Detection reflection

by Bryan Salvage
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KANSAS CITY, Mo. – Producing top-quality, safe meat and poultry products is the daily goal of every processor and has been forever. But sometimes foreign material inadvertently ends up in products due to equipment failure, accidental input or employee carelessness. Foreign material, or non-animal objects, is defined by the Food Safety and Inspection Service, as metal, plastic, rubber, glass, wood, steel, or lead shot. Fortunately, a range of detection technology is available to help packers and processors search for such unwanted materials.

While recently researching this topic for an upcoming article, I was reminded by Richard Hebel, product manager, Fat Analysis, Eagle Product Inspection, that the main technologies used to detect such contaminants include metal detection, x-ray detection, visible/infrared (IR)/hyperspectral imaging systems (camera/laser-based) and mechanical.

Each technology has its own strength with contaminant detection. Metal detection is sufficient to identify metal contaminants in a meat product. When a metal object in a product unbalances a balanced radio frequency (RF)/magnetic field, an electrical signal is generated making it useful for detection of ferrous and non-ferrous metal within the product or on its surface.

X-ray detection systems can detect metal along with other materials. Foreign materials with densities differing from that of the meat attenuate x-rays. These differences appear on an x-ray image that can be analyzed. This makes it useful to detect ferrous and non-ferrous metal, rock, glass, calcified bone, plastics and other materials that present a significant density different to the meat. These can be located within or on the surface of the meat product, Hebel relayed.

He also pointed out there are visible/IR/hyperspectral imaging systems that are camera/laser-based. Camera analogy identifies differences in the intensity or color (wavelength) of light reflected from the foreign material versus the meat creating an image that can be analyzed — which is particularly useful for detecting foreign material on the surface of meat products. One final detection method is mechanical. Mechanical actions interact with the mechanical characteristics of the foreign material to separate it from the meat, making it useful for separating light (films), string, plastic foam and cloth from around the meat.

There are three detection technologies that seem to perform the best: metal detectors, imaging systems and x-ray inspection, according to Hebel. Metal detectors are the cost-effective solution for metallic foreign material, but this is also their limitation. Imaging systems provide detection of foreign material on exposed surfaces of meat. The most enhanced of the three technologies is x-ray inspection, which allows foreign-body detection capable of inspecting for metallic and non-metallic contaminants and presents an adequate density difference to the meat before rejecting the substandard product.

Plastics present serious challenges because they are undetectable with metal detectors, plus their densities tend to be very similar to meat -- making detection by x-ray challenging. The most common types of plastic found in meat are probably low-density polyethylene (LDPE) and polyethylene (PE) films often used in bulk-meat packaging, and pieces of plastic/rubber gloves. If these types of plastics are exposed on the surface of the meat, then an imaging system solution should be suitable, Hebel said. Most plastic gloves used in the meat and poultry industry are blue so they contrast with meat. When plastic is colored and exposed on the meat’s surface, an imaging system is a possible solution.

But some films are colorless and transparent, making them difficult to detect. In these cases, if the film is exposed on the meat’s surface, a processor could potentially detect this plastic with laser-based scanners. This type of imaging system can detect textural and scattering characteristics of meat and foreign materials and can be combined with camera-based technologies. Solutions targeting plastic exposed on the surface of the meat can be helpful in reducing the incidence of this type of contaminant. As these solutions are restricted in detecting plastics when they are entrapped within the meat, sometimes they will not be able to reject these substandard products. In some situations, using an air knife to separate loose, light materials (like plastic film, ear-plugs) from meat portions may be helpful.

Hebel relayed there appears to be no single solution for this contaminant problem. The key to removing these contaminants is to do it as early in the process as possible, but certainly before size reduction, battering or condiment applications. These operations further obscure already difficult-to-detect plastic contaminants.

Being a low-margin industry, some processors may resist installing the appropriate number of detection units they should have inside their plants. But being penny-wise and pound foolish isn’t a good idea when it comes to protecting your products, customers and consumers.

(Look for the special foreign material detection article exclusively in the July issue of Meat&Poultry magazine.)

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