CELLULOSE-BASED BISMUTH PHOSPHINATE COMPOSITES AS ANTIBACTERIAL FOOD PACKAGING MATERIAL

摘要

Food packaging plays a very important role in ensuring food safety. Active food packaging materials with good barrier properties, biodegradability as well as antimicrobial properties are necessary to maintain food quality and improve shelf life. This study aims to investigate the preparation of a material that meets these requirements. Cellulose, being the most abundant biopolymer, is a promising material due to its biodegradability and being environmentally friendly and thereby can potentially replace the currently used petroleum based materials. Thus, a cellulose-based antibacterial packaging material has been developed in this study using a non-toxic inorganic complex as the antibacterial agent incorporated within nanocellulose matrix. An organobismuth complex, phenyl bismuth bis (diphenyl phosphinate), has been added to nanocellulose suspension and sheets were prepared by spraying onto stainless steel plates moving on a constant speed conveyor belt. The water vapor permeability tests were carried out to understand the barrier properties. The loading of the bismuth phosphinate complex resulted in slight increase in water vapor permeability from 2.67 × 10~(-11) g/Pa.s.m for pure nanocellulose sheet to 4.48×10~(-11) g/Pa.s.m when the loaded with 5% bismuth (Ⅲ) phosphinate complex. However, it was still comparable to the water vapor permeability of PET and PLA. FE-SEM imaging was done to study the distribution of the complex particles within the composite. The morphological structure showed that the organobismuth complex is present not only on the surface, but also buried inside intertwined within the fibres. Antibacterial tests were carried out using the disk-diffusion method for Gram-positive and Gram-negative multidrug resistant bacteria. The disk diffusion tests showed that the composites were active against both types of bacteria at low loadings of maximum of 5 wt. % (g bismuth complex/g cellulose), showing proportionate reduction in effectiveness with lower loadings. However, the Gram-positive bacteria were found to be more susceptible to the composite papers than the Gram-negative ones. Thus, the bismuth-phosphinate nanocellulose composite has the potential to be used as a packaging material having good antibacterial property at the cost of only slight reduction of water vapor barrier performance.