How Do Metal Detectors Work in the Food Industry?

In The Power of Habit: Why We Do What We Do in Life and Business, Charles Duhigg explains how the creation of keystone habits centered around employee safety helped to turn the Aluminum Company of America, or Alcoa, into one of the safest companies in the world – and a very profitable one at that. When it comes to the food production process, safety must be the absolute center of attention… no food product in the world, no matter how delicious and Instagram-worthy it may seem, is going to be a success if it becomes known that you might occasionally find yourself chomping down on bits of stainless steel every few bites.

In this short article, we will talk about the role of metal detectors in the food industry. First, we will discuss what they are and why they are useful, and then present a couple common types of food-grade metal detectors and how they work. Finally, we will talk about where they should be integrated into the food production pipeline.

What are food-grade metal detectors and what are they used for?

Without the appropriate safety measures in place, food can become contaminated at several points throughout the production process by substances such as ferrous and non-ferrous metals, and stainless steel. Larger pieces of metal can also damage machines, risking further food contamination and requiring costly repairs if the machines begin to break down.

Although there are different types of metal detectors for food industry use, they all serve the same two purposes: to protect the consumer from ingesting harmful metals (and instigating lawsuits), and to prevent production-level machine failure. While no machine will be able to detect the most minute metal contaminants, metal detectors are still vital to the food-production process when it comes to ensuring that a brand is trustworthy because their products are safe and inspected.

Common types of metal detectors in the food industry

Metal detectors come in different forms, and no one model can suit every need. That said, some are for more general-purpose use than others, and can work successfully on a variety of foods, beverages and packaging. An example of this would be the commonly used balanced coil metal detector, which can detect ferrous and non-ferrous contaminants in most products, including frozen ones, so long as they are not packaged in foil. They can also detect stainless steel, if the product is not wet and does not contain a high level of salt. To detect metal contaminants in foil-packed products, you would need to make use of metal detectors with a special ferrous-in-foil search head rather than a general-purpose head.

As modern metal detectors are equipped with sophisticated user interface systems, they can provide you with data so that you may carry out different analyses to understand your production process better. More importantly, if ever a product needs to be recalled, you will have hard data to assist you in this process, such as the time and date a contaminant was detected.

How do balanced coil metal detectors work?

Balanced coil metal detectors work by creating an electromagnetic field via a transmitter coil. When a product is passed through a metal detector’s tunnel, the electromagnetic field will be disrupted if there are metal particles present in the product. Two receiver coils that are connected to each other will then pick up on this electromagnetic interference, which will in turn be analyzed by the metal detector to signal a source of contamination. Depending on the make and model of the metal detector, contaminated products will automatically be rejected and separated from other uncontaminated products.

How do metal detectors work on foil-packed products?

When it comes to detecting sources of ferrous metal contamination in foil-packed products, a different detection method must be applied. The products must pass through a tunnel in the metal detector with a strong magnetic field, which will magnetize any ferrous contaminants. This will not work on non-ferrous metals such as aluminum, copper and aluminum alloys, as these metals do not contain iron and are not magnetic.

As the target contaminants are magnetized, a series of coils in the tunnel will react to the magnetized metals, causing a disturbance which is then amplified by an electric current. The user is then alerted to the presence of ferrous contamination in the product.

Where are metal detectors installed in the food production process?

Metal detectors can and should be placed at more than one location throughout the food production process. Where you choose to place them depends on a particular product’s characteristics, however when working with food, you will definitely want a metal detector at all Hazard Analysis and Critical Control Points (HACCP).

For instance, there should be a metal detector in place to inspect all raw materials. This will prevent damage to your processing equipment, and it also improves the reliability of other inspections further down the processing line. This is because if a contaminant is processed along with raw material, it may lead to things like broken blades, which will cause further contamination and a halt to the production process until the broken equipment is dealt with. Furthermore, if metals are processed to the point where they become too small to be picked up on by metal detectors at later points in the line, you can no longer reliably guarantee the safety of your product.


As we have discussed, metal contaminants that go unchecked can lead to injuries and lawsuits from unsuspecting customers, and can also cause production equipment to break down. Broken equipment can lead to a nasty cycle of further metal contamination, and puts your employees at risk of hurting themselves. It is therefore essential to take preventative measures by figuring out the HACCPs in your production line, and providing solutions to problems before they happen.

Food-grade metal detectors are only one part of guaranteeing the reliability of a brand’s products. Given that there is no one-size-fits-all solution to ensuring food safety, it is important to think of a combination of ways to address potential sources of problems and to use the appropriate equipment for your product. Ultimately, customer and employee safety must always be at the forefront of every decision in the food production process.

Leave a Reply