Molecular forces involved in heat-induced freshwater surimi gel: Effects of various bond disrupting agents on the gel properties and protein conformation changes

Abstract

Urea, sodium dodecyl sulfate (SDS) and N-ethylmaleimide (NEM) were employed to monitor the contributions of hydrogen bonds, hydrophobic interactions and disulfide bonds in heat-induced surimi gel. Surimi gels were prepared with the bond disrupting agents followed by texture profile, gel strength, rheological and Raman analysis. The rheological analysis demonstrated that remarkable changes of storage moduli (G′) were presented below the critical temperature, especially for SDS treatments. Gel strength significantly decreased as the concentration of urea and NEM increased, while it was slightly improved by 1% SDS. With the involvement of bond disrupting agents, hardness and gumminess of surimi gel presented a dramatical decrease. The Raman results indicated that protein secondary structure tended to transform to random coil, with content of α-helix and β-sheet decreasing. Textural properties were in correlation with protein conformation. Less of random coil led to improvement of gel strength, and springiness was mainly contributed by β-sheet and β-turn. The results suggested that different bond disrupting agents induced various changes in surimi gel properties and protein secondary structure.