Comparative study on the effect of different salts on surimi gelation and gel properties

Abstract

The effects of four representative salts, KCl, NaCl, CaCl2 and MgCl2, on surimi gel properties were comprehensively investigated. During gelation, monovalent salts are prone to convert α-helix to β-sheet while divalent salts tend to change α-helix to β-turn, thus altering the protein conformation differently. Monovalent salts extract and swell myofibrillar proteins more effectively, generating an ordered and smooth gel network with appreciable water-holding capacity (WHC). Ca2+ activates transglutaminase (TGase) to crosslink surimi proteins by forming ε-(γ-glutamyl) lysine bonds, while Mg2+ forms salt bridges with adjacent proteins, leading to a gel with more developed protein complexes. However, excessive divalent salts would induce serious protein coagulation, forming poor networks and lowering water retention. Ionic strength within 0.2–0.5 effectively reinforced the gel structure, while the WHC of surimi gels reached its peak with an ionic strength of around 0.6. At the optimal salt concentration of 1.5%, K+ with a larger ionic radius showed inferior effects on forming ionic bonds among proteins, whereas other metal ions induced more hydrophobic interactions within surimi gels. Mg2+, with higher oxidability than other metal ions, could enhance the formation of disulfide bonds and inhibit the browning caused by the Maillard reaction, thus improving gel whiteness. This study provides new insides into the roles of common salts during surimi gelation and gel properties and is expected to guide further gelation innovation and gel product development.