Metal Detection Systems: Still A Safe Bet For Food Manufacturers

By Karen Mills, former director of quality assurance, High Liner Foods Inc.

Robust product inspection systems are most successful when they are designed with many support methods and principles. For years, Metal Detection  Systems have provided safeguards against physical contamination. These systems grow more sophisticated each year, and, consequently, their ability to detect smaller metal contaminants becomes more refined.

As with X-Ray inspection systems, metal detectors used in food production facilities are primarily for consumers' protection. With all the care the industry takes at all stages of making food products, there isn't a 100 percent guarantee some impurities won't make it into some finished goods. With that said, metal detection as part of an overall inspection program can contribute to a significantly-reduced level of metal impurities being found in the finished goods. This, in turn, lends itself to a company's brand protection, reduced or eliminated risk of withdrawals or recalls, and more sustained consumer/ customer confidence in your company.

Metal detectors have been around, conceptually, since the 19^th century. One of the first to be brought out as an industrial detector was in 1948 in the UK. The basic style or design used mainly in the food industry operates with what is called a coil transmitter- receiver method.

When a metal particle passes through this style of machine, it interferes or breaks the electromagnetic field. This triggers a response such as an alarm, retractor belt, air or ejector arm etc. to alert the operator an irregularity or contamination is present.

In the food manufacturing and processing industry, there are generally four reasons to implement metal detection systems, some or all may apply to your business:

• Product safety
• Equipment protection
• Contract (customer) requirement
• Regulatory compliance

Metal detection, for most of the food industry, is a CCP (Critical Control Point) and is part of HACCP programs, product hazard flow charts and food safety SOPs. It will always be considered and checked during any third-party food safety audit both for how it is written into a company's program, as well as how it is monitored, verified, and validated by plant employees and QC/QA personnel within the written program(s).

They can be set up to detect for fully-packed food products or for material(s) that are exposed on the belt, prior to being packaged. Metal detection systems can detect, to a certain degree of accuracy and sensitivity, ferrous and non-ferrous metals, such as stainless and aluminum. They are also very flexible for their uses as they can be placed at pretty much any stage of a company's production process. They are used in many different food applications, such as grain bagging, dry ingredient bagging, sugar, seafood, bread and bakery, poultry processing, dairy, spices, and fruit and vegetables, just to name a few. Some detector designs have built-in magnets to "pull" magnetic metals out of the material(s) as they are free flowing through the detector. Some are designed to be able to detect foil wrapped food types.

Food companies should choose a detector style and size that best suits the specific product(s) produced at their facilities. The opening (or aperture) size of the metal detector needs to be matched to the product type(s) in order to provide optimum performance and detection sensitivity.

Industry will want to maximize the sensitivity of their detection systems. There should be guards against potential instability, where the effects of product/environment could cause false rejects. In seafood, for example, salt or extra moisture even in frozen product(s) can contribute to trigger a metal detection alarm even though there is no metal present.

Here are some guidelines for sensitivity and settings:

3 Types Of Metal Contaminants

• Ferrous - is both magnetic and conductive so easily detected

• Non-Ferrous - is non-magnetic but a good or excellent conductor so relatively easily detected

• Stainless Steel - is the most difficult contaminant to detect as it is usually non-magnetic and a poor conductor.

Detection of these depends on the magnetic or conductive properties of the contaminant.

Stainless steel comes in various grades, some of which are magnetic while others are completely non-magnetic. The conductivity of stainless steel also varies, but is generally low. Both of these factors contribute to poor detectability. The two most-common grades of stainless used in the food industry for equipment, belts, etc. are 304 and 316 grades.

Metal detection can be very successful in precluding metal impurities from various sources from getting into finished goods. It must also be emphasized though raw material screening via processor/suppliers, incoming material inspection program(s), and inspections at the CCP points during a facility's production process. All of these contribute to finished goods that are reduced or free from foreign (metal) contaminants. For optimal results, metal detection is recommended at various stages of production, as well as immediately after packaging to provide the most assured result of metal contaminant-free food.

Metal detection is only one part of a truly comprehensive contamination inspection program. The technology is a critical point in that system when chosen correctly, installed, programmed, operated and maintained. They even contribute to improved product quality, integrity, and reduced losses.

It is, however, important to note that installing metal detection technology is not a guarantee or insurance against all potential metal-contamination incidents. It is an important tool in diagnosing potential metal contamination and plans and programs need to be in place at all stages of a product life cycle to best ensure metal is NOT in the material(s) prior to further processing or when it is ready for direct sale. The identification of possible metal should be used to identify source(s) and from there, improve programs for removal in the very beginning stages of material development.

About The Author
Karen Mills is Director of Quality Assurance for High Liner Foods Inc. (Canada) and operates out of High Liner's processing facility in Lunenburg, Nova Scotia. She leads teams that are responsible for internal food safety and compliance, as well as supplier/ vendor import and regulatory compliance. She and her team members work corporately with other High Liner facilities based in the U.S. Karen received her B.Sc. in Animal Science from the Nova Scotia Agricultural College in Truro, Nova Scotia.