Soluble and insoluble fractions of soy protein isolate affect the properties of its high-moisture extrudates

Abstract

This research focused the impact of the variation in insoluble soy protein isolate (ISPI) and soluble soy protein isolate (SSPI) contents on the rheological properties of highly-concentrated SPI during extrusion-like conditions and the physiochemical, mechanical, and morphological characteristics of its extrudates. Results showed that increased ISPI content could resist great shear forces and increase the viscoelasticity of SPI samples. In addition, the increase of ISPI content in SPI samples also contributed to enhance the tensile strength and mechanical anisotropy, further created a distinct fibrous structures of extrudates. While higher SSPI content can form heat-induced reverseble aggregates via hydrophobic interaction and disulfide bonds, reduce the water mobility and facilitate the formation of a more uniform protein-water phase. The differences in solubility revealed the dominance of non-covalent bonds in ISS-40 extrudate (100% ISPI) and highlighted the important role of disulfide bonds in ISS-04 extrudate (100% SSPI). Possible mechanisms are proposed to explain the contrasting behavior of ISPI and SSPI under thermomechanical treatment. These insights explore the formation of protein multiphase system structures and offer valuable guidance for developing meat analogue products.