Biodegradable films from isolate of sunflower (Helianthus annuus) proteins

The film-forming potential of isolate of sunflower proteins (ISFP) was investigated. Homogeneous films were obtained by dissolution of ISFP in alkaline water (pH 12), addition of a plasticizer, casting, and drying. Maximum protein solubilization and unfolding led to films with the highest elasticity. The effects of five dissolving bases and five plasticizers on the mechanical properties were studied. The use of ionic bases (LiOH, NaOH) capable of interfering with the interproteic noncovalent bonds resulted in the greatest tensile strength (sigma(max)) and elongation at break (epsilon(max)) values (3.9 MPa and 215-251%, respectively). Plasticizers conferred diverse tensile properties to the films: the use of 1,3-propanediol resulted in the highest sigma(max) (27.1 MPa), and glycerol resulted in the greatest epsilon(max) (251%). Different mechanical properties were obtained by using mixtures of these plasticizers.