Packaging is an especially important step in the complete process to which food is exposed, from its processing or preservation to its supply or distribution chain. The main function of packaging is to contain and protect the products. This, in turn, has led to concerns about the environmental friendliness, biodegradability and sustainability of the packaging materials. And there have also been many developments focused on improving the performance of packaging systems.
Regarding this issue, multilayer packaging can offer higher performance than monolayer. This is because they merge the functionalities of several polymers with the aim of developing a package that performs better in terms of food protection and durability. In many cases, it is not possible for a monolayer to meet all the food packaging requirements, either in terms of containment (strength and sealing properties), protection (moisture, gas, light, taste, smell), machinability (tensile strength, softening, gliding, stiffness, flexibility), while ensuring cost effectiveness and adherence to all aspects of food safety. Therefore, the aim of the multilayers is to develop a single structure that combines multiple properties to meet all the functional requirements of the packaging.
Applications of the multilayer packaging system for food materials
As mentioned above, progress is being made in the development of multilayer packaging systems, because their functionalities are superior to the monolayer. In the research ‘Multilayer packaging: Advances in preparation techniques and emerging food applications’, several studies in favour of these types of polymers are mentioned, e.g. the development of multilayer films for microbial inhibition and another on the extension of shelf life of high-fat foods.
A third study shows how the antioxidant properties of an apple increase from 13% to 44% when a two-layer package is used. Finally, it should also be mentioned that PET-based polymer packaging films have been found to be suitable for microwave pasteurisation of ready-to-eat foods.
Recycling of multilayer packaging
Multilayer films are used for their functional potential and barrier properties, but it is also true that recycling is quite difficult, and most packages are incinerated or deposited in landfills. In addition, it must be noted that the inadequate recycling of composite polymers would increase the risk of unintentional substances coming into contact with the food, posing a threat to health.
When preparing a multilayer package, adhesives are used for the lamination of intermediate layers. Recycling of these materials therefore requires additional delamination steps, making the process more difficult. RepetCo Innovations has developed a unique solution to recycle post-consumer PET/PE multilayer packaging. Thanks to their innovative, environmentally friendly technology, the different layers can be separated, rPET generated and reused in the food industry.
Safety in multilayer packaging
The main concern when incorporating multilayer films is the selection of the active agents, those that allow the shelf life of the packaged food to be extended. Therefore, the design of a multilayer package always takes into account that the active ingredients used are far below the recommended limits that must be met to ensure safe consumption of the packaged food. In Europe, the Act 450/2009 regulates at EU level the use of active and intelligent substances intended to come into contact with food.
Multilayer packaging solves the problem of monolayers in terms of its properties as barrier against gas, water vapour, light and other smaller molecular taste and flavour molecules. Thus, it provides an innovative solution for food quality and product marketing.
