Patino Juan M Rodríguez, Sánchez Cecilio Carrera, Fernández Marta Cejudo, Niño M Rosario Rodríguez
Departamento de Ingeniería Química, Facultad de Química, Universidad de Sevilla, c/o Prof. García GonzAlez, 1, E-41012-Sevilla, Spain.
J Phys Chem B. 2007 Jul 19;111(28):8305-13. doi: 10.1021/jp071994j. Epub 2007 Jun 20.
In this work we have used different and complementary interfacial techniques (surface film balance, Brewster angle microscopy, and interfacial shear rheology), to analyze the static (structure, topography, reflectivity, miscibility, and interactions) and flow characteristics (surface shear characteristics) of milk protein (beta-casein, caseinate, and beta-lactoglobulin) and monoglyceride (monopalmitin and monoolein) mixed films spread and adsorbed on the air-water interface. The structural, topographical, and shear characteristics of the mixed films depend on the surface pressure and on the composition of the mixed film. The surface shear viscosity (eta(s)) varies greatly with the surface pressure (pi). In general, the greater the pi values, the greater were the values of eta(s). Moreover, the eta(s) value is also sensitive to the miscibility and/or displacement of film-forming components at the interface. At surface pressures lower than that for protein collapse, protein and monoglyceride coexist at the air-water interface. At surface pressures higher than that for the protein collapse, a squeezing of collapsed protein domains by monoglycerides was deduced. Near to the collapse point, the mixed film is dominated by the presence of the monoglyceride. Different proteins and monoglycerides show different interfacial structure, topography, and shear viscosity values, confirming the importance of protein and monoglyceride structure in determining the interfacial characteristics (interactions) of mixed films. The values of eta(s) are lower for disordered (beta-casein or caseinate) than for globular (beta-lactoglobulin) proteins and for unsaturated (monoolein) than for saturated (monopalmitin) monoglycerides in the mixed film. The displacement of the protein by the monoglycerides is facilitated under shear conditions.
在这项工作中，我们使用了不同且互补的界面技术（表面膜天平、布儒斯特角显微镜和界面剪切流变学），来分析在空气 - 水界面上铺展和吸附的乳蛋白（β - 酪蛋白、酪蛋白酸盐和β - 乳球蛋白）与甘油单酯（单棕榈酸甘油酯和单油酸甘油酯）混合膜的静态特性（结构、形貌、反射率、混溶性和相互作用）和流动特性（表面剪切特性）。混合膜的结构、形貌和剪切特性取决于表面压力以及混合膜的组成。表面剪切粘度（η(s)）随表面压力（π）变化很大。一般来说，π值越大，η(s)值越大。此外，η(s)值对界面处成膜组分的混溶性和/或置换也很敏感。在低于蛋白质塌陷的表面压力下，蛋白质和甘油单酯在空气 - 水界面共存。在高于蛋白质塌陷的表面压力下，推测甘油单酯会挤压塌陷的蛋白质区域。接近塌陷点时，混合膜以甘油单酯的存在为主导。不同的蛋白质和甘油单酯表现出不同的界面结构、形貌和剪切粘度值，证实了蛋白质和甘油单酯结构在决定混合膜界面特性（相互作用）方面的重要性。在混合膜中，无序蛋白质（β - 酪蛋白或酪蛋白酸盐）的η(s)值低于球状蛋白质（β - 乳球蛋白），不饱和甘油单酯（单油酸甘油酯）的η(s)值低于饱和甘油单酯（单棕榈酸甘油酯）。在剪切条件下，甘油单酯促进了蛋白质的置换。
