By Will Soutter
Active or "Smart" Packaging
Despite much enthusiasm, the adoption of nanotechnology in the food
industry has been slow and limited. Due to restrictions imposed by
increased costs, uncertain legislation and fear of a consumer reaction,
food manufacturers have been reluctant to push research into proposed
"nanofood" technologies, and those that are still being considered are
at a very early development stage.
In the realm of food packaging, however, nanotechnology is being
adopted much more rapidly. Whilst there are still concerns about the
degree to which nanomaterials can leach into food from the packaging,
and the effect they may have on the health of consumers, most research
so far looks promising, and the benefits are highly tangible - several
nano-enhancements for packaging are already on the market,
helping to prolong the shelf life of food and making it easier to
manufacture, process, and manage.
For some time now, food has been packaged in a protective,
oxygen-free atmosphere. Standard packing film made from flexible
plastics, however, is slightly permeable to oxygen and other gases.
Over time, this means that the protective atmosphere can leak out, and
oxygen can leak in, damaging the food.
A coating of metal or glass, which are totally impermeable to gases,
would prevent this from happening - this is obviously impractical
however, as it would reduce flexibility, and would be much more
expensive than plastic packaging.
This is where nanotechnology comes to the rescue - a coating just a
few nanometres thick is sufficient to create an impermeable layer,
without compromising on flexibility or adding a great deal to the cost.
Figure 1. Schematic of a nanostructured,
multi-layer barrier film for use in packaging. The polyamide and metal
nanofilms ensure impermeability to gases and moisture, keeping the
product fresh for longer, whilst retaining the flexibility of the
polyester and polyolefin films.
As well as behaving as a simple passive barrier, packaging can be
enhanced to actively reduce the growth of harmful microbes.
Antibacterial coatings most often use silver nanoparticles, which are
becoming more and more common in everything from wound dressings to
Other antimicrobial materials have been investigated, and will most
likely see increased use in packaging in the coming years. These
include zinc oxide nanoparticles, which become more antibacterial as
their particle size gets smaller, and chitin, which is a natural
substance found in the shells of crustaceans like crabs and shrimps.
Active or "Smart" Packaging
Researchers have started to explore the possibilities of "smart"
packaging. Rather than just keeping food from going off for as long as
possible, packaging with embedded smart materials and flexible
nanoelectronics could actively control the environment inside the
packaging, and alert consumers when the food has begun to decay.
Self-cooling packaging has been suggested, which would use a
chemical or physical process, such as evaporation of a gas, to keep the
temperature inside the packaging cool. Powered systems could also use a
thin-film photovoltaic cell to power cooling using a thermoelectric
This would reduce the need for large-scale refrigeration along the
supply chain, although it is unclear whether or not there would be a
cost benefit in this case.
Self-healing polymers have been under investigation by researchers
for quite some years now, and some examples have appeared on the
market. Use of these materials as an outer layer in food packaging
could allow small punctures and tears in the wrapping, reducing wastage
due to damaged packaging.
One interesting development is the use of nanoparticles to create
colour-changing plastic packaging which indicated when food is going
off. There are two main mechanisms to achieve this - chemical and
The chemical mechanism uses a chemical indicator which changes
colour in the presence of gases given off when food oxidizes.
The physical mechanism uses nanoparticles embedded in the polymer
layers which change their optical properties depending on their
relative position in the lattice structure. This can be designed so
that an intense colour is produced when the packaging stretches,
creating an obvious indication of gas-releasing decomposition.
RFID (Radio Frequency Identification) tags have been used for some
years now. They work much like a barcode, uniquely identifying a large
number of products, but they work at a distance of up to tens of metres.
Nanotechnology techniques are already used in the manufacture of
RFID tags, and improvements in these techniques in the coming years
will result in smaller, cheaper RFID systems. This will make them ever
more common - it is likely that they will eventually replace barcodes
Figure 2. Bar codes and sell-by dates could
soon be a thing of the past in food packaging, replaced by RFID tags
and smart materials to alert consumers to the food going off. Image
credit: Wikimedia Commons.
The research clearly shows that nano-enhanced packaging has much to
offer the food industry. Benefits range from stronger and more flexible
films, to smart packaging which can vastly simplify stock management
and monitor food condition.
However, as with many burgeoning areas of nanotechnology, there are
some concerns which must be raised. It is not yet completely clear to
what extent nanoparticles embedded in packaging films can leach into
food products, and what the effects of exposure to various
nanomaterials on consumer health might be.
The sustainability of nano-enhanced packaging must also be
considered. Whilst multilayered thin films may perform excellently,
they will most likely be very difficult to reuse or recycle, and may
use limited raw materials and manufacturing processes which are
energy-intensive and produce significant quantities of waste.
Whilst these issues are still being explored, one thing is for sure
- the next few years will bring important and fascinating developments
in nanotechnology for packaging, which may well act as a model for
progress across all commercial applications of nanotechnology.