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Detectable plastics: busting some myths

12 December 2016

Will Anderson highlights some of the most common, incorrect assumptions about the use of detectable products. 

Despite the increased availability and usage of detectable products and materials, physical contamination –particularly from rubbers and polymers – continues to cause expensive recalls. BST Detectable Products has published the details of 16 such events, which resulted in high profile product recalls, in 2016 so far.

Some of the leading, incorrect, assumptions about detectable products include: 
• They are detectable so will work on my pre-calibrated metal detector: This is a dangerous assumption. A metal detectors capability will depend on the model, size of the aperture and the type of product it is inspecting. For example, a large metal detector aperture inspecting cases of frozen meat (with an increased product effect) is not likely to achieve a consistent sensitivity of <3.0mm FE, whereas some small piece of metal detectable plastic will need a sensitivity of around 1.0mm FE for reliable detection.

Take, for example is detectable brush bristles. These require a smaller, more sensitive aperture to achieve reliable detection. This makes detectable brush bristles more suited to nutraceutical manufacturers who although manufacturing tablet forms are bound by the same risk management and safety framework as food manufacturers. 

Aluminium product packaging can also mask the contamination caused by certain detectable products, making them completely invisible to the metal detector. Producers using aluminium packaging should, therefore, take extra care when selecting appropriate detectable products.

• The more detectable the better: Again, this is potentially a dangerous assumption. A highly detectable material is not necessarily the safest. Making a material more detectable can compromise its mechanical strength and impact resistance. BST has been manufacturing detectable plastics for many decades and it believes that, a highly detectable, but brittle material is more likely to cause contamination than a slightly less detectable material that is incredibly difficult to snap or shatter. 
The level of detectability of a product is dependant on the base material. For example with softer materials like silicone the addition of detectable elements weaken the structure of the material, decreasing its tear resistance and increasing the chances of the part failing and becoming a foreign body risk. If a detectable plastic is pulverised you are not likely to find all the fragments, especially the small ones! This is why tear and impact resistance are just as important as detectability.

• If my items are detectable it doesn’t matter if I lose them:  Absolutely not! Detectable plastics are a final line of defence in preventing plastic foreign body contamination. They should be treated and cared for like any other high-risk item, following best practice for preventative checks, maintenance and replacement.

• Detectable products are also X-ray visible: Not always and this is a very important point. Metal detectors work by looking for unexpected magnetic field disturbances, X-ray inspection systems work by looking for unexpected variations of density. These are two very different technologies that require detectable plastics to contain two very different additives. BST XDETECT is a dual detectable material so can be detected by both methods. However, food processors should never make assumptions about the capabilities of detectable products and if unsure should check with their manufacturer. 

Best practices 
• Always test your detectable products on your inspection system: It is important to ascertain that the sensitivity of your inspection equipment it sufficient, that it is compatible with the chosen detectable product and that the detectable product is compatible with your foods product effect on the inspection system. Test the whole detectable product, then break it down into pieces or request a material test piece from your manufacturer. This is essential to understand the capabilities and limitations of the whole system and should form part of your risk analysis.

• Inspect detectable products and detectable machine parts on a regular basis: This is particularly true for items such as detectable scoops and scrapers – are there any signs of wear or cracks and should they be replaced? Detectable plastic machine parts should also be inspected – don’t forget the reason they are detectable in the first place is because they are high risk!

• Don’t wait for an incident or an audit non-conformance: If you are aware of a machine part or production area item that poses a foreign body risk, ask your detectable product manufacturer what they can do. Today there are more detectable materials available than ever before, so it has never been easier to have a safer alternative. 

Will Anderson is head of product development at BST Detectable Products.

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