Breaking the temperature limitation of zein-rice starch dough by microwave pre-gelatinization: Morphological, structural and rheological properties of the dough.

[Display omitted] • Microwave pre-gelatinized zein-starch dough maintained viscoelasticity below zein's T g. • Zein improved starch dough with a smooth surface and compact structure. • Unextruded zein formed fine fiber and was uniformly distributed in the starch base. • Extruded zein tended to present as protein lumps in the starch base. Zein has gluten-like viscoelasticity, but its use is limited due to high glass transition temperature (T g). To break the temperature limitation of zein-starch dough, microwave heating was used to pre-gelatinize a partial of the starch with zein, and then the remaining was added and kneaded to form a dough. Pre-gelatinized doughs formed by rice starch (PRS), zein-starch (PUZS), and extruded zein-starch (PEZS) were included in this study. The thermal, morphological, rheological, and secondary structural properties of the dough were investigated. The results showed that zein and starch formed a composite gel network and firmly bound starch granules, which improved the dough properties with a smooth surface and compact internal structure, increased strain tolerance, and decreased stiffness. Unextruded zein was distributed uniformly and had strong interactions with the starch. Extruded zein tended to form large particles and had limited interaction with starch but improved dough extensibility. Microwave pre-gelatinization increased the stability of the secondary structure of zein and maintained the viscoelasticity of dough below zein's T g , which provided a safe and effective way to break the temperature limitation of zein as a structural protein used in foods. [ABSTRACT FROM AUTHOR]