## 3 Results
### Profiles of Volatile Compounds Generated by Different FAs
\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** & **C18:2n6c + LOX** \\ \hline
41 & Tetradecane & 5.10 \(\pm\) 0.08 a & 4.29 \(\pm\) 0.21 a & 4.45 \(\pm\) 0.87 a \\
42 & Octanoic acid, methyl ester & 0.00 \(\pm\) 0.00 a & 327.76 \(\pm\) 6.89 b & 380.37 \(\pm\) 30.00 c \\
43 & 9,12-Octadecienoic acid (Z,Z)-, methyl ester & 0.00 \(\pm\) 0.00 a & 0.00 \(\pm\) 0.00 a & 27.68 \(\pm\) 2.65 b \\
44 & Dodecanoic acid, methyl ester & 0.00 \(\pm\) 0.00 a & 2.71 \(\pm\) 0.29 a & 83.34 \(\pm\) 14.25 b \\
45 & Hexadecenoic acid, methyl ester & 0.00 \(\pm\) 0.00 a & 8.39 \(\pm\) 0.65 b & 10.10 \(\pm\) 0.54 c \\
46 & 9-Hexadecenoic acid, methyl ester, (Z)- & 0.00 \(\pm\) 0.00 a & 7.23 \(\pm\) 0.28 b & 6.99 \(\pm\) 0.66 b \\
47 & Butylated Hydroxytoluene & 1.25 \(\pm\) 0.02 a & 0.00 \(\pm\) 0.00 a & 9.86 \(\pm\) 1.77 b \\
48 & Naphthalene & 0.00 \(\pm\) 0.00 a & 0.00 \(\pm\) 0.00 a & 1.14 \(\pm\) 0.17 b \\
49 & Osime-, methoxy-phenyl- & 0.00 \(\pm\) 0.00 a & 23.15 \(\pm\) 2.15 b & 0.00 \(\pm\) 0.00 a \\ Total & & 13.06 & 2362.20 & 2469.81 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: _Cont._4.6. Changes in the Contents of Volatile Compounds Produced from C20:5 and LOX-Induced C20:5 Oxidation  
The total content of volatile compounds in the LOX-treated C20:5 group was 567.53 \(\mathrm{\SIUnitSymbolMicro g}\)/L, which was 0.45 times higher than without LOX treatment (392.36 \(\mathrm{\SIUnitSymbolMicro g}\)/L) (Table 7). The key oxidative products of C20:5 (aromatic hydrocarbons and alkenes, aldehydes, alcohols, and ketones) were not detected. However, six types of alkane olefines and five types of aromatics were detected after LOX treatment, which suggests that LOX may aggravate the oxidation of alkyl radicals. Similarly, the total contents of volatile compounds in the C22:6n3 and LOX-treated C22:6n3 groups were 1943.45 and 1642.75 \(\mathrm{\SIUnitSymbolMicro g}\)/L, respectively (Table 8). A total of 31 types of oxidative products of C22:6n3 were detected, including 10 types of alkene olefines, 12 types of aromatics, 6 types of esters, and 3 types of other substances. The main olefines were decane and undecane, while the main aromatics were m-xylene and o-xylene. Due to their high thresholds [27], most olefines and aromatics contribute less to flavors. Toluene has a typical fish aroma, and most of the toluene from C20:5 were derived from LOX-induced oxidation, with a relatively low concentration of 15.45 \(\mathrm{\SIUnitSymbolMicro g}\)/L, which may not contribute much to flavor formation. Therefore, volatile compounds derived from C20:5 and C22:6n3 may have no significant effect on the overall flavor of dry-cured mackerel. \begin{table}
\begin{tabular}{c c c c} \hline \multirow{2}{*}{**Number**} & \multirow{2}{*}{**Compounds**} & \multicolumn{3}{c}{**Concentration of Volatile Compounds (\(\mathrm{\SIUnitSymbolMicro g}\)/L)**} \\ \cline{3-4}  & & **Blank** & **C16.0** & **C20.4 + LOX** \\ \hline
22 & Dodecanoic acid, methyl ester & 0.00 \(\pm\) 0.00 a & 0.00 \(\pm\) 0.00 a & 3.47 \(\pm\) 0.31 a \\
23 & n-Hexadecanoic acid & 3.41 \(\pm\) 2.41 a & 0.00 \(\pm\) 0.00 a & 0.63 \(\pm\) 0.08 a \\
24 & D-Limonene & 0.00 \(\pm\) 0.00 a & 141.47 \(\pm\) 195.47 a & 577.24 \(\pm\) 15.00 b \\
25 & Naphthalene, decahydro-, trans- & 0.00 \(\pm\) 0.00 a & 21.02 \(\pm\) 26.72 a & 0.00 \(\pm\) 0.00 a \\
26 & cis-Decalin, 2-syn-methyl- & 0.00 \(\pm\) 0.00 a & 0.00 \(\pm\) 0.00 a & 268.51 \(\pm\) 33.67 b \\ Total & & 50.53 & 919.34 & 2100.93 \\ \hline \end{tabular} 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{table} 
Table 6: _Cont._