Synthesis and physicochemical properties of casein-derived surfactants

We prepared novel surfactants through the reactions of casein with various fatty acids (C10–C18) and evaluated their surface activities in terms of their surface tension, wetting ability, and foaming properties. Increases in the length of the hydrophobic chain and the number of attached alkyl chains led to increased surface activity. We studied the critical micelle concentrations of the casein derivatives through surface tension, conductivity, and fluorescence measurements (namely, the intensity ratio of pyrene emissions at 374 and 394 nm) as a function of concentration; we found that the micellization and surface activity properties in aqueous solutions decreased upon increasing the length of the alkyl chain.