'Everyone can play their part'


02 October 2023
Keeping contaminants out of potatoes isn't just a processor's job says designer of new detector system.

FORTRESS Technology has designed an industrial-sized Bulk Potato Slider Detector System to keep potatoes free of metal contaminants, stressing that everyone in the supply chain can play their part in keeping tubers contaminant-free.

When creating the robust design, Fortress was mindful that potatoes have a number of product attributes that can affect the accuracy of metal detectors. These factors can impact a metal detector’s ability to distinguish between potatoes and metal contaminants, leading to false signals and consequently wasted produce.

Drink cans casually discarded in crop fields, machinery nuts and bolts, or wire fencing blown down in a storm, can all be turned into the smallest metal fragments by powerful harvesters which can then become embedded within a potato. Detecting any fragments will depend entirely on the direction that a bouncing potato is passing through the metal detector. In one orientation, the signal for the needle may be huge. But if turned 90 degrees, a needle-like piece of metal may pass through the metal detector’s electromagnetic field undetected with little to no disturbance.

To combat this, Fortress has engineered a metal detector with a rolling-system rather than traditional belt. It provides a stronger signal than stagnant objects. 

Fortress European managing director Phil Brown said: “The potatoes roll through the metal detector to limit the chance that a needle misses detection due to orientation effect." He said the technique worked remarkably well in all test cases, with the customised metal detection unit reporting minimal false positives and superior accuracy and metal detection sensitivity.

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To ensure the potatoes were run at the highest performance level, Fortress engineered a special VLF (very low frequency) coil. This allows all potatoes to appear as dry products on the machine, essentially ignoring the product effect caused by soil, grit and moisture.

Another essential feature designed for harsh, rigorous production environments is the BSH rugged casing. This helps to provide better stability and metal detector performance for when rolling potatoes collide with the sides of the system as they are funnelled down the conveyor.  

Phil said the task of contamination control is no longer reserved for food processors. It stretches right up the supply chain. With the focus shifting from analysing hazards to preventing them, contaminant detection from farm right through to fork is essential to securing new business deals and guaranteeing the delivery of consumer-safe products. 

Safety in the fast-evolving food sector places heavy emphasis on shared responsibility, said Phil. "Upstream inspection after harvesting and before processing is now widely regarded as best practice. Although product tampering is extremely rare, in the last decade Fortress has observed a large uplift in enquiries from root vegetable and potato farmers and bulk processors for robust gravity and conveyor metal detection systems. These can help to prevent future adulteration and contamination events from causing potentially catastrophic damage to brand reputations.” 

Enhanced detection
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