Enhancing bio-based polysaccharide/protein film properties with Natural Deep Eutectic Solvents (NADESs) and NADES-based bioactive extracts - A review

Biodegradable films show promise as eco-friendly alternatives to petroleum-based plastic films. However, single substrate-based biopolymer films have limitations like poor water-barrier qualities due to their hydrophilicity and low water resistance. Biopolymer films can be prepared by mixing proteins or polysaccharides to improve their physicochemical properties and may include additives such as bioactive compounds to confer added antioxidant and antibacterial characteristics. Recently, Natural Deep Eutectic Solvents (NADESs) have been a popular research topic. NADESs are green solvents with high extraction capabilities and are comprised of common metabolites that can act as film additives. However, few studies have explored the incorporation of NADESs into bio-based polysaccharide/protein film formulations and the effect on film properties for applications such as active food packaging. In this review, we discuss the limited research currently available on NADESs and NADES-based extracts as film additives. While most of the current studies have focused on hydrophilic NADESs and chitosan-based films, more research is needed to explore the incorporation of hydrophobic NADES extracts into different bio-based polysaccharide/protein films and the effect on film properties, such as water vapor permeability. Further consideration is given to the sustainability of this novel approach to film formulation and future prospects.