Hydrophobisation approaches of protein-based bioplastics

Abstract

Background: The problems arising from the accumulation of plastic have led to comprehensive research for bio-based packaging materials. Proteins are a promising alternative to traditional plastic because of their great barrier properties and multifunctional properties. However, the hydrophilic nature of proteins limits their wide application for the packaging of low and medium-moisture content foods. Distinct functional groups of proteins allow various modifications to obtain hydrophobic films that meet the requirements of suitable packaging. Besides, the valorization of agro-industrial by-products is considered a promising solution for obtaining packaging materials. Scope and approach: Herein, protein-rich agro-industrial by-products and various hydrophobisation techniques including blending, emulsification, grafting, nanocomposite, cross-linking, plasticizer alternatives, and physical treatments for the fabrication of protein films are comprehensively investigated. The challenges and prospects are also evaluated. Key findings and conclusions: Hydrophobisation is generally based on reducing the hydrophilic groups, compacting the protein network, or incorporating hydrophobic groups. It mostly resulted in a protein matrix with low water sensitivity, high tensile strength, and low elongation. However, lipids incorporation into the protein matrix may overcome the brittleness of hydrophobised protein films. Physical treatments by unfolding protein chains make functional groups accessible for further treatment. Nevertheless, commercialization of protein-based packaging is still in its early stages, although there have been some recent advancements including water-soluble pouches and coating materials. Further research is still needed on optimizing the current techniques or utilizing emerging technologies such as 3D printing, plasma deposition, corona discharge, and pulsed light to accelerate the commercialization of hydrophobic protein films.