Protection from food recalls using X-ray technology

Between the rhythmic whirring of machines, the rattling of packaging and the tantalising aroma of freshly produced delicacies, X-ray inspection systems occupy an important place in many production facilities around the world.

X-ray inspection systems not only recognise products that are contaminated with metal, glass, rubber, stones, plastic parts or bone splinters, they also enable inline quality checks such as weight determination, counting of components, detection of missing or defective products, fill level control and checking the integrity of closures. As part of the HACCP concept (Hazard Analysis and Critical Control Points), they help to fulfil the increasing requirements of consumers, authorities and protect manufacturing companies from costly and brand-damaging product recalls.

How does it work?

X-ray machines in the food industry work in much the same way as X-ray machines at airports check luggage for security reasons. The product runs on a conveyor belt at a constant speed through the X-ray beam. As the product continues to move, a new image line is generated at regular intervals (eg, every 0.8 mm). Once the product has been fully recorded, the greyscale image generated is analysed and inspected for foreign objects.

“X-ray inspection systems recognise contaminated products by the fact that foreign bodies such as metal absorb X-rays more than the actual food product,” said Liang Mengqi, Global Product Manager at Minebea Intec. Hence, the success of foreign body detection depends on the density of the foreign bodies. For example, Minebea Intec X-ray machine could detect 2 mm metal wire inside of a yoghurt whereas the conventional metal detector has no chance because the metal detector will be stopped due to the aluminium foil from the yoghurt packaging.

The selection process

There is a wide range of X-ray systems for the inspection of packaged products. Typical applications include cartons, boxes, bags, pouches, trays and portion packs, which can contain a wide variety of dry or liquid foods. To select a suitable X-ray system for the production, the product and its orientation need to be considered.

Systems with top-mounted X-ray generators are the most common in the food industry, ie, where the X-ray beam hits the product directly from above. These inspection systems are usually installed at the end of a production line and inspect the packaged products. For this purpose, the packs are positioned flat on the belt so that the X-ray beam can pass through as little pack thickness as possible, which contributes to higher detection sensitivity. The Minebea Intec Dylight and Dymond models have been developed for these applications. They are characterised by a hygienic design and high detection sensitivity with low power consumption.

Systems with a side-mounted X-ray generator, where the X-ray beam reaches the conveyor belt from the side, are often used for upright products such as a jar of baby food. In this case too, the product must be aligned so that it passes the detector system with the upright side facing the X-ray beam. For example, Minebea Intec’s Dymond S, as a sideshooter X-ray, combines high detection sensitivity with low power consumption. The unit is optionally available with a chicane belt, suitable for situations where only very limited space is available. Dymond D is a dual-beam X-ray inspection system that produces two X-ray images at a 90° angle. Whether it’s tins, Tetra Paks or glass jars, multi-sided inspection provides maximum safety, thus opening up a wealth of possibilities for manufacturers in product design.

Special designs of X-ray inspection

Minebea Intec recently launched the Dypipe X-ray inspection system for viscous and liquid products. “The Dypipe is equipped with an innovative test specimen insertion system that enables the test specimens to be inspected during operation,” Mengqi said. “This means that manufacturing companies can be sure at all times that their production processes are running smoothly and safely.”

In order to meet the high hygiene requirements for meat applications, the Dypipe is equipped with an easy-to-open separator that was developed for this purpose.

Another design of X-ray inspection systems is the Dymond Bulk. It is used for X-ray inspection of bulk materials in the food industry. Foreign bodies such as stones or metal are detected and removed from the material flow to protect both products and machines. Dymond Bulk has suitable detection performance for raw materials such as vegetables, nuts, dried fruits or cereals; an optional multi-segment separator with four segments also assists in the targeted and cost-effective elimination of foreign bodies from the product stream.

Image caption: Multi-track solutions for up to 8 lines with one detector are possible. Image credit: Minebea Intec