Metal Contamination: Can you really detect metal in your products?

There seems to be several food recalls every week due to metal contamination in finished product. If a metal detector was in place and operational, how is it that product has been recalled for metal contamination?


Metal contamination is one of the most common foreign matters identified during the hazard analysis process. Control measures can vary depending on the nature of the food business with maintenance activities and routine pre-operational inspections common. However, the most popular control measure seems to be the use of a metal detector. 

The metal detection step also seems to be a very common critical control point (CCP).  This all sounds good on paper, but what is the real value of a metal detector in protecting your food business against food recall or customer action?

Process Verification

Verifying the capability of the metal detection unit is required on regular basis.  When auditing, I find that food companies who use metal detectors, test anywhere from once a day to hourly during the production shift.  Generally, I request a test of the unit as part of the audit process which often reveals operators testing the unit by placing the test pieces on top of the product or just passing the test piece on the conveyor.

Since metal doesn’t always position itself on top of the product, here are my Top 5 tips to challenge the metal detectors ability to actually detect metal contamination.

Tips for verifying the metal detector

• Place the metal detector test piece inside the product that is being scanned through the metal detector.  This will provide a better indication of the ability for the metal detector to actually detect any metal contamination.

• Put the test pieces at different angles within the product including at the top, bottom and skewed from side to side.  Pieces of metal don’t discriminate.

• Try contaminating the product with different metal fragments types including ferrous, non-ferrous and stainless steel.  This will indicate if the machine is in fact doing its job.

• Refer back to the metal detectors machine specifications to review the size and metal type limitations.  This is an excellent validation point to support why you have chosen particular detection sizes.  Don’t forget to also acknowledge the metal detectors limitations around heat and density issues.  Document these limitations as part of your machinery validation (a requirement of BRC).

• Regularly maintain and service the metal detector to ensure capability.

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