Are there metals in food? Use magnets as a metal detector

Metal in breakfast

We were contacted back in 2018 by a larger danish newspaper, which wanted to write an article about metal in breakfast food. It was set up for the big show, and they had bought several packs of cornflakes etc., which we were to test for traces of metal or metal residues.

They were quite convinced that there was plenty of metal in danish breakfast food.

So, we started with some of our largest magnets, and all food was thoroughly tested and chopped into small pieces to ensure that we didn’t overlook even the smallest piece of metal.

But we found nothing. there was no reaction and no metal shavings to be found afterward. Meaning, we could not spot the slightest reaction or find any kind of metal parts.

It was not the result the journalists had hoped for. unfortunately! we thought, however, that the news of "no metal in danish breakfast food" was at least as good as having found metal in the food, because it was good news. But such good news does not sell as many newspapers as a scandal story... so the newspaper completely dropped the story about breakfast being magnetic and filled with metal scrap.

Metal in grains

in all production with machinery, there can be metal residues, because there is wear on the machines over the years, which is unavoidable. The same applies to grains. We were therefore contacted about rebuilding a chute, which was to transport the grain over magnets, so any metal shavings could be sorted out (i.e., caught by the magnets).

The solution was constructed with a chute in 2 parts: first a wide part, made in a funnel shape (like a y), where it was easy to pour the grain through in larger amounts without spillage. Then a gap, where we placed 3 large 60x30x15 mm power magnets. and finally, the last part of the chute, which functioned as a sort of runway for the grain when it had jumped over the magnets, where it was collected in a container before the last processing.

Subsequent tests in the metal detector showed that the magnets worked, as there was nothing to trace, and the construction therefore worked completely as intended. But not only that: because magnets first begin to lose magnetism measurably after about 80 years and noticeably after about 100 years, it is a simple construction that works without power, and which only needs to be checked by simple inspection to keep an eye on any metal. Completely different from large machines, which depend on a lot of factors that must interact along the way and be continuously inspected by a technical employee. Here, magnets are different and "cooperative" - and will probably outlast all other parts in the construction by many years.

Unfortunately, we cannot show pictures of the chute. but if you need help building a similar model, we will gladly send you drawings for a similar solution.

Metal in chocolate and candy

The last task requires a bit more explanation, because the magnets can easily get the metal to "react," but it is not as simple as with the grain and breakfast products.

The task was to sort out pieces of candy from the production, which had gotten metal shavings in them during production. The company's problem was (as in the case with grain), that wear and metal fatigue can occur in the machinery. This can lead to metal shavings entering the products during production.

We have made a video(in danish), which can be watched further down on this site.

 Preliminary tests

To determine what was effective, we started with the Ø75 hook magnet: it’s easy to handle because you can slip a finger through the hook, giving you complete control over the magnet in your hand.

Next, we had to implant a piece of metal into some candy and chocolate to observe its reaction before testing larger quantities. This was done by breaking a piece of chocolate and molding it around a metal splinter and cutting a small hole in a piece of candy to insert a tiny metal piece.

The magnets have a large magnetic field and can easily induce a response in magnetic metal from a distance of up to 10 cm. (the closer, the stronger the reaction - but it begins to "dance" at about 10 cm. distance). And it makes no difference if plastic or a wooden tray is placed in between - the magnetic field penetrates everything. This meant we could conduct the test by placing the candy and chocolate on a tray with the magnet underneath to perform the test.

Challenges along the way

The first challenge was creating a setup where larger quantities could be processed. It wouldn’t be a viable solution if you had to empty a whole packet of small chocolate lenses and inspect each lens individually. Ideally, you should be able to pour an entire bag into a box or onto a tray, where within a maximum of 1 minute, you can spot the part that made the metal detector reject the batch during production.

