Handling a metal contamination food recall

The temptation to cut corners on equipment and the connection between compromising on food safety standards was recently highlighted in a report compiled by global insurance broker Lockton International. A total of 42% of surveyed food manufacturers believed that cost-cutting is to blame for the recent rise in the number of recalls. The study also points to a significant increase in food recalls by the UK Food Standards Agency (FSA), with the number doubling in the last five years, and a sharp rise in those with physical contaminants, including metal. 

So what causes a metal contaminant to slip through the HACCP safety net? Quality assurance often runs deeper than the obvious. To mitigate future contaminant risks means you are not looking for patterns but future potential holes in the security chain. From a practical perspective, food processing inspection risks should be reviewed every 12 months as part of a defined HACCP assessment.

It is advisable to run dress rehearsals for different product scenarios. Involve everyone that would be connected to a recall – from quality assurance managers to production line operators, customer service personnel to marketing. Testing the process regularly helps to clarify everyone’s role.  

Stainless steel, which is used widely within the food industry, specifically the 300 series, is non-magnetic and is also a poor electrical conductor compared to other metal types. These characteristics make stainless steel the most difficult metal type to detect. In practice, this means that in a sphere of stainless steel hidden in a dry product typically needs to be 50% larger than a ferrous sphere to generate similar signal strength. That disparity can rise from 200 to 300% when inspecting wet products with conductive characteristics.

Food products come in all shapes, sizes and density. What’s more, products don’t always travel consistently in the same direction when passing through the metal detector aperture. Since size, shape, orientation and position of metal contaminants cannot be controlled, operating a metal detector at the highest possible sensitivity is generally viewed as the best method to detect the smallest possible contaminants. 

Metal detector performance is usually measured using spheres. However, metal contamination may not be spherical, so the signal generated a contaminant can vary drastically in amplitude. It is therefore important to optimise the performance of the detector to cope with the worst-case scenario. 

It is vital to check that any metal detection system is failsafe. For example, if a fault with the reject system means that a contaminant is detected but not rejected, the line should stop automatically until the situation is resolved. 

Both the detector performance and fail-safe capability should be tested regularly with results kept on record to support traceability. Some metal detector equipment manufacturers integrate secure, automatic logging of all such information into their systems. This often modest investment up front can lead to future savings by narrowing the time window during which a problem can go undetected and reducing the number of suspect products that must be discarded or recalled in case of an incident. 

Because sensitivity is measured at the geometric center of the aperture, the ratio of the aperture to the size of the product is an essential consideration. Maximum sensitivity occurs when the belt and food item is closest to the edge of the metal detector opening, making sense that the smaller the aperture, the more capable it is of detecting the smallest possible contaminants. Users could optimise performance by using several smaller detectors positioned at critical control points throughout the process.   

Utilising upstream metal detection can also identify smaller contaminants.  HACCP guidance states that critical control points (CCPs) should be located at any step where hazards can be prevented, eliminated, or reduced to acceptable levels. Detecting any contaminant at the upstream phase means that the rejected product will be a small amount of raw material/unfinished product versus finished/packaged product.  This will also help identify possible sources of the contaminant, as the point of inspection is closer to the manufacturing process where fragments of metal may be introduced from equipment.