An x-ray inspection system is ideally suited for the detection of internal defects in the products. By Anritsu.

An X-ray inspection system is becoming a vital tool for the inspection of food products on the production line. X-ray inspection systems are implemented for the purpose of detecting physical contaminants in the products, which accounts for more than 80 percent of total implementation of x-ray systems in the food industry.

In addition to the detection of foreign objects, there are increasing demands from manufacturers for better and consistent product quality in order to raise the value of final products and strengthen their brands. In this article, we would like to introduce some of our customised x-ray inspection solutions that are designed to meet such demands for food applications.

Defects In Agricultural Products

In some cases, internal defects can be found in agricultural products such as an incomplete kernel set near the ear tip of corn and an open cavity in the middle of a potato. This kind of defect does not cause any health damage. However, it can generate consumer complaints and product recalls, especially when the product has a premium value because it specifies the place of production.

Vision systems can hardly perform internal quality inspection of products. Thus, an x-ray inspection system is ideally suited for the detection of internal defects in the products.

Example: Empty Kernels Near The Ear Tip

Seal Defects

Bits of food product caught in the seal area can cause a decrease in the seal strength, which can spoil the air-tightness of a package and give rise to product deterioration prior to best before date. Moreover, sealing faults (product trapped within the seal area) can cause the damage to the product when it is being opened by consumers.

Packaging materials are classified into two broad categories: a transparent body (without printing) and a non-transparent body (with printing). Through optical camera inspection, the contents and the seal area can be clearly identified so that subtle faults in the seal area can be detected in the products packed in a transparent package. As for the product in a non-transparent package, it is hard for the optical camera to distinguish between the product and the seal area as the colour and shape of the product are hidden by printing used on the surface of the package.

X-ray inspection systems are capable of identifying product trapped within the seal area of a non-transparent package. Since x-rays pass through food products without being affected by printing on the package, x-ray systems can accurately distinguish between correct sealing and faulty sealing by seeing the difference in x-ray transmission levels.

On the other hand, since the seal area of a transparent package has high x-ray transmittance, it is difficult for x-ray systems to identify where the seal area is located before seeing the difference between the product and the seal area. However, with recent developments in sensing technology, x-ray systems are capable of capturing a slight amount of x-rays absorbed in the seal area, making remarkable improvement in the ability of detecting product caught in the seal area of a transparent package.

Since one single x-ray machine can perform package integrity check of both transparent and non-transparent packaging, it is highly prized by food manufacturers whose production lines have limited square footage for inspection equipment.

Image Of A Rice Cake Caught In A Transparent Package

Image Of A Retort Pouch Product Trapped In A Non-Transparent Package

Inspection Of Bone Fragments

In the inspection of bones in poultry, visual or touch inspection by human operators has been used as a conventional method to identify bone contaminants. However, with the increase in production and shortage of workers, x-ray inspection systems are being more widely used in production lines.

Bones in poultry meat have low density, which can trigger false rejects in conventional x-ray inspection systems. The arrival of x-ray systems with dual-energy sensors solves this problem. Dual energy technology analyses two different x-ray energy signals simultaneously and dual energy subtraction using unique image processing algorithms allow the system to distinguish between the product and contaminants, delivering enhanced detection sensitivity for those hard-to-detect bone contaminants. Other than poultry bones, dual-energy x-ray systems are used to detect seafood shell fragments in the production line where stripped scallops are processed.

X-Ray Transmission Image Of Poultry Meat With Bone Fragment

Inspection Of Presence And Absence Of Multiple Ingredients

When inspecting a single item product such as cookies that are placed in a container, the count check method has been used to evaluate presence and absence of the product from the x-ray transmission image of a product by the area of the shadow and grey scale level. Advanced count inspection is the ideal solution for the inspection of multiple items such as a lunch box product which several different items are placed in a partitioned box container. X-ray systems can detect the presence and absence of each dish by setting multiple inspection areas with different threshold levels.

Example: Inspection Of A Lunch Box

Generating Algorithms By Deep Learning

When inspecting raw material products which vary in shape and thickness, skilled inspection operators can distinguish between contaminants and the variations in shape of the product by seeing a subtle shadow appear on the x-ray transmission image. With a conventional x-ray inspection system, an operator will choose the algorithms that seem optimum and adjust the contaminant detection limit in order to enhance the detection sensitivity. This method can trigger false rejects when the detection limit is set strictly.

The deep learning approach in an x-ray inspection system uses a large quantity of inspection images of both working and faulty products to extract characteristics of the product with a variation of shapes to design an exclusive algorithm. It is currently in the process of research and development and is expected to be widely used for the detection of harder-to-find contaminants in the food industry in the future.

Conclusion

Other than those introduced in this article, x-ray inspection systems can carry out a wide range of food inspection. However, the inspection of low-density contaminants such as rubber and resin still pose challenges for x-ray inspection technology to fully meet the demands from the food industry. We, as the x-ray inspection manufacturer, will put more effort in the development of new sensing technology in order to best serve processors’ specific needs.

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