## 3 Results and Discussion
### Water-Holding Capacity  
Figure 3 presents the water-holding capacity (WHC) of pangasius gel at different salt concentrations. HPP improved the WHC of all pangasius gel treatments compared to HIGs (\(p<0.05\)). Pangasius gels with 2% added salt and treated at 500 MPa/10 \({}^{\circ}\)C/10 min achieved the highest WHC at 88.62%, while HIGs had the lowest WHC at 76.28%. HPP pangasius gels with 1% added salt exhibited similar WHC to those with 2% added salt \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Treatment** & **\(\alpha\)-Helix (\%)** & **\(\beta\)-Sheet (\%)** & **\(\beta\)-Turn (\%)** & \
\begin{tabular}{c} **Random** \\ **Structure (\%)** \\ \end{tabular} &
\begin{tabular}{c} **Aromatic Side** \\ **Chain** \\ \end{tabular} \\ \hline HIGs & 19.41 \(\pm\) 2.27\({}^{\mathrm{a}}\) & 31.18 \(\pm\) 0.73\({}^{\mathrm{a}}\) & 19.64 \(\pm\) 1.33\({}^{\mathrm{a}}\) & 10.57 \(\pm\) 0.51\({}^{\mathrm{a}}\) & 19.17 \(\pm\) 0.37\({}^{\mathrm{a}}\) \\ PG300/1\% salt & 24.74 \(\pm\) 1.99\({}^{\mathrm{b}}\) & 29.55 \(\pm\) 0.96\({}^{\mathrm{a}}\) & 20.14 \(\pm\) 0.81\({}^{\mathrm{a}}\) & 8.49 \(\pm\) 0.66\({}^{\mathrm{b}}\) & 17.05 \(\pm\) 3.76\({}^{\mathrm{a}}\) \\ PG300/2\% salt & 24.14 \(\pm\) 1.07\({}^{\mathrm{b}}\) & 29.54 \(\pm\) 1.32\({}^{\mathrm{a}}\) & 19.84 \(\pm\) 0.84\({}^{\mathrm{a}}\) & 8.95 \(\pm\) 1.36\({}^{\mathrm{b}}\) & 17.52 \(\pm\) 3.89\({}^{\mathrm{a}}\) \\ PG400/10 \% salt & 24.66 \(\pm\) 1.87\({}^{\mathrm{a}}\) & 29.22 \(\pm\) 2.86\({}^{\mathrm{a}}\) & 19.85 \(\pm\) 1.08\({}^{\mathrm{a}}\) & 8.02 \(\pm\) 1.26\({}^{\mathrm{a}}\) & 18.21 \(\pm\) 1.34\({}^{\mathrm{a}}\) \\ PG400/2\% salt & 23.53 \(\pm\) 1.11\({}^{\mathrm{b}}\) & 30.72 \(\pm\) 1.72\({}^{\mathrm{a}}\) & 19.89 \(\pm\) 1.33\({}^{\mathrm{a}}\) & 9.06 \(\pm\) 0.45\({}^{\mathrm{a}}\) & 16.77 \(\pm\) 3.73\({}^{\mathrm{a}}\) \\ PG500/1\% salt & 23.65 \(\pm\) 0.98\({}^{\mathrm{b}}\) & 30.18 \(\pm\) 1.79\({}^{\mathrm{a}}\) & 20.11 \(\pm\) 1.03\({}^{\mathrm{a}}\) & 7.69 \(\pm\) 1.38\({}^{\mathrm{a}}\) & 18.32 \(\pm\) 3.16\({}^{\mathrm{a}}\) \\ PG500/2\% salt & 23.82 \(\pm\) 1.76\({}^{\mathrm{b}}\) & 29.43 \(\pm\) 0.89\({}^{\mathrm{a}}\) & 20.16 \(\pm\) 1.96\({}^{\mathrm{a}}\) & 9.19 \(\pm\) 1.12\({}^{\mathrm{a}}\) & 17.37 \(\pm\) 3.81\({}^{\mathrm{a}}\) \\ \hline HIGs: conventional heat-induced gels; PG300/1\%: salt concentration 1% and 300 MPa/10 \({}^{\circ}\)C/10 min; PG300/2\%: salt concentration 1% and 300 MPa/10 \({}^{\circ}\)C/10 min; PG400/1\%: salt concentration 1% and 400 MPa/10 \({}^{\circ}\)C/10 min; PG500/1\%: salt concentration 1% and 500 MPa/10 \({}^{\circ}\)C/10 min; PG500/2\%: salt concentration 1% and 400 MPa/10 \({}^{\circ}\)C/10 min; PG500/10\%: salt concentration 1% and 500 MPa/10 \({}^{\circ}\)C/10 min. Different letters (a, b) in the same column indicate significant differences (\(p<0.05\)). & \\ \hline \hline \end{tabular}
\end{table} 
Table 3: The secondary structures (%) determined by FTIR self-deconvolution of HIGs and pressure-treated pangasius gel added 1 and 2% salt. (\(p\geq 0.05\)). The improved mechanical properties of pangasius gel under low salt conditions could be attributed to the enhanced interactions among myofibrillar proteins by HPP, which promote protein solubility and gel formation at low salt concentrations, resulting in a gel with better WHC [9]. Additionally, the myofibrillar structure is disrupted and degraded into smaller protein fragments, leading to an increased solubility of proteins under low-salt conditions. This also facilitates the binding of free water and fish proteins, resulting in gels with high strength and water-holding capacity under low-salt conditions [38]. Furthermore, HPP creates a stable and compact spatial structure of the gel, which helps immobilize and retain water within the gel structure [1]. HPP also exposes hydrophobic groups, enhancing hydrophobic interactions and stabilizing the water/protein system [5].