Reducing the risk of food safety breaches is of paramount importance to all food manufacturers. Ian Robertshaw, outlines the key considerations to prevent physical contamination in food production when tackling such a high-profile issue.

Food safety breaches are a serious matter, and despite advances in technology and scrutiny around food safety processes, the danger of foreign bodies or physical contaminants getting into the food chain remains a significant problem for the food industry. One study in 2019 found more than a quarter (34) of the 124 product recalls reported by the US Department of Agriculture’s Food Safety and Inspection Service that year1 were the result of “extraneous material” being present in the food products. An almost identical number of recalls (35) were listed as being for “Other” reasons, which can include products “produced without inspection”, as well as issues such as labelling.

Without even stopping to consider the direct and indirect costs involved for the manufacturers of these products in dealing with product recalls, it is clear from these figures how important it is for food manufacturers to be vigilant and committed to preventing, detecting and removing physical contaminants from their food products.

The risks and costs are very real, and they can be long-lasting. Factors such as the severity of the product recall, the nature of the company’s post-recall remedy efforts and the degree of brand equity the company enjoys all potentially impact how customers will respond to the brand going forward. Research by Springer2 about different types of product recalls investigated the links between failure severities, remedy and brand equity on satisfaction. It found that for companies with low and high brand equity, full remedies were important, especially when the failure severity was high. The research provided evidence that the relationship between remedy and brand equity is contingent on failure severity.

This confirms that in addition to the immediate costs of a product recall – which can be tens of millions of pounds – there is great importance attached to the ways in which a manufacturer responds to a product recall. Balancing its own brand reputation and the nature of the problem that has caused the recall. Consumer trust is a precarious matter and, if lost, can have a significant negative impact on sales going forward.

While vigilance and commitment are necessary qualities for food manufacturers to try and overcome physical contamination in food production and avoid food safety breaches, these alone are not enough. Technology plays a part, but smart planning must be behind its implementation. Planning based on a good understanding of the nature of physical contamination in food production, how it happens and how to mitigate against future errors.

To prevent physical contamination in food products, manufacturers should put in place a multi-faceted plan, based on the following six steps:

1 Understand how food contamination occurs

Food contamination incidents can be extremely varied in their nature. There might be foreign bodies such as stones, bones, metal and glass among raw materials. Other contaminants can be personal effects, e.g. jewellery, keys, glasses or similar which are accidentally introduced by employees. Alternatively, faulty or broken production line equipment can provide further risks of metal and wire contaminants coming into contact with the product. 

 Food manufacturers must also be aware of how the size and density of physical contaminants can make their detection difficult, depending on the type of product and application. For example, if a contaminant is of a similar or lower density to that of the product or packaging itself, it presents an inspection challenge. “Wet” products, such as those with high salt or moisture content, also naturally generate their own “product effect”, which can mask the presence of contaminants when using certain types of product inspection systems. Other factors can also create a product effect, including the temperature of the product, its size and shape, its position and orientation as it passes through product inspection systems, and the type of packaging material used.

In short, an inspection of products and the detection of foreign bodies are rarely straightforward. Food manufacturers must understand the challenges involved in these processes, as well as the likely ways that contaminants can be introduced in the first place.  

2 Identify areas of weakness on your production line

Formal frameworks exist to help food manufacturers assess their production processes and the most likely areas of risk for foreign body contamination to occur. Hazard Analysis and Critical Control Point (HACCP) and Hazard Analysis Risk-based Preventive Controls (HARPC) audits are designed to help manufacturers identify weak points in the production line – from the raw material stage to packaging – where food safety hazards from physical contamination can occur. While HACCP helps to identify the risk of contamination, HARPC assists in planning to mitigate against incidents such as intentional adulteration, food fraud and terrorist acts. The earlier a hazard can be identified in the production process, the better. 

The manufacturer will know where to set up control points from the results of these audits so that checks and systems are correctly positioned to help eliminate food safety hazards. These are known as Critical Control Points (CCPs) and Preventative Control Points (PCPs). With an understanding of how contamination occurs added to the identification of weak points in the production line, a plan to minimise the risks of physical contamination can be put in place.  

3 Implement a strong line (or lines) of defence

Defences against foreign body contamination can be put in place at different parts of the production and packaging process. This can be split into three areas: early detection, during production, and end of the line.

Early detection includes inspecting raw and incoming materials before they are mixed, blended or processed further. Detecting physical contaminants at this stage has the additional benefit of protecting downstream processing equipment from potential damage by an undetected contaminant. It also aims to remove foreign bodies before value-adding production processes take place. If a contaminant is discovered later in the production process, this could potentially increase the waste and cost levels.

