Synergistic effect of high-intensity ultrasound and pH-shifting on the functionalities of chicken wooden breast myofibrillar protein: Reveal the mechanism of protein structure change

Due to the deterioration of wooden breast myofibrillar protein (WBMP) functional properties (such as gel and emulsification performance) caused by oxidative stress, making it difficult to use as normal MP in the processing and utilization of protein gel/emulsion products. The functional properties of chicken deteriorate, affecting its processing and utilization. High-intensity ultrasound (HIU) was introduced in the unfolding‒refolding process of pH-shifting treatment to improve functional properties on WBMP. The results showed that the WUH-R group (HIU applied during the WBMP unfolding stage) had the higher solubility, emulsification, and rheology. The zeta potential and particle size indicated that HIU significantly disrupted the protein structures (P < 0.05). The fluorescence spectrum showed that protein hydrophobicity was significantly (P < 0.05) reduced from 69.60 ± 2.03 (WBMP) to 43.39 ± 1.33 (WUH-R). Similarly, circular dichroism and Fourier transform infrared spectroscopy indicated that HIU facilitated the conversion of α-helix (25.12 ± 0.78% to 46.37 ± 2.14%) to β-sheet (27.61 ± 2.47% to 7.28 ± 0.89%). Our results demonstrate that HIU can promote the complete unfolding of WBMP. Nonetheless, in the WU-RH group (HIU applied during the WBMP refolding stage), HIU inhibited the assembly of proteins. In the WU-RH group, the particle size became larger, while the solubility and emulsibility became worse. In general, HIU is only added in the unfolding phase of protein pH-shifting to improve its functional properties and facilitate the reuse of WBMP.