挤出处理对玉米粉流变及其成膜特性的影响

采用高温高压挤出改性技术对玉米粉进行质构优化及稳定化处理，通过研究玉米粉粒度、挤出温度和水分质量分数对玉米粉流变特性和成膜特性的影响，确定挤出改性玉米粉的制备工艺参数，并通过分析玉米粉分子间相互作用以及玉米粉膜结晶结构探究玉米粉的成膜机理。结果表明，高温高压挤出改性处理能够使玉米粉膜结构致密、膜表面较平整光滑、孔洞明显减少。当玉米粉粒度为120 目、挤出温度为165 ℃、水分质量分数为34%时制备的玉米粉膜具有良好的机械性能、阻水性以及较低的溶解度，并且此条件下制备的玉米粉成膜液具有较高的黏弹性和较大的触变环面积，体系内部分子之间的相互作用较强。此外，挤出改性处理使玉米淀粉由A晶型转变为V晶型，淀粉结晶度下降，部分支链淀粉发生降解生成直链淀粉以及小分子质量支链淀粉，易形成有序性较高的分子链排布状态，改善玉米粉的凝沉性和成膜特性。挤出改性处理还使玉米粉中淀粉、蛋白质、纤维等分子之间的相互作用增强，并且形成强烈而稳定的氢键，有利于分子间形成致密的结构网络。

Effect of Extrusion Treatment on the Rheological and Film Formation Properties of Corn Flour

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.