Influence of natural biomaterials on the absorbency and transparency of starch-derived films: An optimization study

A D-optimization design was applied to examine the water absorbency and transparency of composite films made from starch and natural biopolymers such as lignin, gelatin, cellulosic fibers, and chitosan. The individual influence of each component and their overall interactive effects were investigated. With regard to water absorbency, it was found that lignin and gelatin can effectively enhance film water resistance, while the incorporation of cellulosic fibers had a limited positive effect on film hydrophobicity. However, increasing the levels of cellulosic fibers significantly diminished the hydrophobicity. The last component, chitosan, always contributed to reducing the hydrophobicity of starch films. The last property studied in this design, transparency, was mainly compromised by the cellulosic fibers and lignin. Cellulosic fibers, because of their bulk dispersed state in the starch films, caused higher light scattering and a concomitant film transparency reduction. Lignin also decreased film transparency because of its chromophoric nature and made the films appear darker; however, it inhibited UV radiation, even at low levels.