Study on the morphology, crystalline structure and thermal properties of yam starch acetates with different degrees of substitution

• 来源期刊: 中国科学B辑(英文版)
• 年，卷（期）: 2008,（9）
• 页码范围: 859-865
• 页数: 7页
• 语种: 英文
• DOI: 10.1007/s11426-008-0089-1

摘要

School of Pharmaceutical Science and Technology, Tianjin University, Tianjin 300072, China;College of Bioengineering, Tianjin University of Science and Technology, Tianjin 300457, China;Institute of Medicine Plant, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100094, China;College of Chinese Medicine, Tianjin University of Traditional Chinese Medicine, Tianjin 300193, ChinaThis study was carried out to understand and establish the changes in physicochemical properties of starch extracted from Chinese yam (Dioscorea opposita Thunb.) after acetylation. Yam starch acetates with different degrees of substitution (DS) were prepared by the reaction of yam starch with glacial acetic acid/acetic anhydride using sulfuric acid as the catalyst. Their formation was confirmed by the presence of the carbonyl signal around 1750 cm-1 in the Fourier transform infrared (FT-IR) spectra. The thermal behavior of the native starch and starch acetate were investigated using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The results reveal that the starch acetates are more thermally stable than the native starch. The starch esters showed 50% weight loss at tem-peratures from 328℃ to 372℃, while the native starch underwent 50% weight loss at 325℃. The glass transition temperature (Tg) of the starch decreased from 273℃ to 226℃. The X-ray diffraction (XRD) patterns could be classified as typical of the C-type for yam starch. X-ray diffraction also showed the loss of the ordered C-type starch crystalline structure and the degree of crystallinity of starch de-creased from 36.10% to 10.96% with the increasing DS. The scanning electron microscopy (SEM) sug-gested that the most of the starch granules disintegrated with many visible fragments with the in-creasing DS.