脱乙酰魔芋葡甘露聚糖对玉米淀粉糊化及凝胶特性的影响

Effects of Konjac Glucomannan with Various Degrees of Deacetylation on Gelatinization and Gel Properties of Corn Starch

利用脱乙酰魔芋葡甘露聚糖(DKGM)改善玉米淀粉糊化和凝胶性能,并通过分析混合体系糊化特性、流变学特性、质构及微观结构评估其改善效果。结果表明,魔芋葡甘露聚糖(KGM)与DKGM均可提高玉米淀粉的糊化黏度、糊化时间及糊化温度,并降低其糊化焓值;相比于KGM,DKGM降低了玉米淀粉的崩解值及回生值,增强了淀粉糊热稳定性并能延缓其短期回生。KGM与DKGM均提高了玉米淀粉的储能模量、损耗模量、损耗角正切值、稠度系数K及触变性,特别是DKGM显著提高了玉米淀粉凝胶的黏弹性。与KGM相比,DKGM使淀粉凝胶硬度由180.77 g增加到226.92 g。整体而言,脱乙酰度为56.36%的DKGM对玉米淀粉凝胶的稳定性及黏弹性改善效果最好。经扫描电镜观察,DKGM显著增强了淀粉凝胶微观结构的致密性,适度脱乙酰度(56.36%)的DKGM可使凝胶网络排列更有序。因此,适当脱乙酰的DKGM能够明显增强玉米淀粉的热稳定性与凝胶强度,对淀粉基食品的开发具有借鉴意义。

The gelatinization and gel properties of corn starch were improved by using the deacetylated konjac glucomannan(DKGM),and the improvement effect was evaluated by analyzing the properties of gelatinization,rheological,texture,and microstructure.The results indicated that both the konjac glucomannan(KGM)and DKGM increased the gelatinization viscosity,gelatinization time and gelatinization temperature of corn starch,whereas decreased the gelatinization enthalpy.In comparison to KGM,the DKGM reduced the value of breakdown and retrogradation of corn starch,indicating that DKGM could enhance the thermal stability of starch gel and delay its retrogradation.It improved remarkably the storage modulus,loss modulus,loss tangent,consistency coefficient K and thixotropy,especially the viscoelasticity of corn starch gel.Moreover,the hardness of starch gel increased from 180.77 g prepared by DKGM to 226.92 g prepared by KGM.Overall,DKGM with deacetylation degree of 56.36%exhibited the best improvement effect on the stability and viscoelasticity of corn starch gel.The observation by using scanning electron microscope revealed that the density of starch gel microstructure was enhanced by DKGM,and the network structure of starch gel prepared from DKGM with a deacetylation degree of 56.36%was more ordered.Hence,the DKGM with appropriate deacetylation degree can significantly enhance the thermal stability and gel strength of corn starch,providing a reference for the development of starch-based foods.