Influence of process (extrusion/thermo-compression, casting) and lentil protein content on physicochemical properties of starch films.

Starch films often present high water sensitivity, affecting their barrier and mechanical properties. The effects of processing technique, extrusion/thermo-compression and casting, and lentil protein concentration (0, 0.75 wt.% and 1.5 wt.%) on biodegradable starch films were investigated. Extrusion/thermo-compression process increased in 90% the mechanical resistance of starch films produced following the casting methodology and decreased their moisture content, water solubility and water vapor permeability in 35%, 23%, and 50%, respectively. In the presence of the protein, the mechanical properties (Young modulus and stress at break) and the water tolerance improved due to the crosslinking phenomenon prompted between the protein and the polymeric backbone, being these effects more pronounced on the extruded formulations. All samples resulted thermal stable until 240 °C and biodegraded in compost in 5 weeks. This work revealed that extrusion/thermo-compression process and proteins as crosslinking of starch are two alternatives to improve the drawbacks of starch-based materials.