Solutions for Food Inspection

Modern Inspection Systems

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Food safety is at the centre of every production line, as contamination by foreign bodies not only endangers product quality, but also poses a serious health risk to consumers. In the food industry, contamination goes beyond merely affecting quality and can also have legal consequences. With this in mind, the use of precise technologies for detecting foreign bodies is essential. The requirements are now more complex than the simple detection of metal parts. Today, food manufacturers must be able to recognise a wide range of foreign bodies - from glass, stones and plastic to bones. Modern technologies play a central role in this by enabling reliable quality control. However, choosing the right technology, accurately positioning the inspection systems and selecting the best system remains one of the biggest challenges for the food industry.

HC-M-MDi from Wipotec: Combined solution of checkweigher and metal detector in one device. © Wipotec GmbH

Detection of different types of foreign bodies and quality defects

Foreign bodies in food can take on many different forms: Metals (magnetic and non-magnetic), glass, stones and plastics pose safety risks. The detection of these different materials requires specialised technologies, as each type of foreign body has different properties. Metals are often easier to detect than glass or plastic because they are magnetic or electrically conductive. Glass and ceramics, on the other hand, require new technologies such as X-ray inspection in order to be reliably recognised.

In addition to detection of foreign bodies, products are checked for completeness, filling quantity, shape and arrangement. Modern inspection systems also offer the option of integrating additional inspection parameters, such as the correct placement of labels, the legibility of production and expiry dates and lid film verification. In addition, the use of detection systems for foreign bodies at HACCP (Hazard Analysis and Critical Control Points) checkpoints in accordance with Regulation (EC) 852/2004 is not only a legal obligation, but also a measure for ensuring product quality and safety.

Classic technology – metal detectors

Metal detectors are one of the traditional systems for detecting foreign bodies. The mode of operation is based on the basic principle of measuring changes in the electric field caused by the magnetic or electrical properties of metals.

Two companies with modern solutions that make a significant contribution to safety in food production are presented below:

Wipotec GmbH is a provider of intelligent weighing and inspection technology with headquarters in Kaiserslautern, Germany. The company was founded in 1988 and has since developed into a leading manufacturer on national and international markets. Its core competences include the development and production of precise load cells, checkweighers, X-ray scanners and the integration of weighing and inspection solutions in industrial processes, including food production.

Wipotec offers a number of metal detectors as part of its checkweighers and inspection systems.

HC-A-MDi: A precise checkweigher combined with sensitive metal detection to fulfil the requirements of food production.
HC-M-WD-MDi: A robust combination of checkweigher and metal detector in a wash-down hygienic design, suitable for environments in which wet cleaning is frequently required.
HC-M-MDi: A solution that combines the functions of a checkweigher and metal detector in one device. The machine is capable of detecting up to 250 product pieces per minute (see Fig. 1).

These systems can be used either as a stand-alone solution or in combination with weighing technologies, explains Hasan Uygul, Director Global Sales Product Inspection at Wipotec.

The Varicon+ GLS metal detector from Sesotec with integrated conveyor belt. © Sesotec GmbH

Sesotec GmbH from Schönberg, Germany (founded in 1976 as S+S Electronic KG) is one of the leading suppliers of solutions for the detection of foreign bodies and material sorting. It operates in various sectors such as the food, chemical and plastics industries. For the food industry, Sesotec offers tunnel metal detectors that can detect both magnetic and non-magnetic metal contaminants. These detectors are available in variants such as single, dual, multi or multi-simultaneous frequency technology and are suitable for both packaged and unpackaged foods.

The company also offers detection systems with an integrated conveyor belt:

VARICON+: A complete system with an integrated conveyor belt that can be combined with the GLS metal detectors (the entry-level model for inspecting piece goods and bulk goods on a conveyor belt, see Fig. 2),
GLS MF (a standard model with excellent detection accuracy) and
INTUITY (a high-end model that ensures high detection accuracy, even for products with a high product effect, e.g. high salt content).
UNICON+: A conveyor belt series that is suitable for customised adaptations and solutions.

