微胶囊形成过程中蛋白质二级结构变化的红外光谱分析

选用乳清蛋白、大豆分离蛋白分别与麦芽糊精共混作为微胶囊壁材,用红外光谱法研究这两种蛋白质在微胶囊形成前后的结构变化。结果表明:两种蛋白质分别与麦芽糊精共混,经过加热和喷雾干燥后,蛋白质的二级结构发生了改变,其中乳清蛋白二级结构α-螺旋含量降低1.90%,β-折叠含量增加0.89%,β-转角增加8.19%,无规卷曲减少7.18%。大豆分离蛋白二级结构α-螺旋含量降低1.64%,β-转角含量降低0.47%,β-折叠增加10.20%,无规卷曲减少了9.03%。同时,两种蛋白质的酰胺Ⅰ带均向低波数方向移动,说明在微胶囊壁结构形成过程中两种蛋白质与麦芽糊精之间发生了相互作用,形成的氢键作用力较强。利用扫描电镜观察分别用两种蛋白质作为壁材包埋大豆油脂微胶囊的表面微结构,发现使用α-螺旋含量高的乳清蛋白为壁材的微胶囊表面更光滑、完整。

Study on Secondary Structural Changes of Protein in the Formation of Microcapsule by FTIR Spectroscopy

The mixture of whey protein and isolated soy protein with maltodextrin as microcapsules wall material was adopted.The secondary structure constitution of these two kinds of proteins in the process of heating and spray drying together with maltodextrin were studied by Fourier transform infrared spectra.The result showed that both whey protein and isolated soy protein exhibited differences in the secondary structures.The rate of α-helix in whey protein decreased 1.9% and β-turn content of the protein remains virtually unchanged,β-sheet increased 8.19%,and random coil decreased 7.18%.At the same time the content of α-helix in isolated soy protein decreased 1.64%,the change of β-sheet is not obvious while β-turn increased 10.20% and random coil decreased 9.03%.Meanwhile,the amideⅠbands of these two proteins both shifted to the lower wave number direction,indicating that in the formation process of the microcapsule wall structure there are complex interactions between maltodextrin and proteins,and the hydrogen bonds which comes into existence are comparatively strong.With the help of scanning electron microscope,it was discovered that the surface is more smooth and integrated when the microcapsules wall material contains whey protein,which is high in alpha helix.