阳离子淀粉物理形貌及流变性的影响因素

Influence factors of physical properties and rheological property of cationic starch

将玉米淀粉、醚化剂和碱以一定比例进行机械混合,并在加热条件下进行干法反应以制备低取代度阳离子淀粉.研究表明:反应条件如醚化剂用量、NaOH用量、反应时间和反应温度对阳离子化玉米淀粉的物理形貌及流变性能有着很大的影响,阳离子淀粉的糊液黏度会随醚化剂加入量的增加呈先升高后下降的趋势,而NaOH加入量的增加使得阳离子淀粉的糊液黏度有少许下降;在反应温度介于35～55℃时,延长反应时间有利于黏度的提高;产品在反应温度45℃下反应4 h后,阳离子淀粉的糊液黏度趋于稳定.对比原淀粉及阳离子化淀粉的扫描电子显微镜图发现,变性后的淀粉颗粒表面形态有了较大的变化,原淀粉的晶体结构被破坏,颗粒粒径分布范围增大,颗粒表面呈现粘连现象.采用红外光谱与DSC对部分样品进行测试表明,淀粉变性后其内部基团种类基本未发生改变,但部分基团的数量确有所增加.

The cationic modification on corn starch is carried out by mixing corn starch,sodium hydroxide and etherifying agent.The mixture is mechanically activated,stirred and then heated under the certain temperature for producing cationic starch with the low-degree of substitution.The results show that by changing the amount of etherifying agent,sodium hydroxide,the reaction time and temperature,the physical and rheological properties of cationic corn starch can be varied accordingly.The viscosity of cationic starch paste first increases and then decreases with the increase of the amount of etherifying agent;meanwhile the amount of the sodium hydroxide increasing may lead to a little decrease of the viscosity of cationic starch paste.As the reaction temperature ranges from 35 ℃ to 55 ℃,the longer reaction time likely causes a higher viscosity of the paste.However,the viscosity of the cationic starch paste tends to be stable after the reaction is carried out at 45 ℃ for 4 hours.With scanning electron microscopy,it is observed that the particle size distribution increases and the crystal structures disappear after the modification.The analysis of IR chromatography and DSC also show the slight changes before and after cationic modification.In spite of the less change in the types of the inner groups,the height of the peak of some groups is indeed found an increase.