All of the metal detectors mentioned from both companies detect different types of metals, such as ferrous metals, stainless steel and non-ferrous metals such as copper, brass and aluminium. The companies confirm the conformity of their technologies to standards such as HACCP, BRC and IFS, which are recognised worldwide for food safety and quality management.

X-ray technology

The picture from Sesotec shows a product (baguette) with a test card containing 100 foreign bodies. With this method, an inhomogeneous product can be tested transparently and accurately. © Sesotec GmbH

Depending on the nature of the product and the type of foreign body, metal detectors are not always the best choice. "You have to be able to see into the product," explained Johannes von Stein, Vice President Sales Food at Sesotec. X-ray technology is a powerful tool for foreign body detection, as it offers the ability to detect a variety of foreign body types, including glass, stones, plastics, bone and more, compared to metal detection.

"One technology doesn't replace the other. On the contrary, in many respects they are complementary and can supplement each other," emphasised Johannes von Stein. With this technology, X-rays penetrate the product. A detector catches the radiation and produces a grey-scale image. Foreign bodies with a higher density appear darker on the X-ray image because they absorb more X-rays than the surrounding food (see Fig. 3, 4).

X-ray image of a frozen product with a metallic foreign body. © Wipotec GmbH

X-ray technology is particularly advantageous in the beverage industry, for example for packaging in glass bottles, or in fresh meat production, where glass as well as metallic foreign bodies must be recognised. "Glass-in-glass X-ray inspection is one of the most important technologies for packaging beverages in glass bottles. It ensures that no glass fragments or defective bottles enter the production process," explained Hasan Uygul.

Wipotec offers a range of X-ray inspection systems for different types of production:

SC-E series: Entry-level X-ray scanners designed for professional foreign body detection. They have a design and a diode line detector with a resolution of 0.4 mm.
SC-B 30 series: Especially suitable for the inspection of bulk goods such as rice, coffee or nuts. The SC-B 30 model is equipped with a diode line detector (0.4 mm resolution).
SC-W-V model (all-in-one): Combines X-ray technology with checkweigher technology and optical inspection.
SC 40 model: A modern scanner with VioX TDI camera technology, which enables a resolution of up to 0.1 mm.
The SC-V series integrates X-ray inspection and optical inspection systems for comprehensive quality control.

Inspection speeds of up to 2.0 m/sec can generally be realised (see Fig. 5).

The machines in the SC-V series integrate X-ray inspection and optical inspection systems. © Wipotec GmbH

Sesotec GmbH also offers a wide range of inspection systems based on the principle of X-ray technology. The RAYCON series comprises high-precision X-ray scanners for packaged products:

RAYCON EX1 for smaller, lighter containers and cans with an output of over 1,000 cans per minute
Raycon D+ MX with 100 W source
Raycon D+ HX with 200 W source and 0.4 mm detector with the AI option to be unveiled at the IFFA
Raycon D+ TX to be unveiled at IFFA with TDI technology and the AI option
Further solutions for bulk materials and in hygienic areas with IP69 are available in various versions.

Challenges and future development

The positioning of detection systems in production lines is of crucial importance, as Hasan Uygul emphasises. An optimally positioned detector makes it possible to detect foreign bodies early on in the production process and minimise their impact on product quality. In addition to correct placement, food manufacturers must also consider various challenges. These include limited space in the production hall, the compatibility of the detection systems with existing lines and productivity, which must not be impaired by the integration of the new systems. Equally important is the documentation in the form of statistics and images and the continuous training of staff in the use of the latest technologies. Experts agree that customised inspection systems are required for each production line and capacity in order to meet the specific requirements for foreign body detection and quality control.

Foreign body detection technology will continue to develop in the coming years. The integration of artificial intelligence (AI) in particular, as exemplified by Sesotec's THiNK, will enable more precise and faster analyses. THiNK is an AI-based software from Sesotec that improves metal detection in food by better masking the product effect (e.g. high salt content) than conventional detectors. The relevance of optical systems (use of cameras) will also continue to increase, particularly in the serialisation of foodstuffs and label inspection (such as the 2-D code inspection from Wipotec). The future of detection of foreign bodies will be increasingly characterised by combined solutions in which different technologies are combined with each other.