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Addressing waste by reducing false rejects

02 September 2019

Russell Morgan explains how product inspection technology can be used to reduce food waste by maximising yield from raw ingredients, reducing false rejects and ensuring correct weight and fill. 

Currently around one-third of all food produced for human consumption – approximately 1.3 billion tonnes – is either lost or thrown away every year. Food waste also inflicts an environmental toll, creating an unsustainable drain on natural resources such as water, land and energy. 

Cutting food waste on the production line can also help reduce costs and increase profits and can help encourage a wider ethos of operational efficiency, as part of lean principles. 

Perhaps one of the most common sources of food waste is false rejection – when ‘good’ product is erroneously discarded from a production line during safety and quality inspection. Inaccurate weighing is another cause. It can lead to underfilling, which results in product rejection by the retailer, or over-filling, which results in product giveaway. Contamination detection, meanwhile, may result in the rejection of a whole batch rather than the contaminated product alone, or wastage – where a false reading indicates the presence of contamination where none is present. In addition, wastage can be caused by inaccurate labelling, damaged packaging, closure errors or missing items – all of which can trigger costly product recalls and disposal.

Best practice approach
Fortunately, help is at hand. Food manufacturers and packagers can apply product inspection technologies such as metal detection, X-ray, vision systems and checkweighers to help reduce food loss and waste. Often, it is a combination of these technologies that deliver the highest levels of operational efficiency, ensuring products meet regulatory and brand standards, preventing rejections or recalls.

Even though every food production facility is different, there are some general best-practice approaches to food waste that can be applied. Integrating contamination detection technologies early in the production process will remove any ingredients containing unwanted foreign bodies. This protects downline processing equipment and ensures contaminants are removed before additional value is added. Where contaminants are detected early, there is also more potential to re-work ingredients. This can, in turn, help minimise food waste and associated costs.

False rejection needs to be reduced or ideally eliminated, but the wide product variation in a typical food production environment means this is no easy task. It is vital that contamination detection technologies such as X-ray and metal detection are adjusted correctly so only non-conforming products are rejected. This is achieved by regularly testing detection sensitivity levels and by making the most of fully automated product-set up and changeovers to ensure that detection sensitivity is always at optimum levels, regardless of whether food is being processed as bulk, pumped or packaged product. 

Advances in metal detection technology promise to virtually eliminate false rejects from certain production lines, while some X-ray systems now combine fully automated product set-up with an optimum power generator and intelligent proprietary X-ray software to improve uptime, enhance detection sensitivity and minimise false rejection rates.

Recent developments in product rejection mechanisms mean non-conforming products can now be removed with greater accuracy, reducing unnecessary waste on the line. Instead of removing a full belt width of product when a contaminant is detected, the latest X-ray systems use multi-lane scoop devices to accurately reject the area of the belt containing the contaminated product. Likewise, multi-lane air blast rejection devices can remove a smaller, more targeted section of product on the belt – limiting waste. In metal detection applications, meanwhile, advanced sealing technology used in gravity fall systems can now offer a dust-tight seal that reduces the chance of high value fine powders escaping into the reject channel. 

Precision weighing is also an important technological component of reducing food waste. To comply with Weights & Measures legislation and prevent recalls, each product must be equal to or within tolerance of the weight stated on the label. Any underfilled products detected before leaving the line can be reworked, helping to avoid waste. The flipside of this is that manufacturers can also prevent costly giveaway. Accuracy is everything, therefore, and inline checkweighers can be calibrated to exacting customer specifications, with automatic feedback to the filler control. 

Filling and labelling accuracy
Product inspection technologies can also be used for assessing under- and over-filling, depending on the application. For example, X-ray systems can be used to perform zoned mass measurement and fill level inspection, such as highlighting if one compartment is under and another is over-filled in a two-compartment ready meal. Checkweighers, in isolation, can accurately measure the combined weight, but X-ray provides a more specific result for different parts within one packaged product.

Vision inspection technologies can perform numerous quality assurance checks, including inspecting fill levels and closures: such as identifying missing caps, trapped product under the seal or verifying tamper-proof seals. Verifying the accuracy of the label, including its position and content – such as allergen declarations – will also avoid unnecessary product recalls. Vision systems inspect each label in real-time, based on established parameters such as lot numbers, bar codes, and use-by dates. Accurate use-by dates also help avoid unnecessary waste.

Future developments
There are some emerging technologies and trends that will play an important role in reducing food waste. Metal detectors, X-ray systems, vision systems and checkweighers are becoming increasingly digital and connected, with increased data collection underpinning even higher accuracy around false rejection and fill levels. In the longer term, blockchain holds real potential in the food sector as a means of providing greater trust and visibility in the farm-to-fork food chain, allowing specific products to be traced at any given time. This could prove a highly-effective means of helping to reduce food waste. Blockchain is also being trialled as a method of connecting retail businesses with local charities, to facilitate delivery of unsold food.

Russell Morgan is sales manager for UK & Ireland at Mettler Toledo.

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