The objective of this study was to investigate the influence of sodium chloride (NaCl) concentration (0-500 mM) on the physical and oxidative stabilities of filled hydrogel that were stabilized using heat-denatured whey protein concentrate and high methoxy pectin. Our results showed that with an increase in NaCl concentration, the particle sizes, zeta-potentials, and interfacial layer thickness of filled hydrogels significantly increased and the lightness and whiteness gradually decreased (p < 0.05). Moreover, rheological characterization revealed that the apparent viscosity and viscoelastic behavior gradually decreased at higher NaCl concentration, which was mainly ascribed to the influence of NaCl on the electrostatic repulsion between droplets, thereby adversely impacting the physical stability of filled hydrogels. Furthermore, the result of cryo-scanning electron microscopy also verified the abovementioned results. Notably, higher NaCl concentration significantly promoted the oxidation of lipids and proteins (p < 0.05), thereby decreasing the oxidative stabilities of filled hydrogels. Our results indicated that filled hydrogels prepared under different ionic strength conditions can provide the theoretical basis for their future application in emulsion-based foods.
Keywords: electrostatic interaction; filled hydrogel; oxidative stability; physical stability; sodium chloride (NaCl).