The role of disulfide bonds in L-arginine ameliorating the quality of low-salt sturgeon surimi gels induced by microwave: Increasing the diameter and fractal dimension of network

The purpose of this study was to investigate the mechanism of enhancing gelling properties of low-salt surimi by utilizing the complementary advantages of L-arginine (L-Arg) and microwave (MW) from the perspective of gels' network characteristics. At MW 3 min, the diameters of protein filaments were increased from 0.015 μm to 0.06-0.08 μm by 2 % L-Arg. The gel strength was improved from 58.4 to 108.0 g × cm by 2 % L-Arg, the cooking loss was reduced (from 21.8 % to 3.8 %), and they showed a strong correlation (|r| ≥ 0.73) with the fractal dimension (D_f). These results suggested that the improvement (P < 0.05) of L-Arg in macro qualities was attributed to the denser microstructure. The intermolecular forces proved that L-Arg changed the dominant situation of hydrophobic interactions to a more balanced composition containing decreased hydrophobic interactions and increased ionic bonds, hydrogen bonds and disulfide bonds (P < 0.05) during the MW heating. The contribution of disulfide bonds was further proved by the reduced/non-reduced SDS-PAGE, and the increase of disulfide bonds can be explained by the conversion of sulfhydryl and the decreased proportion of α-helix. The present study can not only provide a universal theory for ameliorating the quality of low-salt surimi gels by regulating their microstructures but also promote the application of MW in surimi processing industry.