# Production and Refinement of Omega-3 Rich Oils from Processing By-Products of Farmed Fish Species
## 3 Results and Discussion
### Chemical Characterization and Oxidative Stability of Fish Oils
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Oil Samples**} & \multirow{2}{*}{\begin{tabular}{c} **Refining** \\ **Phase** \\ \end{tabular} } & \multicolumn{4}{c}{**Measured Parameter**} \\ \cline{3-6}  & & \multicolumn{2}{c}{**FFA**} & \multicolumn{2}{c}{**PV**} & \multirow{2}{*}{**TOTOX**} & \multirow{2}{*}{**TBARS**} \\  & & & **(\% Oleic Acid)** & & & & **(uM/g)** \\ \hline \multirow{4}{*}{\begin{tabular}{c} Tuna \\ by-product oil \\ \end{tabular} } & _Crude oil_ & 2.94 \(\pm\) 0.12 a & 2.31 \(\pm\) 0.73 a & 25.2 \(\pm\) 0.08 a & 29.7 \(\pm\) 0.20 a & 0.94 \(\pm\) 0.33 a \\  & _Desummed_ & 3.51 \(\pm\) 0.03 b & 3.93 \(\pm\) 0.18 b & 19.2 \(\pm\) 1.25 b & 27.1 \(\pm\) 0.79 b & 1.02 \(\pm\) 0.14 a \\  & _Neutralized_ & 3.13 \(\pm\) 0.10 b & 3.46 \(\pm\) 0.39 b & 16.9 \(\pm\) 1.23 c & 23.8 \(\pm\) 1.06 c & 2.02 \(\pm\) 0.45 b \\  & _Bleached_ & 2.93 \(\pm\) 0.04 a & 2.88 \(\pm\) 0.11 ab & 14.4 \(\pm\) 0.90 d & 20.2 \(\pm\) 1.34 d & 1.88 \(\pm\) 0.37 b \\  & _Deodorized_ & 2.83 \(\pm\) 0.01a & 3.78 \(\pm\) 0.22 b & 19.5 \(\pm\) 0.94 b & 27.1 \(\pm\) 2.15 b & 1.14 \(\pm\) 0.11 a \\ \hline \multirow{4}{*}{\begin{tabular}{c} Tuna liver oil \\ by-product oil \\ \end{tabular} } & _Crude oil_ & 3.13 \(\pm\) 0.00 a & 2.68 \(\pm\) 0.86 a & 20.9 \(\pm\) 1.34 a & 26.0 \(\pm\) 0.14 a & 2.88 \(\pm\) 0.73 a \\  & _Desummed_ & 2.52 \(\pm\) 0.05 b & 3.01 \(\pm\) 0.05 ab & 19.1 \(\pm\) 2.47 b & 25.2 \(\pm\) 1.17 a & 1.35 \(\pm\) 0.02 b \\  & _Neutralized_ & 2.65 \(\pm\) 0.11 c & 2.89 \(\pm\) 0.22 ab & 17.0 \(\pm\) 4.78 d & 22.7 \(\pm\) 1.22 b & 1.76 \(\pm\) 0.03 b \\  & _Bleached_ & 2.17 \(\pm\) 0.03 b & 2.85 \(\pm\) 0.53 ab & 14.0 \(\pm\) 0.65 d & 19.7 \(\pm\) 0.43 c & 1.92 \(\pm\) 0.35 b \\  & _Deodorized_ & 2.12 \(\pm\) 0.16 b & 4.25 \(\pm\) 0.28 c & 19.2 \(\pm\) 2.22 b & 27.7 \(\pm\) 2.22 a & 1.97 \(\pm\) 0.53 b \\ \hline \multirow{4}{*}{\
\begin{tabular}{c} Seabass and \\ gilthead \\ by-product oil \\ \end{tabular} } & _Crude oil_ & 2.41 \(\pm\) 0.47 a & 4.63 \(\pm\) 1.07 a & 18.1 \(\pm\) 0.19 ab & 19.3 \(\pm\) 2.45 a & 0.53 \(\pm\) 0.05 a \\  & _Dequimed_ & 1.66 \(\pm\) 0.05 b & 2.70 \(\pm\) 0.18 b & 15.7 \(\pm\) 1.12 c & 20.2 \(\pm\) 0.12 a & 3.46 \(\pm\) 2.08 b \\  & _Neutralized_ & 1.43 \(\pm\) 0.18 b & 3.13 \(\pm\) 0.31 b & 12.7 \(\pm\) 0.65 a & 18.9 \(\pm\) 0.26 a & 2.24 \(\pm\) 1.05 b \\ \cline{1-1}  & _Bleached_ & 1.40 \(\pm\) 0.01 b & 3.44 \(\pm\) 0.25 ab & 11.4 \(\pm\) 0.19 b & 18.4 \(\pm\) 0.52 a & 1.14 \(\pm\) 0.10 a \\ \cline{1-1}  & _Deodorized_ & 1.28 \(\pm\) 0.15 b & 4.20 \(\pm\) 0.15 ab & 16.5 \(\pm\) 0.39 c & 24.7 \(\pm\) 0.32 b & 1.42 \(\pm\) 0.53 a \\ \hline \multirow{4}{*}{
\begin{tabular}{c} Seabass and \\ gilthead \\ by-product oil \\ \end{tabular} } & _Control_ & 2.15 \(\pm\) 0.08 & 3.85 \(\pm\) 0.44 & 13.3 \(\pm\) 1.11 & 21.0 \(\pm\) 0.18 & 1.63 \(\pm\) 0.07 \\ \hline \multicolumn{6}{c}{\(n=30\); Different superscript letters (a–d) in the same column denote statistically significant difference (\(p<0.05\)); \(\star\) Measured parameters in deodorized oils marked with \(\star\) do not differ statistically (\(p<0.05\)) from the control sample.} \\ \end{tabular}
\end{table} 
Table 1: Chemical and quality parameters of crude oils from tuna by-products, tuna liver, seagrass and gilthead seabream by-products at different stages of the refining process, and cool liver oil (control). was used to measure the oxidative stability of oils (Figure 1). According to the presented results it can be seen that tuna by-product oil was the most stabile sample among crude oils with IP of 1.54 h at 80 \({}^{\circ}\)C, 0.58 h at 100 \({}^{\circ}\)C and 0.15 h at 120 \({}^{\circ}\)C, while lower values were obtained for the other two oils. The refinement process prolonged the oil oxidative stability in all cases, but unlike for crude oils, refined tuna liver oil and seabass and seabream by-product oil showed higher IP values than tuna by-product oil (prolongation of 36% at 80 \({}^{\circ}\)C, 35% at 100 \({}^{\circ}\)C and 52 % at 120 \({}^{\circ}\)C).