高取代度羟丙基木薯淀粉流变特性研究(I)流变特征及羟丙基取代度的影响

Study on the Rheological Properties of Hydroxypropyl Tapioca Starch with High Molar Substitution (I) Rheological Characteristics and Effect of Hydroxypropylation Extent

研究了高取代度羟丙基木薯淀粉溶液（分子取代度ＭＳ＝１．６～４．５）的流变特性及羟丙基取代度对流变特性的影响规律。结果表明，高取代度羟丙基木薯淀粉呈现假塑性流体特征，符合幂定律τ＝Ｋγｍ。ｍ值在０．７～０．８范围，表明羟丙基化使木薯淀粉偏近牛顿流体。高取代度羟丙基木薯淀粉具有触变性和剪切稀化性质，并随溶液浓度升高而增大。羟丙基取代度对木薯淀粉流变特性有很大影响，当ＭＳ≤３．５时，溶液的表观粘度和剪切稀化现象随ＭＳ的增高而减小，当ＭＳ＞３．５时，溶液的表观粘度和剪切稀化现象随ＭＳ的增高而增大。这种变化规律符合羟丙基化反应机理。

The reological properties of hydroxypropyl tapioca starch solution with high molar substitution as well as the effect of hydroxypropylation extent on them have been studied in this work. The results showed that hydroxypropyl tapioca starch solution with high molar substitution behaved pseudoplastically in accordance with the power law τ= Kγ m. m value ranging between 0.7 and 0.8 indicated that hydroxypropylation resulted in a tendency to Newton fluid in tapioca starch solution. Hydroxypropyl tapioca starch with high molar substitution had thixotropic and shear thining natures which increased with the increase of concentration. Molar substitution strongly influenced the rheological properties of the hydroxypropyl tapioca starch. The apparent viscosity and shear thining nature increased for MS≤3.5 and decreased for MS>3.5 with the increase of MS, which was in agreement with the mechanism of hydroxypropylation reaction.