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Weighing up the benefits of food conformity

15 April 2019

Russell Morgan highlights the business benefits of investing in checkweighing technology. 

Weight regulations aim to protect consumers against short weight or measures. In order to conform, food processors must ensure that all packaged food products are as accurate in weight as possible to advertised values. Investment in technology to achieve this should not be viewed simply as a compliance issue; there are a number of positive business benefits that accrue from delivering accurately weighed products.

Regulations governing food weight conformity differ slightly around the world. In the UK, the Weights and Measures (Packaged Goods) Regulations 2006 stipulate three main rules:

1. The actual contents of the packages should not be less, on average, than the nominal quantity. 
2. The proportion of packages which are short of the stated quantity by a defined amount - the Tolerable Negative Error (TNE) - should be less than a specified level. 
3. No package should be short by more than twice the TNE. 

By contrast, Europe places the onus to comply with the Measuring Instruments Directive (MID) on the supplier of the weighing equipment. The MID covers the exact production and performance requirements of the equipment at purchase stage, plus legal verification on installation. This ensures that manufacturers only purchase good quality weighing instruments. Following installation, the manufacturer must check ongoing compliance with local Weights and Measures standards. 

Arguably, North America has the most lenient legal framework regarding weights and measures. The Food and Drug Administration (FDA) has no minimum weight restriction on food packaging. However, it will consider a product misbranded unless the label accurately reflects the content in terms of weight, measure, or numerical count. 

Technical solutions
Modern food production involves high volumes and high speed, so any compliance checks must keep pace with this fast-moving, increasingly automated environment. The only technology which ensures compliance with weights and measures regulations is a checkweigher. This type of product inspection system works by weighing each packaged product in real time, classifying all items by pre-defined weight parameters and rejecting any non-conforming goods for further investigation. 

The checkweigher is initially calibrated during installation. To comply with regulations, such as MID, the system must be officially verified with test samples at locally pre-defined intervals. It is also vital that all products are stable when presented to the checkweigher, as any vibrations or movements will affect weighing accuracy. Transfer solutions, such as guide rails, sidegrip belts, starwheels or timing screws are used to stabilise products. 

For full regulatory compliance, each product must be presented to the checkweigher individually. Spacing or timing conveyors are used to create a gap between packs to optimise the weighing process for manufacturers with multiple products and/or numerous lanes. To complement fast production line speeds, the conveyors speed up the individual products through the checkweigher. 

Business benefits
While the primary reason for integrating a checkweigher is to comply with weight regulations and supplier agreements, return on investment does not stop there: precision weighing can offer a range of additional business benefits. 

For example, it can help manufacturers to deliver customer satisfaction and protect brand reputation from underfilled products, as well as avoiding product recalls. Checkweighers can also enhance productivity and offer cost savings by measuring and reporting production line efficiency. Real time monitoring and reporting capabilities – including production counts, batch tracking and weight – enables food manufacturers to provide due diligence to authorities. One optional feedback feature on Mettler-Toledo checkweighers can detect deviations away from the target content weight and automatically adjust filling machines further up the line. Another software option facilitates lot quantity checking by regulators. Called Action Counter, it rejects a pre-defined number of accepted products for further scrutiny without stopping or slowing down production. 

Perhaps the most important business benefit is the contribution that checkweighers can make to bottom-line profits by enabling overfill product to be reworked. For example, a manufacturer produces 450 gram packs at a throughput rate of 200 packs per minute, 16 hours a day. Using checkweighing to reduce an overfill of 1 gram, and assuming each gram costs 0.1 pence, could potentially save £19,200 each year. 

Applied thinking
Lamb Weston/Meijer, a frozen potato product manufacturer, is one company to embrace the benefits of checkweighing. Its Dutch plant processes fifteen tonnes of potatoes per hour, with products supplied to quick-service restaurants and food services in 80 countries throughout Europe, the Middle East and Africa. The company has worked with the Product Inspection division of Mettler-Toledo for 25 years to fulfil the quality and food safety standards recognised by the Global Food Safety Initiative (GFSI).

Recently, the company updated its production lines with five new Mettler-Toledo Checkweighers to meet the requirements of net content laws for packaged products, to ensure customer satisfaction and to eliminate product giveaway. The automatic checkweighers are installed downstream of a multi-head weigher where French fries are portioned before being packed in 1kg bags. The bags are then weighed, with non-conforming products being rejected. A light barrier monitors whether the rejection of underweight or overweight products was successful.

Commenting on the application, Sjerk Zoodsma, technical director at Lamb Weston, said: "We are very satisfied with the retrofitting of our production lines. The new checkweighers are aligned with our production speed, ensuring higher throughput and maximum uptime."

New horizons
As more complex conformity requirements continue to emerge, checkweighers are being combined with other technologies, such as metal detection, X-ray detection or vision. 

Checkweighing uses gross mass measurement to check the overall weight of each pack and will reject any non-conforming products outside of a specified weight range. However, zoned mass measurement using X-ray detection is a better solution when multiple areas need to be inspected and the mass of individual items in a pack must be examined – for example in ready meals. This is important because an underfill in one compartment could be compensated by an overfill in another compartment. In this instance, the total weight of the ready meal may meet requirements and remain undetected by a checkweigher: but it would be rejected for non-conformance by the X-ray technology.

Russell Morgan is a product inspection specialist at Mettler-Toledo. 


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