Gel properties and structural characteristics of soy protein isolate treated with different salt ions before spray drying combined with dynamic high-pressure micro-fluidization

Abstract

The gelation properties of soy protein isolate (SPI) were influenced by the addition of salt ions (SI) before spray drying combined with dynamic high-pressure microfluidization (DHPM). Compared with SPI, SPI treated using SIDHPM (SIDHPM-SPI) markedly increased in gel hardness, springiness, cohesivenessand chewiness upon heating (p < 0.05). The changes were mainly attributable to buried functional groups coming to the surface with DHPM treatment, which improved the interactions between protein molecules. FT-IR spectroscopy indicated that the SIDHPM treatment resulted in the conversion of SPI α-helix, β-turns and random coil to β-sheet structures. The analysis of the intermolecular interaction forces indicated that disulfide bonds and hydrophobic interactions were the critical molecular forces in maintaining the gel network structure. Compared with SPI, SIDHPM-SPI increased the water-holding capacity of gels. Analysis using scanning electron microscopy indicated that modification using SIDHPM allowed the formation of SPI gels with a continuous and homogeneous gel complex configuration. Moreover, the sensory evaluation of the SIDHPM gels was consistent with the results of the instrumental analysis. Thus, SIDHPM led to a gel product with better overall performance, which might potentially be used to fabricate SPI with improved functionality for use by the food industry.