PHYSIOCHEMICAL BEHAVIOUR OF CHITOSAN/POLYVINYL ALCOHOL BINARY FILM FOR FOOD PACKAGING

Abstract

viii ABSTRACT The aim of this study is to prepare, characterize and further develop films of polyvinyl alcohol (PVA) and chitosan. Blends which comprise of synthetic and natural polymers embody a fresh group of materials and have attracted considerable attention especially in bio application when used as a biomaterial. The resulting properties of the blends mainly rely on the properties of the constituent polymers and on the phase morphology that has been developed during blending. These antimicrobial packaging films have been of much concern due their ability to slow or kill pathogenic microorganisms that tend to reduce the shelf life of food products. Thus chitosan based films have been studied because of their effectiveness in food preservation. Chitosan is well known for its excellent biocompatibility and biodegradable properties. It also has got a high modulus of elasticity which is due to high glass transition temperature and also its crystallinity. PVA is known to be a semi crystalline, excellent chemical resistance water soluble, better film and fiber forming, non-toxic, good mechanical properties, biocompatible and biodegradable synthetic polymer. The present work describes the structural characterization, thermal study, surface morphology and bioactive behavior of edible cross-linked chitosan-PVA film. An edible film is prepared by blending chitosan and poly (vinyl alcohol) (PVA) with glutaradehyde as cross-linker. The presence of hydrogen bonding between ─OH of PVA and ─OH or ─NH2 of chitosan has been ascertained by IR study. TGA thermogram of chitosan-PVA film has provided a fair idea about the thermal degradation and the energy required to vaporize the water present in the film. Antimicrobial assessment has shown the positive inhibitory effect against E. coli. When chitosan and PVA are blended there is improved strength as well as flexibility of the films. Adding a cross linking agent will further improve the tensile strength but decrease the elongation properties of the films. As the PVA content in the film increase the water uptake increases due to an increase in the hydroxyl groups thus water uptake can be reduced by minimizing the amount of PVA, adding a cross linking agent and adjusting the pH of the solution. Thus bulk and surface hydrophilicity of the films is improved. The findings of the antimicrobial activity has demonstrated that chitosan-PVA solution may be used for the preservation of fruits and vegetables.