The Crystalline Changes of Starch from Rhizoma Dioscorea by Acid Hydrolysis

The changes in crystalline properties of starch from Rhizoma Dioscorea by acid hydrolysis was characterized by X-Ray diffractometry （XRD）. The results revealed that the crystalline type of Rhizoma Dioscorea starch changed from C-type to A-type after 16 days of the acid hydrolysis. This phenomenon was different from that of other starches subjected to the acid hydrolysis. The results revealed that the B-polymorphs of C-type starch constituted the amorphous regions while the crystalline areas were mainly composed of A-polymorphs. The degree of crystallinity of the acid-thinned starch increased gradually with the time of acid hydrolysis.

The Preparation of B-type Starch Spherocrystals by Freezing Crystallization

The B-typed starch spherocrystals were prepared by the dissolution and freezing crystallization of acid-hydrolyzed starch obtained by the mild hydrolysis of maize starch. The spherocrystals were characterized with scanning electron microscope (SEM), X-ray diffraction, thermogravimetry (TG) and gel pervasion chromatogram (GPC). The results show that the preparation was a B-type spherocrystal with the average degree of polymerization of 14 glucose units, and the average diameter of crystal particles was about 7μm.

作物淀粉晶体结构的波谱分析

作物淀粉有A-型、B-型和C-型晶体,本文利用粉末X-射线衍射仪(XRD)和固体核磁共振波谱仪(13CCP/MASNMR)研究了不同植物来源淀粉的波谱特征和相对结晶度。结果表明,水稻、马铃薯和豌豆淀粉分别表现典型的A-型、B-型和C-型晶体XRD波谱,荸荠淀粉则表现CA-型XRD波谱,葛根淀粉为CB-型XRD波谱。以Jade5.0分析软件峰拟合法和曲线作图法计算出来的淀粉XRD相对结晶度差别较大,且无相关性,以曲线作图法计算出来的相对结晶度可信度较高。不同来源淀粉的13CCP/MAS NMR波谱相似,有C1、C4、C2,3,5和C6区域,区别主要在C1区域,在该区域A-型糯玉米和普通玉米淀粉有3个结晶峰,B-型马铃薯淀粉有2个结晶峰,CA-型转基因高直链水稻(TRS)淀粉有3个不明显的结晶峰,而CB-型酸解TRS淀粉有2个结晶峰,无定形淀粉没有结晶峰。利用PeakFit4.12峰拟合分析软件能够计算淀粉13CCP/MAS NMR波谱的相对结晶度和双螺旋含量,其中双螺旋含量比结晶度高,结晶度又比依据XRD波谱计算出来的结晶度高。上述研究结果为应用XRD和13CCP/MAS NMR波谱技术分析作物淀粉晶体结构提供了重要参考。

粉末X射线衍射图谱计算植物淀粉结晶度方法的探讨

植物淀粉有A-型、B-型和C-型3种晶体。以水稻(Oryzasativa)、马铃薯(Solanum tuberosum)、豌豆(Pisum sativum)和莲藕(Nelumbon ucifera)淀粉为材料,利用粉末X-射线衍射仪(XRD)调查了不同晶体类型淀粉的波谱特征,探讨XRD波谱相对结晶度的计算方法。软件峰拟合法、软件曲线法、直线作图法和曲线作图法均可用于计算淀粉XRD波谱的相对结晶度,以曲线作图法计算结果较为可靠。利用曲线作图法得出的结果表明,稻米淀粉的结晶度与直链淀粉含量呈显著线性负相关,酸解莲藕淀粉的结晶度与淀粉酸水解度呈显著线性正相关。酸水解使莲藕淀粉的C-型晶体转变为A-型晶体。上述研究结果为利用XRD分析植物淀粉晶体类型和计算相对结晶度提供了重要参考。