Impacts of extrusion temperature and α-subunit content on structure of zein extrudate and viscoelasticity of the plasticized network

Abstract

To elucidate the effects of temperature and α-subunit content on the physicochemical characteristics and structure of zein, three zeins (commercial zein, α-subunit-rich zein, and total zein) with high to low α-subunit content were extruded at 80, 100, 120, and 140 °C, respectively. The mechanical properties, peptide distribution, particular size, morphological changes in self-assembly, and intermolecular forces of the extrudates were determined; the extrudates were plasticized by acetic acid, and the rheological properties of the resulted viscoelastic network were measured. With the temperature increase, the solubility of zein extrudates decreased, and the peptide weight of α-subunit-rich zein and total zein increased. Excessive extrusion temperature negatively affected zein’s ability to form viscoelastic plasticized networks. Zein with high purity of α-subunit tended to form a fibrous structure. In contrast, the existence of more non-α-subunits (β-, γ-, and δ-zein) formed a compact one and strengthened the plasticized zein network. Therefore, α-subunit content and extrusion temperature could regulate the structures of zein extrudate or the viscoelasticity of plasticized networks to expand flexible utilization of zein in the food industry.