The paper, Review: Nanocomposites in Food Packaging by Amit Arora and G.W Padua, evaluates the possible impact of nanostructures on barrier properties of polymers. It concludes that while the technology is still in its early stages, it has real potential to improve the ability of plastic packaging against migration of gases and flavour compounds, as well as boosting shelf life.
Limiting properties
Over the past decades, plastics have become ever more prominently used in food packaging thanks to their excellent functionality, lightweight properties, ease of processing and low cost. But despite their versatility, a limiting property of polymers in food packing is “their inherent permeability to gases and vapours, including oxygen, carbon dioxide and organic vapours”, said the authors in their review which appears in the Journal of Food Science.
The report reviews current and emerging nanococomposites – materials used as fillers which have at least one dimension smaller than 100 nanometres. Their incorporation is important because of the increased barrier properties, mechanical strength, and ability to withstand the stress of thermal food processing, transportation and storage.
The review examined the use of such materials as nanoclays montmorillonite (MMT) and kaolinite, carbon nanotubes and grapheme nanosheets. It concluded that MMT and kaolinite clays have shown “good potential” for improving properties of polymeric materials. Graphene nanoplates are novel highly promising carbon-based nanofillers, said the review.
Biopolymers
Biopolymers – such as those from plant, animal and microbial products - are attracting increasing attention as potential replacements for conventional plastics. However, bioplastics currently have “relatively poor mechanical and barrier properties, which restricts their use”, said the study. The use of nanocomposites for these have “proven to be a promising option”, continued the authors. The use of starch-clay nanocomposites were highlighted as bringing about “significant improvements in mechanical properties”, while MMT boosted tensile strength.
The review also pointed to benefits from cellulose, polylactic acid (PLA) and protein nanocomposites in improving water and gas barrier properties.
The report concludes the main driver for the application of nanocomposites is the need to improve barrier properties in plastics for food packaging. The implications for the sector are significant, it added.
“Better barriers against the migration of oxygen, carbon dioxide, water vapour and flavour compounds would have a major impact on the shelf-life of fresh and processed foods.”
It added: “For the case of biopolymers, improving water and gas barrier properties is a critical issue.”