Meat + Poultry - October 2009 - 107

Food Safety

Photo courtesy of
Thermo Fisher Scientific

Developing
detection
strategies
'Good is not good enough' when
it comes to metal detection
BY BOB RIES
meatpoultry@sosland.com

ood safety is a topic that grabs
headlines around the world. From
bacterial to metal and foreign object
contamination in food, incidents involving accidental food contamination has caused increasing consumer
concern about the food-supply chain.

Meat and poultry are
among the most difficult
metal-detection
applications.
Progressive processors are stepping up
efforts to improve processes and procedures when it comes to prevention
and detection of foreign objects. Good
is not good enough anymore.
Protecting products such as meat
and poultry from foreign objects requires careful thought. Metal detection
technology has been around for more

than 30 years, but some real-world
challenges have withstood the test of
time and technology. Reliable and easy
to use, metal-detection technology is
the standard bearer for identifying
foreign objects in virtually thousands
of types of products. The technology
is especially easy to apply in the production of dry, lightweight products.
Meat and poultry present different
challenges. Product characteristics like
wetness, density, size, salt content and
the wide range of possible metal contaminants make working with it more
difficult. In addition, processors that
work with meat and poultry must follow specific handling and sanitation
procedures to avoid pathogen contamination and ensure total safety and
brand protection. Meat and poultry
are among the most difficult metaldetection applications.

108 * Meat&Poultry * October 2009 * www.MeatPoultry.com

The 'product effect'
All metals have properties that make
them discernible to metal detectors.
Non-ferrous, stainless-steel and ferrous metals emit X (magnetic) and R
(resistive) signals. Most metal detectors work by balancing a transmitted
radio frequency signal between two
receivers. When the signals are in balance, the product is free from metal
contaminants. Metal objects coming
through a detector emit X and R signals, which distort the receiver signals. A change in the balance of the
signals usually means metal is present,
usually, but not always. Wet, partially
frozen or salty products also emit X
and R signals. When these products
go through metal detectors, they produce a false positive. This is known
as the "product effect."
Traditional metal detectors distinguish the difference between product
and metal by "reading" the product's
X and R signals and creating a normal
range for these signals. The ratio of the
two effects is called the phase angle.
Any readings close to the phase angle are considered normal. For many
years, this has been a cost-efficient, reliable and safe way to ensure product
quality. But this "best effort" sometimes just isn't good enough.
Small metal objects - often smaller
than 2mm - can fall within a product's phase angle and be "phased
out." This can be dangerous because

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Meat + Poultry - October 2009

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