Metal detectors and X-ray equipment have been in use by processors for decades to help keep the food supply chain safe and free from foreign objects. However, changing needs have been the catalyst for shifts in selection and use.

In recent years, food processors have been switching from metal detection to X-ray systems for multiple reasons. First is the growing use of metalized film and foil, or other packaging types such as cans or metal closures. Metal packaging poses problems for metal detectors but works very well with X-ray systems. 

The second is the desire to detect non-metal contaminants such as glass, rocks, bones and plastics. Regarding plastic, we even are seeing increased food processor use of items that are formulated so they can be detectable by X-ray should a piece find its way into a food product. Additives, such as metal powder blended into the plastic used to produce bins, conveyors and gaskets, etc. enable these items to be more readily detected.

The third is that a growing number of large retailers are mandating that products they sell are X-ray inspected due to the superior detection capability. This helps them market products to consumers that are as safe as today’s technology permits.

The fourth reason is that X-ray is intuitive to use. It creates excellent records, including images for root cause problem determination and record keeping.

Physical contamination can have significant consequences

Food processors also need to keep in mind that sometimes physical contamination cases have significant consequences. Consumer complaints can lead to recalls, rework or scrapping large amounts of expensive ingredients and end products, damaging news reports and even lawsuits. The harm to the company’s reputation, let alone the expense of suspending and resuming operations, can be costly. 

The risk and cost-of-failure for small processors can be even higher. Many retailers of product produced by smaller processors are also adopting strict policies where metal detectors or X-ray systems are mandatory. If a foreign object is found in a shipment, the entire product lot is returned. If this happens too many times, the retailer will change suppliers and not look back. This can have a devastating impact on a smaller processor looking to grow.

It should also be noted that the actual cost – on a yearly or per product basis – of foreign object detection, in most cases is very small. The initial cost may be high but over 10-20 years with good preventative maintenance, the cost of inspection, per package or pound, is fractions of a cent. To overcome lack of training and mistakes during operation, the product inspection vendor can be contracted to set up, maintain and train/retrain operators. Built-in security measures also can be used and the systems can be easily designed to be failsafe.

Technology advances

To help processors address these issues, X-ray detection manufacturers have made investments in technology so that the equipment is better performing, more reliable, safer, more compact, easier to operate and less expensive. 

Manufacturers have improved the quality of the X-ray source, the detector and the multifaceted inspection software that controls and interprets the information produced by those two elements. The machines may also come with optional high-power X-ray sources and high-resolution detectors – ideal for dense products or homogenous products where ultra-small contaminants can be detected. Some solutions may also provide a “refine” function so that as you run production, you can tune the machine’s performance on false reject images.

Another improvement that some manufacturers offer is the ability for food companies to upgrade an existing X-ray system, rather than replace it, as new capabilities are introduced. For example, as new ways are developed to capture and process images and new algorithms to find anomalies, these advancements can be transferred with a simple USB memory stick/one-button software upgrade. 

Reliability improvements

X-ray inspection machines of 10 or even five years ago were often susceptible to X-ray tube failures, premature wear to the detectors from constant bombardment by the X-ray beams and computer-related hiccups from use in harsh environments. Those concerns are largely a thing of the past.

One of the biggest improvements is that detectors are two to three times more sensitive now than a decade ago. Consequently, the power needed to produce an image is much lower, so the source runs cooler and lasts longer. Detectors receive less ionizing radiation as well, so they, too, last longer.


While X-ray technology used in food applications is extremely safe, the nature of X-rays is such that they need to be controlled. The latest generation systems may employ a host of safety measures, some of which are mandated by worldwide standards to prevent radiation leakage and create fail-safe designs. 

More compact

Floor space is usually at a premium in food manufacturing facilities. Equipment manufacturers are designing X-ray inspection systems that don’t require much more room than the metal detectors they may be replacing. A system that is not only small but also lightweight provides the added flexibility of wheeling it between lines or removing it for cleaning.

Easier to operate

To enhance productivity, the software running on an X-ray system is designed to be easy to operate. They are equipped with simple menus and buttons with icons and wizards to guide the user through set-up and troubleshooting. Each step may include on-screen help text. When something goes wrong, color graphics help pinpoint the cause. If expert help is needed, built-in software allows a technician sitting thousands of miles away to access and run the machine via the Internet.

Less expensive

In the past, X-ray machines have cost three to five times more than a comparable metal detector. This has decreased to roughly twice as much as metal detectors.

While food processors understandably want to avoid larger capital outlays, the superior performance of X-ray inspection technology helps ensure food quality. At the same time, it helps guard against the potential of physical contaminants entering the food supply and the resultant costs of recalling product, receiving unwanted publicity, losing major customers and facing lawsuits. 

Production line location

In general, both metal detectors and X-ray systems are the most sensitive when the products are as small as possible. Product size minimizes product effect. So X-raying a case is usually not as sensitive as X-raying each individual product going into the case. For this reason we see customers gravitating toward small, inexpensive X-ray machines as opposed to one large, high-power case inspection system at the end of the line. 

Metal detectors, due to their relatively low cost, can be very effective early in the process. An example is screening out contaminants in bulk flow materials before too much value is added to the product and scrap/rework costs are higher. At this location in the processing area, the metal detector aperture also can be very small yielding the highest sensitivity. So in many cases the combination of bulk metal detection in the processing area and X-ray immediately after packaging can offer the most cost-effective approach and highest food safety.