CREPEC, Department of Chemical Engineering, École Polytechnique de Montréal, 2900 Édouard Montpetit, P.O. Box 6079, Station Centre-Ville, Montréal, Québec, Canada H3C 3A7.
Carbohydr Polym. 2013 Feb 15;92(2):1799-808. doi: 10.1016/j.carbpol.2012.11.018. Epub 2012 Nov 14.
Starch gelatinization in the presence of high molecular weight polyol plasticizers and water was studied under static and dynamic conditions and was compared to a glycerol reference. For static gelatinization, glycerol, sorbitol, diglycerol and polyglycerol were examined using polarized light microscopy and differential scanning calorimetry. A wide range of starch/water/plasticizer compositions were prepared to explore the gelatinization regime for each plasticizer. The plasticizers show that the onset and conclusion temperatures for sorbitol and glycerol are in the same range and are lower than the other two plasticizers. On the other hand, polyglycerol shows a higher gelatinization temperature than diglycerol because of its higher molecular weight and viscosity. The results indicate that in the case of all plasticizers, increasing the water content tends to decrease the gelatinization temperature and, except for polyglycerol, increasing the plasticizer content increases the gelatinization temperature. In the case of polyglycerol, however, increasing the plasticizer content had the opposite effect and this was found to be related to the borderline solubility of polyglycerol in water. When the polyglycerol/water solubility was increased by increasing the temperature of the water/plasticizer/starch slurry, the gelatinization temperature dependence was found to be similar to the other polyols. A rheological technique was developed to study the dynamic gelatinization process by tracking the influence of shear on the complex viscosity in a couette flow system. Glycerol, diglycerol and sorbitol were subjected to different dynamic gelatinization treatments and the results were compared with static gelatinization. It is quantitatively shown that shear has a major effect on the gelatinization process. The conclusion temperature of gelatinization is significantly diminished (up to 21 °C) in the presence of shear whereas the onset temperature of gelatinization remains virtually unchanged as compared to static conditions. By comparing glycerol, diglycerol and sorbitol data, it is shown that the molecular weight or structure did not qualitatively affect the changes shear imposed on dynamic gelatinization. Shear had a relatively more pronounced effect on diglycerol as the plasticizer with less hydrogen bonding ability.
在存在高分子量多元醇增塑剂和水的情况下，研究了淀粉的糊化过程，包括静态和动态条件，并与甘油参考物进行了比较。对于静态糊化，使用偏光显微镜和差示扫描量热法研究了甘油、山梨糖醇、二甘油和聚甘油。制备了广泛的淀粉/水/增塑剂组合物，以探索每种增塑剂的糊化范围。结果表明，山梨糖醇和甘油的起始和结束温度处于相同范围，且低于另外两种增塑剂。另一方面，由于分子量和粘度较高，聚甘油的糊化温度高于二甘油。结果表明，在所有增塑剂的情况下，增加水含量往往会降低糊化温度，除聚甘油外，增加增塑剂含量会增加糊化温度。然而，在聚甘油的情况下，增加增塑剂含量产生了相反的效果，这与聚甘油在水中的边界溶解度有关。当通过提高水/增塑剂/淀粉浆料的温度来增加聚甘油的水溶性时，发现糊化温度的依赖性与其他多元醇相似。开发了一种流变学技术，通过在 Couette 流系统中跟踪剪切对复合粘度的影响来研究动态糊化过程。对甘油、二甘油和山梨糖醇进行了不同的动态糊化处理，并将结果与静态糊化进行了比较。定量表明，剪切对糊化过程有重大影响。在存在剪切的情况下，糊化的终了温度显著降低（高达 21°C），而与静态条件相比，糊化的起始温度几乎保持不变。通过比较甘油、二甘油和山梨糖醇的数据，表明分子量或结构没有对剪切对动态糊化的影响产生定性影响。由于具有较少氢键能力的增塑剂，剪切对二甘油的影响相对更为显著。
