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Picking a solution to suit your contaminant

03 April 2017

Suzanne Gill finds out more about the benefits and barriers to the use of both metal detection and X-ray to meet your product contamination detection needs. 

Statistics gathered by DEFRA for the annual Food Statistics Pocketbook, show that SMEs in the UK food sector account for 96% of businesses, 30% of employment and 24% of turnover. There are also an estimated 40,000 artisan food and drink manufacturers in the UK.  

In many applications it is during the preparation and packing phase where a possible contaminant can occur. In the raw ingredient phase, for example, food can be exposed to different processes from slicing, filleting, grinding or mixing ingredients. Later down the line cutting may be required which again could be a source of possible metal contaminant into the food supply chain.

The cycle can involve preliminary washing, often in a metal drum, abrasive peeling to remove fibrous skin, coring, trimming and cutting. Some products are then passed through a vibrating screen to sort produce by size. Before packing can commence, these is often another wash cycle. All of these processes can increase the risk of tiny fragments of metal entering the production chain.

For many food processing operations, particularly SMEs, the cost of equipment will be a big consideration. X-ray – a food inspection alternative – is generally far more expensive than even the newest metal detector and the running costs are higher too. According to Phil Brown, european sales director at Fortress Technology, an SME could, typically expect to pay in the region of £4,000 to £18,000 for a metal detector, depending on the size and complexity of the application. “When compared to around £35,000 to £40,000 to install X-ray, this is quite a price difference,” he said. 

According to Brown metal detectors also tend to perform better on products that have wet or conductive properties because they are more sensitive to product effect. “Many FOTG products are especially prone to this product effect. It comes down to basic physics. Water, like metal, is a conductive. Most fresh produce also comes in varying densities. For example, a sliced carrot compared to grated carrots, or whole mushrooms compared to sliced, will react in different ways in a metal detector’s magnetic field.”

Fortress launched the new Interceptor range to meet the needs of SMEs producing FOTG. It is able to detects the range of ferrous and non-ferrous metals, including aluminium, at a fraction of the cost of X-ray but offers the same performance levels.  “The machine also factors in product density, which continues to pose a particular challenge for X-ray,” said Brown.

What about glass?
Metals are not always the only potential contaminant in the production line, and Paul King, head of sales for Mettler-Toledo Safeline X-ray, says that glass presents a particular challenge for product contamination detection systems. 

Glass can offer numerous benefits. It is a 100% recyclable product, meaning it can be infinitely recycled without any loss of properties, and rates of recycling are very high. In Europe, for example, The European Container Glass Federation (FEVE) reported a recycling rate of 73% towards the end of 2015.

From a brand perspective, glass gives a premium feel to a product, and gives consumers a clear view of the product within – adding to shelf appeal. It is also non-porous and impermeable, so there is no interaction between glass packaging and the product within that will affect the flavour of food and beverages. 

From a safety and quality perspective, regulations are necessary strict in the food sector, and legislation such as The Food Safety Modernization Act (FSMA), Hazard Analysis and Critical Control Points (HACCP) and the Global Food Safety Initiative (GFSI) have been implemented to safeguard manufacturers and consumers alike. A single shard of glass in a product could have a devastating effect – both on the consumer and the brand reputation of the supplier. “If there is a possibility of glass contamination in the production process X-ray inspection systems are therefore vital,” said King.

Glass contamination can occur accidentally in many ways. There could be breakages during the cleaning process, breakages on the line because of conveyor vibrations or back pressure, or breakages during the filling process due to misaligned filling heads striking the top of containers. Over tightened containers can also cause breakages.

“Glass is the most challenging packaging format to inspect, primarily because the main contaminant associated with it is glass itself – which is the same material density as the packaging,” continued King. “The size and shape of containers can add to the complexity of inspection, as the base, sidewalls and neck of containers can cause blind spots, where the packaging itself has the potential to mask a contaminant. Unusual shaped containers can present themselves to the X-ray system in different orientations and have no fixed points, which can lead to false rejects as the X-ray image keeps changing. The product within can also cause ‘product effect’. Products with a high salt content – such as brined items, for example – can affect the level of X-ray absorption and system sensitivity, which may also lead to false rejects.

To overcome these challenges, X-ray systems have been designed and developed specifically for this application. “X-ray is the only product inspection solution capable of detecting glass in glass containers and it does so by measuring the differences in X-ray absorption throughout the container,” said King. “The latest X-ray technology inspects all areas of a container by sending X-rays through the base area, while simultaneously inspecting through the sides. This provides all-round inspection and the crown of the container appears flat – meaning blind spots are effectively removed. The beam passes level with the shoulder of the container (below the threads and cap) and produces a less complex image, enhancing detection capability. The angle of inspection also enables exceptional, full-height fill-level inspection at high speeds.

“For manufacturers producing products in glass containers, X-ray systems are a must-have on production lines,” concludes King. “A number of variables need to be taken into consideration to achieve the optimum configuration, but it is possible to ensure that glass contaminants are detected and rejected effectively.”


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