## 2 Results and Discussion
### Volatile Profile of Marinated Pork Hocks Characterized by GC-MS/O
#### 2.1.2 OAVs of the Odour-Active Compounds  
The OAV (Equation (3)) was employed to evaluate the contribution of volatile compounds to the aroma profile of the investigated samples. The results are summarized in Table 2.  
Twenty-four volatile compounds with OAVs \(>\) 1 were selected as odour-active compounds contributing primarily to the total flavour of the marinated pork hocks. A point worth emphasizing is that six odour-active components with relatively high OAVs were simultaneously detected in four samples: hexanal (OAV at 3.6-20.3), octanal (OAV at 30.3-47.5), nonanal (OAV at 68.6-166.3), 1,8-cineole (OAV at 36.4-133.3), aneth \begin{table}
\begin{tabular}{c c c c c c c c} \hline \multirow{2}{*}{**Code**} & \multirow{2}{*}{**Compounds**} & \multicolumn{5}{c}{**Odour Activity Values (OAVs)**} & \multirow{2}{*}{_p Value_} & \multirow{2}{*}{**VIP Value**} \\ \cline{3-3} \cline{5-8}  & & & **DHM** & & **DXC** & & **HHT** & **TFH** \\ \hline
1 & 2-Methylbutanal & 0.0b & 10.0 \(\pm\) 1.2a & 0.0b & 0.0b & 0.000 & 0.827 \\
2 & 3-Methylbutanal & 0.0b & 10.6 \(\pm\) 1.6a & 0.0b & 0.0b & 0.000 & 0.824 \\
3 & Hexanal & 20.3 \(\pm\) 0.9a & 3.6 \(\pm\) 0.4d & 11.7 \(\pm\) 1.2b & 8.9 \(\pm\) 0.3c & 0.000 & 0.817 \\
4 & Heptanal & 8.0 \(\pm\) 0.5a & 8.5 \(\pm\) 1.0a & 0.0c & 5.5 \(\pm\) 0.8b & 0.000 & 1.068 \\
5 & Octanal & 47.5 \(\pm\) 3.2a & 30.3 \(\pm\) 2.6c & 35.9 \(\pm\) 3.1b & 4.6 \(\pm\) 0.2a & 0.000 & 0.867 \\
6 & Nonanal & 16.6 \(\pm\) 4.6a & 122.4 \(\pm\) 9.5c & 68.6 \(\pm\) 4.9d & 135.9 \(\pm\) 3.2b & 0.000 & 1.078 \\
7 & 2-Octenal isomer & 1.2 \(\pm\) 0.4a & 0.0b & 0.0b & 0.0b & 0.000 & 0.946 \\
9 & 2-Nonanal isomer & 22.2 \(\pm\) 5.7a & 0.0b & 0.0b & 0.0b & 0.000 & 0.956 \\
11 & 2,4-Decadieral isomer & 225.5 \(\pm\) 17.7a & 0.0b & 0.0b & 0.0b & 0.000 & 0.980 \\
14 & 1,8-Cineole & 38.1 \(\pm\) 1.3c & 36.4 \(\pm\) 0.3c & 113.3 \(\pm\) 12.1b & 133.3 \(\pm\) 13.4a & 0.000 & 0.954 \\
15 & 1-Octen-3-ol & 5.3 \(\pm\) 0.2c & 0.0d & 8.3 \(\pm\) 0.9a & 7.2 \(\pm\) 0.7b & 0.000 & 0.943 \\
16 & Linaload & 2.2 \(\pm\) 0.1b & 1.6 \(\pm\) 0.3c & 3.1 \(\pm\) 0.2a & 2.1 \(\pm\) 0.2b & 0.000 & 0.978 \\
28 & Ethly acetate & 3.1 \(\pm\) 0b & 18.6 \(\pm\) 0.9a & 0.0d & 2.1 \(\pm\) 0.3c & 0.000 & 0.892 \\
29 & Ethly hexanoate & 1.1 \(\pm\) 0.0a & 0.0b & 0.0b & 0.0b & 0.0b & 0.000 & 0.983 \\
36 & 3-Carne & 0.0b & 0.0b & 113.0 \(\pm\) 8.3a & 0.0b & 0.000 & 1.078 \\
39 & D-Limonene & 0.0c & 1.7 \(\pm\) 0.2b & 26.4 \(\pm\) 1.4a & 0.0c & 0.000 & 1.082 \\
40 & \(\beta\)-Phellandrene & 0.0c & 1.5 \(\pm\) 0.3b & 12.0 \(\pm\) 0.8a & 0.0c & 0.000 & 1.081 \\
42 & \(p\)-Cymene & 0.9 \(\pm\) 0.0b & 0.9 \(\pm\) 0.1b & 2.8 \(\pm\) 0.5a & 0.5 \(\pm\) 0.1b & 0.000 & 1.039 \\
45 & Estragole & 17.5 \(\pm\) 0.3a & 0.9 \(\pm\) 0.1c & 3.6 \(\pm\) 0.2b & 0.8 \(\pm\) 0.1c & 0.000 & 0.934 \\
46 & Anethol & 28.3 \(\pm\) 1.5a & 8.2 \(\pm\) 0.2c & 25.1 \(\pm\) 0.2b & 5.9 \(\pm\) 0.4d & 0.000 & 0.791 \\
47 & Eugenol & 0.9 \(\pm\) 0.2c & 4.5 \(\pm\) 0.2b & 16.6 \(\pm\) 1.6a & 0.0d & 0.000 & 1.073 \\
50 & 2-Ethylfuran & 0.0b & 0.0b & 5.2 \(\pm\) 1.1a & 0.0b & 0.000 & 1.060 \\
51 & 2-Pentifyfuran & 3.5 \(\pm\) 0.5d & 4.7 \(\pm\) 0.1c & 29.7 \(\pm\) 0.6a & 6.7 \(\pm\) 0.2b & 0.000 & 1.085 \\
61 & 2-Acetylthiarole & 1.1 \(\pm\) 0.2a & 0.0b & 0.0b & 0.0b & 0.00 & 0.0974 \\ \hline \multicolumn{8}{c}{Different letters refer to statistically significant differences (\(p<0.05\)). Values represent means and standard deviation} \\ \multicolumn{8}{c}{(\(n=3\)).} \\ \end{tabular}
\end{table} 
Table 2: OAVs of odour-active compounds in marinated pork hocks. 1,8-Cineole and linalool constituted a large portion of the specific aroma of Chinese marinated meat products and could have originated from the Chinese traditional spices. Hexanal, octanal, nonanal and 2-pentylfuran with fat and meat flavours were generated from the boiling procedure of the marinated meat products. These components were defined as the key odour-active compounds due to their significant contributions (\(p<0.05\)) to the integral flavour.