Corn starch is modified with citric acid (2.5% w/w) in aqueous, alcoholic media and in solid solid reaction (dry heat condition without any solvent). Degree of substitution is similar for both treatments, independent of use of solvent but higher than for dry heated starch citrate. Apparent amylose content of all starch citrates is higher than for native starch. Molecular weight, as determined by triple detection size exclusion chromatography, also decreases, demonstrating hydrolysis of chains. As a consequence, starch citrate prepared using dry heating and ethanol, as compared to aqueous media, show drastic reduction in pasting viscosity. X‐ray diffraction pattern and morphology of the produced starch granules remain unaltered in all three reaction types. Starch citrates prepared using solvent less reactions show similar characteristics as that of conventional hydrolysis performed using concentrated hydrochloric acid. However, the solid solid hydrolytic reaction process using citric acid is far more environmental friendly and less costly than typical conventional hydrolysis processes. The present study is not only useful for starch systems but more generally for studying reactions in, for example, gums and cellulose.

中文翻译：

---

无溶剂反应制备柠檬酸淀粉并与水和乙醇介导的反应进行比较

玉米淀粉在含水，酒精介质中和在固体反应中（没有任何溶剂的干热条件下）用柠檬酸（2.5％w / w）改性。两种处理的取代度相似，独立于溶剂的使用，但高于干燥的加热的柠檬酸淀粉。所有柠檬酸淀粉的表观直链淀粉含量均高于天然淀粉。通过三重检测尺寸排阻色谱法测定的分子量也降低，表明链水解。结果，与水性介质相比，使用干式加热和乙醇制备的柠檬酸淀粉显示出糊化粘度的急剧降低。在所有三种反应类型中，生成的淀粉颗粒的X射线衍射图和形态均保持不变。使用无溶剂反应制备的柠檬酸淀粉显示出与使用浓盐酸进行的常规水解相似的特性。然而，与典型的常规水解方法相比，使用柠檬酸的固体-固体水解反应方法对环境更友好且成本更低。本研究不仅对淀粉体系有用，而且更普遍地用于研究例如胶和纤维素中的反应。