QCM Study of β-Casein Adsorption on the Hydrophobic Surface: Effect of Ionic Strength and Cations

Abstract

The adsorption kinetics of β-casein on a hydrophobic surface has been studied by means of the quartz crystal microbalance (QCM). The self assembled monolayer of 1-octadecanethiol on a gold coated quartz crystal was used as a hydrophobic surface for adsorption. The adsorption kinetics was monitored in different solution conditions. Formation of monolayer is observed in most cases. At high concentration of protein, micelle formation which is interrupted by high ionic strength of solution is observed. Casein binding cations such as Ca 2+ , Ba 2+ and Al 3+ increase the hydrophobicity of the protein and the multiple layer adsorption occurs. The strong and weak points of the QCM method in the study of protein adsorption are discussed.

Characterization of Sample Loss Caused by Competitive Adsorption of Proteins in Vials Using Sodium Dodecyl Sulfate–Polyacrylamide Gel Electrophoresis

“…The R 2 value is higher than 0.95, suggesting a good linearity that agrees with previous studies . The measured quantity of tightly adsorbed milk proteins was 2.0 ± 0.5 μg corresponding to 1.1 μg/cm 2 , which also agreed with previous reports. , The value doubled the amount obtained by 0.5% SDS alone, that is, 0.55 μg/cm 2 . Because major casein proteins in milk, that is, α-S1, α-S2, and β-caseins and major whey proteins, such as β-lactoglobulin and α-lactalbumin, are negatively charged, the effective stripping under basic conditions is likely contributed by the electrostatic repulsion between negatively charged milk proteins and the negatively charged polypropylene vial surface …”

Effect of pH and heat treatment on structure, surface characteristics and emulsifying properties of purified camel β-casein

“…These results are coherent with those of Lee et al (2004) and Pérez-Fuentes et al (2017) which described the adsorption of the −CNB on hydrophobic surfaces and its dependence on the effect of ionic force, including pH. Indeed, the bovine (−CN, of amphiphilic nature, changes it conformation with high ionic forces, which alters its adsorption kinetics at the interface.…”

Molecular Understanding of Fouling Induction and Removal: Effect of the Interface Temperature on Milk Deposits

“…All of these studies confirm the influence of the temperature profile on milk fouling and highlight the role of bulk-wall temperature differences. , Gravimetric approach or monitoring changes of the overall heat transfer coefficient was used in these studies to quantify the fouling kinetics, which is indirect and lacks molecular details. Although quartz crystal microbalance with dissipation (QCM-D) is an excellent technique widely used to measure interfacial adsorption kinetics in situ and to quantify viscoelastic properties of the surface-adhering layer, most QCM studies so far are limited to ambient temperature due to instrument limitations, using model protein solutions to replicate raw milk (e.g., adsorption of β-lg, , whey protein, skimmed milk powder, and caseins). At high temperatures (≤65°C), Yang and co-workers demonstrated the capability of this technique to monitor whey protein fouling and its dependence on calcium content …”