Rodríguez Patino Juan M., Rodríguez Niño M(a). Rosario, Carrera Sánchez Cecilio, Cejudo Fernández Marta
Departamento de Ingeniería Química, Facultad de Química, Universidad de Sevilla, c/Profesor García González, s/núm., Seville, 41012, Spain
J Colloid Interface Sci. 2001 Aug 1;240(1):113-126. doi: 10.1006/jcis.2001.7567.
The surface pressure (pi) area (A) isotherms and Brewster angle microscopy (BAM) of monoglyceride-caseinate mixed films spread on buffered water at pH 5 and 7 and at 20 degrees C were determined as a function of the mass fraction (X) of monoglyceride (monopalmitin or monoolein) in the mixture. The structural characteristics, miscibility, and morphology of monoglyceride-caseinate mixed films are very dependent on surface pressure and monolayer composition. The monolayer structure was more expanded as the pH and the monoglyceride concentration in the mixture were increased. From the concentration and surface pressure dependence on excess area, free energy, and collapse pressure, it was deduced that, at a macroscopic level, monoglyceride (either monopalmitin or monoolein) and caseinate form a practically immiscible monolayer at the air-water interface. The BAM images and the evolution with the surface pressure of the relative reflectivity of BAM images give complementary information on the interactions and structural characteristics of monoglyceride-caseinate mixed monolayers, which at a microscopic level corroborated in part the conclusions derived from the pi-A isotherm at a macroscopic level. Over the overall range of existence of the mixed film the monolayer presents some heterogeneity due to the fact that domains of monoglyceride (especially of monopalmitin) and spots of collapsed caseinate residues are present during the monolayer compression-expansion cycle, giving relative intensity peaks with high relative film thickness. At higher pi, after the caseinate collapse, characteristic squeezing-out phenomenon was observed. At the monoglyceride monolayer collapse the mixed film is practically dominated by the presence of monoglyceride. The prevalence of monoglyceride in the interface increases with the amount of monoglyceride in the mixture and at higher pi. However, some degree of interactions exists between monoglyceride and caseinate in the mixed film and these interactions are more pronounced as the monolayer is compressed at the highest surface pressures. Copyright 2001 Academic Press.
测定了在20℃、pH值为5和7的缓冲水溶液上铺展的甘油单酯-酪蛋白酸盐混合膜的表面压力（π）-面积（A）等温线以及布鲁斯特角显微镜（BAM）图像，该图像是甘油单酯（单棕榈酸甘油酯或单油酸甘油酯）在混合物中的质量分数（X）的函数。甘油单酯-酪蛋白酸盐混合膜的结构特征、混溶性和形态在很大程度上取决于表面压力和单分子层组成。随着pH值和混合物中甘油单酯浓度的增加，单分子层结构更加膨胀。从浓度和表面压力对过量面积、自由能和崩塌压力的依赖性可以推断，在宏观层面上，甘油单酯（单棕榈酸甘油酯或单油酸甘油酯）和酪蛋白酸盐在空气-水界面形成了几乎不混溶的单分子层。BAM图像以及BAM图像相对反射率随表面压力的变化提供了关于甘油单酯-酪蛋白酸盐混合单分子层相互作用和结构特征的补充信息，在微观层面上部分证实了从宏观层面的π-A等温线得出的结论。在混合膜存在的整个范围内，由于在单分子层压缩-膨胀循环过程中存在甘油单酯区域（特别是单棕榈酸甘油酯）和酪蛋白酸盐残留的塌陷斑点，单分子层呈现出一定的不均匀性，产生了具有高相对膜厚度的相对强度峰。在较高的π值下，酪蛋白酸盐崩塌后，观察到了特征性的挤出现象。在甘油单酯单分子层崩塌时，混合膜实际上由甘油单酯主导。界面中甘油单酯的占比随着混合物中甘油单酯的量增加以及在较高的π值下而增加。然而，在混合膜中甘油单酯和酪蛋白酸盐之间存在一定程度的相互作用，并且随着单分子层在最高表面压力下被压缩，这些相互作用更加明显。版权所有2001年学术出版社。
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