Chapter 9
Biodegradable Films from Pectin-Starch and Pectin-PoIy(vinyl alcohol)
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Marshall L. Fishman, and David R. Coffin Eastern Regional Research Center, Agricultural Research Service, U.S. Department of Agriculture, 600 East Mermaid Lane, Wyndmoor, PA 19038
Blends of pectin and high amylose starch, and pectin and poly(vinyl alcohol) (PVOH), both with and without added plasticizer, were used to make solution cast films and characterized to quantify their properties. They were investigated using dynamic mechanical analysis, scanning electron microscopy, tensile testing, FT-IR, oxygen permeability, and solubility studies. The films were found to have high modulus and strength values, with the properties depending strongly on composition. Glycerol was found to be effective as a plasticizer, and PVOH was shown to impart ductility to the pectin. Significant changes in morphology were seen with changes in composition by SEM. Hydrogen bonding of pectin in the film is affected by temperature and glycerol. Oxygen permeability of these films is much lower than found in commercial plastic films.
© 2005 American Chemical Society In Polymer Biocatalysis and Biomaterials; Cheng, H., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2005.
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120 The study of biodegradable films is a rapidly growing area of research due to their ability to degrade rapidly when disposed of in a landfill once the useful life of the product is over. In addition, they come from renewable resources whose use reduces stress on the environment. Some polysaccharides which have been investigated as biodegradable materials are starch, alginate, carrageenan, cellulose ethers, and pectin. We have been actively involved in studying pectin and its properties for over ten years, both in solution and as solid films. This article summarizes the literature on pectin films, and describes the work we have done on both pectin/starch and pectin/poly(vinyl alcohol) films. Pectins are water soluble polysaccharides found in the cell walls of higher plants. They have found extensive use in processed foods as a result of their gelling properties. Because pectin is a film forming material it has desirable physical and mechanical properties. Studies on pectin films were done as early as 1936 (7). Generally these studies involved derivatized pectins and the use of polyvalent cations such as calcium. Much of the work was on coatings for foods. Schultz et al. (2, 3) prepared films from low methoxyl (
