Study on melting and crystallization of short-linear chains from debranched waxy starches by in situ synchrotron wide-angle X-ray diffraction
- 作者：Liming Cai ; Yanjie Bai ; Yong-Cheng Shi ; ycshi@ksu.edu
- 关键词：Short-chain amylose ; A-type ; B-type ; Synchrotron wide-angle X-ray diffraction
- 刊名：Journal of Cereal Science
- 出版年：2012
- 期刊代码：117_07335210
- 类别：abs
- 出版时间：May, 2012
- 卷：55
- 期：3
- 页码：373-379
- 文件大小：722 K
摘要
In situ melting and crystallization of short-linear 伪-1,4-glucan (short-chain amylose, or SCA) from debranched waxy starches were investigated by synchrotron wide-angle X-ray diffraction. Amorphous SCA was prepared by dissolving completely debranched waxy starches in alkaline solution and neutralized by hydrochloric acid. When hydrated with 50%water at 25 掳C, all amorphous SCA crystallized immediately and gave a B-type structure. The SCA from debranched waxy potato starch had a longer average chain length and a higher melting temperature but relatively lower crystallinity upon hydration; it was not completely melted at 100 掳C and retained its original B-type structure during rapid cooling. In contrast, the SCA from debranched waxy wheat and waxy maize starches had a large portion of low molecular weight fractions, a higher crystallinity upon hydration, and a lower melting temperature. These differences suggest that amylopectin short chains crystallized more readily but their crystals were weaker than those of long chains. After the B-type crystals of hydrated SCA from waxy wheat and waxy maize starches melted, they reformed into the A-type polymorph upon rapid cooling. The thermal properties showed that the A-type polymorph of debranched waxy wheat and waxy maize starches had a higher melting temperature than their B-type structure.