Bio-hybrid nanocomposite coatings from polysaccharides and nanoclay

In recent years a lot of effort has been aimed at developing new bio-hybrid nanocomposite barrier packaging materials for foods. Nanocomposite films and coatings with improved properties were produced from nanoclay and polysaccharides such as ultrasonic dispersed chitosan and high pressure fluidized pectin. The intercalation of chitosan in the silicate layers was confirmed by the decrease of diffraction angles while the chitosan/nanoclay ratio increased. Nanocomposite films and multilayer coatings had improved barrier properties against oxygen, water vapor, grease and UV-light transmission. Oxygen transmission was significantly reduced under all humidity conditions. In dry conditions, over 99% reduction and at 80% relative humidity almost 75% reduction in oxygen transmission rates was obtained. All chitosan coating raw materials were "generally recognized as safe" (GRAS) and the calculated total migration was in all cases ≤ 6 mg/dm2, thus the coatings met the requirements set by the packaging legislation. Processing of the developed biohybrid nanocomposite coated materials was safe as the amounts of released particles under rubbing conditions were comparable to the particle concentrations in a normal office environment. Nanoclay-pectin hybrid film formation and high shear induced orientation of nanoclay platelets were investigated by means of model surfaces which were prepared using high shear spincoating. After fluidization, the nanoclay formed uniform and laterally oriented stacks consisting of approximately 15 individual nanoclay layers. Pectin films with different nanoclay concentrations were prepared by casting. Nanocomposite films made of pectin and nanoclay showed improved barrier properties against oxygen and water vapor. Films were also totally impermeable to grease. The developed bio-hybrid nanocomposite packaging materials can be potentially exploited as a safe and environmentally sound alternative for synthetic barrier packaging materials