Recent progress in understanding fundamental interactions and applications of zein

In the last decade, interests in using zein as an ingredient in food and bio-based materials have been increasing. The success of these applications depends on the surface properties of the protein and its interaction with other system components. Interactions of zein have been exploited to develop colloidal dispersions, nanoparticles as delivery systems for bioactive compounds, films, coatings and fibres. Therefore, a state-of-the-art compilation of the interaction mechanisms between zein and molecules of other compounds is necessary to improve the understanding of the structure-function relationship and boost its applications. This review aims to elucidate the zein assembly mechanisms and its aggregation behaviour in single and composite macromolecular systems. Protein interaction mechanisms, including self-assembly of monomeric units, aggregation due to chemical or conformational modification, nucleation and controlled growth of particles, the reversible association of native monomer and surface-induced aggregation, are considered. These aggregation pathways are dependent on solvent properties, such as pH, temperature, ionic strength, electric fields and availability of other compounds in the system. Furthermore, zein interactions with other proteins, polysaccharides, hydrolysates, bioconjugates, and other biomacromolecules encountered in the food and cosmetic industry are also discussed with illustrative examples. The literature survey reveals that zein interactions can be modified by various means, including adjustments in solvent properties and other macromolecules in the system. Understanding zein interactions and their contribution to various structures in a composite of biomacromolecules offer the possibility of developing specialised biomaterials for food, agricultural, biomedical and cosmetic applications.