挤压体系中可得然胶对小麦淀粉回生特性和冻融稳定性的影响

Effects of curdlan on wheat starch retrogradation and freeze-thaw stability in the extrusion system

小麦淀粉的回生现象和较差的冻融稳定性是限制面制品加工的重要原因。为探索一种有效抑制小麦淀粉回生及改善其冻融稳定性的方法,该文研究了挤压体系中不同质量分数的可得然胶对小麦淀粉回生特性和冻融稳定性的影响,利用差示扫描量热仪、X-射线衍射和傅里叶红外光谱等技术表征了可得然胶-小麦淀粉复合物的分子结构,并结合化学试剂处理、质构仪和扫描电镜探讨了可得然胶与小麦淀粉的结合机制。结果表明:随着可得然胶浓度的增加,可得然胶-小麦淀粉复合物的回生值和析水率先降低后增加;与挤压小麦淀粉相比,添加质量分数0.6%的可得然胶能够显著提高小麦淀粉的糊化温度(P<0.05),并降低小麦淀粉的相对结晶度、短程有序性和碘结合力,抑制直链淀粉的重结晶;挤压体系中可得然胶与小麦淀粉主要通过氢键和弱的静电相互作用结合,使小麦淀粉的结构更加致密,从而抑制小麦淀粉的回生并改善其冻融稳定性,该研究可为开发抗回生和低析水率的挤压小麦淀粉基食品提供参考。

Frozen pasta products have been ever increasingly favored in recent years,because of their convenience.Wheat starch is one of the most important components of buns,noodles,and cookies in the staple and leisure foods.The performance and quality of starch-based foods can depend seriously on the processing of wheat starches.Furthermore,starch-based foods easily lose water to be hard in the storage of retrogradation,indicating reduced elasticity.Therefore,it is very necessary to enhance the structure and properties of wheat starch.Starch can also be often modified by physical,chemical,biological and composite methods.Among them,physical modification has been widely used to modulate the properties of starch using hydrophilic colloids,due to their environmental friendliness,excellent performance and lower energy.Fortunately,the curdlan can be expected to compound with the starch for better functional properties,due to the excellent resistance to freeze-thaw stability and dehydration,water-holding,extreme stability,and emulsifying properties.In addition to being a prebiotic,curdlan can also improve the gastrointestinal health.The extrusion can be used as a biochemical reactor to promote the combination of wheat starch and curdlan,particularly for the high yield,easy operation,high degree of integration,and high temperature.The reason is that the high pressure,high shear and hydration can be generated to significantly change the structure and physicochemical properties of starch during operation.The complexes of curdlan and wheat starch can then be prepared to change the physicochemical properties of starch.The retrogradation and syneresis of wheat starch during freezing have been two of the most important limiting steps in the development of pasta products.This study aims to explore an effective way to inhibit the retrogradation and syneresis of wheat starch gels during freeze-thaw cycles.The composites with different concentrations of curdlan-wheat starch were investigated in the extrusion system.The effects of curdlan addition on the structural properties and freeze-thaw stability of wheat starch were analyzed using differential scanning calorimetry,X-ray diffractometry,and Fourier infrared spectrometry.In addition,the binding mechanism of curdlan-wheat starch composites in the extrusion field was revealed by combining the chemical reagents,Texture Analyzer and Scanning Electron Microscope.The results showed that the retrogradation of curdlan-wheat starch composites decreased and then increased with the increasing concentration of curdlan,while the syneresis rate showed a trend of decreasing and then increasing.The freeze-thaw stability of wheat starch was significantly improved to markedly inhibit the retrogradation with the addition of 0.6%curdlan in the extrusion system.The pasting temperature of wheat starch increased with the addition of 0.6%curdlan,compared with extruded starch.There was a decrease in the relative crystallinity,short-range ordering,and iodine binding of wheat starch,where the recrystallization of amylose was suppressed.Texture Analyzer and Scanning Electron Microscope revealed that the curdlanwheat starch composites were dominated by the hydrogen bonding and weak electrostatic interaction forces in the extruded system.Furthermore,the curdlan-wheat starch composites presented a more intact and dense structure,indicating better freezethaw stability.The retrogradation was also effectively inhibited.The finding can provide a strong reference to produce wheat starch-based foods with resistance retrogradation and low syneresis using an extrusion process.