气流超微粉碎对玉米淀粉微观结构及老化特性影响

Effect of Jet Milling on Microstructure and Aging Characteristics of Maize Starch

以蜡质玉米淀粉、普通玉米淀粉和高直链玉米淀粉为原料,利用流化床气流粉碎机制备超微粉,采用激光粒度分析仪、扫描电子显微镜、X射线衍射仪、傅里叶变换红外光谱仪、凝胶渗透色谱结合多角度激光光散射仪、差示扫描量热仪等研究气流超微粉碎处理对淀粉颗粒大小、微观结构以及老化特性的影响。结果表明,3种淀粉经微细化处理后,粒径分别减小至6.05、5.22μm和5.53μm,比表面积增大,形态变得无规则,颗粒表面粗糙且有裂纹;淀粉颗粒晶体结构受到破坏,微细化蜡质玉米淀粉相对结晶度降低13.97%,降低程度大于普通玉米淀粉(13.31%)和高直链玉米淀粉(9.44%),粉碎过程无新的基团产生,但使淀粉分子链发生断裂、分子质量减小及分布变宽;微细化处理降低了淀粉的糊化温度和热吸收焓,改变了淀粉重结晶成核方式,降低低温贮藏环境玉米淀粉老化速率,延缓淀粉回生,利于淀粉质食品贮存和性质稳定;微细化处理对不同直链与支链比例玉米淀粉的粉碎效果、微观结构及性质影响存在差异。

The microstructure and aging characteristics of waxy maize starch, normal maize starch and high amylose maize starch were investigated after superfine grinding with a fluidized bed jet mill. The particle size and size distribution, granular morphology, crystal structure, functional groups, molecular main structure, thermal and aging properties of the three starches were characterized using granularity analysis, scanning electron microscopy(SEM), X-ray diffractometry, Fourier transform infrared(FT-IR) spectroscopy, gel permeation chromatography(GPC) and differential scanning calorimetry(DSC). It was found that the particle size of waxy maize starch, normal maize starch and high amylose maize starch were significantly decreased to 6.05, 5.22 and 5.53 μm, respectively after superfine grinding, while the specific surface area increased. The microscopy analysis showed that the superfine grinding destroyed the surface morphology and crystalline areas. The relative crystallinity of waxy maize starch was more decreased(by 13.97%) than was that of normal maize starch(by 13.31%) and high amylose maize starch(by 9.44%). FT-IR spectroscopy showed that no new functional groups were produced during superfine grinding. But the molecular main of starches were broken and as a result, the molecular mass decreased and the molecular mass distribution widened. Besides, the gelatinization temperature, enthalpy and recrystallization rate constant of maize starch were reduced, retarding the aging process and increasing the storage stability of the starchy food. Finally, superfine grinding had different effects on the microstructure and physicochemical properties of maize starch with different amylose/amylopection ratios.