Lipase- catalyzed synthesis of starch stearate in ionic liquids and its rheological properties

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.