Development of novel, biodegradable, active food packaging

Nowadays, a considerable number of petrochemically derived non-biodegradable and non-renewable synthetic plastics are produced and utilised daily for single-use food packaging applications. These end up as waste in landfills or incineration, resulting in considerable greenhouse gas emissions and major degradation of aquatic and terrestrial environments. As a result, there is significant impetus for the development of biodegradable bio-based materials to replace conventional plastics; these include both biomaterials from microbial fermentation processes such as polylactate (PLA), as well as biodegradable natural polymers (BNPs) such as polysaccharides and proteins derived from biomass and agri-food resources. The downside of BNPs is that their physical properties do not match those of synthetic plastics. Research has shown that BNP blends or multilayer sheets of polymers are more effective than single polymers, while the incorporation of metal nanoparticles (NPs) (1 to 100 nm) can considerably improve the mechanical, gas-barrier and thermal properties of the packaging, as well as potentially add antimicrobial and antioxidant properties leading to the development of active packaging materials, which could potentially extend the shelf life of food products, such as meat/fish and fresh-produce (e.g. fruit, vegetables). Despite the significant commercial and public interest for such novel packaging solutions, there are considerable research challenges still to overcome across a conceptual multi-stage production process. This includes the development of novel NPs with multiple activities (e.g. antimicrobial, antioxidant) or uses (ag. as sensors) and compatible BNP blends, understanding of structure/function relationship of these novel packaging materials, process design and optimisation of scalable packaging production processes (e.g. extrusion), applications in real food systems and storage conditions, and techno-economic analysis to identify opportunities for process/material improvements and cost effectiveness. The hypothesis of this study is that enzyme-grafted metal nanoparticles can improve the functionality of biodegradable materials leading to the development of biodegradable active food packaging materials with advanced properties.
Research objectives:
1)To develop and optimise the reactions for chemically grafting enzymes (oxidase, lysozyme) onto metal NPs and assess their physical, antimicrobial and antioxidant properties using various methodologies (e.g. dynamic light scattering, infrared and UV-Vis spectrophotometry, scanning electron microscopy, microbiological and biochemical assays).
2)To produce packaging sheets through small-scale extrusion using several BNPs including polysaccharides (cellulose, starch, alginate) and proteins (hordein, zein) singly and in mixtures in order to develop in-depth structure/function understanding enabling some of the following attributes: thermal, hydrophobicity (reduced water vapor permeability) and oxygen barrier properties; enhanced radical and oxygen scavenging activities; improved mechanical properties.
3)To obtain a range of packaging materials using up to three formulations (from Obj. 2) where NPs (from Obj 1) will be incorporated, and understand from a mechanistic/molecular perspective the influence of the latter on the thermal, mechanical, barrier, antimicrobial and antioxidant properties.
4)To optimise the conditions for the production of prototype packaging sheets (from Obj 3) through a continuous extrusion process using a pilot scale food-grade twin-screw extruder (available at UoR).
5)To evaluate the effectiveness of the produced prototype sheets (from Obj 4) singly and in combination (e.g. multilayer packaging sheets using adhesives) for the shelf-life extension of high value and highly perishable model crops. assess the interaction of the packaging with food products and its potential benefits on quality and safety.