Multi-Simultaneous Frequency Technology in Food Production: How Advanced Techniques Eliminate Product Effects

Metal detection in frozen foods is particularly challenging – because conductivity changes and product effects lead to false alarms and high costs. Stuart Preston (48), Business Development Manager at Mettler Toledo, explains how modern systems with Multi-Simultaneous Frequency technology and overcome these hurdles.  

To understand the challenges, it's important to distinguish between frozen and deep-frozen products. Deep-frozen products, which are typically stored at ≤ −18 °C, have low or no conductivity and therefore minimal impact on a metal detection field. In contrast, products frozen between 0 °C and -18 °C have conductivity that can affect the detector's signal.

As frozen products begin to thaw, even slightly, as they move along production lines, their conductivity changes. This can lead to false rejections, especially when a production line is stopped and restarted or when there is a decrease in detection sensitivity. Therefore, these changes in conductivity should be taken into account during the initial product training phase of system setup. False rejections remain one of the most persistent and costly problems in frozen food inspection.

Our Profile Advantage metal detection system addresses these challenges with Multi-Simultaneous Frequency (MSF) technology and an intelligent 3S algorithm (signal suppression software). This combination eliminates the active product signal in real time, maintaining high detection sensitivity and virtually eliminating false rejections.

Conventional single-frequency metal detectors widen their detection window to compensate for the effect of conductive products. This reduces detection sensitivity. Modern systems like the Profile Advantage circumvent this problem by operating with multiple frequencies simultaneously. The 3S algorithm collects data during automatic setup and applies it to suppress the product signal, making the product appear virtually "dry." The effect is similar to noise-canceling headphones, except that instead of sound, product noise is suppressed. The result is clearer, more consistent signals and higher detection sensitivity.

Both Profile Advantage systems and Mettler Toledo's M34R series metal detectors use an AI-based machine learning process to analyze the product signal, significantly improving product effect suppression.

The product effect is influenced by six main factors: temperature, humidity or salinity, product format, consistency, orientation in the production line, and size or shape. Products that vary with respect to these factors may generate a stronger background signal, making precise detection more difficult.

Packaging can also be a factor. Aluminum foil is not suitable for inspection with conventional metal detectors—metallized foil, however, is, although it introduces a significant product effect. We always recommend conducting tests before investing.

False alarms usually occur when the product deviates from its originally programmed characteristics. Temperature or humidity fluctuations can alter conductivity and trigger the detector. Therefore, for single-frequency detectors, comprehensive programming that covers all expected deviations is essential. Alternatively, Multi-Simultaneous Frequency systems, combined with intelligent algorithms, automatically adapt to these changes. This eliminates the product effect and significantly reduces the risk of false rejections.

False rejections not only lead to waste but are also time-consuming. Each incident can result in an investigation, production downtime, and potential revenue losses.

Although the underlying technology is complex, the systems are designed for ease of use. The icon-based touchscreen is intuitive and simple to operate. The auto-learn function guides operators step-by-step through the calibration process, which takes only seconds. This simplicity reduces the need for continuous monitoring, frees up personnel time, and minimizes training requirements. For more information about Mettler Toledo Product Inspection, please visit: www.mt.com/pi-pr