Detecting foreign materials in poultry has become more challenging.

Market demand has increased over the past decade, consumers continue to choose poultry over red meat, due to health recommendations and lower price. In 2022, the U.S. poultry sector reached $76.9 billion in sales, 67% more than 2021. Per capita annual consumption grew too, going from 80.4 pounds in 2012 to 99.5 pounds in 2022. Increased automation of labor-intensive steps also increased the risk of contamination with metal and plastic fragments coming from the equipment.

Food safety standards have increased, with retailers such as Costco and Trader Joe's requiring more thorough foreign material inspection and the use of X-ray systems to detect bones.

This poultry guide explores the essential aspects of foreign material detection: challenges of bone detection, advances in X-ray technology, and optimal inspection setup, concluding with the important aspects to look for in poultry inspection equipment, beyond detection capabilities.

Foreign Material Risks in Poultry Processing

Poultry products face contamination risk from different foreign materials. FSIS recalls of poultry products reveal bones, metal, rocks, rubber and plastic as contaminants. However, bones and metal fragments pose the highest contamination risk.

While metal detectors can identify metallic contaminants, bone detection has historically presented greater challenges for X-ray. Bones have a lower density than metals, much closer to that of the surrounding meat, making them harder to distinguish.

Processors focus on three types of bones that most commonly appear in consumer products:

The wishbone forms a distinctive fork shape where the clavicles meet. Due to its higher density, it's the easiest to detect.

Rib bones have relatively high density and consistent structure. However, their sheer number increases the risk of fragmentation during processing, creating detection challenges.

The fan bone poses the greatest detection difficulty. These bones are thin and have low density, appearing almost cartilage-like in young chickens.

The bird’s age adds another challenge. Most chickens are slaughtered before they reach maturity with bones that aren’t fully calcified. Lower calcium content means softer, less dense bones that are harder to detect with X-ray.

Product presentation adds even more complexity when items on the conveyor belt vary in size and orientation.

Source: Anritsu

Dual X-ray System: A Breakthrough in Bone Detection

Dual-energy X-rays have significantly improved bone detection capabilities, addressing many challenges.

They work by emitting two X-ray beams in rapid succession: a high-energy beam producing a brighter image and a low-energy beam creating a darker one. These images are then combined into one by subtracting their grayscale values.

The sensitivity of single-energy X-rays, which use one beam and produce one image, can be limited by the “thickness effect”.  In single-energy systems, absorption is influenced by both material type and thickness. While metal is much denser than meat, tiny metal fragments (0.7 mm or less) in thick meat pieces (around 4 inches) may not produce a detectable spike. This limitation becomes even more pronounced with bones. Consequently, a thick piece of meat can absorb almost the same amount of energy as a small bone fragment, making them indistinguishable in an X-ray image.

The advantage of a dual-energy system- different materials (in this case meat and bone) will absorb two X-ray beams at different wavelengths in distinct ways, regardless of thickness. When the system subtracts the images captured at these two energies, the difference in absorption behavior creates a final image where bones are clearly visible.  

With dual-energy technology, it is possible to detect low-density bones as small as 2 mm. The integration of AI in imaging software has taken this even further, enabling detection of even smaller bones.

A Common Inspection Setup

Here's how a typical inspection setup is structured along the production line:  

1. Upstream inspection. At the start of the production process, a single-energy X-ray is often used to detect bones/metals in raw materials. If the product is in trims, this system is paired with a conveyor, whereas ground chicken typically requires a pipeline X-ray. After inspection, the product can be piped into a mixer or transferred to a grinder for further processing.

This stage also serves to evaluate incoming product quality from other suppliers and allows tracing contaminated materials back to their source.

2. Midstream inspection. After the grinding/mixing process, a second X-ray is introduced to detect bone fragments or metal shavings that may be introduced during processing. Ensuring products are contaminant-free for further stages, such as forming, breading, cooking, and freezing.

3. Downstream inspection. After packaging, the final inspection point typically involves a metal detector. This stage is critical for contaminants that might have slipped through, such as knife tips, blades, or shavings from equipment. Less dense materials, like aluminum flakes, which are harder to detect with X-ray systems than denser metals, are also addressed here.

An X-ray may be added at this stage as an additional safety measure against bones (though these should be rare at this point). For packaged products, X-rays will support quality control by determining virtual weight or identifying products with missing components.

Data from foreign material inspection systems—including rejected images with date and time stamps—can help improve preventive measures in several ways:

• Pinpoint where and when contaminants were detected.
• Provide trend and supplier performance reports and enhance traceability.
• Facilitate faster response to consumer complaints or recalls.

Source: Anritsu

The ROI of Poultry Inspection Equipment

While detection capabilities are the priority, a less-mentioned critical factor is consistency. Managers need systems that can reliably detect contaminants both during demos, and consistently in live production environments, without false rejects.

When a product is rejected, processors normally face two options: reinspect it through the line or divert it to a separate belt leading to a rework station.

When these products turn out to be false rejects, that creates a cascade of costly disruptions. Beyond production delays and wasted labor, they can force processors to seek third-party inspection services, incurring thousands of dollars.  

The true ROI of an inspection system lies in its ability to deliver consistent detection without compromising production flow.