植物淀粉有A-型、B-型和C-型3种晶体。以水稻(Oryza sativa)、马铃薯(Solanum tuberosum)、豌豆(Pisum sativum) 和莲藕(Nelumbo nucifera)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。

Plant starches have A-, B-, and C-type crystallinity. We investigated spectrum characteristics of starches from rice, potato, pea and lotus by X-ray powder diffraction (XRD). Peak-fitting, curved-line, straight-line mapping and curved-line mapping methods are commonly used for determining relative crystallinity of starch XRD spectra. The curved-line mapping method has reliable results. We found the relative crystallinity of rice starch negatively associated with amylose content and that of acid-modified lotus starches positively associated with acid hydrolysis degree by the curved-line mapping method. The crystallinity of lotus starch changed from C- to A-type during acid hydrolysis. These results would be useful for XRD analysis of crystallinity and relative crystallinity of plant starches.