Irradiation of Edible Films of Plant and Animal Origin
Edible films can be prepared from protein, polysaccharide, and lipid materials. Among them, protein-based edible films are the most attractive. These films have impressive gas barrier properties compared with those prepared from lipids and polysaccharides. However, the poor water vapor resistance of protein films and their lower mechanical strength in comparison with synthetic polymers limit their application in food packaging. In the 1990s, there was a remarkable increase in research efforts for the development of biopolymer films and coatings from protein, polysaccharides, and lipid materials. The qualities of renewability, degradability, and edibility make such films particularly suitable for food and non-food packaging applications. Moreover, wide commercialization of biopolymer films would provide a value-added innovative use for traditional agricultural commodities as a source of film-forming materials. There has been ongoing interest in the development of films and coatings, including edible packaging materials, from renewable biopolymers. Opportunities for adding value to underutilized agricultural materials and concerns regarding the potentially adverse environmental impact of synthetic packaging materials are two major drivers of such interest. The effect of irradiation on edible films was found to depend greatly on the kind of substrate. Specifically, whenever there was a chance for cross-linking, the polymeric network became more resistant, resulting in higher tensile strength and puncture strength, but the percentage elongation decreased. On the other hand, cross-linking led to lower gas and water permeability values. In the case in which there was no cross-linking, the irradiated network loosened, and both mechanical and permeation properties decreased considerably. © 2010 Elsevier Inc. All rights reserved.