Meat Processing: The Challenges in Foreign Object Detection

Meat processing is fundamentally associated with risks that pose challenges to food processors in terms of the quality and safety of products. Avoiding the chance of foreign object contamination is a key priority.

Preventing biological contamination in meat processing calls for diligence in adhering to sanitary procedures, such as frequent and harsh cleaning processes with broad temperature fluctuations. Such a stringent sanitation process creates costly, although necessary, downtime. But that's only part of ensuring the safety of meat products.

Food processors should also make sure that the right equipment and procedures are in place so that foreign objects do not enter their process at any stage, in particular when supplier ingredients are being added.

Historically, it has been hard to detect physical contaminants with metal detection technology because meat products are known to have a high product effect that can imitate a foreign object, usually requiring a trade-off in sensitivity to prevent false rejections.

With product size, salt content and temperatures typically varying during the processing stage, the product effect can also differ considerably, thus making it difficult to consistently detect foreign objects. It also presents an ongoing challenge to prevent a high level of false rejects which raise the possibility for expensive rework or scrap.

Novel metal detection technologies can help resolve these meat inspection difficulties. Using five user-changeable frequencies at a time, Multiscan metal detection scans can help raise the probability of detection and thus enhance sensitivity, resulting in greater food safety.

When Multiscan is combined with a design to tolerate aggressive chemicals necessary to sanitize and survive thermal shock, as well as software to adapt to continuous product variations, food processors can realize a new level of food safety that was not possible before in meat applications.

The innovative technology is now exclusively available in the Thermo Scientific™ Sentinel™ 5000 Multiscan Metal Detector.

Meat Processing: The Challenges in Foreign Object Detection

Figure 1. Image Credit: Thermo Fisher Scientific – Solutions for Industrial and Safety Applications

Flexibility to Compensate for High Product Effect

The majority of meat-based products will show a high product effect in an electromagnetic field, providing challenges to traditional metal detectors. A few examples of meat applications include:

  • Sausages
  • Deli-style layered slices
  • Salted and spiced processed products
  • Ready-to-eat meals containing meat
  • Bloody or moist whole muscle cuts

Packaged meat can be extremely conductive because of its moisture content. Conductivity will be even higher if salt is present. When the product passes through a metal detector, the excitation signal can generate a strong product effect that requires compensation. To avoid a false rejection, a metal detector needs to ignore this product effect.

A standard method to decrease product effect and thus enhance detection performance is to use low energy, low frequency excitation. This process is made easy by the Thermo Scientific™ Sentinel™ Multiscan metal detector because frequencies can be chosen from 50 to 900 kHz by simply pushing a button.

If a difficult product is encountered, technicians can implement a low frequency schedule that is more suited to an extremely conductive product and optimizes  performance. Since this method is not invariably needed, the flexibility to run any frequency on any product is an added benefit with Multiscan.

Meat Processing: The Challenges in Foreign Object Detection

Figure 2. Image Credit: Thermo Fisher Scientific – Solutions for Industrial and Safety Applications

Table 1. Source: Thermo Fisher Scientific – Solutions for Industrial and Safety Applications

Ideal frequency
Stainless steel
Garlic herb pork 100 – 300 kHz 1.4 1.9 3.25
Sliced roast beef 100 – 300 kHz 1.1 1.8 3.0
Angus loin 300 – 900 kHz 1.1 1.6 2.25
Packaged bacon 300 – 900 kHz 1.2 1.6 2.25
Mediterranean chicken 300 – 900 kHz 1.2 1.6 2.25


The Sentinel Multiscan metal detector usually outpaces the performance of single frequency metal detectors by as much as 10% to 30%. Since the frequencies are fully adjustable, the Sentinel detector is not only more flexible but also covers a broader range of applications.

Most often, pork and beef reach the processing facilities in slabs—huge, uneven, frozen chunks. These slabs need to be inspected because they can contain hooks, buckshot, or other big metal contaminants that will damage slicing and grinding machines downstream.

For course inspection, large-aperture metal detectors provide an excellent first line of defense and are often utilized. But a problem with this method is that the incoming slabs may not be consistently frozen prior to inspection, which can alter the product effect identified by the metal detector. If this 'drift' is not addressed, the metal detector will ultimately create a false reject and the detector will need to learn the product another time. This leads to downtime and requires interventions by a skilled operator.

To describe the changes of product effect during a thaw, information was collected on a beef slab weighing 3 lb that was initially a frozen solid and was subsequently thawed for 45 minutes. The outcomes are summed up below.

Example of variable product signal during thaw of beef.

