The photo is sourced from rscf.ru
One of the most common long-term food storage technologies is Tetra Pak involving separate sterilisation of packages and their contents. However, its disadvantage is a relatively low environmental friendliness. Packaging made with the Tetra Pak technology is usually multi-layered and not recyclable. The scientists of the Moscow Institute of Physics and Technology and the Institute of Organoelement Compounds of RAS have managed to solve this problem by creating a biodegradable packaging based on tea tree essential oil known for its antimicrobial and antioxidant properties.
Such oil is difficult to introduce into the polyethylene matrix as some of its components are volatile and incompatible with the film components. The researchers were able to circumvent this limitation by using metal-organic frameworks (MOFs), crystalline porous materials made of metal ions interconnected by organic molecules. Metal-organic frameworks can change the size of their pores under the influence of temperature, liquids and electromagnetic radiation. Due to this, molecules of third-party compounds can be placed inside the MOF, and when external conditions change, they can be removed.
As the part of the research, the scientists included active components of tea tree oil in the MIL-100(Fe) metal-organic framework, which is synthesised from iron salts and organic acids. Thus, the metal-organic framework became a sort of nanocontainer, which was then introduced into the matrix based on two plant polymers used in the food industry as thickeners and water-retaining agents. In the end, at the last stage, the researchers conducted a series of experiments to evaluate mechanical properties of the resulting films, their transparency, vapour permeability, and antibacterial properties.
The best results were shown by specimens whose total mass of nanoparticles did not exceed 2% – at a higher concentration, homogeneity of the polymer matrix was disturbed, so the films acquired a rough surface. Experiments have shown that the films developed have antibacterial activity as well as block ultraviolet radiation, which leads to accelerated deterioration of food. At the same time, the proposed materials demonstrated good strength, wear and moisture resistance.
“The combination of metal-organic frameworks with natural polymers may be one of the possible keys to a new generation of a sustainable and biocompatible food packaging. By using renewable raw materials, such packaging will help solve global environmental problems associated with an excessive consumption of synthetic plastics,” the Russian Science Foundation quotes Valentin Novikov, the head of the department of chemical physics of functional materials at MIPT.
