Sensors & Transducers

Food safety hazards and how to choose sensor solutions

November 2018 Sensors & Transducers

In the food industry, product recall is costly not only in terms of lost revenue, wasted materials and production time, but also in terms of brand reputation and brand loyalty. The sooner food safety issues can be addressed and mitigated, the lower the risk of a large-scale recall. This article outlines three of the most common food hazards that can result in recall and describes several sensor technologies that can help ensure food safety in each scenario.

Three common food safety hazards

Three concerns about food safety are undisclosed allergens, pathogens and physical hazards. Choosing the right sensor technology for the application can go a long way towards reducing risk in each of these areas, saving time and money in the long term.

Undisclosed allergens

Food allergies can be potentially lethal to the consumer, so it is essential that food packaging accurately discloses the allergens present in the food item. By law, eight major foods must be disclosed on packaging: milk, eggs, fish, shellfish, tree nuts, peanuts, wheat and soy.

However, one error that can occur during the processing of packaged foods is when a product is placed in the incorrect packaging, resulting in inaccurate labelling of the contents. For example, if a cheese-stuffed hot dog is accidentally packaged in a regular hot dog packaging, the package would not include the required milk allergen warning.

Solution: vision sensor for label verification

A label verification technology is critical to ensure that the proper labels are affixed to the right products. One very effective technology is a vision sensor, which can be used to verify the presence of the correct label on the packaged food item.

For example, bottle filling lines run many different types of products and require frequent changeovers. To prevent mislabelled bottles and ensure quality and food safety, a vision sensor can determine whether a label pattern matches a reference pattern taught to the device. Automating label inspections with a reliable vision solution improves quality control by reducing the risk of error common to manual inspections, which in turn helps reduce the incidence of product recall due to undisclosed allergens.

Pathogens (biological hazards)

Pathogens are another significant food safety concern. Also referred to as biological hazards, pathogens are any type of bacteria, virus or parasite (such as listeria or salmonella) that can cause illness to humans if consumed. Pathogens can be introduced to food products in several different ways before, during, or after food processing.

While there are many points at which biological hazards can be introduced, temperature change is one of the most critical conditions for pathogen growth. For example, when lunch meat products are not lowered to the proper temperature quickly enough, or are not maintained at the correct temperature after processing, harmful bacteria will be allowed to grow. Ensuring that temperature levels remain appropriately controlled at all points – from food processing to distribution – can help prevent many biological hazards from reaching harmful levels.

In addition, pathogens can be introduced if machine components come in frequent contact with food. Components without a hygienic design (e.g. deep grooves where food can become lodged) may not be easily cleaned even with rigorous wash-down practices and can become a food safety risk.

Solution: hygienic sensors with remote temperature monitoring capabilities

Monitoring and documenting temperatures throughout the food chain is imperative. However, manual documentation can be costly, requiring significant investments in time and resources.

An IIoT solution to this problem is wireless temperature sensors. Wirelessly connected temperature sensors can be used to automate the documentation process by transmitting data through a controller. Not only does a wireless solution allow for historical data to be stored and accessed in the future, but wireless sensors also allow for real-time condition monitoring.

This means that, if the temperature of a food storage area rises above a set threshold, instant alerts can be sent, warning a manager that temperature requires adjustment. These alerts can be made viewable in the HMI,

sent via text message, or set to initiate a warning signal on a tower light or other visual indicator. The ability to identify potentially dangerous temperature changes as they occur can help prevent product spoilage, saving costs.

In addition to remote temperature monitoring, another way to protect against the growth of pathogens during food production is to select sensors with hygienic design. Any sensors that regularly come in direct contact with food must be FDA rated. However, this rating is not required of the many sensors that do not typically come in direct contact with food. Still, in some cases, it is possible for food to splash, come into contact with the sensor, and then return back into the process. In these cases, a hygienic sensor – with minimal crevices so food cannot become lodged and difficult to clean – is a must.

Physical hazards

Physical hazards refer to potentially harmful, non-food particles that end up packaged with the food, often due to breakage of mechanical parts on the machine. While metal detectors can identify small pieces of metal before the product is distributed, other materials such as plastic and glass could slip by unnoticed, risking the health of the consumer.

Solution: rugged sensors with all plastic housing

Sensors are not the only machine components from which pieces can break off and fall into food, but they are still important to consider. In environments with frequent wash-down, it is important to ensure that the product is rugged enough to withstand high temperatures and pressure, and a high chemical resistance may also be necessary to withstand caustic cleaning solutions. In these applications, look for an IP69K-rated sensor that has been thoroughly tested to withstand harsh environments.

In addition, the material construction of the sensor makes a difference. While stainless steel might seem like the intuitive choice for food applications, a metal photoelectric sensor will always still have plastic components (e.g. window, light pipes, etc.) that can become dislodged and fall into the process.

Because sensors with metal housing still contain some plastic, this means they have plastic-to-metal joints that are attached either by adhesive or mechanical means. When subjected to temperature change – such as during cleaning – the different materials expand and contract at different rates, creating small air gaps which leave room for water ingress.

On the other hand, a photoelectric sensor made entirely of plastic has joints that are ultrasonically welded together, becoming a single piece. This reduces the risk of the sensor window becoming dislodged and the sensor is also better protected against the ingress of water.

For more information contact Brandon Topham, RET Automation Controls, +27 11 453 2468,,


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