Food & Beverage Asia February/March 2022

PROCESSING AND PACKAGING 51
Metal detection, x-ray – Or both?
Both metal detection and x-ray inspection systems play key roles in
product inspection for food and pharmaceutical companies. Choosing
the right technology requires consideration of many factors – starting
with the application.
By Ian Robertshaw, global key account manager at Mettler-Toledo
A layman might consider it an easy
choice: if you are looking for the best
inspection technology designed to detect
metal contaminants, then opt for a metal
detection system. On the other hand, if
you are looking for a system to detect both
metal and non-metal contaminants, then
choose the x-ray inspection system.
There is a kernel of accuracy in this
supposition, because very often, such as
with aluminium and wire, a metal detection
system will be better at detecting metal
than an x-ray system. However, the
decision is not necessarily so simple. For
example, what if you do need to identify
metal contaminants, but the product is
packaged in aluminium foil? The foil will be
seen as a detectable contaminant by the
metal detection system, thus rendering
the system unusable. An x-ray system,
meanwhile, sees straight through the foil to
get a better view of a contaminant inside.
The choice of technology is not simply
about the potential type of contaminant
that you are looking for; part of the
consideration is where in the production
process should the product be inspected.
For example, if your raw product needs
to be inspected before other valuable
ingredients are added then maybe a metal
detection system is best. However, for
end-of-line inspection when packaging
integrity checks are required, as well
as contaminant detection, then x-ray
technology will be more suitable.
What is certain is that product inspection
is a critical part of the food production
process, ensuring that consumers are
confident in the quality and safety of the
products they buy. Food manufacturers
should therefore consider carefully
when choosing whether to equip their
production lines with metal detection or
x-ray technology, or perhaps with both.
There are fundamental differences in
the ways that metal detection and x-ray
inspection technologies work. It is important
for food manufacturers to understand what
these differences are and how they can
impact the ability to perform optimally on
certain product inspection applications.
Application is key here: the nature of the
product, the fill process (ie., vertical form
fill seal – VFFS), the potential contaminant
types, and factors such as the physical
packaging, must all be brought into
the equation when selecting the right
contaminant detection technology. In
addition, constraints on finance and physical
space, and the range of additional quality
control checks should be considered.
METAL DETECTION
Modern metal detection systems can
identify all metals, including ferrous (such
as chrome and steel) and non-ferrous
(brass and aluminium, for example), as
well as both magnetic and non-magnetic
stainless steels. They work through a system
of coils, charged with an electrical current,
to create a balanced electro-magnetic
field. If a product passing through this
field contains a metal contaminant, the
magnetic field is disturbed; this disturbance
is interpreted by sophisticated electronic
circuitry and software algorithms.
A well-designed metal detector for use in
the food industry can detect a pinhead
in a loaf of bread, while a detector for
FOOD & BEVERAGE ASIA FEBRUARY / MARCH 2022