All-natural oil-filled microcapsules from water-insoluble proteins

The formation and characterization of a novel class of all-natural digestible microcapsules containing a liquid lipid core encapsulated by a water-insoluble protein shell with tunable thickness is demonstrated. As an example of a water-insoluble protein, zein is used - the protein of corn - which is an attractive biomaterial from a sustainable source. The microcapsules are prepared by a direct and simple method, based on the precipitation of protein from the continuous phase of an oil-in-(water/ethanol) emulsion onto the oil droplets without the need of any surfactant. The shell thickness can be controlled by the amount of precipitated protein. An in vitro digestion assay is performed to study the lipid hydrolysis and biodegradability. The rate of lipid hydrolysis and release of fatty acids are highly dependent on the protein shell thickness. All-natural edible microcapsules with controlled degradation under gastrointestinal conditions can enable new applications for oral delivery systems. They may further be used as a model system for controlled release studies of lipophilic compounds and could promote the sustainable use of underutilized water insoluble proteins as functional biomaterials.