Modification of myofibrillar protein structural characteristics: Effect of ultrasound-assisted first-stage thermal treatment on unwashed Silver Carp surimi gel

[Display omitted] •Ultrasound-assisted 40 °C thermal treatment improved unwashed surimi gel strength.•Ultrasound-assisted 40 °C thermal treatment reduced the myofibrillar protein size.•The reduced SH group and conformational conversion promoted the proteins interaction.•Ultrasound gave an impetus to the conformational conversion of proteins. The hardness properties of unwashed surimi gel are considered as the qualities of gelation defect. This research investigated the effect of ultrasound-assisted first-stage thermal treatment (UATT) on the physicochemical properties of unwashed Silver Carp surimi gel, and the enhancement mechanism. UATT could reduce protein particle size, which significantly reduced from 142.22 μm to 106.70 μm after 30 min of UATT compared with the nature protein. This phenomenon can promote the protein crosslinking, resulting in the hardness of surimi gel increased by 15.08 %. Partially unfolded structure of myofibrillar protein and exposures of tryptophan to water, lead to the increase in the zeta potential absolute value, driven by UATT. The reduced SH group level and the conformational conversion of proteins from random coiling to α-helix and β-sheet, which was in support of intermolecular interaction and gel network construction. The results are valuable for processing protein gels and other food products.