PACKAGING THE CHEMISTRY OF CONTAMINANT DETECTION Farming practices, regional soil


structures and natural crop cycles, although rare, can influence the nutrient content of fresh produce Credit: iStockPhoto ArtistGNDphotography


change. Factory temperatures rise and dip. For example, bread dough can warm causing moisture to gradually evaporate. Alternatively, frozen food can thaw. A change of just 5°C is enough to affect the product characteristics and disrupt product signals. Both Fortress and Sparc have a couple of


technologies in their armoury to counteract changing food characteristics as they pass through the processing chain. AutoPhase is a useful tool available on


Phil Brown, European managing director of Fortress Technology and Sparc Systems explains how food characteristics can affect the accuracy of inspection equipment


Density, water concentration, storage temperatures, heat, thawing and even seasonal and soil variations, are among the many factors that could affect the performance of food inspection machines. Digital technologies have quickly


R


transformed how we all run processes. Machine learning especially is pushing the innovation boundaries in food manufacturing and streamlining production processes. It is a science which requires a deep understanding of the chemical makeup and molecular structures of foods. How fats, proteins, carbohydrates and


sugars change during processing and storage will initiate a chemical reaction, barely noticeable to the naked eye. Yet, for wet and conductive foods, such as bread, meats, dairy products and ready meals, to a sensitive metal detector inspecting the same foods over an eight hour shift, they can appear like completely different products. Thermal changes and water content are


the main factors that can interfere with metal detector signals. Dealing with higher amplitudes of product signal can be


elearning product characteristics when inspecting food applications is a common challenge for manufacturers.


especially pronounced in meat processing plants inspecting varying weights and sizes of joints, some boneless and others boned. ‘Plumping’, a common practice to maintain tenderised meat products by injecting salt water or stock - disrupts and mimics the metal detector signal, and can cause traditional systems to make false rejects. Known as ‘product effect’, these false rejects can result in perfectly good food being discarded. To identify a metal contaminant within


conductive products, a metal detector must remove or reduce this ‘product effect’. The solution is to change the frequency of operation to minimise the effect of the product. But there’s a trade-off. Doing this can impact the ability to find different metals. Dropping the frequency tends to enhance ferrous metal detection. Yet this limits performance when it comes to non-ferrous metals, since the lower end of the frequency is more responsive to magnetic effects of the contamination. By the same token, the reverse happens when the frequency is taken higher – it starts to limit the ferrous detection capability but enhances the non-ferrous detection. Simultaneous frequency is the most reliable


A change of just


5°C is enough to disrupt product


signals, but can be overcome by metal detectors running


multiple frequencies simultaneously


way to remove product effect without compromising the sensitivity of a metal detector. Fortress uses ARM microprocessors to adapt to these changing product characteristics. This processing technology powers the Fortress Interceptor, enabling it to run real-time analysis of the low-frequency and a high- frequency signals in parallel. By the same virtue, as


products travel through processing facilities, environmental conditions


12 JUNE 2021 | PROCESS & CONTROL


Fortress Phantom, Stealth and Interceptor metal detectors that tracks long term changes within wet products, adapting and syncing to new characteristics. For example, batch conditions in baked bread can vary very slightly between recipes. AutoPhase accommodates this gradual change without compromising metal detector sensitivity. “Even products that look different to the metal detector won’t be rejected,” said Phil Brown. Brown cites packaging as another common


example where AutoPhase can help. Whereas inert plastic presents minimal signal, metallised films and the application of print can vary between rolls. Although once deemed a major challenge for metal detectors, today’s advanced simultaneous frequency systems are much more reliable inspecting pre-wrapped products. For food packaged in cans, tins or foil, x-ray


inspection systems can play a critical complementary role. “Often, a system like Sparc’s Apollo bridges the gap in inspection capabilities and ensures the most robust screening process for contaminants. If a product has been mispackaged, an x-ray can pick this up, ensuring absolute quality of the end product,” said Brown. The presence of xenobiotic compounds is


routinely monitored and tightly controlled by regulatory bodies. However, farming practices, regional soil structures and natural crop cycles, although rare, can also influence the nutrient content of fresh produce. Changeable protein levels in flour are an example of seasonal variations, and must be considered. Brown recalls an example of butter samples:


“Butter is usually categorised as a wet product. However, when we ran these butter samples through a Fortress metal detector it automatically calibrated to a dry product. No one understood why. Further investigations tracked the cause down to the cattle feed and geographical environmental factors. The milk produced was influencing the butter characteristics, causing it to present to the metal detector as a dry product.” The Fortress Interceptor can run multiple


frequencies simultaneously, so can accurately inspect a variety of conductivities at the same time. Features like single pass product learning and automatic calibration are also helpful.


Fortess Technology www.fortresstechnology.co.uk


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