常用微胶囊壁材的分子结构及流变学特性研究

本文研究了五种壁材分子结构及其流变学特性。以喷雾干燥制备微胶囊的五种常用壁材变性淀粉、阿拉伯胶、明胶、大豆分离蛋白和羧甲基纤维素为研究对象,采用凝胶渗透色谱法(GPC)测定壁材的分子量分布;傅里叶变换红外光谱法(FT-IR)分析不同壁材的特征基团和蛋白类壁材的二级结构;旋转流变仪研究壁材的表观黏度、动态模量和蠕变柔量。研究结果表明:五种壁材溶液均呈现剪切稀化现象,随着温度的上升壁材溶液的表观黏度逐渐下降;壁材的弹性模量G'和黏性模量G'均随着振荡频率的增大而增大;相同时间下,壁材的蠕变柔量J(t)大小为:变性淀粉阿拉伯胶明胶羧甲基纤维素大豆分离蛋白;壁材分子量越大,表观黏度就越大;同一数量级分子量的壁材,分子量分布越宽,非牛顿"剪切稀化"现象越明显;分子结构越刚性,极性越大,表观黏度也越大。

Molecular Structure and Rheological Properties of Common Microcapsule Wall Materials

The molecular structure and rheological properties of five common materials, namely modified starch, gum arabic, gelatin, soybean protein isolate (SPI), and carboxymethyl cellulose (CMC), which are used to prepare microcapsule walls by spray drying were studied. The molecular weight distributions of the materials were determined by gel permeation chromatography (GPC), the functional groups and secondary structures were determined by Fourier transform infrared spectroscopy, while the apparent viscosity, dynamic modulus, and creep compliance were measured by a rotational rheometer. The results showed shear-thinning behavior in all five wall material pastes. The apparent viscosity of wall material pastes gradually decreased with temperature. The elastic modulus G' and viscous modulus G' increased with increasing oscillation frequency. With constant time, creep compliances J(t) values were in the following order: modified starch > gum arabic > gelatin > CMC > SPI. The higher the molecular weight, the greater the apparent viscosity. For the wall materials with molecular weight in the same order of magnitude, the non-Newtonian shear-thinning phenomenon was more obvious with a wider molecular weight distribution. Additionally, the apparent viscosity was higher when the molecular structure was more rigid and molecules had a higher polarity.