featured in this issue - NZIFST - The New Zealand Institute of Food ...

PACKAGING
Role
Mechanical resistance
Gas barrier properties
Water vapour barrier property
Anti-UV action
Anti-fog properties
Sealability
Shine or transparency
“Printability”
Polymer
Polycarbonate, low and high-density polyethylene, polypropylene
Poly vinylidene chloride, Ethyl Vinyl Alcohol, Polycarbonate, PVC
Polyester, polyethylene, PVC, polypropylene polypropylene
Polyamide, Polyethylene, Polypropylene
Polyethylene pherophtalate
The most sophisticated packaging can include as many as ten layers in
a very fine width of scarcely 50 micrometres, which was unimaginable
a few years ago. One of the challenges of the future of packaging is to
reduce the weight and volume of waste packaging material for environmental
reasons.
Machinery for MAP packaging
The equipment required varies depending on the types of packages to
be manufactured:
• Compensated vacuum machines for semi-rigid packaging
composed of a thermoformed and sealed plastic tray
• Vertical or horizontal bagging machines. The correct atmosphere
is achieved using gas flushing.
Progress has been made in sealing technologies with regard to tooling
changeover times and temperature holding systems. In some cases,
these have been completely eliminated, as in Automac’s Atmopack
system using high pressure gas flushing resulting in less than 1% residual
oxygen combined with a stretchable protective film
Controlling the atmosphere and
quality of packaging
Package integrity
A small hole in the package or a faulty seal is enough to undo the benefits
of modified atmosphere and to reduce the shelf-life of the product.
Food companies must ensure the integrity of the package when it
leaves the packaging line, the factory floor or storage room. There is
a choice between two types of technology: statistical control or in-line
control.
Using statistical techniques, package samples are taken manually for
analysis. The sample is then placed under a lid under which a vacuum
is created in order to suck out, where necessary, the “leaked” packaging
atmosphere.
In the first case, the analysis is carried out continuously on all products
at different sequences of the packaging machine using the same principle.
The analysis is instantaneous, provided that a tracer gas is placed
in the packaging atmosphere. CO 2
and helium are two types of tracer
gases that can be used. The advantage of CO 2
is that most of the time
it is already used in the packaging atmosphere. If this is not the case, a
small amount of helium (5%) must be added to the initial atmosphere.
This completely inert and transient molecule is authorised by the regulations.
The operator is alerted to the presence of these gases detected
by the appropriate analysis (infra-red for CO 2
, mass spectrometry for
helium) and will then ensure the packaging line is adjusted accordingly.
In most cases leaks are due to defective seals on the packaging film,
or due to parts of the product becoming trapped in the seal thereby
creating a “chimney”.
Oxygen measurements:
A continuous analysis of residual oxygen levels and the percentage
of CO 2
, where applicable, is carried out during the packaging operation,
to ensure compliance with quality and food safety requirements.
Statistical destructive testing of packaging is also carried out to monitor
changes to the product and its gaseous composition over its shelflife.
An interesting innovation, currently under development, is in the
analysis of residual oxygen levels using non invasive technology. This
oxygen measurement system is manufactured and marketed by the
American company Oxysense. Oxygen is detected by indirectly measuring
the lifetime of the luminescence of an organic substance placed
on the inside wall of transparent packaging and held in place by an
oxygen permeable membrane. When this substance is illuminated
by an exterior light, it emits (by luminescence) a different light which
depends on the O 2
concentrations inside the package. Measuring this
emission using a photo detector and the electronic processing of the
resulting signal make it possible to determine O 2
concentrations with a
precision of