The
‘crust’ of the matter
As
packaging comes in direct contact with food, the quality testing of
packaging material and equipment becomes extremely essential, says Rohit
Chawla
The
trend of quality testing, especially within the ambit of packaging material
and equipment, had not really taken off in first half of the 1990s.
But the viewpoint started changing as the research and development centres
of certain large multinationals initiated a lot of work on packaging
and its effective usage. The Indian Institute of Packaging also made
tremendous efforts in disseminating quality consciousness about packaging
and its importance. But the biggest boost in the demand for quality
was seen only after the introduction of certain quality norms such as
the ISO 9000 series. Quality became a priority to those who did not
care about it just a few years ago, and today, high quality packaging
has become an integral part of the food industry.
Essentials
of packaging
Packaging
can be broken up in two basic categories, primary packaging and secondary
packaging.
Primary
packaging comes in immediate contact with the product and it includes
pouches, sachets, bottles, jars and duplex board cartons. Secondary
packaging is the packaging which houses the primary packages and mainly
comprises corrugated cartons.
The
quality parameters or specifications for packaging can be divided into
two types – material specifications and performance specifications.
While material specifications are those parameters which define the
quality of the material used, performance specifications define and
govern the quality of the actual performance of the package or packaging
material.
Primary
packaging
Pouches
or sachets
Pouches
or sachets can be broadly defined as non-porous semi-rigid or flexible
bags formed from one or two sheets of flexible plastic material and
sealed on a machine after filling. The sealing is done on a form-fill-seal
machine which is generally known as the
FFS
Machine. The plastic material can be either a single layer plastic film
or a multilayer plastic laminate. Plastic laminates are nothing but
multiple sheets of plastic film bonded together in the same plane using
some adhesive, heat or pressure or a combination of
these.
Plastic
film
They
have the following quality specifications:
GSM
or substance: It is the weight of 1 square meter sample of the plastic
film and is expressed in Grams Per Square Metre (GSM). This test is
done on a GSM Indicator.
 |
| Caliper
thickness gauge |
Thickness:
It is the thickness of a sample and is generally expressed in microns.
This parameter is measured on a Dead Weight Type Caliper Thickness Gauge.
WVTR:
Water Vapour Transmission Rate (WVTR) is the measure of the ability
of the plastic film to transfer water vapour or moisture from one side
to the other side. High WVTR can lead to a loss of moisture from the
product or gain of excess moisture from the environment. This can create
an imbalance in the constituents and can lead to the deterioration in
shelf life and quality of the product. The equipment required for this
purpose is called a WVTR apparatus.
 |
| Bursting
strength tester |
OTR:
Oxygen Transmission Rate (OTR) is the measure of the ability of
plastic film to transfer oxygen or gases from one side to the other
side. High OTR can lead to a loss of flavour from the product or gain
of bad odour from the environment. This can create an imbalance in the
constituents and can lead to the deterioration in shelf life and quality
of the product. The equipment required for this purpose is called an
OTR apparatus.
Tensile
and elongation: Tensile strength is the load that a film can sustain
before breaking when subjected to a pull, force or stress. Elongation
is the extension of the film in its longitudinal direction before breaking.
This has a multitude of implications on the final package including
runnability issues on automatic lines. This test can be done on a Tensile
Strength Tester.
Dart
impact: Dart impact is the resistance of a film to rupture when
subjected to a sudden load or impact. Poor impact resistance can lead
to tearing or leakage of pouches when subjected to a little pressure.
This test can be performed on a Dart Impact Tester. Coefficient of friction:
This is a measure of the frictional component of the plastic film and
can be correlated with the behaviour of the film on automatic lines.
A very high or very low coefficient of friction can lead to mis-alignments
in print area and cut area on the formed pouches. Friction testers are
of two types, Slip Friction Tester for static friction and Dynamic Friction
Tester for dynamic or kinetic friction.
Plastic
laminates
Multilayer
plastic laminates have all the above material specification of plastic
films and some extra specifics such as:
Inter-laminate
bond strength or Peel strength: It is a measure of the strength of the
bond between two layers of the laminate. Poor inter-laminate bond strength
can lead to de-laminated sachets, which not only loose their face value,
but also cannot protect the inner product to the desired extent. The
intention of this test is not only to test the bond strength, but also
the uniformity of the lamination. This test is also called the T-Peel
test and can be conducted by a Tensile Strength Tester or a Peel Strength
Tester (a scaled down version of a Tensile Tester).
Seal
strength: It is the strength required to break apart a seal joint formed
on an FFS machine. A good seal is the result of proper material temperature
and pressure settings on the FFS machine. These functions can easily
be set by a skilled operator to give optimum performance. Poor seal
strength of the seal joints can lead to opening up and leakage of pouches
at the time of shipping or even if a slight pressure is exerted on the
samples. The Tensile Strength Tester or a Peel Strength Tester is used
for this test too.
.....CONTD
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