Effects of different recovered sarcoplasmic proteins on the gel performance, water distribution and network structure of silver carp surimi

This study investigated the effects of different recovered sarcoplasmic proteins (SP) (HSP, recovered by heating flocculation; PHSP, recovered by pH-shifting flocculation; PHCSP, recovered by pH-shifting/chitosan flocculation) on the gel performance，water distribution and network structure of silver carp surimi. A proper SP amount could significantly (p < 0.05 ) improve the breaking force, deformation, hardness, springiness and whiteness of surimi gels, 6% PHCSP addition showing the best performance in improving the surimi gel strength. Stress relaxation results indicated that SP addition could increase equilibrium stress, the equilibrium elastic coefficient (E 1 ) and decay elastic coefficient (E 2 ), indicating an increased hardness and elasticity. Rheological tests revealed significantly higher G′ values for surimi/SP composite gels than pure surimi gel, indicating the high elasticity of composite gels. The relaxation time T 2 indicated that free water was converted into immobile water or even bound water when SP added into surimi. Additionally, surimi/6% PHCSP gels were found to retain more water due to chitosan precipitated along with the SP. The lightness and whiteness values of surimi gels were enhanced in surimi gels added with a proper SP amount. However, excessive SP had a dilution effect on fish myofibrillar protein (MP) that dominates gel formation, resulting in weak surimi gels. Scanning electron microscopy (SEM) indicated that surimi/6% PHCSP gels could form a dense and homogeneous network with a pore density of 24.74 ± 0.08/μm 2 . Overall, SP could endow the sliver carp surimi with a satisfactory gelation ability because SP had the self-gelation ability or had an interaction with MP. • Sarcoplasmic proteins (SP) increased storage modulus, improving gel elasticity. • 6% pH-shifting/chitosan sarcoplasmic proteins (PHCSP)remarkedly improved gel strength. • 6% PHCSP contributed most to the compactness and homogeneity of surimi gel network. • Appropriate addition of SP enhanced surimi gel, but excessive SP disrupted network. • SP enhanced surimi gel due to the SP self-gelation and its good solubility.