## 3 Results
### Profiles of Volatile Compounds Generated by Different FAs
\begin{table}
\begin{tabular}{c c c c c} \hline \multirow{2}{*}{**Number**} & \multirow{2}{*}{**Compounds**} & \multicolumn{4}{c}{**Concentration of Volatile Compounds (\(\mathrm{\mu g/L}\))**} \\ \cline{3-5}  & & **Blank** & **C16:0** & **C18:0** + **LOX** \\ \hline
1 & Heptanal & 0.00 \(\pm\) 0.00 a & 13.60 \(\pm\) 1.52 b & 20.73 \(\pm\) 1.46 c \\
2 & Nonanal & 0.00 \(\pm\) 0.00 a & 0.00 \(\pm\) 0.00 a & 7.80 \(\pm\) 0.40 b \\
3 & 2-Heptanone & 0.00 \(\pm\) 0.00 a & 21.40 \(\pm\) 0.78 b & 25.46 \(\pm\) 3.09 b \\
4 & 2-Nonanone & 0.00 \(\pm\) 0.00 a & 0.00 \(\pm\) 0.00 a & 7.31 \(\pm\) 0.28 b \\
5 & Eicosane & 0.00 \(\pm\) 0.00 a & 4.43 \(\pm\) 0.32 b & 0.00 \(\pm\) 0.00 a \\
6 & Heptane & 0.00 \(\pm\) 0.00 a & 53.78 \(\pm\) 4.18 c & 46.48 \(\pm\) 2.59 b \\
7 & Octane & 0.00 \(\pm\) 0.00 a & 37.23 \(\pm\) 1.74 b & 48.72 \(\pm\) 1.58 c \\
8 & Tridecane & 0.00 \(\pm\) 0.00 a & 0.00 \(\pm\) 0.00 a & 0.56 \(\pm\) 0.02 b \\
9 & Benzene, propyl- & 1.36 \(\pm\) 0.19 b & 0.00 \(\pm\) 0.00 a & 36.13 \(\pm\) 1.82 b \\
10 & Benzene, n-butyl- & 12.34 \(\pm\) 0.94 b & 8.57 \(\pm\) 0.24 a & 9.45 \(\pm\) 1.52 a \\
11 & Toluene & 0.00 \(\pm\) 0.00 a & 3.49 \(\pm\) 0.26 b & 7.28 \(\pm\) 0.49 c \\
12 & Ethylbenzene & 0.00 \(\pm\) 0.00 a & 4.55 \(\pm\) 0.22 b & 7.33 \(\pm\) 0.29 c \\
13 & Dodecanoic acid, methyl ester & 0.00 \(\pm\) 0.00 a & 19.17 \(\pm\) 2.63 b & 19.03 \(\pm\) 1.15 b \\
14 & 2-Octanamine & 0.00 \(\pm\) 0.00 a & 6.18 \(\pm\) 0.51 b & 11.22 \(\pm\) 1.09 c \\
15 & Butylated Hydroxyltouluene & 1.25 \(\pm\) 0.02 a & 0.00 \(\pm\) 0.00 a & 42.18 \(\pm\) 1.93 b \\
16 & Naphthalene & 0.00 \(\pm\) 0.00 a & 0.00 \(\pm\) 0.00 a & 0.03 \(\pm\) 0.00 b \\ Total & & 14.95 & 172.40 & 289.71 \\ \hline  & & Values are mean \(\pm\) standard deviation (SD, \(n\) = 3). The letters in the same row indicate that there is a significant difference between the groups (\(p<0.05\)). & & \\ \end{tabular}
\end{table} 
Table 3: Changes in the concentration of volatile compounds produced from C18:0. 3.4.3. Changes in the Contents of Volatile Compounds Produced from C18:In9c and LOX-Induced C18:In9c Oxidation  
Table 4 displays the changes in the concentrations of volatile compounds produced from C18:In9c oxidation with or without LOX. Overall, the concentration of volatile compounds by the autoxidative system was 1020.50 \(\upmu\)g/L and increased by 0.53 times in the LOX-induced oxidative system, reaching 1563.68 \(\upmu\)g/L. A total of 28 types of C18:In9c oxidative products were detected, with esters accounting for the highest number (nine), followed by aldehydes (six). (E)-2-decenal, heptanal, decanal, hexanal, nonanal, and octanal were all detected in the two oxidation systems. (E)-2-decenal production in the presence of LOX treatment had no significant change compared with its production in the absence of LOX, while heptanal, Kuabal, hexal, nonal, and octanal production in the presence of LOX treatment showed an obvious increase compared to their production in the absence of LOX (\(p<0.05\)). 1-nonanol, 2-dodecenol, heptanol, and octanol are the top four types of alcohols produced by the degradation of C18:In9c. 2-dodecenol was detected after LOX treatment. Furthermore, 2-decanone, 2-nonanone, 2-undecanone, and 3-octanone are the top four ketones produced by the degradation of C18:In9c. However, 3-octanone was detected only after LOX treatment. Most of the C18:In9c degradation products can be produced by autoxidation and LOX enzymatic oxidation, with 2-undecanone, heptanal, kasal, nonanal, and octanal being the key flavors in dry-cured mackerel. This further demonstrates that the oxidative products of C18:In9c contribute significantly to the overall flavor of dry-cured mackerel.