【作者】 何传波；

【导师】 潘丽军； 姜绍通；

【作者基本信息】 合肥工业大学 ， 农产品加工及贮藏工程， 2002， 硕士

【摘要】 本文以甘薯淀粉为原料，系统研究了甘薯淀粉磷酸单酯制备过程中不同因素与取代度的关系、对产物的结构变化及其理化性质的影响。 采用湿法工艺以甘薯为原料与混合正磷酸盐作用制备甘薯淀粉磷酸单酯。在制备过程中，以取代度为指标，研究了酯化剂配比、酯化剂用量、pH值、反应温度、反应时间、催化剂用量及真空条件对取代度的影响，结果表明：淀粉磷酸单酯的取代度随酯化剂用量、反应温度、反应时间、催化剂用量的增加而增大，随pH值升高先增后减，酯化剂配比和真空条件对取代度影响不明显。在单因素实验的基础上，选取酯化剂配比、pH值、酯化反应温度、反应时间、催化剂用量五个因素为变量，以产物的取代度DS为试验指标，通过五因素二次正交旋转组合试验得出这五个因素与DS的关系表达式。并在此基础上确定的最佳制备工艺条件为：NaH₂PO₄：Na₂HPO₄（摩尔比）=3：1，pH 5.5左右、反应温度130～140℃、反应时间2～3h、催化剂用量为淀粉重量的4～5％。所得产品的取代度在0.012左右。 通过对反应后产物的红外光谱分析，证实经过酯化反应后，淀粉葡萄糖单元确实引入了P=O双键及P—O—C基团，淀粉分子结构发生了变化；扫描电镜分析显示酯化反应后，淀粉颗粒受侵蚀而在表面出现程度不同的凹陷和裂缝，并且取代度越高，这种侵蚀的程度越深；酯化反应产物的X-射线衍射曲线中的尖峰衍射特征逐渐减弱，而弥散衍射特征则逐渐增强，随DS的增加，这种趋势越来越明显，表明了酯化反应不仅发生在无定形区，而且也破坏了淀粉分子的结晶区。 淀粉磷酸单酯的糊透明度均比原淀粉有显著提高，低取代度产品的透明度高于较高取代度的产品：酯化反应可以减弱糊的凝沉倾向，中低取代度产品的凝沉倾向最弱；不同取代度的淀粉磷酸酯的冻融稳定性较原淀粉均有所改善；溶解度和膨润力也有增加；淀粉磷酸酯的表观粘度随剪切速率的升高而急剧降低，具有剪切变稀现象，符合假塑性流体的性质。加入尿素制备的淀粉磷酸单酯与不使用尿素的样品相比，糊粘度有显著提高，但透明度降低很多。将样品分散于NaCl溶液中与分散于蒸馏水中形成的糊液相比较，糊液的透明度降低，凝沉倾向显著增加，冻融稳定性变差，溶解度和膨润力降低很多，糊的表观粘度变小；在蔗糖溶液中时，透明度提高，凝沉性减弱，冻融稳定性显著提高，溶解度和膨润力略有增加，糊液的表观粘度则显著增加。更多还原

【Abstract】 The factors influencing the degree of substitution in preparation ,structure changes,physical and chemical properties of phosphate monoesters of sweet potato starch were systematically studied.The starch phosphate monoesters were produced with sweet potato starch by the wet process,which were esterified by disodium hydrogen phosphate(Na2HPO4) and sodium dihydrogen phosphate(NaH2PO4). We studied the effects of different factors in preparation on degree of substitution(DS) of phosphate monoesters,the results indicated that the DS increased with the level of esterifying agent,reaction temperature and time,the amount of catalyzer;however,when pH increased,DS first increased and then decreased,the combination of Na2HPO4 and NaH2PO4 and vacuum had no marked influence on DS. On the basis of one-factor experiments,we select the ratio of Na2HP04 and NaH2PO4,pH value,esterization temperature and time,amount of catalyzer as the variables,DS as the experiment index. Using the five-factors quadratic regression orthogonal rotary method,we can obtain the following optimum processing conditions for preparation:Na2HPO4:NaH2PO4=3:1,pH value was about 5.5,reaction temperature was 130-140C,reaction time was 2-3h,and the concentration of catalyzer was 4-5% of starch dry weight,the DS of final products were about 0.012.The structure of products were token by FTIR spectrum,and the infra-red spectrogram verified that after esterization,the P=O and P-O-C groups were added in the starch glucose units indeed. The analysis of scan electronic microcopy (SEM) showed that there existed fallings and splits of different degree on the starch granules surface,moreover,the broken degree increased as the DS increased. With the feature of peak diffraction in the diffractogram weakened,the feature of dispersion diffraction increased,these results demonstrated that esterization not only occurred in the amorphous region,but also damaged the crystalline region.Compared with the native sweet potato starch,the paste clarity,solubility and swelling power of the phosphate monoesters increased dramatically. Esterization can also improved the retrogradation and freeze-thaw stability of native starch notably. Furthermore,the properties of lower DS products were superior to those of higher DS products. The apparent viscosity of phosphate monoesters decreased rapidly withthe increase of shear rate,the shear-thinning behavior was found,and it belongs to the character of pseudoplastic fluid. The paste viscosity of phosphate monoesters catalyzed with urea were higher than those of the products which were produced without urea,but the paste clarity value of former were much lower. When the phosphate monoesters were dispersed into the sodium chloride (NaCl),the properties of these paste changed:paste clarity,freeze-thaw stability,solubility,swelling power and apparent viscosity all decreased,and the retrogradation increased. All these changes made the paste properties inferior to those of native starch. While in the sucrose dispersion,we observed the contrary phenomenon,which showed that the paste properties had improved in some degree.更多还原