## 3 Results
### Identification of the Odor-Active Compounds in Braised Pork  
In the above analysis, the results showed that the compounds obtained by the two extraction methods (SPME and SDE) had complementary effects. However, from a quantitative perspective, only the SDE extraction method was used for odor-active compounds analysis. Table 3 summarizes the aroma-active compounds detected in the extracts of two types of braised pork by AEDA. A total of 36 aroma-active compounds were observed by AEDA, including 16 aldehydes, 4 hydrocarbons, 3 alcohols, 1 ketone, 2 esters, 2 ethers, 1 phenol, 1 nitrogenous compound, 4 oxygen-containing heterocycles, and 2 unknown compounds. Thirty compounds were detected in sample A and 28 in sample B. The FD profiles of the aroma-active volatile compounds are shown in Figure 2. The RI of the larger FD factor (FD \(\geq\) 27) aroma compounds fell within the range of RI 1135-2053, and these compounds were selected as potent compounds in the SDE of two types of braised pork extracts by AEDA. Furfuryl alcohol (sauce-flavor), anethole (anise, slight sweet), and unknown compound 1 were proved to be the most powerful aroma-active ones with the same highest FD factor of 243. Based on the sniff description of above aroma-active compounds, it was concluded that the main aroma of braised pork was meaty, caramel, sauce flavor, and spicy. \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline \multirow{2}{*}{RI *} & \multirow{2}{*}{**Compounds**} & \multirow{2}{*}{**Odor Description b**} & \multirow{2}{*}{**Odor Threshold (\(\mu\)g/g)**} & \multicolumn{3}{c}{**A**} & \multicolumn{3}{c}{**B**} \\ \cline{5-10}  & & & **CN * & \multicolumn{1}{c}{**FD 4**} & **OAV * & \multicolumn{1}{c}{**CN**} & \multicolumn{1}{c}{**FD 0**} & **OAV** \\ \hline \multicolumn{10}{c}{Aldehydes} \\ \hline
935 & 3-Methylbutanal & burnt-swet, roast & 0.001 & 0.335 & 3 & 335 & 0.211 & 3 & 211 \\
942 & Pentanal & almond, puppent & 0.009 & 3.0012 & 81 & 333 & 0.1045 & 3 & 12 \\
1076 & Hexanal & grass, tallow, fat & 0.0045 & 1.4725 & 9 & 34 & 0.2148 & 9 & 5 \\
1385 & Nonanal & fat, green & 0.0011 & 0.5744 & 9 & 522 & 0.5637 & 27 & 512 \\
1461 & Purfural & bread, almond, swet & 3 & 0.3468 & 81 & \(<\)1 & & & \\
1522 & Benzaldehyde & almond, burnt sugar & 0.35 & 0.3242 & 27 & \(<\)1 & 4.6550 & 9 & 13 \\
1635 & (E)-2-Deconal & grass, earthy & 0.0004 & 0.0735 & 27 & 180 & & & \\
1639 & Phhenylacetaldehyde & hawthorne, honey, sweet & 0.004 & 0.8829 & 9 & 220 & 1.4606 & 3 & 365 \\
1666 & (E)-Cimamaldehyde & cinnamon, paint & \(-\)f & 1.0826 & 27 & 0.4173 & 9 & & \\
1669 & Neral & lemon & 0.053 & 0.4836 & 3 & 9 & 0.1457 & 9 & 3 \\
1693 & Dodecaneral & lily, fat, citrus & 0.002 & 0.6133 & 3 & 307 & & & \\
1775 & 3-Phenylprogan & grass, fat & 0.12 & & 1.8005 & 9 & 9 & \\
1854 & (E,E)-2,4-Decadical & fat, roast & 0.00007 & 0.0913 & 27 & 1304 & 0.0237 & 27 & 339 \\
1977 & 2-MeMehybenzaldehyde & wax, medicinal & - & - & 1.1077 & 27 & & & \\
2042 & 4-Mehybenzaldehyde & similar hawththorn & 0.03 & 0.2233 & 9 & 7 & 1.3564 & 9 & 45 \\
2053 & (Z)-Cinnamaldehyde & cinnamon & 0.16 & 3.4719 & 27 & 22 & 4.2745 & 81 & 27 \\ \hline \multicolumn{10}{c}{Hydrocarbons} \\ \hline
1036 & \(\alpha\)-Pinene & green, fresh & 0.006 & 0.1321 & 27 & 22 & 0.2148 & 9 & 36 \\
1135 & 9-Pinene & mild, green & 0.14 & 0.6577 & 27 & 5 & 0.6634 & 27 & 5 \\
1169 & 8-3-Carene & lemon, resin & 0.77 & 0.1547 & 27 & \(<\)1 & 0.6634 & 27 & \(<\)1 \\
1204 & Limonene & fruity, orange & 0.01 & 0.7133 & 81 & 71 & 1.1866 & 81 & 119 \\ \hline \multicolumn{10}{c}{Alcohols} \\ \hline
1530 & Linalool & floral, lvender & 0.006 & 0.3115 & 27 & 52 & 1.7199 & 9 & 287 \\
1589 & 1-Perpinen-4-ol & turpentine, nuttmg, must & 1.29 & & 0.3126 & 27 & \(<\)1 \\
2330 & Cinnamyl alcohol & oily & 0.077 & 0.7314 & 9 & 9 & & \\ \hline \multicolumn{10}{c}{Ketones} \\ \hline
1270 & Acetoin & butter, cream & 0.8 & & & 0.8223 & 27 & 1 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Odor-active compounds detected in in the SDE extracts of two types of praised pork by AEDA. \begin{table}