Quality control is an integral part of any food manufacturing process. Kimberly Durkot from Thermo Fisher Scientific looks at the technologies available and what to consider when designing a detection system.
Raw material production inspection includes weighing products to ensure that each package has the correct mass, screening for unexpected objects picked up during harvesting, and checking for small components of food handling systems that may have become detached and made their way into the production line.
Metal detectors and X-ray inspection systems are frequently used during quality control (QC) to check for potentially hazardous materials, but their success depends heavily on the point of inspection and the type of contaminants being identified.
There are strengths and limitations of these technologies when designing detection systems and factors that need to be considered due to the importance of raw material screening in enhancing food safety for consumers.
A 2022 report for Food Standards Australia New Zealand (FSANZ) estimated that by 2019, foodborne illness and its sequelae were costing Australia around $2.44 billion each year, the largest contributor to this sum being lost productivity.
The cost of some pathogens was particularly high – most notably Campylobacter ($365 million per year) – with Salmonella, norovirus, and pathogenic strains of E. coli also each estimated to cost the economy over $100 million every year.
But pathogens are not the only cause for concern in food production; despite stringent controls, many hazardous or unexpected items still make it into the end-products bought by consumers.
This could be due to the limitations of existing detection methods, or because manufacturers simply aren’t employing food inspection techniques early enough in the manufacturing process.
Understanding both the benefits and limitations of the metal detection and X-ray inspection technologies currently used in food inspection applications can help to address this issue, plugging the gaps in existing food safety strategies.
A tailored approach
There is no one-size-fits-all approach to food inspection; the most appropriate method is influenced by numerous factors and is unique to the particular needs of each food manufacturer.
Hazard analysis identifies which foreign objects are most likely to be introduced, depending on the food item itself and its provenance.
Product composition, as well as the packaging material and potential contaminants, will determine which detection technology to use, and at which point in the process it should be implemented.
Metal detectors can be installed at almost any stage of production, and can accommodate a wide range of operation and production conditions. They are known for being cost-effective and having a long operational lifetime, but X-ray systems offer detection of both metallic and non-metallic contaminants, such as glass, ceramic, and stones.
Typically, X-ray inspection systems are included at the end of the production line after packaging, but can be used at critical control points throughout the manufacturing process.
Both X-ray inspection systems and metal detectors can be used for identifying metal contaminants – including ferrous, non-ferrous, and stainless steel metals – but it is worth noting that neither technique is suitable for non-conductive, low-density objects like wood, pits, hair and insects.
X-rays generally detect contaminants of a higher density more effectively than those of a lower density and, for metal detectors, higher operating frequencies are more effective for picking up stainless steel foreign objects, whereas lower operating frequencies lead to better detection of ferrous contaminants.
It is also important to consider potential ‘product effect’, signals caused by the intrinsic conductive and magnetic properties of the food item itself.
This can sometimes be strong enough for the food to be flagged as a contaminant by metal detectors, especially in materials with high moisture and salt content, such as pickles and cheese. X-ray inspection systems can therefore be more effective for this type of application.
Packaging trends also continue to be a critical factor in choosing the detection technique, and create greater demand for novel inspection solutions. For example, many food manufacturers are moving towards metalised films or foil-based packaging to improve the shelf life, visual appeal, and cost efficiency of products. In this instance, X-ray inspection systems are recommended, since this type of packaging creates too much signal and reduces contaminant detection sensitivity, ultimately causing false rejects when metal detectors are used.
The early bird catches the worm
The critical control points (CCPs) are the stages in the manufacturing process that require rigorous monitoring, as they have a significant impact on downstream processes and the finished goods.
Common CCPs are at the beginning of the process (after cutting, grinding, or mixing); immediately after a bag or box is filled; and at the end of the production line after packaging. For example, factories handling bulk raw products, such as almonds, may install X-ray inspection or metal detection at the front-end where raw material comes in from the farms, in the middle, where preliminary and advanced processing occurs, and at the final boxing and packing stage.
Additionally, contaminants can be introduced at any point during manufacturing due to wear and tear of the processing equipment, human error, or insufficient cleaning schedules, so inline inspection is vital to remove unwanted objects as soon as possible.
Raw material intake is the beginning of the food manufacturing journey, and detecting and eliminating foreign objects before processing improves product quality and food safety for consumers.
From an industrial point of view, raw material product inspection reduces food waste, increases throughput, and helps to protect downstream equipment from damage, improving profitability and safeguarding the economic wellbeing of the food industry.
The future of food inspection
Recent engineering and software improvements, and earlier inspection of raw materials, continue to raise the standards of hazard detection, promising greater food safety for customers.
Detection hardware and software is always being updated and fine-tuned, with the aim of identifying a greater range of contaminant types and sizes.
More and more customers are now requesting the detection of low-density contaminants – such as stones, golf ball pieces, and plastic – further driving these hardware and software innovations.
There is currently no single solution that is capable of identifying all the possible unexpected objects across all types of food products. However, by correctly identifying manufacturing needs and potential hazards, X-ray inspection systems and metal detection can be indispensable additions to food manufacturing sites.
This article first appeared in the October-November edition of Food & Drink Business magazine.
