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

Gergana M. Radulova, Konstantin Golemanov, Krassimir D. Danov, Peter A. Kralchevsky*, Simeon D. Stoyanov, Luben N. Arnaudov, Theodorus B.J. Blijdenstein, Eddie G. Pelan, Alex Lips

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

25 Citations (Scopus)


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.

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

ASJC Scopus subject areas

  • General Materials Science
  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Spectroscopy
  • Electrochemistry


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