While the metal detector can identify the few bags of treats that need to be discarded, subsequent troubleshooting and analysis of the products, can narrow down and pinpoint exactly where in the production the issue with metal shavings arises. But even though magnets and metal are a perfect match, it wasn't so simple to get the rum ball and chocolate nuts with magnetic shavings to easily roll towards the magnet. We could easily identify which rum ball contained a metal shaving (it vibrated slightly near the magnet), but we could not get it to roll and stick to the magnet, leaving the client baffled (and disappointed).

So, unfortunately, the conclusion was that even though large, powerful magnets are wonderful and clever for many things, they are not a magic wand that can magically do everything; for example, making a chocolate nut or rum ball roll.

But we did not give up...

Why the magnets didn't work as hoped

The conclusion cannot stand alone, as we’d like to explain "why":

Let’s say the rum ball weighs 10 grams and has a diameter of 2 cm. The metal splinter might weigh 0.01 grams and measure 2 mm. Even using our strongest magnet, the tiny metal splinter has to pull a load that’s 100 times heavier than itself, and while the metal splinter is indeed magnetic, it isn't a magnet in itself. A magnet with a strength of 130 kg can make the metal splinter "dance" but it won't make the rum ball roll. The same result is achieved with a setup of four 60x30x15 mm magnets with a combined strength of over 220 kg: the metal splinter is attracted to the powerful magnetic field, but only the splinter "dances" inside the rum ball.

For the sake of comparison: imagine towing a caravan with a car. More pictorially, a fine new caravan weighing 1100 kg, towed by a grand BMW X7 with 335 horsepower. It works well, as the size ratio and horsepower are balanced against each other. Then you remove the caravan from the hitch and instead attach it with a suction cup and a skipping rope from a toy store. It’s not hard to deduce that you won’t get far with this setup, even if both the car and caravan are top-notch.

In our case, the magnet is powerful enough, and the metal stub is fine magnetically, but it simply cannot pull enough to move a weight 100 times greater than its own.

Magnets can do an incredible amount, but unfortunately, they can’t do everything. So some modifications were necessary, such as cutting the larger candy into smaller pieces... which wasn’t an issue, as it had to be examined anyway to determine which layer contained the metal.

And as we said, we didn’t give up

As with so much else, one just has to persist. Watch our Danish video here to see how we succeeded with the project:

PS! The type of candy and certain ingredients have been altered to protect the companies’ identities.

How is metal detected in food?

The fact that we couldn't get the simple reaction with magnets we had hoped for from the start doesn't mean consumers should worry about metal in food and sweets. All food producers are subject to strict requirements regarding food safety, including metal detection. This means that any metal parts are detected by their metal detectors. But when a package or bag is sorted out due to a detector's signal, it’s crucial to determine:

• What kind of metal parts are involved
• Where in the production they come from
• How the machinery is secured afterwards to prevent more metal in the food

So, as a consumer, you shouldn’t be nervous about biting into a steak or a piece of chocolate with metal in it. It HAS been sorted out in the large metal detector setup.

Can we draw a conclusion?

This article focuses solely on being able to spot the metal parts and then determine where in the production process the metal originates because in food production, there are multiple machines and steps along the way where the metal may come from. In candy production, it could be a piece of candy made up of, for instance, licorice and gummy or marshmallow and chocolate. It’s important to locate the exact piece of candy containing metal and see which part the metal is in. If you cannot identify where in the process it may have occurred, several machines might need to be inspected. This is a costly process. Therefore, magnets can be a very good part of the subsequent analysis of metal in foodstuffs. But as you can read above, it's not that simple since it requires actually moving the small piece of metal enough that you can easily spot the piece of candy or the like, where the metal has lodged. And that requires a larger setup with very strong magnets, as you can see in the video.

In conclusion, it is possible, but magnets aren't magical; the project needs a little help along the way with small modifications.

Feel free to browse through our FAQ if you want to learn more about magnets/magnetism - otherwise you are more than welcome to contact our support, if you have any unanswered questions or specific requests.