Changes in the Physicochemical Properties of Reduced Salt Pangasius (Pangasianodon hypophthalmus) Gels Induced by High Pressure and Setting Treatment

Pangasius (Pangasianodon hypophthalmus) minced muscle with 1 and 2% salt was treated with different high-pressure processing and thermal methods, including conventional heat-induced gels (HIGs), high-pressure processing (HPP) prior to cooking (PC), HPP prior to setting (PS), and setting prior to HPP (SP), to evaluate for their effects on the selected physicochemical properties. The results showed that the PC treatment produced gels with a significantly higher gel strength (496.72–501.26 N·mm), hardness (9.62–10.14 N), and water-holding capacity (87.79–89.74%) compared to the HIG treatment, which showed a gel strength of 391.24 N·mm, a hardness of 7.36 N, and a water-holding capacity of 77.98%. PC gels also exhibited the typical microstructure of pressure-induced gels, with a denser and homogeneous microstructure compared to the rough and loosely connected structure of HIGs. In contrast, SP treatment exhibited the poorest gel quality in all parameters, with gel strength ranging from 319.79 to 338.34 N·mm, hardness from 5.87 to 6.31 N, and WHC from 71.91 to 73.72%. Meanwhile, the PS treatment showed a comparable gel quality to HIGs. SDS-PAGE analysis revealed protein degradation and aggregation in HPP-treated samples, with a decrease in the intensity of myosin heavy chains and actin bands. Fourier-transform infrared spectroscopy (FTIR) analysis showed minor shifts in protein secondary structures, with the PC treatment showing a significant increase in α-helices (28.09 ± 0.51%) and a decrease in random coil content (6.69 ± 0.92%) compared to α-helices (23.61 ± 0.83) and random coil structures (9.47 ± 1.48) in HIGs (p < 0.05). Only the PC treatment resulted in a significant reduction in total plate count (TPC) (1.51–1.58 log CFU/g) compared to 2.33 ± 0.33 log CFU/g in the HIG treatment. These findings suggest that HPP should be applied prior to thermal treatments (cooking or setting) to achieve an improved gel quality in reduced-salt pangasius products.