title: Conformation and location of amorphous and semi-crystalline regions in C-type starch granules revealed by SEM, NMR and XRD.
abstract: The conformations and locations of amorphous and semi-crystalline regions in C-type starch granules from Chinese yam were evaluated by a combination of morphology and spectroscopy studies during acid hydrolysis. Scanning electron micrographs showed that amorphous or less crystalline areas were essentially located in the centre part of C-type starch granules, whereas the semi-crystalline and amorphous growth rings were found mainly in the outer part of the granules. (13)C cross-polarization magic angle spinning NMR ((13)C CP/MAS NMR) showed that amorphous regions were hydrolyzed faster than the crystalline ones. In addition, B-type polymorphs were shown to be hydrolyzed more rapidly than A-types. Powder X-ray diffraction (XRD) also revealed that the B-polymorph was hydrolyzed more rapidly than the A-type. XRD showed that the amorphous or less crystalline areas were mainly located in the core of starch granules, while the amorphous growth rings are distributed toward the outside of the granules and alternatively arranged with semi-crystalline growth rings. The amorphous or less crystalline areas predominantly consisted of the B-polymorph whereas the outer semi-crystalline and amorphous growth rings were mostly composed of the A-polymorph.
authors.affiliation: College of Pharmaceutical Science and Technology, Tianjin University, Tianjin 300072, China. Electronic address: edwinwa@hotmail.com.
authors.forename: Shujun
authors.initials: S
authors.lastname: Wang
authors.affiliation: College of Traditional Chinese Medicine, Tianjin University of Traditional Chinese Medicine, Tianjin 300193, China.
authors.forename: Jinglin
authors.initials: J
authors.lastname: Yu
authors.affiliation: College of Science, Department of Chemistry, Tianjin University, Tianjin 300072, China.
authors.forename: Jiugao
authors.initials: J
authors.lastname: Yu
keywords: Amorphous; C-type starch; Growth rings; Polymorphs; Semi-crystalline