Improving the water barrier properties of alginate packaging films by submicron coating with drying linseed oil. Issue 5 (3rd February 2021) - Nehchiri, Narges
Abstract: Alginates with excellent film‐forming ability have a promising potential as a safe and biodegradable food packaging material, but as a hydrophilic biopolymer, its general weakness against water has limited its applications. To surpass this weakness, in this study, coating of calcium alginate films with linseed or sunflower oils in micrometric (about 4.55 μm) and submicrometric (about 0.45 μm) thickness was performed, and the characteristics of the films were evaluated. All of the films were homogeneous, transparent and almost colourless. Micro‐coated films presented improved ultraviolet absorbing spectra. The scanning electron microscopy (SEM) images proved the formation of homogeneous and continuous submicron‐coated oil layers for both types of the oils, while some inhomogeneity and defects were observed in the micro‐coated films. Oxidative polymerization of linseed oil was confirmed by Fourier transform infrared (FTIR) spectral analyses. The mechanical strength of the films micro‐coated with linseed oil increased. Submicron coating improved water vapour barrier properties (from 2.20 to 2.92 g/mm/m 2 /day/kPa) as well as water vapour absorption of the alginate film compared to other films. This result was confirmed by thermogravimetric analyses. The increase in surface hydrophobicity of the films by coating resulted in a significant increase in contact angle (from 46.3° to 89.9° in maximum) and reduction of wettability. The film submicron coated with linseed oil showed the best performance with the least water vapour permeability, water vapour absorption and wettability. Abstract : The submicron coating of Ca‐alginate films with linseed or sunflower oil created superior properties in comparison with micro‐coating. Continuous and noncontinuous layers of oils were formed in submicron‐ and micro‐coated films, respectively. Reduced water vapour permeability (WVP), wettability and water vapour absorption was obtained for submicron‐coated films, while the micro‐coating of alginate films did not improve water barrier properties.