title: Using self-consistent-field theory to understand enhanced steric stabilization by casein-like copolymers at low surface coverage in mixed protein layers.
abstract: We present a statistical mechanical approach to predicting the properties of mixed copolymer layers using the Scheutjens-Fleer self-consistent-field theory. Our model copolymers are based on the primary structures of the major bovine casein monomers, alpha(s1)-casein and beta-casein. Numerical calculations have been carried out to determine the polymer segment density profiles at an isolated hydrophobic surface and the interaction forces as a pair of polymer-coated surfaces is brought to close interlayer separation. For a copolymer model containing hydrophilic and hydrophobic segments, we show how the steric stabilizing capacity of a casein-like macromolecule at very low surface coverage is enhanced in the presence of a thin dense layer of shorter tethered amphiphilic chains. Using a more refined protein model, which also distinguishes between the charged and uncharged hydrophilic segments along the chain, we clearly demonstrate that the enhanced steric repulsion from beta-casein exceeds that from alpha(s1)-casein. These calculations explain how the replacement of just a few percent of beta-lactoglobulin by casein can inhibit the heat-induced thickening and flocculation behavior observed experimentally with some whey protein-stabilized oil-in-water emulsions.
authors.affiliation: Procter Department of Food Science, University of Leeds, Leeds LS2 9JT, UK.
authors.forename: Emma L
authors.initials: EL
authors.lastname: Parkinson
authors.forename: Rammile
authors.initials: R
authors.lastname: Ettelaie
authors.forename: Eric
authors.initials: E
authors.lastname: Dickinson
mesh_terms: D000327:Adsorption; D000818:Animals; D001672:Biocompatible Materials / Q000737:chemistry*; D048128:Casein Kinase Ialpha / Q000737:chemistry; D002364:Caseins / Q000737:chemistry*; D007782:Lactoglobulins / Q000737:chemistry; D046911:Macromolecular Substances / Q000737:chemistry*; D008894:Milk Proteins / Q000737:chemistry; D015233:Models, Statistical; D008962:Models, Theoretical; D009821:Oils / Q000737:chemistry; D011108:Polymers / Q000737:chemistry*; D055672:Static Electricity; D013237:Stereoisomerism; D013816:Thermodynamics; D013997:Time Factors; D014867:Water / Q000737:chemistry; D000067816:Whey Proteins
chemical_list: D001672:Biocompatible Materials; D002364:Caseins; D007782:Lactoglobulins; D046911:Macromolecular Substances; D008894:Milk Proteins; D009821:Oils; D011108:Polymers; D000067816:Whey Proteins; D014867:Water; D048128:Casein Kinase Ialpha