Staying on top of metal contaminants - detection solutions

Packaging Professional magazine
14 May 2013

Metal contaminants are still a huge quality issue in food production and
packaging. Sarah Ketchin, MD of Fortress Technology, discusses
detection solutions to combat the problem 

Metal is the biggest and most likely contaminant risk within a food plant. Wire and swarf from processing equipment such as sieves and conveyors can easily find their way into food or packed products.

For hygiene purposes, food factories are packed with stainless steel equipment that can degrade or become damaged, with bits breaking off blades and cutters for example. Items such as staples or paperclips can also be brought in.

No food company wants to see its name in a recall headline due to metal contamination, but it is not enough to just install a metal detection system and assume that all is well. Companies must make sure that the detector is being used as a process measurement and improvement tool. Proper procedures must be in place for controlling rejects and the examination of rejected contaminants to determine the source and decide on appropriate action.

Metal detectors need to be designed for ease of testing. This ensures the system is working correctly, identifying and rejecting potentially contaminated product. The detection level should be set to ignore any packaging or product characteristics that could affect accuracy. For example, meat and cheese are conductive. For testing conventional metal detection systems, ferrous, non-ferrous and stainless steel test packs must be used.

It is important not to overlook the advantage of installing metal detectors at specific checkpoints along the manufacturing process. Adding detection units just at the end of the production line is not effective. A manufacturer should assess the process and identify the critical points (HACCP) and place a metal detector there. If the product is of high value, a manufacturer may want to inspect earlier in the process.

Metal detectors are available in a range of application configurations. For instance, gravity detectors inspect free-falling products such as powders and grains, and pipeline detectors check pumped liquids and sauces. Metal detector manufacturers can provide advice on the right metal detector for the application. Where possible it is advised to use hot balanced coil metal detectors, as these will identify ferrous (iron or steel), non-ferrous (aluminium or brass), and stainless metals.

To obtain the maximum performance from a metal detector, it is vital that the guidelines of a proper installation are adhered to and an area survey is performed prior to delivery and install. An incorrectly set-up, installed or maintained metal detector can result in a high level of false rejects and the unnecessary disposal of good product. With most applications being end of line, at this stage all the expense has been incurred making it high-cost waste.

Regular manual testing procedures ensure that if a failure such as incorrect set-up does occur, the amount of product that needs to be rechecked is kept to a minimum. Furthermore, automated test systems can be unitised in some applications in support of manual testing. Such built-in features will alert the operator to a potential problem sooner, yet do not incur the cost of additional personnel.

There are a lot of food safety initiatives coming at processors from all sides – government agencies, supermarkets and consumer groups. Keeping up with these demands can be very challenging and it is the metal detector suppliers’ responsibility to assist the manufacturers in staying ahead of both current and future requirements. Some new models have now been designed to be backwards compatible. These incorporate Ethernet, USB and wireless connectivity for easy data collection and adhere to HACCP compliance, and more importantly the detection technology can be installed in a detector built up to 15 years ago.

Fundamentals of metal detection have not changed much over the years and the basis of the technology is the same today as it was 50 years ago, but the electronics processing and capability has moved on significantly. Software improvements have now also led to higher reliability and less down time, as well as better sensitivity without rejecting good product. These advances all help ensure quality on the production line and with so many simple and user friendly detector systems now available there is no excuse for companies to be caught out.