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/m2/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.

Concerns about the environmental issues have increased the tendency to package the food stuffs with natural biopolymers. However, the use of these compounds has limitations such as the weakness in mechanical, barrier and optical properties. Alginate, as a biopolymer, has a good film forming potential; meanwhileit has poor moisture barrier properties.In order to overcome this problem, in this study, the calcium alginate film was coated with two types of lipids including sunflower oil (as a liquid oil) and tallow (as a solid fat) at two concentrations (0.5 and 5%, with and without 0.1% lecithin). Afterward, the physicochemical, barrier, and mechanical properties of the produced films were investigated. The results showed that thelamination of the alginate films with tallow fat increased the film thickness, which increased with the fat concentration. In addition, sunflower oil significantly reduced the permeability of the films to water vapor, that was more evidentin 0.5% sunflower oil coated film. The results also showed that the use of these hydrophobic materials for the coating of alginate films changed the color properties and the turbidity of the films. The mechanical properties of the film, including tensile strength and elongation at the breaking point, improved by coating the alginate film with 0.5% tallow fat.Thickness, water vapor permeability, and the mechanical properties were not affected by the addition of lecithin. The SEM images proved the formation of small holes or cracks on the films surfaces.In general, this study showed that sunflower oil or tallow fat can be used as natural compounds to improve the properties of calcium alginate-based edible films, depending on the goals of packaging.