Study on β-lactoglobulin microgels adsorption onto a hydrophobic solid surface by QCM-D

Microgel particles formed from β-lactoglobulin (Blg) are able to stabilize Pickering emulsions, yet their interfacial properties have not been fully characterized. In this study, quartz crystal microbalance with dissipation (QCM-D) was employed to investigate adsorption behavior of Blg microgels on a hydrophobic solid surface. The QCM-D results showed that adsorption efficiency of the microgels was strongly dependent on the particle charge and the ionic strength of the aqueous phase. The adsorption of weakly charged Blg microgels (pH 5.6) was characterized by highly covered particles, producing a relative rigid monolayer at the interface. Significantly fewer amount of the microgels was adsorbed when they were strongly charged (pH 3.2 and 7.4) with surface being covered by discrete particles. Those estimations were supported by the direct visualization of sensor surfaces by atomic force microscopy (AFM). Addition of salt effectively screened the electrostatic repulsion between microgel particles, which resulted in a more densely packed layer. QCM-D showed the ability to characterize the microgels interfacial properties and viscoelasticity of absorbed layer on solid surface, which may be used to predict microgels’ interfacial behavior at oil-water interface and provide insights in their stabilization effect in Pickering emulsions.