The improved gel properties of myofibrillar protein under low salt condition by ultrasound-assisted sodium tripolyphosphate.

Excessive salt intake is associated with increased risks of cardiovascular disease, while directly reducing salt content significantly decreased the quality of meat. The objective of this study was to investigate the synergistic effects of sodium tripolyphosphate (STP) and ultrasound treatment on the gel properties of MP under low-salt conditions (0.3 M NaCl). The results of FTIR spectra showed that P₃O₁₀^5- group of STP bound to -NH₂ or -OH group of MP form C-N-P or C-O-P bond, indicating the STP was successfully introduced to MP. The addition of STP significantly increased the absolute value of Zeta-potential, suggesting that the presence of STP increased the electrostatic interaction of MP-MP. Importantly, STP combined with ultrasound treatment under low salt condition (STP-U_0.3) significantly increased solubility and decreased particle size of MP. Besides, STP-U_0.3 treatment also promoted the exposure of hydrophobic groups and improved the rheological behavior of MP, resulting in the highest gel strength (37.78 ± 0.71 g) and the lowest cooking loss (26.73 ± 0.90 %) especially in 10 mM STP combined 100 W ultrasound treatment. These results corresponded by the gradually increases of α-helix content and the decrease of tryptophan fluorescence intensity. Furthermore, results of SEM illustrated that STP-U_0.3 treatment contributed to formation of more homogeneous and dense gel network of MP gel. The above results displayed that the STP-U treatment under 0.3 M NaCl resulted in an equivalent effect to control group of 0.6 M NaCl, indicating that the combined application of STP and ultrasound has a promising potential in the low-salt meat processing industry.