ABSTRACT:The physical and chemical properties of composite starch-based films containing cellulosic fiber, chitosan, and gelatin were investigated. Films containing both cellulosic fibers and chitosan demonstrated tremendous enhancements in film strength and gas permeation. The water absorbency of composite films could be greatly reduced in film composites containing cellulosic fibers and gelatin, but the inclusion of chitosan into these films provided a higher hydrophilicity, increasing water absorbency. Film transparency was not noticeably affected in the composite films that were made. These films may have wide application in the food packaging, agricultural mulching, and the medical industries.

A D-optimization design was applied to investigate the strength properties of biomaterial-doped starch films. The individual effect of each additive and associated interactive effects were investigated. Cellulosic fibers and chitosan were able to substantially enhance film strength. Lignin and gelatin also demonstrated significant interactive effects on strength, while different interactive effects were evident between the major biopolymers (fiber and chitosan) and minor biopolymers (lignin and gelatin). The film stretch depended on the material composition where diminishing returns were observed for stretch, while strength increased for increasing levels of each of the biopolymers. An increase in fiber and chitosan contents led to increases in film density that correlated well with strength. The latter data indicate that fiber and chitosan biopolymers act synergistically by providing increased film bonding that eventually generates a stronger film.

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.