Yakubu P I, Baianu I C, Orr P H
University of Illinois, College of Agriculture, Department of Food Science, Urbana 61801.
Adv Exp Med Biol. 1991;302:585-97. doi: 10.1007/978-1-4899-0664-9_31.
Deuterium Nuclear Magnetic Resonance (NMR) measurements at 4.7 Tesla were used to study the hydration properties of potato starch suspensions as a function of the starch-to-water ratio. The deuterium NMR spectrum of potato starch suspensions consisted of a relatively tall, single Lorentzian (D2O) peak and a resolved doublet ('powder' pattern) of about 1 kHz quadrupole splitting and low amplitude. The deuterium NMR transverse relaxation rate (R2) was measured for the single Lorentzian, deuterium oxide peak; this rate increased with increasing starch-to-water ratio. Deviations of such R2 dependences from linearity were observed only at high ratios of starch-to-water, above approximately 40% solids. In addition to the 'free' or bulk population (which has a very fast rotational correlation time of 5 ps), a second population of water weakly sorbed on the starch granule surface was monitored and found to be in fast exchange with the bulk water; this second water population has a rotational correlation time of 17 ps at 298 K, only about three times slower than that of bulk water. Additionally, a third population of slowly exchangeable water is present, which is "anisotropically bound" and has a highly restricted motion within the potato starch granule structure; well-defined quadrupole splittings are observed from this latter population of water in potato starch. Potato starch exhibits unique hydration properties that have not been found in cereal starches.
利用4.7特斯拉的氘核磁共振（NMR）测量技术，研究了马铃薯淀粉悬浮液的水化特性与淀粉-水比例的关系。马铃薯淀粉悬浮液的氘核磁共振谱由一个相对较高的单洛伦兹（D2O）峰和一个分辨出的双峰（“粉末”模式）组成，双峰具有约1千赫兹的四极分裂和低幅度。对单洛伦兹的氧化氘峰测量了氘核磁共振横向弛豫率（R2）；该速率随着淀粉-水比例的增加而增加。仅在淀粉-水比例较高（固体含量高于约40%）时，观察到这种R2依赖性与线性关系的偏差。除了“自由”或大量的水分子群体（其具有非常快的5皮秒旋转相关时间）外，还监测到了第二类弱吸附在淀粉颗粒表面的水分子群体，发现其与大量水分子快速交换；在298K时，这第二类水分子群体的旋转相关时间为17皮秒，仅比大量水分子的旋转相关时间慢约三倍。此外，还存在第三类缓慢交换的水分子，其“各向异性结合”，在马铃薯淀粉颗粒结构内的运动受到高度限制；从马铃薯淀粉中这后一类水分子中观察到了明确的四极分裂。马铃薯淀粉表现出在谷物淀粉中未发现的独特水化特性。
