Submitted to: Journal of Applied Polymer Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 30, 2007
Publication Date: July 30, 2007
Citation: Liu, L.S., Finkenstadt, V.L., Liu, C., Jin, Z.T., Fishman, M., Hicks, K.B. 2007. Preparation of poly(lactic acid) and pectin composite films intended for application in antimicrobial packaging. Journal of Applied Polymer Science, 106(2)801-810. Interpretive Summary: Billions of pounds of low-valued pulp and peel are generated yearly by the U.S. beet sugar and fruit juice industries. These residues are generally sold, at low or no profit as animal feeds. These residues contain millions of pounds of a potentially valuable polysaccharide called pectin, yet due to lack of markets, only a negligible amount of pectin is extracted and marketed in the U.S. Finding new uses for this biodegradable polysaccharide is critical for the long term economic viability of U.S sugar beet and citrus agribusiness. In this study, pectin was used to make a composite (mixed) film by extrusion with another biomass-derived compound, poly(lactic acid). The new composite films are water resistant and mechanically strong enough to use as packaging materials for food products. In this study we showed that we could mix a food preservative (antimicrobial compound) into the film during manufacture and then used those films to package food products. These foods resisted spoilage and the growth of dangerous food-poisoning microorganisms (pathogens) because of the presence of the food-grade antimicrobial compound. These composite films can thus function as novel antimicrobial food packaging materials. Developing news uses for pectin such as these will help to create new markets for pectin and eventually create new uses and value for sugar beet and citrus byproducts. This will benefit fruit growers and processors.
Technical Abstract: Composite films of pectin and poly(lactic acid) (PLA) were compounded by extrusion. A model antimicrobial polypeptide, nisin, was loaded into the film by diffusion. The incorporation of pectin into PLA resulted in a heterogeneous biphasic structure as revealed by scanning electronic microscopy, confocal laser microscopy, and fracture-acoustic emission. The incorporation of pectin also created a rough and cragged film, which was hydrophilic and facilitated the access and absorption of nisin. The nisin-loaded composite films suppressed L. planturam growth, as indicated by agar diffusion and liquid phase culture tests. The incorporation of pectin in the amount of ~20% total mass did not alter the Young’s modulus of the PLA films. These films were able to retain their tensile strength, flexibility, and toughness to an extent, which satisfies the requirements for packaging materials. Results from this research indicate the potential of Pectin/PLA composite films for the application of antimicrobial packaging.