木薯羟丙基淀粉合成工艺优化及其性质分析

摘要

[目的]在碱性条件下,利用木薯淀粉和环氧丙烷发生醚化反应制备羟丙基淀粉,为木薯淀粉改性工艺提供参考.[方法]通过单因素实验分析反应温度、反应时间、pH值、环氧丙烷用量、硫酸钠用量和对羟丙基淀粉取代度的影响,选取环氧丙烷添加量、pH值、温度、时间为反应因素进行响应面实验,并对不同取代度的羟丙基淀粉的性质进行研究.[结果]在一定范围内,随着反应温度、反应时间、无水硫酸钠添加量、pH值、环氧丙烷添加量的增加,羟丙基淀粉的分子取代度也随之增加;但当反应温度高于50℃、环氧丙烷添加量大于13.0％、pH值超过10.9时,局部糊化等现象会产生,导致取代度下降.响应面实验结果表明,对木薯羟丙基淀粉取代度的影响为:反应pH＞环氧丙烷添加量＞反应温度＞反应时间,最佳制备工艺条件为:反应时间20 h、反应温度45℃、环氧丙烷添加量13.0％、pH 10.9,硫酸钠添加量为15.0％,此条件下羟丙基取代度为0.1419.[结论]利用木薯淀粉制备成的羟丙基淀粉在黏度、冻融稳定性和透明度方面,均优于原淀粉,且随着取代度的增加,性质趋于更优.%[Objective] The hydroxypropyl starch was prepared by esterification of tapioca starch and propylene oxide under the alkaline condition,to provide reference for cassava starch modification process.[Method] The reaction temperature,reaction time,pH value,amount of propylene oxide and Na2SO4 content on the degree of substitution of hydroxypropyl starch was analyzed by single-factor experiment,and the addition of propylene oxide,pH value,temperature and time was selected as factors to response surface experiment,and the properties of hydroxypropyl starch with different degrees of substitution were studied.[Result] The molecular degree of substitution of hydroxypropyl starch increased as the addition of propylene oxide,reaction pH,reaction time,reaction temperature and anhydrous sodium sulfate growing within a certain range.However,the localized gelatinization phenomenon would occur and cause degree of substitution to decrease when the reaction temperature was higher than 50 ℃,the addition of propylene oxide was more than 13.0 ％,and pH value was higher than 10.9.The results of response surface experiment showed that the influence level on the degree of substitution of tapioca hydroxypropyl starch was:reaction pH ＞ addition of propylene oxide ＞ reaction temperature ＞ reaction time.The optimum preparation conditions were as follows:reaction time was 20 h,reaction temperature was 45 ℃,addition of propylene oxide was 13.0 ％,pH 10.9,sodium sulfate addition was 15.0 ％.Under this condition,the degree of substitution of hydroxypropyl was 0.1419.[Conclusion] The hydroxypropyl starch made from tapioca starch is superior to the original starch in terms of viscosity,freeze-thaw stability and transparency,and tends to be better with the increase of the degree of substitution.