Allied Bakeries and Sainsbury's investigate metal contamination scare

By Vince Bamford

- Last updated on GMT

A batch of wholemeal bread was recalled by the retailer. Photo: iStock - RynioProductions
A batch of wholemeal bread was recalled by the retailer. Photo: iStock - RynioProductions

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Manufacturer Allied Bakeries and UK supermarket chain Sainsbury’s have launched an investigation into how metal may have contaminated a batch of the retailer’s own-label bread.

Earlier this week,​ Sainbury’s recalled its thick-sliced and its medium-slice 800 g By Sainsbury’s-branded wholemeal loaves (best before date: 19 January) after a Sainsbury’s employee raised the issue.

We were made aware of the possible presence of tiny pieces of metal​,” a Sainsbury’s spokesman told BakeryandSnacks. “We launched a full investigation as a matter of urgency and, as a precaution, took the decision to remove the product from our shelves​.”

Sainsbury’s said no other date codes or products were affected by the issue, and apologized to any customers who may have been affected by the recall.

Batch produced in Walthamstow

Allied Bakeries – which also produces branded bread including Kingsmill and Allinson – said the issue affected a single batch of bread produced on a line at its bakery in Walthamstow, London, on January 14.

While the risk to consumer health has been assessed as low, some product has been recalled as a precautionary measure​,” the manufacturer said. “Our priority is always the safety of our consumers and quality of our products and we have launched a full investigation​.”

Allied said it could not comment further on the matter - including whether there were metal detectors on the line or why they did not identify the contamination - until the investigation was complete.

‘Metal is most likely contaminant risk’

Metal is the most likely contaminant risk in a food processing and packing plant, claimed Sarah Ketchin, managing director of metal detection equipment supplier Fortress Technology.

The preparation of bread means it can be exposed to a variety of mixing, sieving and baking processes where metal fragments could potentially enter the food chain​," she added.

The supplier will have had metal detection equipment in place, said Ketchin, adding that no system can entirely eliminate the risk of metal contamination, and that a number of factors can impact detection (see box-out below).

Mitigating metal detection risks in bakery manufacture

Fortress metal detector
Product attributes and varying density of baked goods means they react in different ways in a detector's magnetic field

Sarah Ketchin at Fortress Technology highlights issues that can impact inspection for metal contaminants in bread and other baked goods:

Material difference

“There is widespread use of stainless steels in the food industry, and this is more difficult to detect than ferrous metals such as iron and steel or non-ferrous metals such as copper or zinc. In practice, this means that a sphere of stainless steel in a dry product typically needs to be 50% larger than a ferrous sphere to generate a similar signal size. That disparity can rise up to 200% to 300% in wet products such as bread.”

Product effect

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

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. For example, a stainless steel wire that passes through the detector’s aperture upright or sideways generates a higher signal than straight-ont.  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.”

Test and record

“It’s vital to check that any metal detection system is fail-safe. If a fault with the reject system means a contaminant is detected but not rejected, the line should stop automatically until the situation is resolved.”

Size matters

“Users could optimise performance by using a number of smaller detectors positioned at critical control points throughout the process, rather than a single, big ‘catch-all’ detector at the end of the line. Metal detector units can be deployed in different checkpoints on a bakery processing line, including packing conveyors, pipeline configurations for raw dough, or gravity systems for inspecting ingredients such as flour.”

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