l-lysine modified whey protein isolate: Mechanism on the improvement of the gel properties and its application as model fish sausage

In this study, whey protein isolate (WPI) was used as raw material to study the effects of l-lysine (Lys) on the gel properties and structure of WPI, and the application of modified WPI in fish sausage was studied. The results showed that with the increase of Lys concentration, the gel properties and water holding capacity of WPI were greatly improved, while the Lys concentration exceeding 4 mg/mL would produce adverse reactions, such as the decrease of chromaticity and gel hardness. At Lys concentration of 1.6 mg/mL, WPI showed the highest texture properties and good water holding capacity, which depended on the dense microstructure and reduced pore size. This was because WPI crosslinks with Lys through electrostatic interaction, reducing electrostatic repulsion and promoting its crosslinking and polymerization, which was manifested by the change of WPI structure and the increase of particle size. In addition, the hardness, chewiness, and cooking loss capacity of the surimi added with modified WPI were better than those of the pure fish sausage, corn starch and WPI single treatment group. This study can provide a theoretical basis for the study of WPI modified gel and provide guidance for the modified WPI used as gelling agent in surimi products.