Films prepared with oxidized banana starch: Mechanical and barrier properties

Films were prepared using oxidized banana starch and glycerol. Oxidized banana starch was synthesized at three oxidation levels (0.5, 1.0 and 1.5% of active chlorine). Thermal gelatinization and casting were used for film preparation. Tensile strength, elongation, X-ray diffraction pattern and water vapor permeability were tested. The tensile strength of the films was higher when the oxidation level of the banana starch was higher. When films were stored for 30 and 60 days, there were no statistical differences in tensile strength. However, differences occurred when those films were compared with the films stored for 90 days. The film with added sunflower oil presented the lowest value of elongation at 30 and 60 days of storage. When elongation values were assessed at 90 days of storage no statistical differences (alpha=0.05) were found among the films prepared from native starch with added sunflower oil, oxidized banana starch with 1.0% and oxidized banana starch with 1.5% oxidation level. All films had a B-type X-ray pattern. When the oxidation level in the starch increased the, peaks of crystallinity of the films increased as well. An additive effect was shown due to the higher interactions among polymer chains and among polymer and glycerol molecules as determined by the mechanical properties of the films analyzed. The corrected water vapor permeability (WVPc) of the films stored for 30 and 60 days did not show statistical differences (alpha=0.05). The films prepared with oxidized banana starch had the highest WVPc and those values increased when the oxidation level in the starch was higher. Oxidized banana starch can be used for preparation of films with adequate physicochemical characteristics.