Abstract: The high-temperature and high-pressure extrusion modification technology was used to improve the texture and stability of corn flour. The effects of corn flour particle size, extrusion temperature and water content on the rheological and film-forming properties of corn flour were studied to determine the optimal extrusion conditions. The film-forming mechanism of corn flour was explored by studying the intermolecular interaction and crystal structure of corn flour membrane. Results showed that after high-temperature and high-pressure extrusion the structure of corn flour film became more compact, and the surface became flatter and smoother with significantly fewer holes in it. When the corn flour particle size, extrusion temperature and water content were 120 mesh, 165 ℃ and 34%, respectively, we successfully prepared a corn flour film with high mechanical properties and water resistance as well as low solubility. The extruded corn flour paste had high viscoelasticity and large thixotropic loop area and the molecular interactions of the system were strong. In addition, the extrusion process changed the crystal structure of corn flour from type A to type V, decreased the crystallinity, and partially degraded amylopectin into amylose and low-molecular-mass amylopectin, which easily form a highly ordered molecular chain arrangement to improve the retrogradation and film-forming properties of color flour starch. The interactions among biomacromolecules in the extruded corn flour such as starch, protein and fiber were enhanced, which was accompanied by the formation of strong and stable hydrogen bonds, contributing to the formation of a more compact structure network.

Key words: extrusion modification; corn flour membrane; rheological property; intermolecular interaction; crystal structure