## 3 Results
### Identification of the Odor-Active Compounds in Braised Pork
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**No** & **Compounds** & **Quantitative Ions 1 ** & **R2 ** & **LOD (ug/kg) 3 ** & **LOQ (ug/kg) 4 ** \\ \hline
1 & 3-Methyl-butanol & 41,43,44 & 0.987 & 1.8 & 6.0 \\
2 & Pentanal & 41,44,58 & 0.974 & 4.4 & 14.7 \\
3 & \(\alpha\)-pinene & 91,92,93 & 0.992 & 2.0 & 6.7 \\
4 & Hexanal & 44,56,57 & 0.978 & 25.1 & 83.6 \\
5 & 9-pinene & 69,91,93 & 0.988 & 1.5 & 5.0 \\
6 & 8-3-Carene & 77,91,93 & 0.995 & 6.4 & 21.3 \\
7 & Limonene & 67,68,93 & 0.996 & 1.9 & 6.3 \\
8 & 1,8-Cineole & 43,81,108 & 0.995 & 1.6 & 5.3 \\
9 & Acetoin & 43,45,58 & 0.996 & 6.2 & 20.6 \\
10 & 2-Methyltetrahydrofuran-3-one & 43,72,100 & 0.978 & 2.1 & 7.0 \\
11 & Nonanal & 41,56,57 & 0.986 & 7.0 & 23.3 \\
12 & Furfural & 39,95,96 & 0.986 & 10.6 & 35.3 \\
13 & 2-Acetyfuran & 39,95,110 & 0.976 & 1.2 & 4.0 \\
14 & Benzaldehyde & 77,105,106 & 0.985 & 16.3 & 54.3 \\
15 & Linalool & 55,71,93 & 0.971 & 4.3 & 14.3 \\
16 & 1-Terpinen-4-ol & 71,93,111 & 0.983 & 1.5 & 5.0 \\
17 & (E)-2-Decneal & 41,55,70 & 0.977 & 0.3 & 1.0 \\
18 & Phenyl acetaldehyde & 69,91,92 & 0.972 & 4.3 & 14.3 \\
19 & Furfuryl alcohol & 81,97,98 & 0.994 & 6.8 & 22.6 \\
20 & (E)-Cinnamaldehyde & 103,131,132 & 0.964 & 3.2 & 10.7 \\
21 & Neral & 41,69,94 & 0.979 & 11.8 & 39.3 \\
22 & Dodecanal & 41,57,82 & 0.986 & 2.2 & 7.3 \\
23 & 3-Phenylpropanol & 91,92,134 & 0.974 & 2.4 & 8.0 \\
24 & Anethole & 132,133,148 & 0.995 & 1.7 & 5.7 \\
25 & (E,E)-2,4-Decaional & 41,67,81 & 0.995 & 0.8 & 2.7 \\
26 & 2-Methyloxybenzaldehyde & 77,118,136 & 0.986 & 5.3 & 17.6 \\
27 & 2-Acetypyrrole & 66,94,109 & 0.976 & 1.7 & 5.7 \\
28 & 4-Methoxybenzaldehyde & 77,92,135 & 0.989 & 14.6 & 48.6 \\
29 & (Z)-Cinnamaldehyde & 103,131,132 & 0.977 & 0.6 & 2.0 \\
30 & Phenol & 65,66,94 & 0.994 & 5.4 & 18.0 \\
31 & Ethyl cinnamate & 103,131,176 & 0.974 & 1.6 & 5.3 \\
32 & \(\gamma\)-Undecalactone & 55,85,128 & 0.983 & 2.1 & 7.0 \\
33 & Cinnamyl alcohol & 91,92,134 & 0.986 & 0.6 & 2.0 \\
34 & Coumarin & 89,118,146 & 0.976 & 2.1 & 7.0 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Standard curves of key aroma compounds in braised pork. Figure 2: (**a**) FD chromatogram of the volatile fraction of braised pork with braised sauce; (**b**) FD chromatogram of the volatile fraction of braised pork with white granulated sugar. (FD: Flavor Dilution factor, RI: retention indices). a minor contribution to the overall aroma. Compared with A, sample B presented anethole (anise, slight sweet) and unknown 1 (almond, caramel, toasty) with the highest aroma intensity (FD = 243). For sample B, Limonene (fruity, orange) and (\(Z\))-cinnamaldehyde (cinnamon) gave the higher FD factor of 81. However, 3-phenylpropanol, 2-methoxybenzaldehyde, \(\beta\)-pinene, 1-terpinen-4-ol, acetoin, and unknown1 had no FD factor in sample A; and nonanal, (\(Z\))-cinnamaldehyde, \(\gamma\)-undecalactone, coumarin, and anethole showed a lower FD factor in sample A. Therefore, the two samples exhibited different aromas in sensory evaluation. However, owing to the strong complexity of the analyte, which led to very rich chromatographic profiles and made it quite difficult to sniff, the evaluation of a single peak or a given chromatographic region was often affected by the former eleuents. Thus, odor descriptions of the sniffers were prone to differ from the literatures. Anyway, some compounds have been previously identified as key odor-active compounds in fried bacon, fried pork loin, and roasted pork of mini-pig by GC-O [29; 30], for instance pentanal, limonene, furfural, \(\beta\)-pinene, and anethole. For the present work, spice ingredients (onion, ginger, garlic, cinnamon, and star aniseed) were used in the cooking, and thus, a high amount of spice compounds, e.g. (Z)-cinnamaldehyde, \(\beta\)-pinene, 1-terpinen-4-ol, anethole, \(\alpha\)-pinene, \(\delta\)-3-carene, 1,8-cineole, ethyl cinnamate were contained in the volatiles of the braised pork; they were basically similar to the results in Reference [31].