Nanoreinforcement as a strategy to improve physical properties of biodegradable composite films based on biopolymers.

Food packaging is evolving from inert plastic to renewable biopolymer film that acts as barrier against gases, light radiation, and microorganisms, reducing food waste without environmental damage. Distinct starting systems were selected to prepare films: single polymer matrix, blend of polymers, cross-linked polymers, and emulsion-based matrix. The blend of polymers was one of the best approaches to improve mechanical and barrier properties of films, especially when one of the polymers was pectin, gelatin or xanthan gum. These polymers can form a gel and increase the viscosity of the starting systems leading to a more elastic matrix. Although some of these films showed potential to replace plastic materials, their physical properties were poor compared to plastics. Thus, several strategies were used to strengthen matrix building block connections or interactions between nanoreiforcement and matrix compounds with the aim of improving physical properties. Among metal oxides, TiO, ZnO, CaO, and MgO were the most studied, alone or in combinations with other reinforcements. Natural fillers, like chitosan and cellulose nanofibers were also added to improve the biopolymer's performance. Several of these systems successfully extended the shelf life of food systems by retarding spoilage, showing great potential to improve food quality and reduce waste. However, most of the studies were carried out on a laboratory scale and it would be necessary to explore the feasibility of producing these films on an industrial scale.