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X-ray Inspection vs. Metal Detection for Food Safety

Written by | Published: 02.16.2024

Helping Manufacturers Keep Food Safe and Avoid Recalls

Detecting foreign objects in food is integral to food safety and quality. Millions of pounds of food are recalled each year due to the presence of physical contaminants. Recalls are not only expensive, but can harm the consumer. Broken glass jars, stones, sharp pieces of plastics, nuts and bolts from vibrating machinery, and even fishhooks can easily enter into the production line.  The key, however, is to make sure these dangers don’t reach the shelves.

Metal detection and X-ray inspection are first lines of defense in identifying the presence of foreign contaminants in food products before they leave the processing plant.

For food quality professionals, process engineers, and corporate food safety executives, the type of product that is being processed should be one of the main considerations. Meats, frozen foods, bulk nuts, foil pouched drinks, glass jarred items, and even pre-made dinners all have different characteristics that will dictate which technology would be best suited for each specific application.

Here is a snapshot of two different technologies that can be used for food inspection and how manufacturers can use them to avoid these expensive and potentially harmful hazards.

Metal detection

Metal detectors are one of the most common types of food inspection systems and are highly effective at detecting small particles of ferrous, non-ferrous, and stainless steel contaminants.

Metal detectors find small particles of ferrous, non-ferrous and stainless steel using coils wound on a non-metallic frame and connected to a high-frequency radio transmitter. When a particle of metal passes through the coils, the high frequency field is disturbed, changing the voltage by a few microvolts. The high frequency field is no longer balanced. The output is used to detect metal and then the contaminated product will be rejected from the production line.

To improve sensitivity and enable the detection of many metal types and smaller sizes, multiscan technology can be utilized.  Metal detectors with multiscan technology utilize up to five completely adjustable frequencies to find metal types and sizes previously undetectable. Using a true broad-spectrum approach reduces the probability of an escape by many orders of magnitude. This technology is analogous to having several metal detectors sequentially in a production line.

Multiscan technology is especially useful for food companies that process wet, salty, and high-mineral foods as well as frozen foods. These types of foods experience something called “product effect” – meaning they have conductive properties that can mimic a metallic object, and cause the detector to incorrectly signal a physical contaminant. But with multiscan technology, those challenges can be overcome.

Metal detectors can also be used for ‘reverse detection’ – where a metal component is intended to be present in the finished product.  An example of this is a packaged muffin mix which has a metal can of blueberries inside of each box along with the bag of powder mix.  The metal detector will then reject any final product that does not contain the metal can of blueberries.

Watch this video on metal detection for additional details.

X-ray inspection

X-ray inspection is common for food manufacturers to use in their food quality and safety programs since the technology can detect both metallic and non-metallic contaminants – including metal, glass, plastic, stone, and bone – without being vulnerable to product effect.

Food X-ray systems are also better suited for finished products made with metallic packaging, including juice pouches and snack bags. X-ray systems can “see through” all types of packaging, including metallic packaging, to generate images of the contents inside to ensure they are contaminant free.

Scanning systems using X-ray technology pass high energy, short wavelength light waves through the entire process stream.  As an X-ray penetrates the materials, it loses energy depending on the density of the materials it passes through.  Detectors capture the changes in the X-ray’s energy and convert these signals into a grayscale image showing variations in material density. Analysis of this image can detect contaminants, inconsistencies within the product itself, packaging problems, and more.

X-ray inspection systems in the food industry do not use radioactive materials to generate X-rays; instead, they use high voltage X-ray tubes to generate power. When the tube is turned off, no X-ray energy is emitted.

Another application for X-ray inspection is to inspect for product integrity.  Vision algorithms can be used to ensure there are no missing pieces in your finished product and reject ones that are not complete.

Watch this video on X-ray inspection for additional details.

Which technique is best?

Selecting the right inspection equipment and supplier is very important, and both must be carefully considered.

In general, metal detection systems are less expensive than X-ray units and last two-to-five times longer. If your main concern is metal contamination in small, dry products, a metal detector might be the most appropriate choice. If you want to find glass, rocks, bones or plastic, or have metallic packaging, an X-ray detection and inspection system may be a better investment.

But every food facility is different, and needs vary.  Before choosing the best detection system for your application, several things need to be carefully considered, such as:

  • The type of food product being inspected and the size and type of the foreign contaminant to be detected?
  • What type of packaging is being used? Is there a metallic liner?
  • What is the probability of detection while also reducing the occurrence of false rejections?
  • Ease of use. Is the system intuitive, requiring minimal training?

In fact, metal detectors and X-ray inspection offer complementary strengths, meaning it can often be beneficial to employ both techniques – such as combining a metal detector to scan raw materials with an X-ray scanner inspection system to guarantee final product integrity.

View video on evaluating Metal Detection and X-ray Inspection

Summary

Whatever your individual needs, working hand-in-hand with a leading provider of food inspection technologies is the most effective way to ensure that contaminants are left with nowhere to hide.

Small incidents can cost millions of dollars, disrupt business, and can be damaging to your company’s brand. How much are you willing to risk? Weigh this against the total cost of ownership for the metal detection or X-ray system including installation, training, maintenance, repairs, and the cost of downtime. Also, keep in mind that the best approach may be to use both. Both technologies are frequently deployed at different points in the production process to meet different detection needs. Keep your eyes on the final result: implementing the best solution to keep consumers and your brand safe.

Additional Resources

Editor’s Note:  Some content in this article was originally authored by By Bob Ries and published in June, 2014, but this article has been updated and refreshed with new content.

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