Regulatory mechanism of leucine-amidated pectin on the gel properties of shrimp surimi as a salt substitute.

To address gel deterioration in low-salt shrimp surimi, leucine-amidated pectin (Leu-Pe, 21.89% grafting degree) was synthesized via enzymatic modification. Leu-Pe (4.0%) showed approximately 100-fold higher apparent viscosity than native pectin and formed an elasticity-dominated network. In low-salt surimi, Leu-Pe enhanced gel properties: hardness, chewiness, and gel strength reached 6.72 N, 17.77 mJ, and 9.97 N·mm, respectively, while water-holding capacity (WHC) peaked at 97.16%. Mechanistic analysis showed that Leu-Pe promoted ordered β-sheet formation and disulfide cross-linking, reducing free thiols to 254.93 μmol/g. Microstructural observations confirmed a compact filamentous network driven by hydrophobic anchoring and hydrogen bonding, which restricted water migration. These findings demonstrate that Leu-Pe provides structural reinforcement and superior water retention, offering an effective strategy for developing healthier low-salt surimi products.