Micellar properties of β-casein-cationic surfactant solutions

Abstract

The micellar properties of β-casein in solution with a homologous series of cationic surfactants have been investigated using turbidity, fluorescence spectroscopy, and quenching fluorescence measurements. Turbidity measurements indicated that monomeric cationic surfactants initially bind cooperatively with a site on the β-casein micelle in negatively charged amino acids. This leads to the formation of low-soluble β-casein micelle-monomeric surfactants complexes. Further addition of surfactant leads to the formation of more highly soluble complexes of β-casein micelle-cationic surfactant. The fluorescence experiments were also used to study the formation of β-casein-cationic surfactant complexes and to determine critical micelle concentration of surfactants and β-casein. The mean aggregation number of β-casein and cationic surfactant micelles at various experimental conditions and the dependence of aggregation phenomenon on the chain length of cationic surfactants were investigated. The mean aggregation number for β-casein micelle has been determined to be 45.70 using quenching fluorescence. © 2013 Springer-Verlag Wien.