Dilational visco-elasticity of BLG adsorption layers at the solution/tetradecane interface – Effect of pH and ionic strength

• Published in: Colloids and surfaces. A, Physicochemical and engineering aspects Physicochemical and engineering aspects, 2017-05, Vol.521, p.204-210
• Main Authors: Won, J.Y., Gochev, G.G., Ulaganathan, V., Krägel, J., Aksenenko, E.V., Fainerman, V.B., Miller, R.
• Format: Article
• Language: English
• Subjects: Beta-lactoglobulin; Dilational visco-elasticity; Drop profile analysis tensiometry; Ionic strength effect; Oscillating drop method; pH effect; Water-tetradecane interface
• ISSN: 0927-7757; 1873-4359
• DOI: 10.1016/j.colsurfa.2016.08.054

Dilational elasticity as a function of the interfacial pressure obtained from dynamic experiments at three pH values for BLG adsorbed layers at solution/air (W/A) surfaces and solution/tetradecane (W/TD) interfaces. [Display omitted] •pH and ionic strength have small impact on β-lactoglobulin layers adsorbed at the solution/tetradecane (W/TD) interface.•The interfacial properties of BLG adsorbed layer at the W/A surface and W/TD interface are compared.•The dilational visco-elasticity modulus of BLG solutions is only slightly influenced by the solution pH.•Although BLG is most hydrophobic at the isoelectric point (pIBLG≈5), the highest interfacial tension and dilational elasticity values are observed at pH 7. Drop profile analysis tensiometry is applied to measure the dilational visco-elasticity of BLG at the buffered aqueous solution/tetradecane (W/TD) interface using oscillating drops of TD immersed in W at frequencies between 0.01–0.2Hz. The buffered solutions were investigated at pH 3, pH 5 (isoelectric point) and pH 7 at different buffer concentrations (1mM, 10mM and 100mM). The real part of the complex visco-elasticity shows a maximum when plotted as a function of the interfacial pressure Π. In contrast to the water/air surface (W/A) where we observe maximum elasticity values between 15 and 20mN/m, at the W/TD interface these maximum values are up to 65–70mM/m, which is in parallel with the much higher interfacial pressure values at the W/TD interface when compared to the W/A surface.