How good is good enough when it comes to food safety? And what level of risk are we willing to accept? Foodmach director Phil Biggs looks at how to avoid the horror of metal contaminants in food and beverage manufacturing. This article first appeared in the August 2021 issue of Food and Drink Business.
The cost of food safety failure can be enormous, resulting in serious damage to both consumer health and your brand. Metal detectors are a given in food processing facilities. They are most commonly used at the end of the line and as the last line of defence to support food quality and safety before a packaged product is on its way to the consumer. But the core technology has always had its limitations. Signal interference from external noise, the product ingredients and packaging, and the size, shape, orientation and sensitivity of the metal in the contaminant can all contribute to false detections or worse, no detection.
While metal detection technology has evolved slowly over the years, food processors' challenges have changed rapidly. There are increasing regulatory demands, retailer detection mandates and greater productivity demands. The stakes are higher, too: the potential for a costly recall and collateral damage via social media. Global Food Safety Standards dictate that fragments above 7mm be detected and removed. However, research shows that customers prefer anything above 2mm removed (or ideally, nothing at all).
Although production lines are designed to minimise the number of metal-on-metal parts, given how industrialised our food system is, the potential for ‘extraneous metal materials’ exists and can cause product recalls.
Thermo Scientific’s Sentinel MultiScan detectors enable users to identify contaminants that are up to 70% smaller in volume than previous technologies.
Every detection system has a probability of an escape. For instance, assuming that one out of every one million packs contains a metal fragment; at a pack/second, 16 hours a day, 5 days a week, that’s a potential escape about every 3-4 weeks.
Depending on the efficiency of your metal detector, it’s like playing roulette.
The challenges
So why is it so hard to detect metals in food? A simple analogy may help: why does a coin or piece of jewellery set off a metal detector on your outbound flight but not your inbound flight? Why the inconsistencies? The same unpredictable performance can exist when trying to detect metal in food. Metal detection is easy – when it works – but it doesn’t always work.
The core principle of operation for food metal detectors is that a transmitter excites a radio frequency signal. As food contaminated with metal transverses the aperture, it interferes with the signal and triggers a detection.
There are three key barriers to achieving 100 per cent metal-free products:
1. The metal detector must find anything, anywhere in any product all the time. That can be daunting considering the production volume from just one line in a day and all the different types of metal pieces that might be part of your factory or in the ingredients. As well, most metal detectors don’t easily discriminate between metal shards and foil packaging. The metal signal is already high because of the foil, and it makes it hard to detect a small foreign object.
2. Metal detectors use electromagnetic fields to find things that are magnetic and conductive. Most food products are wet, have salt or contain minerals which when subjected to electromagnetic fields also look magnetic and conductive. Ignoring the ‘product effect’ as it’s termed and finding the metal is not as easy as it seems.
3. Small metal foreign objects have very small signals. The metal detector is operating in a factory with many possible noise sources that can confuse the metal detector electronics and software.
You need metal detection, but an on-again, off-again contaminant detection approach is not acceptable… You need multiple frequencies, and more is better.
While some companies are transitioning to X-ray inspection to find foreign objects, the costs can be prohibitive for smaller producers and hard to justify in many applications due to low risk of non-metallic contaminants. The prices of X-ray equipment have come down, but they’re still 2-5 times higher than metal detectors, with more maintenance and a shorter life.
You need metal detection, but an on-again, off-again contaminant detection approach is not acceptable. There is no single best frequency for detecting small field differences because you're dealing with the variables of the metal lurking in your food or beverage product. Using single or dual frequencies isn't safe enough. You need multiple frequencies, and more is better.
What’s needed is a completely new approach to metal detection.
Multiscan technology
Developed by global technology leader Thermo Fisher Scientific, this is the premise behind MultiScan technology. You select a set of up to five frequencies from 50 kHz to 1000 kHz and MultiScan scans through each frequency at a very rapid rate, effectively acting like five metal detectors in one. You get the benefits of running a frequency close to ideal for any type of metal you might encounter. The probability of detection goes upexponentially and escapes are minimised.
Thermo Scientific’s Sentinel MultiScan detectors enable users to identify contaminants that are up to 70 per cent smaller in volume than previous technologies. Via a simple graphical user interface and report, the user can easily see which frequency(ies) is doing all the work. The frequencies are balanced automatically to reduce errors. They use a proprietary multicoil design to boost 'receive' signals, filtering noise interference and detecting foreign objects. It’s five times the metal detection without five times the false rejects.
Sentinel 5000
The Sentinel 5000 provides complete flexibility around frequency use. It features per-frequency adjustments, gain, phase, sensitivity and automatic set-up on 1-10 packs. The software has been designed with a user-friendly interface to allow field set-up and balance in minutes. It is suitable for challenging products and applications such as dairy, meat, poultry, bread and other products or packaging with high signal distortion during production and final fill. The software makes it easy to meet the record keeping and traceability requirements that have become integral to so many food safety programs.
Foodmach is the newly-appointed product inspection distributors for Thermo Fisher Scientific in Australia. If you need a metal detector that can be set up, adjusted and diagnosed in minutes, not hours, then chat to the Foodmach team.
