Film‐forming properties and edible films of plant proteins

Film-forming properties of plant proteins vary, depending on the protein's amino acid composition and molecular characteristics. Proteins from soy bean, wheat, and corn are readily available and films from these proteins have been investigated extensively. The proteins are normally dissolved or dispersed in suitable solvents. Then the resulting solutions or dispersions form free standing films either on an air-liquid interface by surface dehydration and heat-initiated polymerization or on a plate by casting the mixture and subsequent solvent evaporation. Various disulfide, hydrophobic, and hydrogen bonding interactions are involved in the film-forming mechanism which contribute to the development of film characteristics. Plant protein films in general are water sensitive and lack mechanical strength. However, they are good barriers against oxygen, and can be found in special applications as food products or edible food wrappers. Efforts are being made by modifications in processing conditions to improve the food-use functionality of the films. Future research to upgrade plant-protein films to be used packaging material is also discussed.