Comparison of the dilational behaviour of adsorbed milk proteins at the air-water and oil-water interfaces.
Comparison of the dilational behaviour of adsorbed milk proteins at the air-water and oil-water interfaces.
复制标题
DOI：
10.1016/0927-7757(96)03534-0
复制
发表时间：
1996-08
期刊：
影响因子：
--
通讯作者：
A. Williams;A. Prins
中科院分区：
文献类型：
--
作者：
A. Williams;A. Prins
比较了两种乳蛋白β-酪蛋白和β-乳球蛋白在空气-水和石蜡-油-水界面上的界面膨胀特性。使用改进的朗缪尔槽技术，以0.1赫兹的频率进行测量，作为散装蛋白浓度的函数。无论上相是石蜡、油还是空气，这两种蛋白质的膨胀特性似乎都是相同的。这归因于蛋白质分子对油相的渗透相当有限。界面性质已被证明依赖于蛋白质的体积浓度。这一点，连同表面的历史，可能决定了蛋白质分子的界面浓度和构象。在低体积浓度下，两种蛋白质的弹性模数和损耗角正切相似。据推测，这两种蛋白质在界面上具有相似的、合理延伸的结构。在较高的堆积浓度下，这两种蛋白质的行为有所不同。β-乳球蛋白的界面膨胀系数约为62mN m−1，体积浓度为⩾3×10−2g L−1，且表面粘度较低。据推测，该蛋白质在界面内形成了一个粘性的弹性网络。在相似浓度下，β-酪蛋白的界面膨胀模数约为13mN m−1。人们认为界面上存在一定的分子间凝聚力，但这种凝聚力比球形蛋白弱得多。高浓度的β-酪蛋白赋予界面显著的扩张粘度，这要么是由于扩散松弛，要么是由于吸附的第一层和多层蛋白质的重排。
The interfacial dilational properties of two milk proteins, β-casein and β-lactoglobulin, have been compared at the air-water and paraffin oil-water interfaces. The measurements were performed as a function of bulk protein concentration using a modified Langmuir trough technique at a frequency of 0.1 Hz. It appears that the dilational properties of the two proteins are essentially the same whether the upper phase is paraffin oil or air. This is attributed to rather limited penetration of the oil phase by the protein molecules. The interfacial properties have been shown to be dependent upon the bulk concentration of the protein. This, together with the history of the surface, presumably determines the interfacial concentration and conformation of the protein molecules. At low bulk concentrations both the modulus and the loss tangent are similar for the two proteins. It is conjectured that both proteins have a similar, reasonably extended, structure in the interface. At higher bulk concentrations the behaviour of the two proteins diverges. The interfacial dilational modulus for β-lactoglobulin is around 62 mN m−1for bulk concentrations ⩾ 3× 10−2g l−1, and the viscosity of the surface is rather low. It is postulated that this protein forms a cohesive elastic network within the interface. The interfacial dilational modulus for β-casein at similar concentrations is around 13 mN m−1. It is thought that some intermolecular cohesion is present in the interface, but that this is much weaker than for the globular protein. High concentrations of β-casein impart significant dilational viscosity to the interface, due either to diffusional relaxation or to rearrangement of the adsorbed primary layer and multilayers of protein.