Metal detectable hand tools – taking due diligence to a new level
August 1st 2005 Harold Moore announces the expansion of its detectable range of hand tools, which include hand scoops, scrapers, stirrers, paddles and shovels. Richard Brown* explains
The first time these products will be shown at a major exhibition will be at Anuga FoodTech in Cologne in April 2006, though samples are available now. There is an increasing awareness amongst food manufacturers across Europe and the United States, if not the world, of the need for careful planning and documentation of systems and methods that enhance food quality and safety.
Traceability and accountability are highly important throughout the supply chain. HACCP is here to stay and due diligence is very much the watchword. This is why such an announcement from a relatively small niche product manufacturer is important.
Most food production lines employ an in-line metal detection system at some point. Hand tools, either for cleaning or in the production process itself, will also be employed somewhere along most food production lines. These hand tools are often not of metal but of plastic.
Plastic is often preferred for reasons of durability, lower weight, ease of cleaning, flexibility and so on but what if a piece of it should break off in use and fall into the food being produced? Whilst an in-line detector is likely to pick up a metal contaminant, it is obviously not going to detect plastic. Therefore, how does one harness the advantages of plastic products without increasing the chance of contamination going undetected? The answer lies in a special formulation of detectable plastic. That is, a metal fill is added to the plastic during the manufacturing process, to produce a material that displays all of the properties associated with plastic plus the facility of being detected in a standard metal detector.
Then it is essential to get the metal fill to mix consistently throughout the plastic, so that any piece of the product can be detected, should it ever break off. This is not easy to achieve and has taken some years to perfect. We are not just talking about a metal strip or button somewhere on the product. It is a physical feature of the entire material from which the tool is made – a truly detectable plastic.
Furthermore, having the product certified as suitable for contact with food materials also takes some time and investment.
Food safety and colour coding Hygiene does not depend upon the tools and machinery used in a food factory. It depends upon the system that employs them. Good hygiene is underpinned by good training, organisation, application of best practice and discipline. These ensure that any hygiene tools are used to best effect and any time and money saving features are fully utilised.
For example, a green shovel offers no advantages on its own.
However colour coding is becoming more and more widespread as a means towards cutting the risks of cross contamination. Areas within a factory are zoned depending on their use and allocated a colour. For example, green for the cooked foods area and yellow for the raw and red for cleaning materials used in the toilet areas. Any tools used in these areas carry these colours so that they may be quickly identified if they stray into the wrong area. Then, a green shovel becomes part of a hygiene system and carries an advantage to the user in helping to reduce cross contamination.
Therefore, to enhance their usefulness where such systems are in place, any detectable products should also be coloured.
However, until recently, the number of colours in which detectable products could be produced was limited, since the metal fill substantially darkens the colour of the plastic. This problem has now been overcome and it is possible to provide clearly recognisable colours of blue, red, green and yellow. Therefore, there is no more need to compromise between detectability and colour coding – the two features are now avaialble as one product. However, are these products still safe in contact with food? Product certification Any plastic article that comes into contact with food must not itself provide a source of contamination. Have you ever been out on a hot day and drunk sun-warmed water from a plastic bottle? Did it taste faintly of plastic? This is caused by molecules from the plastic leaching out into the water.
Under European Union (2002/72/EC) and United States FDA (CFR 21 § 177.1520) regulations, there are fixed limits to this molecular migration. All plastic articles used in the production and storage of foodstuffs must be tested, approved and certified that they do not cause contamination outside of the set limits laid down in the regulations.
Materials that go into the production of most plastics for food use are certified to these standards – that is both the base polymer itself and the dye used to colour it. Any other additives must also be approved for food contact, which normally excludes any fibrous material or ferrous metals.
However, it should be noted that any process that applies heat and pressure to a material is likely to affect the properties of that material.
Such is the case with moulded plastics, where the raw polymer and dye are mixed and subjected to high pressure and temperature, which changes its form into the finished product. This means that the input of food approved materials into the start of the process does not guarantee that the resultant product is also food approved. There is a good likelihood but no guarantee.
Therefore, any good manufacturer will test the finished article also and be able to provide appropriate certification that the completed product also meets the accepted migration levels. Such is the case too with detectable plastic products: an injection moulded plastic with a metal fill has been through a lot of processing and the manufacturer ought to be able to provide proof that their products do meet the regulations. This should be for peace of mind if nothing else, leaving nothing to chance.
Detection – how does it work? This article is not intended to discuss the whole body of physics around metal detection or the working of metal detectors. Nevertheless, the basic outline is as follows.
A metal detector produces an electromagnetic field of a fixed orientation, power and frequency. If a metal article passes through this field at the right speed and orientation and there is no other interference, the field is effectively broken and this break can be detected and measured. The result can be used to trigger an alarm to indicate the presence of metal within another material.
What even this brief paragraph should reveal is that detection relies upon many factors, including the phase, power and frequency of the field generated by the machine, its sensitivity and the orientation, speed and make-up of the product passing through it. This means that it is again down to a system of risk assessment, calibration and inspection to ensure that the most is made from such equipment.
How much is detectable? As outlined above, a metal detector can be set up in many different ways, depending upon the requirements of the manufacturer and the attributes of both machinery and product to be 47 Food Hygiene examined. This means that the answer to the question, “How much is detectable?” is: “It depends.” However, the key lies in the calibration of the detector. This is normally done by passing a ferrous ball bearing of known diameter through the detector. The alarm is then set to ring as soon as an object larger than this is detected. For example, a company may select, in its HACCP system, a setting that will detect a 0.8mm diameter ball bearing and the system is said to be “set at 0.8mm ferrous.” The same can now be done with detectable plastic. Harold Moore have produced a set of spheres and cubes of different sizes that will facilitate a comparative calibration. To show how this might work, the following tables show the results of tests on the detectability of their formula compared to standard ferrous ball bearings. These results imply the following, for example. If a factory runs an inline metal detector for a dry food product, such as biscuits, set at 300kHz at 0o and sensitive enough that a 0.8mm diameter ferrous ball bearing will trigger an alarm, then a 4mm cube (or 0.06g) of Harold Moore’s metal detectable plastic may be needed to set off the alarm.
Another factory running a similar detection system set for a wet product, such as a microwave meal, set at 25kHz at 90o and sensitive enough that a 0.8mm ferrous ball bearing will trigger an alarm, should detect a 2mm cube (or 0.01g) of material.
Another tool in the box As part of an integrated hygiene and quality system, detectable products have much to offer. Well made, high grade plastic products do not wear down or break easily in normal use and provide advantages in weight and durability, making them less fatiguing to use and kinder to the surfaces of more expensive machinery.
Coupled with the possibility of integration into a colour coding system and with the added assurance of detection in the production line sensors should the product ever fail, detectable plastic offers full weight to the assertion of using all due diligence in production of foods of all types. This is one of those rare occasions where a little planning and a minimum of investment go a very long way indeed and detectable products provide another valuable tool for the food manufacturer.
Not only is there a range of existing tools made from detectable plastic but the material is also available for manufacturers to specifiy or produce their own items, such as containers used to transport food along the production line or other machine parts.
* Richard Brown, BBA(Hons) is Sales Manager for Harold Moore More articles from Harold Moore Ltd.: | 
