Evidence and characterization of complex coacervates containing plant proteins: application to the microencapsulation of oil droplets

The potentiality of using vegetal proteins in complex coacervation was studied through zeta potential and turbidity measurements. Two model proteins were tested and compared: a cereal protein (alpha gliadin) and a leguminous protein (pea globulin). The effect of pH and value of the protein–anionic compound ratio were mainly investigated. The morphology of the coacervate was studied under different conditions and encapsulation of oil was achieved from the two proteins. Optimum coacervation was obtained with arabic gum at pH 2.75 for pea globulins with a protein–polysaccharide ratio of 30:70, and at pH 3 for alpha gliadins with a protein–polysaccharide ratio of 50:50. In addition to their charge density profile, this study showed that the steric conformation of both macromolecules forming the complex was a key parameter determining the ability of the coacervates to encapsulate oil droplets.