Structure of protein texturates obtained by thermoplastic extrusion

Abstract The structure of texturates of moistened proteins (0.33 g water per 1 g protein) obtained by thermoplastic extrusion was investigated using X‐ray scattering, differential IR‐spectroscopy, optical microscopy and mechanical cut testing. Texturates were cooled at the output of the extruder using additional die preventing explosionlike evaporation of water. It was shown that textures of individual proteins (ovalbumin and BSA) had amorphous isotropic structure, whereas texturates of soybean protein isolates (SPI) exhibited mechanically anisotropic amorphous structure. The fraction of β‐sheet structure in polypeptide chains increased during extrusion process. Besides non‐covalent interactions and S‐S bonds other covalent bindings are suggested to stabilize texturate structure. The obtained data was used to discuss possible mechanisms leading to the creation of fibrous texturates.