Competitive Adsorption between β-Casein or β-Lactoglobulin and Model Milk Membrane Lipids at Oil−Water Interfaces

Abstract

This study investigated the competitive adsorption between milk proteins and model milk membrane lipids at the oil-water interface and its dependence on the state of the lipid dispersion and the formation of emulsions. Both protein and membrane lipid surface load were determined using a serum depletion technique. The membrane lipid mixture used was a model milk membrane lipid system, containing dioleoylphosphatidylcholine, dioleoylphosphatidylethanolamine, milk sphingomyelin, dioleoylphosphatidylserine, and soybean phosphatidylinositol. The model composition mimics the lipid composition of natural milk fat globule membranes. The interactions were studied for two proteins, beta-lactoglobulin and beta-casein. The mixing order was varied to allow for differentiation between equilibrium structures and nonequilibrium structures. The results showed more than monolayer adsorption for most combinations. Proteins dominated at the oil-water interface in the protein-emulsified emulsion even after 48 h of exposure to a vesicular dispersion of membrane lipids. The membrane lipids dominated the oil-water interface in the case of the membrane lipid emulsified emulsion even after equilibration with a protein solution. Protein displacement with time was observed only for emulsions in which both membrane lipids and beta-casein were included during the emulsification. This study shows that kinetics controls the structures rather than the thermodynamic equilibrium, possibly resulting in structures more complex than an adsorbed monolayer. Thus, it can be expected that procedures such as the mixing order during emulsion preparation are of crucial importance to the emulsification performance.

Ordering Transitions Triggered by Specific Binding of Vesicles to Protein-Decorated Interfaces of Thermotropic Liquid Crystals

“…As discussed below, it is likely that that some streptavidin is bound to biotinylated lipid on the LC interface (via biotin-streptavidin binding) or co-exists along with phospholipid in an adsorbed state on the LC interface. 45 …”

“…We conclude that it is likely that the phospholipid exists at the LC interface in at least two states. 45 One state of the phospholipid interacts with the LC, and thus contributes to the observed ordering of the LC. A second population of phospholipid, while bound to the interfacial region, likely does not interact directly with the LCs but is bound to the streptavidin at the LC interface (e.g., adsorbed vesicles).…”

A novel infant milk formula concept: Mimicking the human milk fat globule structure

“…6A, C and E). As the phospholipidrich beta-serum was added to the protein aqueous phase before injection of the oil phase and emulsification, it is anticipated that phospholipids and proteins are both competing and interacting at the interface of the Concept IMF fat droplets, and thus form a mixed protein-phospholipid monolayer [45]. Fig.…”

Food Emulsifiers and Their Applications

“…Waninge et al (Waninge et al, 2005) studied the interaction between β-lactoglobulin and β-casein and milk membrane lipids at the oil-aqueous interface in emulsions. They found that the membrane lipid emulsified emulsions were dominated by the membrane lipids even after equilibrium with protein solutions.…”