Surface shear rheology of adsorption layers from the protein HFBII hydrophobin: Effect of added β-casein

Research output: Contribution to journalArticlepeer-review

Authors

  • Gergana M. Radulova
  • Konstantin Golemanov
  • Krassimir D. Danov
  • Peter A. Kralchevsky
  • Simeon D. Stoyanov
  • Luben N. Arnaudov
  • Theodorus B.J. Blijdenstein
  • Alex Lips

Colleges, School and Institutes

External organisations

  • Sofia University St. Kliment Ohridski
  • Unilever Research and Development
  • Unilever

Abstract

The surface shear rheology of hydrophobin HFBII adsorption layers is studied in angle-ramp/relaxation regime by means of a rotational rheometer. The behavior of the system is investigated at different shear rates and concentrations of added β-casein. In angle-ramp regime, the experimental data comply with the Maxwell model of viscoelastic behavior. From the fits of the rheological curves with this model, the surface shear elasticity and viscosity, E sh and η sh, are determined at various fixed shear rates. The dependence of η sh on the rate of strain obeys the Herschel-Bulkley law. The data indicate an increasing fluidization (softening) of the layers with the rise of the shear rate. The addition of β-casein leads to more rigid adsorption layers, which exhibit a tendency of faster fluidization at increasing shear rates. In relaxation regime, the system obeys a modified Andrade's (cubic root) law, with two characteristic relaxation times. The fact that the data comply with the Maxwell model in angle-ramp regime, but follow the modified Andrade's low in relaxation regime, can be explained by the different processes occurring in the viscoelastic protein adsorption layer in these two regimes: breakage and restoration of intermolecular bonds at angle-ramp vs solidification of the layer at relaxation.

Details

Original languageEnglish
Pages (from-to)4168-4177
Number of pages10
JournalLangmuir
Volume28
Issue number9
Publication statusPublished - 6 Mar 2012