The effects of ultrasonic power (0, 150, 300, 450, and 600 W) on the extraction yield and the structure and rheological properties of pepsin-soluble collagen (PSC) from albacore skin were investigated. Compared with the conventional pepsin extraction method, ultrasonic treatment (UPSC) significantly increased the extraction yield of collagen from albacore skin, with a maximum increase of 8.56%. The sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis revealed that peptides of low molecular weight were produced when the ultrasonic power exceeded 300 W. Meanwhile, secondary structure, tertiary structure, and X-ray diffraction analyses showed that the original triple helix structure of collagen was intact after the ultrasonic treatment. The collagen solutions extracted under different ultrasonic powers had significant effects on the dynamic frequency sweep, but a steady shear test suggested that the collagen extracted at 150 W had the best viscosity. These results indicate that an ultrasonic power between 150 and 300 W can improve not only the extraction yield of natural collagen, but also the rheological properties of the collagen solution without compromising the triple helix structure.

To investigate the interaction effects of resting times (0, 6, and 12 h) and NaHCO₃ concentrations (0, 2, 4, and 6 g/kg) on chicken myofibrillar protein (CMP), this study analyzed the changes in solubility, active sulfhydryl groups, rheological behavior, fluorescence, and gel properties of CMP solutions (60 mg/mL). The results indicated that pH significantly increased with higher NaHCO₃ concentrations and longer resting times. Consequently, solubility, active sulfhydryl groups, apparent viscosity, shear stress, G’ value at 80 °C, hardness, springiness, and cohesiveness all significantly increased, while particle size, turbidity, and whiteness significantly decreased. However, these trends were not observed in samples treated with an amount of 6 g/kg NaHCO₃ and/or a resting time of 12 h. The findings suggest that treatment with 4 g/kg NaHCO₃ and a resting time of 6 h effectively reduced protein aggregation and enhanced solubility. Conversely, excessive NaHCO₃ or prolonged resting times resulted in decreased protein solubility and deteriorated textural properties.

To investigate how sodium bicarbonate concentrations (0, 10, 20, 30, 40, and 50 mM) modulate the turbidity and molecular interactions of pork myosin, the pH, turbidity, particle size, active and total thiol content, surface hydrophobicity, rheology properties, and chemical forces were analyzed. Results revealed that increasing sodium bicarbonate concentration from 0 to 50 mM significantly elevated (p < 0.05) pH, surface hydrophobicity, apparent viscosity, active thiol content, and storage modulus (G′), while significantly reducing (p < 0.05) turbidity, mean particle size, gel whiteness, and ionic bonding strength. The alkalinization-induced pH reduced protein turbidity and enhanced molecular unfolding, thereby exposing hydrophobic regions and reactive thiol groups; this promoted hydrophobic interactions and facilitated disulfide bond formation during heat-induced gelation. Consequently, higher sodium bicarbonate levels (40 and 50 mM) markedly strengthened intermolecular forces and improved the rheological performance of the resulting myosin gels.