摘要
在氢氧化钠存在的情况下,以玉米淀粉和氯乙酸(MCA)为原料,采用单步和多步干法合成了羧甲基淀粉(CMS)。在醚化温度60℃、醚化时间6 h、氢氧化钠和氯乙酸与淀粉的摩尔比为2.6:1.3:1的条件下可以制备取代度(DS)为0.801的羧甲基淀粉,反应效率(RE)为61.2%。多步干法羧甲基化反应从第一步到第五步取代度逐渐增大,可以制备取代度为1.124的羧甲基淀粉,但是反应效率从61.2%降到了47.9%。红外光谱中出现了-COOH的特征吸收峰,证明淀粉分子上接入了羧甲基。扫描电镜照片显示羧甲基化破坏了淀粉颗粒的表面结构。X衍射(XRD)谱图表明羧甲基化使淀粉的结晶度显著下降。羧甲基淀粉溶液是剪切变稀的假塑性流体。CMS溶液黏度随着DS的增大而增大,随着温度的升高而减小。此外,CMS的黏度也随着p H的变化而变化。
Carboxymethyl starch（CMS） was synthesized by a single and multi-step dry process as a product of reaction of corn starch and monochloroacetic acid in the presence of sodium hydroxide.The degree of substitution（DS） up to 0.801 was obtained for reaction at 60 ℃ for 6 h with molar ratio of sodium hydroxide and monochloroacetate to starch being 2.6：1.3：1,the RE was 61.2%.The DS increased progressively as the steps of carboxymethylation increased from 1 to 5 and a DS of 1.124 was obtained,but the RE declined from 60.2% to 47.9%.The new bands in infrared spectra,which attributed to-COOH,indicated carboxymethyl had been connected to starch molecule.Scanning electron microscopy showed that carboxymethylation distorted the granular appearance of the native starch.X-ray diffractometry revealed that starch crystallinity was reduced significantly after carboxymethylation.A shear thinning pseudoplastic behavior of CMS was observed.The viscosity of CMS solution rised with increasing DS and decreased with increasing temperature.In addition,viscosity changed along with pH.
出处
《食品科技》
CAS
北大核心
2016年第3期264-270,共7页
Food Science and Technology
关键词
羧甲基淀粉
多步干法制备
取代度
黏度
carboxymethyl starch
multi-step dry process
DS
viscosity
