Effect of Lysine on Gel Properties of Reduced-Salt Surimi Prepared from Tilapia (Oreochromis niloticus)

Abstract

Low-sodium surimi was prepared from tilapia (Oreochromis niloticus) using lysine, and the gelation properties were systematically evaluated. The primary objective of this study was to optimise the concentrations of salt and lysine using response surface methodology (RSM) with a central composite design (CCD), with salt and lysine concentrations ranging from 0.29 to 1.70% and 0.39 to 1.10%, respectively. The optimum salt concentrations were 1.00%, 1.01%, and 1.09%, with corresponding lysine concentrations of 0.71%, 0.69%, and 0.69%, respectively, to maximise gel strength and hardness and minimise expressible moisture content. The predicted maximum gel strength and hardness were 428 g cm and 6.36 N, respectively, with a predicted minimum expressible moisture content of 2.75%. In addition, the whiteness, TCA-soluble peptide content, and protein pattern of the surimi gel were assessed. Whiteness varied with both salt and lysine concentrations, with lower whiteness generally observed at higher lysine concentrations within the experimental region. The lower TCA-soluble peptide content was associated with higher gel strength, reflecting reduced proteolytic degradation and improved gel network formation. SDS-PAGE analysis revealed that the polymerisation of myosin heavy chain (MHC) was more pronounced in gels exhibiting maximal gel strength and hardness. These findings indicate that incorporating lysine can significantly improve the gelation properties of tilapia surimi under low-salt conditions, thereby enhancing its quality as a functional food ingredient.