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Detectable product considerations

03 July 2017

A newly released whitepaper discusses considerations before the introduction of detectable products and materials into the food production environment. Food Processing reports on the highlights. 

Detectable products are being used more frequently today. A detectable product is any item that has been modified to be easily identifiable by either a metal detector or X-ray product inspection system. Detectable products and materials most commonly address contamination risks posed by plastic and rubber articles because they do not, under normal circumstances, exhibit the properties needed to trigger rejection through metal detection or X-ray inspection. 

However, despite developments in both detectable materials and inspection technology foreign bodies remain the fifth most common cause of incidents recorded by the UK Food Standards Agency. According to its 2015 annual report of incidents, foreign bodies still account for 5% of all incidents. 

Detectable products and materials can be broken down into four key types: 

• Metal detectable, 
• Part metal detectable,
• X-ray visible; and
• Dual detectable 

The type of product required will depend on the inspection system being used and the product in question. 

The first detectable products were used in food production in the late 1980's and featured iron filings embedded within, or stuck to, high-risk items, in order to trigger the end of line metal detector. Today’s approach is much more scientific, refined, regulated, and researched. The ferromagnetic additives used have an ultra-fine particle size and should carry full FDA and EU food safety approvals. 

Because detectable materials only contain a small percentage of metal content they do not trigger a metal detector as easily as a fully metallic contaminant, so testing of a detectable material with the detection device is always recommended before making any final decisions. 

Further, detectable products featuring aluminium foil for detectability will not perform well when used with a metal detector inspecting food with aluminium packaging. This affects prepared meals in foil trays and aluminium canned foods, as the signature of the packaging makes small aluminium contaminants invisible to the metal detector. 

It is not always possible or practical to make the entire composition of an item metal detectable. Examples include woven polypropylene mesh hair and beard nets which contain steel clasps to provide metal detectable properties. By being only part-metal detectable the foreign body contamination risk is significantly reduced. It is important to be conscious of the fact that if a part-metal detectable item is fragmented through a process such as cutting, blending or mixing, then non-detectable fragments will remain and this should be documented as part of risk assessment. 

X-ray visibility
It is a common mistake to assume that a metal detectable product is also X-ray visible. X-ray inspection works in a completely different way to metal detection and so products and materials will require completely different modifications to become X-ray visible. Ferromagnetic additives are used to make a plastic or rubber detectable for the purpose of metal detectability, but food safe ultra-dense additives (with a high atomic number) also need to be used to achieve good X-ray contrast performance. 

While the use of ferromagnetic additives alone will increase the specific gravity of a base polymer, they do not always do so sufficiently to achieve reliable X-ray visibility. A detectable product should only be classified as X-ray visible if it is constructed entirely from metal or a polymer that specifically contains high-density additives to enhance X-ray contrast. 

The World’s first dual detectable polymer was developed by BST Detectable Products in 2009. The plastic compound contains the appropriate levels of both ferromagnetic and high-density additives to trigger metal detection and X-ray inspection systems, while still functioning as a high-performance polymer. 

Adding metallic additives to a polymer weakens its structure, which dispels any myths about the fact that heavily loading metallic additives to the polymer mix would be a benefit because it is more likely to trigger a detector. In reality, it is more likely to cause contamination due to the reduced tensile strength of the material and its lower flexural modulus and impact resistance. 

If a detectable material doesn’t break in the first instance, it isn’t at risk of becoming a foreign body. The purpose of a detectable material is to lower risk and this needs to be considered at all levels. Reducing one risk by increasing another doesn’t lower the risk, it just changes the risk. 

System considerations
To safely and successfully implement detectable products and materials into a food production area it is also necessary to have a good understanding of the capabilities of the inspection system, and the relative performance of the detectable products and materials in use. 

It is also important to take into consideration the benefit that will be gained by changing from a non-detectable material or product to a detectable alternative.  Do discuss your needs and requirements with your detectable product manufacturer. They should be able to offer help and advice and may even have a solution already based on an enquiry from a different manufacturer. 

Review the technical information of any proposed material or product to ensure that it includes the properties that you require.  It is also a good idea to obtain a sample and test this on your inspection system to determine how small a piece will trigger a rejection. Record and store this information for future use.  If the piece is larger than expected, or larger than would be physically capable of being enclosed in the products packaging, a re-consideration of the product or material may be required. 

Once you are happy with the detectable product ensure that you create a file with any necessary technical data sheets that accompany it for review by an auditor. 

Once in use ensure that the product is included in any daily/weekly/quarterly checks as deemed necessary on site. It is also vital to educate supervisors on the basic principles of detectable products, as they are on the front line of safety for food manufacturers. The more knowledge they have of the limitations of the detectable product, the greater the chance of using the product most effectively. 

Always make sure that employees are aware that detectable products are more expensive than their non-detectable counterparts, so there is a need to take care of the product and ensure, as far as possible, that they are only used in the manufacturing environment where they add value. 

The increasing use of detectable products today means that there is now more product choice – ranging from stationary items through to engineering parts. Before introducing anything new into your production area do first double-check all the claims made by your detectable product manufacturer.

Will Anderson and Joseph Armstrong-Gore from BST Detectable Products authored the original whitepaper, which is available from the company.

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