微波辐射下木薯淀粉结构与性质的变化

采用2 455 MHz微波对0.5 g/mL的淀粉乙醇悬浮液进行处理。运用傅里叶红外光谱仪、紫外-可见分光光度计、扫描电子显微镜、X射线衍射仪、乌氏黏度计和热重分析仪对不同微波辐射时间的木薯淀粉结构与性质进行研究。结果表明：微波辐射未能使淀粉产生新的官能团，但分子间及分子内氢键发生变化。随微波辐射时间延长，淀粉-碘复合物最大紫外-可见吸收波长及蓝值呈现先升后降的趋势，淀粉颗粒表面出现凹陷或皱褶数量增多。微波辐射增强了对应的X射线衍射峰的强度，但未能改变淀粉颗粒结晶类型。黏度测定数据显示微波辐射淀粉的特性黏度呈减小趋势。热重分析表明，微波辐射提高了淀粉热稳定性。

Variations in Structure and Properties of Cassava Starch after Microwave Irradiation

Cassava starch was suspended at a concentration of 0.5 g/mL in 20% aqueous ethanol and then subjected to
microwave irradiation at 2 455 MHz. After different durations of microwave irradiation, the structure and properties of
cassava starch were examined by Fourier transform infrared spectrometer (FT-IR), ultraviolet visible spectrophotometer
(UV-Vis), scanning electron microscope (SEM), X-ray diffractometer (XRD), Ubbelohde viscometer and thermogravimetric
analyzer (TGA). It was suggested that new functional groups were not formed under the condition of microwave irradiation.
However, the intermolecular and intramolecular hydrogen bonds were altered. With increasing microwave irradiation
time, the maximum UV-Vis absorption wavelength and blue value of the starch-iodine complexes increased first and then
decreased. Much more concaves or ruffles on the surface of the starch granules were observed. Moreover, the XRD peak
intensity of cassava starch was enhanced by microwave irradiation. However, the crystal types of the starch granules were
not changed. Viscosity data demonstrated that intrinsic viscosity of the microwave irradiated-cassava starch displayed a
decreasing trend. Additionally, thermogravimetric analysis proved that the thermal stability of the starch was improved by
microwave irradiation.