IMPROVED WATER RESISTANCE IN EDIBLE ZEIN FILMS AND COMPOSITES FOR BIODEGRADABLE FOOD-PACKAGING

Zein, corn prolamine, was dissolved in several organic solvents to mak e films and their properties were examined. Ethanol with 20% water and acetone with 30% water were found to dissolve zein well and transform it into a transparent flexible film after moderate drying. Both films showed similar breaking strength to that of commercial thin film of p olyvinylidene chloride for food use and were digested with proteases. Only the film prepared from acetone solution showed a relatively low w ater permeability. This water permeation was found to depend strongly on the rate of diffusion. 1,2-Epoxy-3-chloropropane (ECP) was added in to the acetone solution to cross-link the zein molecules for the purpo se of improving the breaking strength and water-resistant properties o f the film. Alpha-chymotrypsin was found to digest the film even after the modification with ECP. However, this cross-linking resulted in li ttle improvement in the water-resistant properties of the film and als o reduced its flexibility.