Viscoelastic properties and microstructures of 11S globulin and soybean protein isolate gels: Magnesium chloride-induced gels

Heat-induced gels of 11S globulin (11S) or soybean protein isolate (SPI) were prepared using magnesium chloride (MgCl₂) as a coagulant. Viscoelastic properties and microstructures of 11S and SPI gels were quantified using dynamic viscoelastic measurement (DVM) and confocal laser scanning microscopy (CLSM). The addition of sodium chloride was necessary for 11S and SPI to form MgCl₂-induced gels. DVM indicated that 11S formed stiffer and more solid gels than SPI under all experimental conditions. CLSM showed that the microstructures of 11S gels were coarser and more heterogeneous than SPI gels in comparable conditions. The microstructures of 11S gels were highly affected by MgCl₂ concentration whereas those of SPI gels were relatively insensitive to MgCl₂ concentration. The microstructures of 11S and SPI gels were analyzed by two parameters: the fractal dimension and the average density of gel networks. Compared to SPI, 11S forms MgCl₂-induced gels with a lower fractal dimension and a higher density of network structures.