淀粉在DMSO／水溶剂体系中的形态结构及相变研究

通过热台偏光显微镜、差示扫描热量仪（DSC）、布拉班德粘度仪、扫描电子显微镜（SEM）、X-射线衍射仪（XRD），系统研究了不同比例的二甲基亚砜（DMSO）/水混合液体系（质量比：0/100, 50/50, 80/20, 100/0）对蜡质玉米淀粉的形态、结晶结构及相变变化（溶解和糊化）的影响。结果表明：随着DMSO浓度的增加，淀粉的颗粒形态和结晶结构破坏程度逐渐增大，经纯DMSO溶液处理后的淀粉，其颗粒呈不规则块状形态及无序结构，无偏光十字存在，可直接溶解在水溶液中。同时淀粉的糊化温度呈现先升高后降低的趋势：当混合液体系中DMSO/水的比例为50/50时，淀粉糊化温度最高（温度区间为76.44 ℃~91.37 ℃）；吸热峰强度逐渐减弱，焓值?H逐渐减小，在纯DMSO溶液中，无明显的相变峰出现。淀粉糊在DMSO混合溶液中的峰值粘度均高于水中的峰值粘度，DMSO/水比例为80/20时达到最大值。
The effect of dimethyl sulfoxide (DMSO)/water mixtures at various ratios (weight ratio: 0/100, 50/50, 80/20, and 100/0) on the morphology and phase-transition (dissolution and gelatinization) of waxy corn starch was systematically studied using a polarized microscope with a hot stage, a differential scanning calorimeter (DSC), a Brabender Viscograph, a scanning electron microscope (SEM), and an X-ray diffractometer (XRD). As DMSO concentration increased, the extent of damage in morphology and crystalline structure of starch granules also increased. After treatment with pure DMSO, the granules showed an irregular shape and a disordered structure with an absence of polarization cross, and they could be dissolved in water. Moreover, gelatinization temperatures showed a downward trend after the initial increase. When the ratio of DMSO/water was 50/50, the highest gelatinization temperature was obtained (range: 76.44 ℃~91.37 ℃); then, the endothermic peak intensity and the enthalpy ?H value gradually decreased. In pure DMSO, no apparent phase transition peak occurred. The peak viscosity of starch pastes in DMSO was higher than that in water, and the maximum viscosity was reached when the ratio of DMSO/water was 80:20.