Microencapsulation by surfactant-gelatin insoluble complex: Effect of pH and surfactant concentration

The interactions between gelatin and sodium dodecyl sulfate (SDS) were studied, and the conditions which favor formation of insoluble complex of gelatin-SDS were applied to form microcapsules of oil droplets. It was found that the insoluble complex is formed only while the protein has a net positive charge, at pH 4.0, and only at a narrow range of surfactant concentrations, below the critical micellar concentration. The composition of the coating layer around the oil droplets was evaluated as a function of SDS/gelatin ratio. The maximal adsorbed amount of gelatin and SDS on the oil droplets corresponds to the SDS concentration in which the zeta potential was minimal and in which insoluble gelatin-SDS particles were obtained in absence of the oil phase.