Figure 3. Example of variable product signal during thaw of beef. Image Credit: Thermo Fisher Scientific – Solutions for Industrial and Safety Applications

The above image demonstrates that when there is an increase in the product signal over time, the phase angle used to offset this signal also changes. Such changes may lead to false rejects over this duration of time.

Software to Learn Variability and Adapt to Changes

The Sentinel Multiscan metal detector includes an auto-learn routine that can adjust according to the change in product signal. This routine accepts numerous products at different temperatures with both contaminant-free and target contaminants. 

To improve the setup, the information from this product then sets all the operating parameters automatically. If the metal detector is taught this way, one can rapidly arrive at a setup that would normally take an expert technician many hours or even days to finish.

And once in production, the latest reject data can be quickly reviewed to see if a modification to a parameter is needed to prevent false rejects. To manage phase variations over time, a phase tracking capability is included in the Sentinel metal detector.

This phase tracking capability monitors work by automatically modifying the product phase in real-time while the meat is being inspected. With the help of a proprietary algorithm, data from uncontaminated meat is fed back and performance is maintained as the ratio of magnetic and conductive product signal changes.

The outcome of this adaptive, intelligent software is that throughput is increased and user intervention is reduced. This is applicable even in complex and variable product effect meat applications.

Designed to Survive Thermal Shock and Harsh Chemicals

Washdown needs in the meat sector can be highly challenging. The USDA specifies sanitation standards that can necessitate the use of high pressure, high temperature  washdown with caustic chemicals.

While some metal detectors are designed to meet the IP69K rating (80°C water at up to 1450 PSI), this alone does not offer long-term protection from water entering into the metal detector case. In a standard meat processing facility, the system is used at an ambient temperature of 40°C but it may be cleaned many times a day, using 80°C water.

This thermal shock cycling can create cracks in the seal between the metal case and the epoxy aperture, such that water can enter into the detection coils. The outcome is an irreversible imbalance that can only be addressed by a costly factory repair that would be usually needed every few years.

The Sentinel Multiscan metal detector has a Heavy Duty (HD) option for the meat sector to increase uptime in these harsh conditions. The metal detector was tested and tolerated up to 10,000 thermal shocks without any sign of performance degradation. The improvements of the HD design are:

  • Complete fill with epoxy avoiding space where water could be confined
  • Soft epoxy fill and liner impervious to separation from the metal case
  • Welded aperture flanges strengthen the liner seams

Example of high pressure washdown.

Figure 4. Example of high pressure washdown. Image Credit: Thermo Fisher Scientific – Solutions for Industrial and Safety Applications

The HD option, apart from these design features, also has an anti-corrosive 316 stainless steel case (medical grade). This prevents rust if aggressive cleaning chemicals are not fully removed at the time of rinsing.

All told, the system has the highest uptime, does not degrade in performance and eliminates long-term repair costs.

How to Detect Non-Metallic Contaminants

In the meat-processing environment, all of the contaminants are not metallic. At times, low-density plastics, stones, bones and even glass can enter the process. Non-metallic contaminants cannot be found with a metal detector. 

Therefore, X-ray inspection is needed. X-ray inspection works by finding variations in thickness and density inside the product. It can detect a range of conductive and non-conductive contaminants. A product test is needed to confirm sufficient sensitivity. 

The use of metal detection coupled with X-ray may also surpass that of a metal detector. The Thermo Scientific™ Xpert™ series of X-ray systems meet the IP69-rated needs for meat applications.

X-ray can detect bones where metal detectors cannot.

Figure 5. X-ray may be able to detect bones while metal detectors cannot. Image Credit: Thermo Fisher Scientific – Solutions for Industrial and Safety Applications

Key Takeaways

Meat applications are among the most challenging for foreign object detection and food safety.  The Sentinel Multiscan metal detector enables food processors to achieve a higher level of food safety.

The Multiscan technology boosts both the sensitivity and probability of detection and, at the same time, provides an unrivaled level of flexibility.

An intelligent Autolearn function makes set up both fast and simple, and an HD construction option can withstand harsh washdown. 

The outcome is a new level of operational efficiency and food safety. Considering the challenges faced by meat processors in protecting their brand and consumers, it is important to put the most effective metal detection technology in place to prevent recalls and ensure brand protection and consumer safety. 

 To determine the right detection technology it is prudent to arrange for a demonstration or complimentary product test to find the right detection solution for the job.

This information has been sourced, reviewed and adapted from materials provided by Thermo Fisher Scientific – Solutions for Industrial and Safety Applications.

For more information on this source, please visit Thermo Fisher Scientific – Solutions for Industrial and Safety Applications.


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