Fortress comments on sliced bread recall

High-profile product recalls highlight the question every food business should be asking when deciding to invest in metal detection inspection equipment - how much is your company’s reputation worth? Here, managing director Sarah Ketchin at Fortress Technology discusses the impact of metal contamination on brand reputation

Any contamination is a food safety issue that can have an incendiary effect on a food business’s reputation. Of all the potential contaminants, metal is still the most likely contaminant risk in a food processing and packing plant and the preparation of bread means that it can be exposed to a variety of mixing, sieving and baking processes where metal fragments could potentially enter the food chain.

On 18th January 2016, the Food Standards Agency announced that Sainsbury’s, as a precautionary measure, was recalling nationwide it’s own-branded wholemeal bread medium sliced and thick sliced with a best before date of 19th January 2016. This was due to a possible presence of tiny pieces of metal in the bread. No other products or date codes were affected by this recall.

The supplier will certainly have had metal detection equipment in place, so how could this happen? The answer is that no system can entirely eliminate the risk of metal contamination. However, optimising metal detection systems can manage that risk more effectively and reduce it as far as is practical.

Material difference

First, there’s the widespread use of stainless steels in the food industry. These are more difficult to detect than ferrous metals such as iron and steel or non-ferrous metals such as copper or zinc. That’s because metal detectors work by spotting materials that create a magnetic or electrical disturbance as they pass through an electromagnetic field. Ferrous metals are both magnetic and good electrical conductors so they’re relatively easy to spot. Non-ferrous metals aren’t magnetic but they’re good conductors. Stainless steels are not magnetic and are also poor conductors, so they present an added challenge.

Understanding product effect

One of the biggest challenges when using metal detectors to inspect food for contaminants has long been ‘product effect’. It occurs when a product has a conductive property, such as high moisture or mineral content, which affects the electromagnetic field generated by the metal detector. In the bakery category, bread, muffins, cakes, pastries, raw dough, chilled pastry and fortified cereal bars have this conductive property.

The scientific reason behind this ‘product effect’ occurrence is largely due to physics. Water and mineral content can create a large conductive signal that the detector must overcome in order to detect small pieces of metal. As well as salt content, warm baked bread can impact the metal detector’s ability to distinguish between any actual stainless steel metal contaminants that may have been introduced during the mixing process and the false signal given by the combination of product attributes. 

Orientation effect

The signal produced from a wire shape will vary greatly depending on the type of metal it is and on its angle when it passes through the detector. This is known as orientation effect. For example, a stainless steel wire that passes through the aperture upright or sideways generates a higher signal than a straight.  In the worst case a wire may produce a signal no bigger than a sphere of the same size as the diameter of the wire. It’s therefore important to optimise the performance of the detector to cope with the worst-case scenario.

Businesses need to look at this from a risk assessment perspective. Think of it like fire insurance. No one intends to allow metal to contaminate their food products any more than they intend to burn down their factory, but that doesn’t stop them from investing in fire protection and insurance. In the same way, investing in metal detection reduces the risk of a company’s hard-won reputation for food safety going up in flames.

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