Packaging is a crucial tool in containing and protecting food as it moves through the supply chain to the consumer. The main function of packaging is to protect the product and extend the shelf life of food. Food packaging materials have been traditionally based on petroleum-based plastics due to their versatile and durable nature with reliable gas and water barriers.
Despite all of its benefits, the production of petroleum-based plastics leads to greenhouse gas emissions, environmental pollution, damages in marine ecosystems, and negative effects on our food chain due to the effect of bioaccumulation. The decomposition of petroleum-based polymers can take about 200-500 years or more if placed in a landfill. Most food packaging material has a short use-phase, and a substantial amount of those plastics ends up as a litter at short notice.
One way to solve those problems is the replacement of plastics derived from petroleum with renewable sources such as bio-based products. Currently, more research underway in both food industry and academia is to develop new biodegradable food packaging materials, and to improve and strengthen their barrier properties and to validate their application in real working environments inside the food industry. Also, the economic advantages of weight reduction have become essential for many industries.
The manufacturing of a biopolymer is more environmentally friendly than petroleum-based plastics as it generates significantly less greenhouse gas emissions over the lifetime when compared to traditional materials. However, there are certain obstacles and limitations for a transition to bio-based production. Bio-based polymer materials are still relatively expensive compared to other alternatives and these materials have limited use of in certain applications due to their poor mechanical and barrier properties. Thus, the first step, before use of bio-based plastics alone in the food industry, could be combining of these bio-based plastics with synthetic polymers or enhancing with natural nanofillers such as nano-cellulose. This also means to increase the availability of bio-based polymers for packaging applications.
Nanocomposites are getting more popular because nano-sized reinforcing agents have proven to be effective in enhancing the barrier and mechanical properties of bio-based polymers. Among nanofillers, nano-cellulose particles have a potential to enhance the properties of bio-based polymers due to the similarity between cellulose and other bio-based polymers. Even though bioplastics is not yet regarded as a substitute for more traditional forms of packaging, bio-based nanocomposites present numerous advantages. For example, nanocomposites can be served as carriers of active compounds which are useful in extending product shelf life while maintaining their nutritional and sensory qualities.
Bio-based nanocomposites have a potential to improve the functionalities of food products by adding nutrients to packaging material that are absent in the original product. Antioxidants and antibrowning agents embedded into packaging material can delay degradation of nutrients and flavors, or it can be incorporated with antimicrobials that can suppress proliferation of spoilage microorganisms and food-borne pathogens. On the other hand, bio-based packaging materials have been started to use as carriers of living microorganisms to confer a probiotic ability to the food product, to control of postharvest disease in fruits or to increase the shelf life of food products by using bacterial strains with antimicrobial activities.
In this area, it seems that bio-based nanocomposites will substitute petroleum-based plastics. As researchers of food packaging applications, we are trying to improve the properties (mechanical, barrier) of bio-based plastics (such as chitosan, whey protein, carrageenan) by using fillers like nano-cellulose. We have also focused on enhancing the active properties of those plastics by incorporating natural active compounds like plant extracts, essential oils to extend the shelf life of food products.
In the study, published in Carbohydrate Polymers, we aimed to combine chitosan (CH), a bio-based polymer, with polycaprolactone (PCL), a synthetic biodegradable polymer. We produced a packaging film which consists of an antimicrobial and antioxidant internal layer (CH) with nanocellulose and an outer layer (PCL) with better mechanical and barrier properties. Then, we evaluated the compatibility of a bio-based polymer with a petroleum-based biodegradable polymer in a simple way.
Stand-alone PCL films can be used as a food packaging material however the concern about the reducing synthetic plastics have led to the combination of bio-based polymers with common synthetic materials. PCL has interesting properties such as compatibility with many types of polymers, including biopolymers. PCL can enhance the poor mechanical, and barrier properties of biopolymers. It can also extend the use of biopolymers and provide you with an excellent toolbox to create competitive and more sustainable products. Although CH has better mechanical properties than many other bio-based plastics, it is water-sensitive and cannot compete with synthetic plastics for food packaging applications.
Active packaging is used for packaging materials which constituents have been deliberately included in or on either the packaging material or the package headspace to enhance the performance of the package system. In this study, the development of an active packaging system made of PCL and CH bilayer film, that carry active properties, resulted in a bio-based flexible packaging material with adequate barrier and mechanical properties. Bilayer film formation based on CH and PCL with the inclusion of nanocellulose was shown to be one of the most straightforward methods to obtain new materials with desired functional properties. However, future studies are needed to evaluate the performance of these bilayer films by contact with food.
These findings are described in the article entitled, Development of Chitosan and Polycaprolactone based active bilayer films enhanced with nanocellulose and grape seed extract, recently published in the journal Carbohydrate Polymers. This work was conducted by Ece Sogut and Atif Can Seydim from Suleyman Demirel University.