What Food X-Ray Inspection Can and Cannot Detect

Short answer

An X-ray inspection system finds contaminants by density difference: metal, glass, stone, calcified bone and dense plastic show up because they absorb more radiation than the food around them. It struggles with anything close to the product's own density — a soft plastic fragment in a block of cheese, a piece of cartilage in meat, or a contaminant hidden inside a liquid-filled pouch.

How it works

A generator fires X-rays through the product onto a detector array. Denser material absorbs more, so the detector sees a darker patch. Software compares each product image against a learned reference and flags anomalies above a sensitivity threshold, then signals a reject arm or air blast to remove that item.

What it reliably detects

• Ferrous and non-ferrous metal: broken blades, wire, screws, mesh fragments
• Stainless steel, which metal detectors often miss
• Glass shards and hard plastic
• Stone, ceramic and sand
• Bone and shell in poultry, fish and processed meat

What it may miss

• Low-density contaminants such as wood splinters, cardboard, hair, insects
• Fragments whose density is close to the product — soft plastic in cheese, gristle in meat
• Thin foils or films lying flat and parallel to the beam
• Contaminants outside the beam path, near the edge of the belt or inside a thick package seam

What changes the detection limit

• Product thickness: a thicker product absorbs more X-rays and hides small contaminants
• Packaging: aluminium foil, metalised film and tins block the beam entirely
• Belt speed: faster lines give fewer photons per pixel
• Contaminant orientation: a wire seen end-on is much harder than a wire lying flat

This is why the honest way to specify a system is to test your own product with your own contaminants, not to quote a single millimetre figure.

X-ray or metal detector?

A metal detector is cheaper and faster for dry, non-metallic packaging, but it only sees metal. X-ray covers glass, stone, bone and dense plastic as well, and works through most packaging except foil. Many lines run both: metal detector first for speed, X-ray second for the rest.

Selection checklist

• What products and pack formats — loose, flow-wrapped, tray, jar, can?
• What contaminants have actually occurred in your plant?
• Line speed and belt width
• Reject method: pusher, air blast, or flap
• Hygiene requirements: IP rating, washdown, stainless frame
• Traceability: image storage, reject logs, HACCP export

Next step

Send us your product sample and the contaminants you need to catch, and we will test and report the achievable sensitivity. See the X-ray food foreign object machine or the food inspection range.