A nanocomposite film fabricated with simultaneously extracted protein-polysaccharide from a marine alga and TiO2nanoparticles

Abstract

This paper describes an edible nanocomposite packaging film fabricated with simultaneously extracted protein-polysaccharide (biopolymers) from the marine red alga Gracilaria lemaneiformis and TiO2 nanoparticles. Both proteins and polysaccharides were synchronously extracted using the alkali extraction method. Different amounts of TiO2 nanoparticles (TiO2 to biopolymer content ratio of 3.33, 5.00 and 10.0% w/w) were added to prepare the TiO2-protein/polysaccharide nanocomposite film. The addition of TiO2 nanoparticles increased the tensile strength and decreased the water vapor permeability of the film. This was because the uniformly embedded TiO2 nanoparticles interacted strongly with the biopolymers which enhanced the mechanical properties of the film, whereas the particles increased the diffusion pathway distance and lead to lower water permeability. These hypotheses were confirmed by UV spectra, FTIR, and X-ray diffraction studies. Antibacterial measurements against food-borne pathogenic bacteria revealed that the growth of Escherichia coli and Staphylococcus aureus was effectively inhibited by the TiO2-biopolymer nanocomposite film. Additionally, nutrition retention and quality improvement were observed in cherry tomatoes when coated with the TiO2-biopolymer nanocomposite film. These findings suggested that this alga-sourced nanocomposite film could serve as a promising coating material in the food industry.