During production, the second line of defence can inspect bulk or loose-flow products, virtually eliminating debris that might be a by-product of the grinding, pulping or blending process. Inspection at the end of the line represents a final check and could pick up contaminants introduced by a breakdown in the packaging process, such as glass splinters from the capping process. However, manufacturers should not rely solely on this last line of defence. It could prove more cost-effective to identify the weak point in production, i.e. where contaminants can be introduced as early as possible before additional valuable ingredients have been added, thereby reducing operational costs and waste. 

4 Select the appropriate technology to detect contamination in food production

There are two leading inspection technologies to detect physical contaminants in food production: metal detection and x-ray inspection. Choosing the most appropriate technology is intrinsically linked to the nature of the likely contaminant and the type of product and application, including the packaging material. Generally, a metal detector serves best when metal contaminants are likely, and x-ray systems are more appropriate with non-metallic foreign bodies. However, other factors can further impact the choice of product inspection equipment.

For example, a product packaged in aluminium foil presents challenges for a metal detector to inspect, whereas an x-ray will better be able to identify a metal contaminant within the packaging due to its ability to measure mass. Metal detectors, meanwhile, are better suited to inspecting products in gravity-fed conditions such as vertical form, fill and seal (VFFS) applications.

An X-ray can perform additional product integrity checks. As well as detecting contaminants based on their densities, it can count components, identify missing or broken products and damaged packaging, monitor fill levels, measure head space, and detect product trapped in the film/seal.

There are times when a combination of both inspection technologies works best, namely when different foreign body risks are identified at different CCPs, or when compliance with retailer contracts requires multiple inspection technologies.

5 Future-proof detection capabilities

Optimising contaminant detection capabilities for a specific product or application is advisable, and product inspection systems should always be set up for success. But requirements change. New products are launched, new processes and equipment introduced, and new demands are placed on manufacturing facilities. Food producers should therefore consider future needs in any decisions they make with regard to detection equipment, giving them and their customers confidence that robust quality assurance is in place going forward.

Modular systems help companies adapt to these evolving needs while still satisfying compliance and productivity requirements. In many factories, floor space is a major challenge. Combination systems, where multiple inspection technologies – such as combining check weighing with metal detection or x-ray –can help to alleviate this problem. 

Further approaches to future-proofing include investing in inspection systems capable of digital data collection, which supports evolving supply chain and compliance needs. Or deploying inspection systems that facilitate preventative maintenance to help maximise inspection performance from day one and reduce the total cost of ownership. 

6 Embrace digitalisation

The food manufacturing supply chain is being transformed by digital technology. Digitalisation incorporates implementing real-time monitoring and control of automated inspection devices, including collecting performance data. The connectivity of these systems and data streams within a supply chain delivers transparency and traceability for all stakeholders. If a product recall is necessary, this transparency and traceability will be a key advantage.

The connection between digitalisation and food safety is strengthened further with the development of digital systems and networked supply chains to support higher quality standards in production. This can result in the ability to quickly identify when machinery is not functioning optimally and allow manufacturers to take corrective action, in addition to enabling complete documentation for compliance auditing in support of food safety standards.

The digitalisation process is not without its costs nor challenges, but most food manufacturers are already collecting data from their inspection processes in some shape or form. Digitalisation makes that easier, enhances operational performance and efficiency, and renders compliance and due diligence simpler to prove. Digitalisation is unquestionably one of the key trends in the food industry. The digital supply chain is coming; food manufacturers that get started now can be ready for the moment where a nice-to-have becomes a must-have. 


Food manufacturers need to be confident that they are on top of food safety, and implementing these six steps to prevent, detect and reject physical contaminants from their food production processes is critical. They must understand the nature of potential problems and where these might occur. Companies must also develop a robust plan to mitigate or eliminate such threats and equip themselves to maintain high food safety standards with immediate and future needs in mind.

Data-driven decision-making helps improve production line efficiencies, management control, and regulatory and commercial requirements compliance. Food manufacturers should therefore look to embrace digitalization as part of their future-proofing perspective. Alternative inspection technologies could also be part of the answer: check to weigh, vision inspection and track and trace solutions can all play a role in food safety.

Food safety incidents are too serious, and product recalls are too costly to take anything other than a strong, decisive and technologically-smart approach to foreign body detection in food manufacturing.

For more information on this topic:




Ian Robertshaw, Global Key Account Manager, Mettler-Toledo, and focuses on reducing the risk of food safety breaches for food manufacturers.

subscribe processed food industry magazine