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Linking food safety and packaging

03 December 2018

New packaging trends and formats require specially adapted product inspection solutions to provide consumers with reliable protection from physical contaminants. Russell Watson explains the important link between food safety and packaging. 

New packaging formats are booming. Demographic change, changes to consumer shopping and consumption habits and an increasing demand from retailers are driving innovations in food packaging. 

At the same time, retailer demands for modern food packaging go far beyond the traditional function of protecting the product. Along with good barrier properties, protection against breakage during transport and taste neutrality, retailers now also demand shelf-ready packaging that is stable and stackable and is available in different sizes to serve the widest range of buyers across all channels. Retailers also require the lowest possible weight and minimal material use to keep transport costs, waste and potential environmental impact low.

Trend leaders for food packaging primarily include packaging made of flexible material, multi-layer plastics and foils such as those used for stand-up pouches. These provide excellent barrier properties, even with low film thickness and offer noticeable weight efficiency compared to metal cans and rigid plastic containers, reducing transport costs and saving resources. The same applies to the single-use sachets that, for example, are increasingly being used in ready meals. 

Further growth is also forecast for aluminium as a raw material for packaging, primarily in film composites with plastics. The raw material’s absolute barrier function is impressive and good forming properties, coupled with a stable shape, make aluminium particularly suited for food with paste-like consistency packed in tubes. The size and shape of the range of packaging used for drink and food cans made of aluminium alloys has increased: indented can edges provide weight and material efficiency and a highly stable shape. Heatproof and sterilisation-proof aluminium shells and containers provide consumers with the simplest handling for oven-ready meals and are the preferred containers for frozen products and portion packaging. 

At the same time, sustainability and environment are high on shoppers’ agendas. Plastic pollution is recognised as a significant threat to the marine environment and has led to increasing attention from consumers and governments on the reduction of waste from single-use products. According to Mintel, a market intelligence agency, 72 % of UK consumers would be interested in buying products with packaging made from recycled plastic. The packaging industry reflects this trend. New bioplastics made from plants, sugar bagasse and palm leaf are all emerging as plastic alternatives that can quickly biodegrade. Furthermore, the downgauging of plastic films minimises the use of resources.

Foreign body inspection
New and more diverse types of packaging and materials bring with them a range of challenges. From a product inspection perspective, they introduce more complexity for the food industry in detecting potential physical contaminants on production and packaging lines. Food manufacturers must ensure that their product inspection systems can be adjusted for a change in packaging as quickly as possible and with a high degree of automation, using high-performance software and intuitive user interfaces to keep changeover times short and overall equipment efficiency high. A highly automated inspection solution – for example, through simple access to product profiles stored in databases and easy handling when setting up new products – also minimises the risk of operating errors. Inspection systems with interactive, touchscreen-based user interfaces that guide the employee through the operating process are therefore recommended.

Optimising detection
Factors such as the size and location of the contaminant, the speed of the production line, the product packaging material and the difference in density between the contaminant and the product influence the sensitivity and performance of metal detection devices and X-ray inspection systems. Given the increasing complexity of packaging types and materials, the detection of contaminants at an early stage of processing and production is recommended. In many production processes, raw materials are supplied in liquid, paste or slurry format and pumped through pipework systems before being mixed and blended. These materials are normally more homogeneous and easier to inspect than the processed food, and the contaminants in such incoming materials tend to be larger and easier to detect. Early detection and removal of foreign bodies also protects the production equipment downstream from possible damage by contaminants during further processing, while product loss and food waste are also minimised.

Product inspection for contaminants after processing and packaging demands particular care in the choice of product inspection system. For example, when it comes to aluminium contaminants in non-metal packaging, metal detection would be deemed the most suitable technology. Aluminium is a lightweight metal and a good electrical conductor, but its radiographic absorption is lower compared to other metals such as ferrous and stainless steel. This causes a reduction in the sensitivity on an X-ray inspection system and means that it can only detect aluminium at twice the size of ferrous or stainless steel contaminants. In contrast, due to its good conduction properties, aluminium can be detected at smaller sizes using metal detection, which makes it a better solution. 

By contrast, when attempting to detect metal contaminants in aluminium foil packaging, metal detectors struggle to spot the contaminants amidst the packaging. Due to the way in which an x-ray system works, aluminium packaging has a negligible impact on detection levels. X-ray inspection can see straight through the low-density foil to get a better view of the metal contaminants within and offers the better solution in this case. 

Particular challenges 
Flexible packaging such as stand-up pouches, as well as glass jars and weight-optimised tin cans with vaulted bottoms, bring with them the hidden danger of blind spots. Contaminants can become lodged in the edges of these types of packaging, making detection more difficult. A particular challenge is presented by glass-in-glass contamination – for example, where the glass at the rim of the jar has broken off, fallen into the container and, in the worst-case scenario, became lodged in the edges of the jar’s vaulted bottom. In general, recognising contaminants at the base and sides – particularly in glass containers and tin cans – presents major technical demands for inspection technology. Modern X-ray solutions inspect every product from two angles, comparing the two images to optimise the chance of detection. 

Further technological developments also make identifying very small contaminants quicker and more reliable. For example, the new X34 x-ray inspection system from Mettler-Toledo provides a combination of technologies which enables producers to detect smaller contaminants at high-throughputs. One of its key features is its enhanced ‘Optimum Power’ generator, which automatically maximises detection sensitivity by optimising power and contrast levels for every product. The software of the X34 also allows for automated product set-up without the need for manual adjustment by the operator, increasing production uptime and overall equipment effectiveness.

Product inspection demands are increasing against a backdrop of progressively diverse packaging types. In many cases, metal detection or X-ray inspection technology will provide the correct solution for reliable foreign object detection. However, there are also scenarios in which it is necessary to install metal detection technology and X-ray inspection equipment in different positions on the same production or packaging line. It is, therefore, always advisable to seek advice from inspection experts and to conduct product tests to determine the most suitable technology for foreign body detection. 

Russell Watson is sales manager – UK & Ireland, at Mettler Toledo Inspection.

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