离子液体中酶催化合成硬脂酸淀粉酯及其流变学特性研究
Lipase- catalyzed synthesis of starch stearate in ionic liquids and its rheological properties
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摘要: 以1-丁基-3-甲基咪唑醋酸盐（BMIMAc）和1-丁基-3-甲基咪唑四氟硼酸盐（BMIMBF4）的混合离子液体为介质,脂肪酶催化淀粉硬脂酸甲酯合成硬脂酸淀粉酯,并采用核磁共振（1H NMR）、X-射线衍射对其进行结构表征。通过快速黏度仪及动态流变仪分析了硬脂酸淀粉酯的流变学特性。结果表明:和原淀粉相比,硬脂酸淀粉酯的峰值黏度显著降低,并随着取代度的增大,黏度呈下降趋势;动态流变学测定结果显示酯化后的淀粉储能模量和损失模量比原淀粉显著下降（p<0.05）;静态流变学测定结果显示淀粉（包括酯化淀粉）为非牛顿流体,出现了剪切稀化的现象,且取代度越高,黏度越低,表明长链硬脂酸基团的引入,削弱了淀粉分子之间氢键作用。Abstract: The synthesis of starch stearate with lipase in the mixed ionic liquids ofBMIMAc andBMIMBF4was investigated.The structure of the starch stearate was characterized by1 H NMR and XRD and the rheological properties were studied by rapid viscosity analyzer( RVA) and dynamic rheometer. The results showed that the peak viscosity of starch stearate significantly was decreased compared to raw starch. Dynamic rheology studies showed that the storage modulus and the loss modulus of starch significantly dropped after esterification. Static rheology studies showed that starch and modified starch were both non- Newtonian fluids,which exhibited shear thinning.With the increase of the degree of substitution,the viscosity was decreased,indicating introduction of long chain stearic acid weakened the hydrogen bond forces between starch molecules.
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