Effects of Ca²⁺ on the Gel Properties and in Vitro Digestibility of HG-added Surimi Gel

Hsian-tsao gum (HG) possessed of good biological activity and gel-promoting property could improve the textural properties of surimi gel. Ca²⁺ was commonly used in surimi products, however, effects of Ca²⁺ on the gel properties of HG-added surimi were not clear. The effects of Ca²⁺ on the sensory properties, gel properties (gel strength, texture properties, gel-forming forces and microstructure) and in vitro digestibility of HG-added surimi gel were therefore studied. The results showed that Ca²⁺ reduced the disulfide bonds, ionic bonds and hydrogen bonds, and increased the hydrophobic and non-disulfide covalent bonds, in which the disulfide bonds and non-disulfide covalent bonds determined the gel properties (gel strength, hardness and springiness) and microstructure, thus affecting the gel solubility and in vitro digestibility. Adding 3 mmol/kg Ca²⁺ could improve sensory properties (elasticity, hardness and tissue status), water holding capacity, gel strength and texture characteristics (hardness, springiness) of HG-added surimi gel, accompanied with the decrease in gel dissolution rate and in vitro digestibility. With the continuous increase of Ca²⁺ concentration, the structural porosity, gel dissolution rate and in vitro digestibility of HG-surimi gel were increased, but the gel strength, hardness, elasticity and water holding capacity were decreased. Based on PCA results, in vitro gel digestibility was positively correlated to microstructure porosity and gel solubility, but negatively correlated to gel strength, hardness, springiness, water holding capacity and gel forming force (disulfide bonds, ion bonds, hydrogen bonds). Therefore, the HG-added surimi gel with different sensory and structural properties could be designed by adding different concentrations of Ca²⁺, which provided a theoretical reference for the diversified development of HG-surimi gel products.