Watching The Detectives

Stuart Pritchard July 27, 2017




Keeping confectionery free from foreign bodies can be tricky. But, says PHIL BROWN, Sales Director at Fortress Technology UK, with the right kit, it can be like taking candy from a baby…

Last year Mars recalled its products from more than 55 countries after plastic was discovered in one of its chocolate bars. The company’s swift response helped to protect the confectionery manufacturer’s reputation for quality.

Let the sugar ruin
teeth, not metal

Highlighting that foreign body hazards in confectionery are more likely to be metal fragments from processing equipment wear and tear rather than malicious tampering of products, producers have to weigh-up the risks and why the sensitivity of their metal detector plays a vital role in mitigating a metal contamination product recall.

Candy is sold in so many different formats, ranging from miniature to family sized chocolate bars, to hardboiled sweets, fondants and jellies; it means that even similar products have high variations in density. This is especially true for bags or multi-packs of confectionery. Because of this, the aperture size of the metal detector head is vitally important, as the smaller the aperture the more sensitive the metal detector is.

Very often, sweet manufacturers inspect sugar based products when in ‘rope’ format using small, high-performance metal detectors. Here, the sensitivity levels are extremely high and looking for extremely small metal fragments. There’s little point looking for a 3mm metal sphere in a fruit gum – for individual pieces of chewing gum you would be reaching pharmaceutical performance levels.


The sensitivity of a detector is dependent on many factors: aperture size, operating frequency, product speed and environment. Most limiting is, in fact, conductive (wet) products, which act like metal. On the face of it, sweet treats like chocolate bars, biscuits, sweets and

Get better gear
and end the risk

chewing gum should be easy to inspect. However, the metallised film wrapper which they are often packaged in also puts them in the ‘wet’ product effect zone. If you’re inspecting goods after wrapping, the metal detector needs to be set to factor in the worst case product effect – the wrapper.

For metallised film that is made up of aluminium dots on film, the product effect changes according to the format and quality. It’s not so much of an issue for those producing a small range of candy bars, but those manufacturing and packing an extensive range using multiple types of wrappers, the metal detectors sensitivity is usually set to the worse case wrapper scenario. To further complicate matters, you may need to consider orientation effect, especially with sealed packs, such as chewing gum, as this creates a dense line of metallised dots.

Years ago, the main limitation of metal detection was that each detector had to be set to a fixed operational range. These were picked to suit the product and for conductive products the frequency had to be set low to cope with the product effect. Developments in multi-frequency enabled a metal detector to operate at any frequency typically between 15kHz to 1000kHz (1MHz).  While these newer machines were designed to autoselect the ‘correct’ operating frequency in seconds, there were still limitations for confectioners producing a more expansive product range, especially conductive products. To solve this, Fortress engineered a simultaneous frequency option where the product and metal detection frequencies are split. This technology essentially ignores the product effect, making it ideal for conductive products that vary in size and density or are wrapped in a metallised film.


Another factor to consider is how candy is fed into packs. Manufacturers that use Vertical Form-Fill-Seal (VFFS) bags, will typically opt for inline gravity feed systems, like the Fortress Vertex, often combined with a checkweighing system. These compact systems inspect

Get to the bottom of real candy contaminant risks

free-falling products prior to packing. The inconsistent density of the falling product stream will generally rule x-ray systems out. Furthermore, the detector head geometry delivers higher sensitivity, so can detect the smallest ferrous, non-ferrous and stainless steel contaminants.

For many candy makers, it’s a case of weighing up the risks versus the likely contaminants. There’s no single rule; it all boils down to balancing the risks against protecting brand reputation. But when children are your consumers, it’s often advisable to adopt a more cautious approach and inspect during the processing and packaging phases.

As well as protecting brand reputation, confectionery manufacturers are under equal pressure to reduce – or eliminate – false rejects. These can cost manufacturers exorbitant sums of money and primarily occur when a metal detector cannot discriminate between ‘product effect’ and a metal contaminant. Take the example of sweet multi-packs. Inspecting at the end of the line when there are multiple products in the pack will increase waste considerably. As a result, Fortress advises confectionery producers to consider installing metal detectors at specific checkpoints along the manufacturing process. For example, on a pipeline machine that is processing liquid and semi-liquid product like melted chocolate, and then later down the line in the packing section.


Summing up, the latest advances in metal detection technology mean that systems are now even more sensitive to metal contaminants. It’s also very straightforward to integrate a small aperture metal detector with a checkweighing system to verify proper fill levels and streamline production. By carefully assessing the most prevalent risks, confectionary manufacturers can protect their brand and international reputation.