & 1.8-Cineole-M & 1027.8 & 0.25 & 1.22 & 0.39 & — \\
4 & 1,8-Cineole-D & 1028.8 & 0.10 & 0.34 & 0.12 & — \\
5 & 1-Octen-3-ol & 985.6 & 0.29 & 0.52 & 0.38 &
\begin{tabular}{c} Earthy, green, \\ vegetative-like, fungal \\ \end{tabular} \\
6 & 2-Furfurylthiol & 942 & 0.10 & 0.31 & 0.19 & — \\
7 & (E)-2-Hexenol & 848.9 & 0.73 & 10.83 & 1.54 & Green, fruit, vegetable \\
8 & 1-Pentanol & 760.7 & 2.40 & 1.52 & 1.09 & — \\
9 & (Z)-2-Pentenol & 777.5 & 0.21 & 1.83 & 0.51 & — \\
10 & 1-Butanol & 694.1 & 0.39 & 0.78 & 0.36 & — \\
11 & Isobutanol-M & 600 & 0.28 & 0.25 & 0.17 & — \\
12 & Isobutanol-D & 600.7 & 0.04 & 0.24 & 0.03 & — \\
13 & Ethanol & 425.7 & 4.87 & 2.53 & 4.26 & — \\
14 & 2-Ethlyhexanol & 1031.4 & 0.66 & 0.35 & 0.43 & — \\
15 & 2-Octanol & 989.4 & 0.50 & 0.17 & 0.79 & — \\
16 & 1-Hexanol & 881.7 & 0.51 & 0.38 & 0.63 & — \\
17 & Methanol & 399.1 & 5.06 & 2.62 & 3.73 & — \\
18 & 2-Propanol & 523.7 & 0.70 & 0.52 & 2.26 & — \\
**sum** & & & **18.04** & **26.83** & **18.10** & \\
**Ketones** & & & & & & \\  1 & Sulactone & 994.7 & 1.14 & 1.26 & 2.49 & Green, fruity \\  2 & 2-Heptanone-M & 895.3 & 1.59 & 0.66 & 1.29 &
\begin{tabular}{c} Benana, cheese, fruit, \\ medicinal \\ \end{tabular} \\
3 & 2-Heptanone-D & 893.8 & 0.12 & 1.22 & 0.09 &
\begin{tabular}{c} Banana, cheese, fruit, \\ medicinal \\ \end{tabular} \\
4 & 2,3-Pentanedione & 671.8 & 0.70 & 0.45 & 1.61 & — \\
5 & 2-Butanone & 560.2 & 4.96 & 4.24 & 1.44 & — \\
6 & 2-Propanone & 480.6 & 14.83 & 10.52 & 12.21 & — \\
7 & 2-Octanone & 1002.2 & 0.61 & 0.38 & 0.72 & — \\
8 & 1-Octen-3-one & 981.7 & 0.23 & 0.15 & 0.44 & Earth, mushroom \\
9 & Cyclohexanone & 901.5 & 0.58 & 0.31 & 0.98 & — \\
10 & 2-Hexanone & 781.5 & 0.15 & 0.08 & 0.13 & — \\
11 & Acetoin & 702.6 & 0.18 & 0.19 & 0.32 & — \\
12 & 3-Pentanone & 683.9 & 0.14 & 0.22 & 0.31 & — \\
**sum** & & & **25.23** & **19.68** & **22.03** & \\
**Esters** & & & & & \\
1 & Methyl Salicylate & 1234.1 & 0.54 & 1.27 & 0.79 & Minty, winter green-like \\
2 & Propyl acetate & 736.5 & 0.36 & 0.83 & 0.09 & — \\
3 & Ethyl Acetate & 579.1 & 1.04 & 0.36 & 2.46 & Fruit \\
4 & Butyl propanoate & 909.4 & 0.44 & 0.08 & 0.57 & — \\
5 & Propyl butanoate & 898.1 & 0.39 & 0.14 & 0.73 & Fruit \\
6 & Butyl acetate & 802.7 & 0.17 & 0.07 & 0.39 & — \\
**sum** & & & **3.20** & **3.93** & **5.37** & \\
**Acids** & & & & & \\
1 & 2-Methylbutanoic acid & 902.1 & 0.13 & 0.59 & 0.17 & — \\
**sum** & & & **0.13** & **0.59** & **0.17** & \\
**Heterocyclics** & & & & & & \\  1 & 2-Pentylfuran & 997.5 & 0.31 & 0.61 & 0.35 &
\begin{tabular}{c} Caramel, cooked, fruity, \\ green \\ \end{tabular} \\
2 & 2-Ethlypyrazine & 932.9 & 0.20 & 0.31 & 0.27 & Nutty, potato, toasted, \\  3 & 2-Acetylfuran-M & 912.8 & 0.34 & 0.62 & 0.54 &
\begin{tabular}{c} Scotcoa \\ Nutty, sweet, roasted, \\ baked \\ \end{tabular} \\ \hline \hline \end{tabular}
\end{table} 
Table 1: _Cont._To show the changing regularities and relative content of the volatile compounds of the FTLs in different treatments, we performed gallery plot analysis as a fingerprinting technique [24]. The differences in volatile compounds in each sample are presented in Figure 3. Significant differences in volatile compounds observed in GC-IMS were marked as fingerprints. The content of the compounds varied with signal intensity.