Frozen food production is a high volume, high speed business. Pizzas, ready meals, chips and vegetables all travel quickly from processing to packing, destined for cold storage and supermarket freezers. But along this fast-paced journey, one small variable can have a big impact: temperature. As frozen products move through production lines and can begin to thaw, even slightly, their behaviour in metal detection fields can change. This often results in false rejects or a loss of sensitivity. The consequences are not just technical. They are commercial. Wasted product, rework and unnecessary downtime all hurt the bottom line.
False rejects remain one of the most persistent and expensive problems in frozen food inspection. While the products themselves may be perfectly safe, small temperature shifts alter the products signal when passing through the metal detector which can trigger unnecessary rejections. This does not reflect a fault in the metal detector but a mismatch between changing conditions and the normal inspection parameters.
Advanced metal detection systems with adaptive signal processing are changing this. Systems like the Profile Advantage from Mettler-Toledo use Multi-Simultaneous Frequency technology with multiple inspection modes and an intelligent inspection algorithm (3S) which eliminates the active product signal in real time. This enables the metal detector to maintain accurate detection sensitivity without increasing false reject rates. The result is increased brand protection, less waste, more reliability and improved productivity.
Reducing giveaway in frozen fries
One frozen French fries manufacturer faced exactly this issue. Running at a rate of one hundred packs per minute, they needed to detect all metals down to two millimetres or less while minimising false rejects to a level of less than 1 in a million. Temperature fluctuations caused by occasional line stoppages were interfering with detection levels and increasing waste.
To tackle the challenge, the manufacturer installed the Mettler-Toledo Profile Advantage metal detection system and trialled the unit over a 4-week period to assess how the technology handled signal variation. One of the Multi-Simultaneous Frequency modes proved most effective, achieving detection levels of 1.4 millimetres for ferrous, 1.8 millimetres for non-ferrous and 2.0 millimetres for stainless steel with zero false rejects.
A key factor for the customer was the system’s built in histogram screen, which displays the product signal in real time. This feature helped operators visualise the product signal and track changes and respond quickly if required. The system also includes a thawing product alarm feature that triggers an alarm should signal levels move outside expected parameters, allowing the team to intervene before waste occurs.
Smarter technology for a changing environment
Frozen food production is subject to a wide range of variables. Moisture levels, packaging formats and environmental conditions all influence how products interact with metal detection equipment. Today’s metal detection systems are built to manage these changes.
Automatic moisture monitoring, Multi-Simultaneous Frequency that incorporates high frequency operation and adaptive signal processing help manufacturers maintain high levels of sensitivity across varying conditions. This reduces the risk of over rejection and supports a more stable production process.
In many facilities, metal detection is integrated into a wider product inspection strategy. Combination inspection systems combine metal detection with weight verification, label checks and package integrity inspection. This provides a compact, multi-function solution well suited to frozen food lines with limited space or varied packaging formats.
Accurate reject mechanisms are also critical. Audible and visual signals guide teams to the affected product quickly, reducing the time and disruption caused by contaminant events. These systems make it easier to keep lines moving and focus interventions where they are needed.
Real world impact
Across frozen categories from bakery to vegetables, inspection control is evolving. Metal detection is no longer just about removing risk. It is about creating a more efficient, consistent and profitable operation. Sensitivity remains important, but consistency and adaptability are now just as critical. Systems that adjust to thawing and other environmental changes without compromising performance are key to helping manufacturers stay ahead.
False rejects do more than waste product. They demand more from staff, slow down production and create unnecessary cost. Better signal processing reduces the number of good packs mistakenly rejected, supporting both yield and sustainability.
Frozen lines often run multiple product types. The ability to switch quickly between settings while maintaining high performance is essential. Metal detection solutions like the Profile Advantage offer flexible setup, intuitive controls and detailed reporting tools. This supports traceability, continuous improvement and performance benchmarking across sites.
Conclusion
In an industry where margins are tight and speed is critical, the right inspection technology delivers more than compliance. It supports uptime, quality and smarter decision making. Frozen products will always be subject to temperature changes. But with adaptive metal detection, false rejects do not have to follow. This offers manufacturers a clear way to combat rising costs, boost productivity and protect brand reputation with confidence.
For more information, click here or visit: www.mt.com/pi-profile-pr
By Rob Stevens, Market Manager, Mettler-Toledo Safeline Metal Detection
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