Evaluating the physical, mechanical and morphological properties of calcium-alginate films coated with sunflower oil or tallow fat

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; meanwhile it 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 the lamination 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 evident in 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.