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Detecting Foreign Matter

July 16, 2007
Advances in detection technologies are helping to make the food supply safer than ever. Plus, these machines can do other things, as well.

I'm old enough to remember baking soda submarines (yes, mine finally arrived!) and have fond recollection of that mostly bygone era when you wanted to find a surprise in your cereal box. But in this era of food safety vigilance, keeping surprises out of our food is one of the industry's most sincere ambitions.

More often than not, the threat to food safety comes when some unwanted element -- whether it be fragment of metal or grain husk -- enters a food or its package. Devices that enable processors to detect unwanted elements at desirable production speeds are invaluable. They help to ensure product safety and quality and keep away the lawyers.

But safety and quality aren't the only drivers to improvements in detection technology. Maintaining uptime can have immense impact on the bottom line, and effective detection of foreign matter can maximize production time without sacrificing safety.

While metal detectors continue to do their jobs, other detection technologies that recognize non-metal particles increasingly are being worked into the processing line.

Ease of use and connectivity are other issues driving new technologies and improvements and configurations of existing equipment. Here's a look at some of the latest advances and refinements in the field.

Digital advantage

Metal detection is a mature technology. The current generation of equipment has come close to reaching maximum sensitivity and detection capability. Thus, most of the improvements have aimed at easier system operation. The shift to digital systems, however, has gone a long way to do just that.

"The [digital] unit doesn't need to be calibrated with each product that runs through the line," explains Kevin Jesch, product manager for Heat and Control (www.heatandcontrol.com), Hayward, Calif., which markets CEIA metal detectors and Ishida X-ray devices. "You can use multiple frequencies. If the plant is running different products, you can accommodate each with a different frequency and easily change." Digital signals also help to avoid ambient interference from motors and other devices, Jesch notes.

Variable frequency operation offers distinct advantages over single or limited frequency detectors. Loma Products (www.loma.com), Carol Stream, Ill., has a range of metal detection systems called Loma IQ3 that can operate at frequencies between 40 and 900 KHz. The systems also can adjust to the proper operating frequency almost instantly with each product or set of conditions, eliminating the expense and time of engineer set-up or adjustment.

Making metal detectors more simple means making them more problem-free. Heat and Control's CEIA THS series metal detectors have been designed to withstand the rigors of washdown and tough sanitary practices. "We've had good success in poultry operations in particular," he says, underscoring the stringent sanitary practices in that food segment. "The systems resist water and chemicals, as well as high temperatures and high pressures."

Simplicity of design is a plus, too. Fortress Technology (www.fortresstechnology.com), Scarborough, Ontario, claims to have only 50-60 percent of the parts of its competitors. Other advances in metal detectors have included tougher designs, able to resist damage due to vibration and thermal shock. Driving much of the improvement in both metal detection and X-ray detection systems has been the quest to make such systems easier to use.

"X-ray has come a long way. Today, you can learn to operate a machine in five minutes," says Oscar Jeter, national sales manager for Safeline (www.metaldetection.com), Tampa, Fla., a unit of Mettler Toledo. "You can also set it up in five minutes. It gives the plant something it can easily use and get up and operating fast. If it's part of your HACCP [hazards and critical control points] plan, it is important to get it up and running quickly."

New features of Safeline's Powerphase Pro metal detector incorporate features sush as color touch control and icon identifiers aimed at easier use. "Everyone knows how to use an ATM machine," says Jeter. "By using icons, you can guide people in their use of the machines. It's the same with us. We can walk people through. You don't need a 'retraining' program every time you change employees." Uptime, Jeter emphasizes, is of paramount importance. Plants can't afford to have processing lines down, but they can't afford to run without the assurance and protection that sophisticated detection systems provide.

"A growing trend -- although it's not huge yet -- is Ethernet availability," says Heat and Control's Jesch. "As processors want to integrate more discrete equipment into the packaging line, they want to have this capability. Not many are ready for it yet from a control standpoint. It's being used more for data collection than interpretation so far."

Everyone wants connectivity today, Jeter emphasizes, underscoring the importance of safety data collection to HACCP programs. "Processors need to connect to a central data point where they can prove a detection system was turned on and operating during a production run; log and document the monitoring of product during production; and log and document rejects," he adds.

Two techs, twice safe

Unwanted materials such as wood, insects, certain plastics, pieces of conveyor belt remain difficult to detect with metal detectors and other detection technologies. This fact has expanded opportunities for X-ray and other types of vision systems. Experience in the positioning of systems also has added to their effectiveness.

Processors are using multiple detection systems -- and often multiple detection technologies. "Metal detectors find only metal, but X-ray systems find any kind of solid contaminant," adds Jeter. While metal detector refinement aims at detection of tinier metal particles, X-ray and other emerging technologies can single out glass, stone, bone and some other materials.

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 (www.keytechnology.com), 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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