## 3 Results and Discussion
### FTIR Analysis  
The vibrational spectra of PG and HIGs at different salt concentrations were analyzed by FTIR to gain insights into their secondary structure. Spectral analy  
Figure 4: SDS-PAGE pattern of SDS-soluble protein (S) and sarcoplasmic protein (R) of pangasius gel obtained under various pressure treatment conditions. M: molecular ladder; 1S/1R: HIGs; 2S/2R: PG300/1%; 3S/3R: PG400/1%; 4S/4R: PG500/1%; 5S/5R: PG300/2%; 6S/6R: PG400/2%; 7S/7R: PG500/2%. 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 concen-tration 1% and 400 MPa/10 \({}^{\circ}\)C/10 min; PG400/2%: 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 concen-tration 1% and 500 MPa/10 \({}^{\circ}\)C/10 min. sis within the frequency range of 4000-500 cm\({}^{-1}\) revealed peaks at 435 \(\pm\) 8.6 cm\({}^{-1}\), 1391 \(\pm\) 9.4 cm\({}^{-1}\), 1455 \(\pm\) 2.2 cm\({}^{-1}\), 1549 \(\pm\) 12.1 cm\({}^{-1}\), 1624 \(\pm\) 0 cm\({}^{-1}\), 2921 \(\pm\) 3.37 cm\({}^{-1}\), and 3267 \(\pm\) 7.37 cm\({}^{-1}\). Among these bands, the amide I band was observed at 1624 \(\pm\) 0 cm\({}^{-1}\), amide II at 1549 \(\pm\) 12.1 cm\({}^{-1}\), and amide A at 3267 \(\pm\) 7.37 cm\({}^{-1}\) (Figure 5). The amide I region, characterized by C=O stretching vibrations, typically consists of overlapping component bands derived from structural elements such as \(\alpha\)-helices, \(\beta\)-sheets, turns, and disordered or irregular conformations [41]. Amide II (1480-1575 cm\({}^{-1}\)) primarily corresponds to CN stretching and NH bending, while the amide A band (3100-3600 cm\({}^{-1}\)) is mainly linked to OH and NH stretching vibrations, with a broadened absorbance reflecting the muscle's high water content [42; 43]. Within the myofiber spectrum, the amide I band (ranging from 1700 to 1600 cm\({}^{-1}\)) is particularly significant due to its high sensitivity to hydrogen-bonding, dipole-dipole interactions, and the structural configuration of the protein's polypeptide backbone [5]. Like the study of [PERSON] et al. [41], the application of HPP resulted in a reduction in the absorbance of the amid I band in pangasius protein as compared to HIGs. This reduction indicates structure alterations, due to the disruption or formation of protein interactions. However, the amide I frequencies were similar in all treatments, suggesting that high pressure caused only minor changes in the protein structure. To enhance spectral resolution and investigate the changes in the secondary structure of myofibrillar proteins, the amide I region (1700-1600 cm\({}^{-1}\)) was analyzed using second-derivative spectra (Figure 6). This analysis found nine different bands including 1604 \(\pm\) 0.58 cm\({}^{-1}\), 1625 \(\pm\) 0.73 cm\({}^{-1}\), 1637 \(\pm\) 0.35 cm\({}^{-1}\), 1648 \(\pm\) 1.3 cm\({}^{-1}\), 1654 \(\pm\) 0.84 cm\({}^{-1}\), 1665 \(\pm\) 1.32 cm\({}^{-1}\), 1675 \(\pm\) 0.26 cm\({}^{-1}\), 1680 \(\pm\) 0.66 cm\({}^{-1}\) and 1696 \(\pm\) 0.66 cm\({}^{-1}\). The bands at 1625 \(\pm\) 0.73 cm\({}^{-1}\), 1637 \(\pm\) 0.35 cm\({}^{-1}\), and 1696 \(\pm\) 0.66 cm\({}^{-1}\) were attributed to \(\beta\)-sheet structures; the band at 1654 \(\pm\) 0.84 cm\({}^{-1}\) and 1665 \(\pm\) 1.32 cm\({}^{-1}\) corresponded to \(\alpha\)-helices; the bands at 1675 \(\pm\) 0.26 and 1680 \(\pm\) 0.66 cm\({}^{-1}\) were assigned to \(\beta\)-turns [43]. On the other hand, the band at 1648 \(\pm\) 1.3 cm\({}^{-1}\) was attributed to random structures, and the band at  
Figure 5: FTIR spectra of pangasius gels with 1 and 2% salt under different HPP treatments over the frequency range 4000–500 cm\({}^{-1}\).