## 3 Results
### Profiles of Volatile Compounds Generated by Different FAs
A total of 26 types of oxidative products of C20:4 were detected, including 3 aldehydes, 8 alkenes, 9 aromatic hydrocarbons, 3 esters, and 3 other substances. The three aldehydes were trans,trans-2,4-decanodienal, hexal, and carlinal; trans,trans-2,4-decanodienal and carlinal were detected with LOX treatment, indicating that these two aldehydes were mainly produced by C20:4 via LOX-induced oxidation. The concentration of hexal after LOX treatment was 3.88 \(\mathrm{\SIUnitSymbolMicro g}\)/L, 0.60 times higher than without LOX addition. The alkane olefines were significantly increased after LOX treatment (\(p<0.05\)), suggesting that LOX promotes the oxidation of alkyl radicals. Furthermore, hexanal was the only volatile compound produced by C20:4 degradation that was a key flavor in dry-cured mackerel. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Number**} & \multirow{2}{*}{**Compounds**} & \multicolumn{3}{c}{**Concentration of Volatile Compounds (\(\mathrm{\SIUnitSymbolMicro g}\)/L)**} \\ \cline{3-5}  & & **Blank** & **C16:0** & **C20:4** + **LOX** \\ \hline
1 & 2,4-Decadienal, (E,E)- & 0.00 \(\pm\) 0.00 & 0.00 \(\pm\) 0.00 a & 3.21 \(\pm\) 0.19 a \\
2 & Hexanal & 0.00 \(\pm\) 0.00 a & 2.44 \(\pm\) 0.20 b & 3.88 \(\pm\) 0.35 c \\
3 & Heptal & 0.00 \(\pm\) 0.00 a & 0.00 \(\pm\) 0.00 a & 15.17 \(\pm\) 2.41 b \\
4 & Benzene, decyl- & 0.00 \(\pm\) 0.00 a & 0.38 \(\pm\) 0.37 a & 0.00 \(\pm\) 0.00 a \\
5 & 5,8,11,14-Eicostetraenoic acid, & 0.00 \(\pm\) 0.00 a & 0.00 \(\pm\) 0.00 a & 22.65 \(\pm\) 2.26 b \\
6 & 8-Heptadecene & 0.00 \(\pm\) 0.00 a & 0.61 \(\pm\) 0.02 b & 1.37 \(\pm\) 0.17 c \\
7 & Dodecane & 22.15 \(\pm\) 0.81 a & 135.95 \(\pm\) 11.07 b & 229.05 \(\pm\) 23.00 c \\
8 & Tetradecane & 5.10 \(\pm\) 0.08 b & 3.25 \(\pm\) 0.13 b & 5.64 \(\pm\) 10.9 c \\
9 & Undecane & 5.10 \(\pm\) 0.07 a & 469.21 \(\pm\) 14.74 b & 769.46 \(\pm\) 30.64 c \\
10 & Heptlyckohexane & 14.77 \(\pm\) 10.48 a & 0.00 \(\pm\) 0.00 a & 10.04 \(\pm\) 0.21 a \\
11 & Cyclohexane, pentyl- & 0.00 \(\pm\) 0.00 a & 4.46 \(\pm\) 0.29 b & 0.00 \(\pm\) 0.00 a \\
12 & Benzene, 1,2,4-trimethyl- & 0.00 \(\pm\) 0.00 a & 72.94 \(\pm\) 6.27 b & 73.54 \(\pm\) 5.75 b \\
13 & Benzene, propyl- & 0.00 \(\pm\) 0.00 a & 20.24 \(\pm\) 1.31 b & 27.20 \(\pm\) 2.88 c \\
14 & p-Xylene & 0.00 \(\pm\) 0.00 a & 0.00 \(\pm\) 0.00 a & 6.42 \(\pm\) 0.13 b \\
15 & Toluene & 0.00 \(\pm\) 0.00 a & 2.40 \(\pm\) 0.24 b & 4.51 \(\pm\) 0.15 c \\
16 & Benzene, 1,3-dimethyl- & 0.00 \(\pm\) 0.00 a & 18.79 \(\pm\) 1.20 b & 30.59 \(\pm\) 0.56 c \\
17 & Benzene, 1,3,5-trimethyl- & 0.00 \(\pm\) 0.00 a & 13.62 \(\pm\) 0.97 b & 13.12 \(\pm\) 1.53 b \\
18 & o-Xylene & 0.00 \(\pm\) 0.00 a & 8.32 \(\pm\) 0.28 b & 25.80 \(\pm\) 5.30 c \\
19 & Benzene, 1-ethyl-2-methyl- & 0.00 \(\pm\) 0.00 a & 3.34 \(\pm\) 0.07 b & 6.54 \(\pm\) 0.99 c \\
20 & Ethlybenzene & 0.00 \(\pm\) 0.00 a & 0.90 \(\pm\) 0.03 b & 1.20 \(\pm\) 0.26 b \\
21 & Decanoic acid, methyl ester & 0.00 \(\pm\) 0.00 a & 0.00 \(\pm\) 0.00 a & 1.69 \(\pm\) 0.28 a \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Changes in the concentration of volatile compounds produced from C20:4.