Detecting Foreign Matter

Advances in detection technologies are helping to make the food supply safer than ever. Plus, these machines can do other things, as well.

By Mike Pehanich, Plant Operations Editor

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The broader detection range of X-ray systems is a big reason for their popularity in processing plants. That versatility has allowed the technology to broaden its capability not only into detection of diverse substances but into a variety of process- and production-related functions as well.

Smiths Detection, the U.K.-based security corporation, introduced its own X-ray systems eight years ago. "Today our [X-ray] systems can checkweigh as well as check for bone, stone, glass, metal, dense rubber and other contaminants," says Terry Woolford, Smiths Detection director. "They can even count product, shape-sense and detect metal contaminants inside metal containers -- all on one pass of 600 to 700 packages per minute. That's on machines running 100 meters a minute."

Its fifth generation image analysis software (SimulTask 4.0) was designed for ease of use and customized control. Operators can view stored images and change image views. It also features an "auto-learn" for foreign materials detection and weight functions. The system can be set for automatic change for different shifts and batches.

A North American processor of garlic baguettes is employing a Smiths Detection system precisely because of this multi-functional capability. The process calls for the insertion of garlic butter between the slots, or layers, of the baguette.

"The unit can check to make sure there are enough slots in the bread and that there is butter in each slot," says a company representative. "That's in addition to finding contaminants."

A meat producer is using yet another system for fat analysis in addition to its primary detection function. "This is big news for the industry since the lean value of meat is key in industry marketing today," says Woolford.

Finding glass shards -- particularly very small pieces -- in glass jars has challenged some processors. A baby food manufacturer is employing Smiths Quad View, featuring a pair of two-beam X-ray generators, providing four beams for viewing.

The processor, one of the largest baby-food manufacturers in the world, claims the Quad View system can detect 1.5-2mm fragments of glass inside a glass container, including fragments situated in the difficult-to-view area behind the crown at the bottom of the jar. The advance may help other processors of glass-packed products.

The baby-food maker also uses the system to check fill level, cap fitting and, of course, contaminant detection.

Fluorescent laser sensing

The vegetable industry has been a great proving ground for optical sorting systems, particularly fluorescence-sensing camera and, more recently, laser systems.

The fluorescent sensing phenomenon has been around for decades but its application to food products is relatively new. Key Technology (, Walla Walla, Wash., became a pioneer in food applications with its introduction of a pea-pack sorter under the Tegra label more than a decade ago. The camera-based system, which required black light or other special sources of illumination, would cause product with high chlorophyll content, such as a pea, to fluoresce. The degree of fluorescence varies with the chlorophyll content.

A vegetable processor utilizing the most sophisticated fluorescence-sensing systems available today can easily target product defects and foreign material and separate them from good product based on differences in the fluorescent properties of the object.

"We wanted to separate wood and stock from good (sunflower seed)," says one West Coast seed processor. "Some of the colors overlap, so the distinction is difficult."

In April, Key Technology introduced a new fluorescence-sensing sorter in its Optyx Raptor line, called FluoRaptor. It incorporates what it has called "the most powerful laser in the food industry" to improve high-speed detection and removal of defective product, extraneous vegetable matter (EVM) and foreign material based on varying chlorophyll levels, coupled with color, size and shape variables.

The seed processor is incorporating the FluoRaptor into its processing lines. Today it is able to effect rapid and efficient sorting. His line is equipped with both camera and fluorescent laser sensing systems. "We can put multiple sensors into the sorter for a more comprehensive solution."

The FluoRaptor can be used with a wide variety of vegetable products including peas, corn, carrots, potatoes, and spinach and other tender leaf products. It can be used to remove lettuce and cabbage core as well as insects, animal parts, cardboard, plastic, metal and glass.

A mix of sorters may include two or more cameras and a laser positioned for different view of the product. "You can find a lot of flexibility in how we configure our equipment to applications," says Bret Larreau, product manager-sorters for Key.

The user interface displays an image of the food product as the laser illuminates them. Operators can adjust "reject" levels so product falls within prescribed quality parameters.

The more powerful laser system makes differentiating objects with and without chlorophyll much easier. The power density of the FluoRaptor laser improves the signal-to-noise ratio, thus providing a more accurate image, or "product signature," to enhance detection capability of even very small defects.

The laser is protected by the only Class 1 laser enclosure in the industry, the company claims. "The great thing about a laser is you get a lot higher intensity than you do with a black light tube," says Larreau.

One of the advantages of the system is quick changeover.  Larreau notes that camera-only fluorescence-sensing sorters require changing mechanical parts. Changeover may take several hours. The FluoRaptor, however, can be changed in seconds with simple product setting procedures.

While the laser system is state-of-the-art, it does not need to displace other devices, including mechanical systems to sift out foreign matter before it gets near the packaging systems.

"People forget about mechanical systems, and they shouldn't," says Larreau. "We use vibratory sorters before product even reaches the detection devices. A small piece of wire or glass run across a bar grader will let small pieces of foreign matter fall through. Foreign particle removal is a system solution, not just a piece of equipment."

Key's Optyx system offers high-performance connectivity standards including Camera Link, FireWire and Ethernet.

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