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September 17, 2023


Snack, bakery, and food-to-go manufacturers are feeling the squeeze from every direction. Stricter processing regulations, faster production loads, escalating operating and ingredient costs, combined with the rise of factory real estate prices, has left many seeking higher throughput, smaller footprint machines. Jodie Curry, Commercial Manager at Fortress Technology Europe, sheds some light on the pros and pitfalls of implementing multi-solution strategies onto metal detection, x-ray and checkweighing lines.  


HACCP states that critical control points (CCPs) are the areas on your production line where hazards can be prevented, eliminated, or reduced to acceptable levels. The first step is identifying your main contamination hazards. For most manufacturers, this will be metal, predominantly stainless steel. Metal is commonly used throughout a production line and in processing and packing environments. Tiny pieces may shred off cutting blades or grinders, faulty packaging machinery might discharge small shards into products, or metal fragments can even be unintentionally introduced further upstream during harvesting.

When assessing the risks, cost of the product at each checkpoint needs to be factored in. Jodie explains: “Ideally you want to catch the metal contaminant in its larger form before it has been processed and packaged, where it could potentially break into many smaller fragments. This results in higher quantities of finished product going to waste, and an increased risk of very small, undetectable contaminants reaching the consumer. The most advisable CCPs in the majority of food production environments are before processing, checking incoming raw materials, with an additional inspection system as close as possible to the end of the production line, after primary packaging.”  


Following a risk analysis, if metal is determined the highest contamination risk, installation of a metal detection system is regarded as crucial. So, which one is best? Start by determining the optimum detection frequency for the product application being inspected.

There are generally three metal detection frequency options – fixed frequency, multi-frequency and simultaneous multi-frequency.

With a single fixed frequency device, the operating frequency is picked to suit the individual product. These fixed frequency devices are ideal when inspecting the same product day in and day out, for example, sliced white bread or a chocolate bar. However, with challenging conductive products like meat or cheese, or a larger product, the frequency must be set low to overcome the product effect. This makes the system less sensitive to the detection of some metals, especially stainless steel.

Conversely, multi-frequency metal detectors perform well on a range of products passing down the production line, as the machine will dial into a pre-defined menu of frequencies. However, not all multi-frequency systems are designed equally.  Some utilise untuned coils where higher power switching devices are used.  This can cause an increase in noise and background signal which can limit sensitivity in high-performance dry product applications. Machine operators on the production line may have to select the frequency from a menu, raising concerns about the basis of their decision-making. Automatic product learning can reduce the possibility of human error.

Simultaneous multi-frequency delivers a far higher and more sensitive performance on challenging wet product applications that vary in size and conductivity. For example, meat cuts, fish, cheese wedges or prepared chilled and frozen meals. Compared to the traditional approach of tuning into specific frequencies, simultaneous multi-frequency technology applied to the Fortress Interceptor range combines the signal from each channel to overcome product effect and improve metal detection performance.


For snack and food-to-go producers especially, high speed packing, weight and fill systems are essential to generating more products to meet consumer demands. Although throughput determines the cost of production, it’s not purely about speed. Packing and processing lines must also accommodate multiple products in a growing assortment of sizes, packaging, private label and branded products. “This is where flexibility really excels,” notes Jodie.

Multi-lane metal detectors, checkweighers and combination systems can cater to these fast product changeovers and support expansion without having to increase physical footprints or employ more people to oversee production. Available in configurations of up to five lanes, the Fortress multi-aperture metal detector or combination metal detector and checkweigher, can provide a smarter and smaller option.

Given that rental for commercial prime real estate in the UK increased by another 4.3% in 2022[i], every centimetre of floor and vertical space carries economic worth. Jodie expands: “The under-utilisation of vertical and horizontal space can often be attributed to piecemeal rather than considered machinery investments. Even small changes, such as switching out bulky equipment for a combination or multi-lane machine can add rapid value.”

Singling out and rejecting products from just one conveyor also significantly reduces the volume of good product being wasted. Plus, if one lane requires unplanned downtime or maintenance, the remaining can continue to run. Different products can also be run side-by-side, increasing flexibility for production plants that have multiple SKUs, different product flavours and size variants to inspect.


Food processors are surrounded by immense volumes of data. Keeping track of every contaminant reject, report, parameter change and data-logged event can be especially challenging for production managers.

The processes for extracting and managing data are becoming more streamlined.  With integration of equipment commonplace in production environments, for example with baggers, gravity hoppers and checkweighers, it is now feasible to have a single screen setup. By connecting machinery together, it becomes much easier to gather and consolidate data into a comprehensive performance overview that can help to speed up changeovers.

Integrating a metal detector, x-ray or checkweigher with existing weighers, baggers and factory management systems, is typically straightforward. However, it does depend on the complexity of the interface technology.


Where there might appear to be a need for multiple machines to cope with the increase in upstream output, Fortress recommends closely examining the options. Ask numerous questions. For example, could a multi-lane system offer a better return on investment in a smaller footprint? Is it possible to channel multiple product lanes through a larger aperture? What sort of reject system is required?

Examine how modular the inspection systems are. Do they provide integration flexibility? Can you extract data and merge this information into a common reporting template? Can you upgrade to newer software?

Jodie concludes: “Managed well, multi-everything technology can elevate your business and deliver a cost-efficient inspection solution, without compromising on any performance criteria, space and inspection sensitivity.”

[i] CBRE Prime Rent & Yield Monitor