Adsorption Experiments from Mixed Protein + Surfactant Solutions - Food Colloids: Self-Assembly and Material Science - page 223

Figure 10 Dynamic surface tension of 7 10 7 mol L 1 lysozyme: J , experiment; —,
theory
14.5 Conclusions
The adsorption kinetics of lysozyme has been studied by measuring the
dynamic surface tension for different bulk concentrations and applying a
thermodynamic model assuming adsorption with different molar areas for
each subsequent adsorption step. The theoretical analysis of the kinetic curves
shows satisfactory agreement between the experimental data and the model,
and the obtained diffusion coefficients suggest diffusion-controlled adsorption
for low lysozyme concentration and a mixed mechanism for higher concentra-
tions. The equilibrium surface tension isotherm is described well by the theory,
but better agreement is found if the fitting procedure adopts a higher value for
the maximum molar area, o max . This is a parameter which is highly significant
at low surface pressures, where the conformation of the protein is most
unfolded.
Acknowledgement
The work was financially supported by a project of the European Space Agency
(FASES MAP AO-99-052).
References
1. E. Dickinson and J.M. Rodriguez Patino (eds), Food Emulsions and
Foams: Interfaces, Interactions and Stability, Royal Society of Chemistry,
Cambridge, UK, 1999.