Tech Update: X-ray & Optical Inspection
New types of foreign material and product flaws detected
X-ray, camera and laser sorting technologies are coming of age in new configurations and applications that improve productivity and reduce false rejects while detecting harder-to-find flaws.
May 13, 2013
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For food products, advanced hardware and software recognize visible imperfections such as discoloration or deformation; spot “hidden” faults based on a measurement of the content of water, oil or chlorophyll present; and “see” invisible flaws ranging from Aflatoxin on nuts to softness/bruising in blueberries to the presence of sugar ends and zebra chips in potatoes. Identifying transparent contaminants like glass and low-density materials including plastic is a new development.
For the packages containing finished product, optical inspection systems outperform traditional checkweighing systems that don’t venture beyond an analysis of the aggregate product weight. The newer technologies can examine a multi-ingredient product such as a ready meal and confirm that all components are present in the correct proportion and position.
X-ray systems are diversifying from single energy beam configurations to include several multiple beam styles in new configurations. These include the use of two energy beams that operate at different kilovolt levels at the same point of inspection and dual energy beams with similar energy levels operating in tandem, where the first beam diverts suspect product to the second beam for inspection. The product is rejected if there is a defect or contaminant. However, if the product is stuck together or on top of one another, it is diverted for reworking and then reintroduced to the inspection system for checking. An X-ray system can weigh a packaged product and detect metal, as well as inspect additional user-defined parameters simultaneously.
Retailers are no longer just mandating metal detection or product weight; they are asking food processing companies to add an extra measure of inspection protection—such as X-ray, camera or laser systems—to remove contaminants and identify damaged or missing product. “We are writing codes of practice on product fill/underfill, conformity, missing product, the gamut,” says Laura Studwell, Loma Systems North American marketing manager. “Several firms have in-house standards that exceed their HACCP protocols, not only to protect themselves and ensure quality to their clients, but to differentiate their product from competitive items in the market and to meet future, more stringent regulations,” Studwell says.
Ray Spurgeon, product manager at Eriez, says he is seeing calls from major retailers mandating their suppliers put X-ray on their lines. “It started as a subtle admonishment, and now it is more of a corporate edict. We booked an order for 27 systems last year from one customer for that reason alone,” Spurgeon says.
Productivity is another driver. “Yield is a big motivator. We’ve developed a field potato sorter [FPS] that removes stones and other contaminants as the product comes from the field, to maximize the storage of good product,” says Bjorn Thumas, Tomra Sorting director of food market development.
“We also developed a new sorter and technology that can detect softness in fruit. [Shipments of products can be rejected if the percentage of soft fruit exceeds a set amount.] Our machine takes out the soft fruit, reducing the chance of a recall to near zero while enabling harvest of previously uneconomical fruit,” says Thumas.
Premium packaging is also challenging processors to stay ahead of the food quality curve. “Metal detection is ubiquitous as a first level of inspection, but if the processor has new detection requirements for even smaller bits of metal, they can have difficulties meeting those levels with a metal detector,” says Todd Grube, Heat and Control product manager, inspection systems. According to Grube, this can be more challenging if the product is not dry and neutral but wet or conductive, which decreases the sensitivity of the metal detector. “Examining a product contained within a metalized film brings another level of difficulty. These factors are convincing more processors to seek newer solutions,” states Grube.
Robert Rogers, Mettler-Toledo Safeline senior advisor of food safety & regulations, says each technology has value and should be examined carefully. “It all goes back to the customer’s original [HACCP or qualification] plans. It is not just about using any or every technology out there, but designing a good program around the correct selection of technology, making sure the process is documented, maintaining control over rejected product and understanding the risks with reworking a project or having an unsecured reject area. Users of an inspection system have to use effectively what the system is telling them,” Rogers says. “Metal detectors won’t detect stone or glass, and X-ray technology is still challenged to detect low-density metals like aluminum. The technology and system it is running under needs to run production successfully and also identify the smallest possible contamination, day after day,” says Rogers.
Dual energy X-ray inspection advances
Anritsu Industrial Solutions USA is expanding its X-ray product line with a new dual energy system that targets harder-to-find low-density contaminants. “Detecting minute pieces of glass or chicken bone, or even plastic, which is the holy grail of X-ray technology today, are some of the more difficult applications that challenge traditional single energy systems,” says Christopher Young, Anritsu Industrial Solutions business development manager.
Anritsu’s new dual energy system was introduced last year as a focused product targeting the poultry industry. The company offers nine different single energy models, including a new high-definition X-ray system for the inspection of lightweight dry products and products in small bags. The firm has more than 7,000 single energy units installed globally, but sees dual energy equipment as the next frontier.
“A single energy system might spot a low-density contaminant like a chicken bone in meat, but it may not see it all the time. You are always on the edge of detection if the contaminant does not have a lot of density. If you are looking for a defect that may be close in density to the product, or does not have a lot of signal, that could generate a high false reject rate if a traditional single energy system is set too tightly. Therefore, this type of application needs a different type of technology to find the imperfection yet keep false rejects low,” Young adds.
Anritsu’s dual energy X-ray system generates a low-energy and a high-energy image from a single X-ray generator. The system generates two separate images to enhance detection capabilities. “Items like a chicken bone react differently to different energy levels, so the image of the bone may show up better at 30 kV or at 60 kV,” Young says. Two points of data allow the system to determine concretely if the object is truly a contaminant.
Anritsu’s dual energy system works best on poultry products that are two to three in. and thinner. If the dual energy X-ray system is set up for a thicker product and realizes the dual energy isn’t adding additional benefits, it automatically switches to a traditional single energy system that looks only at the high-energy image.
All of Anritsu’s X-ray systems use very small high-definition diodes for image generation and offer a standard 0.4mm diode that can detect contaminants as small as 0.4mm diameter. The physical size of the diode is similar to pixels on a flat-screen television: the smaller the diode, the sharper the image. Anritsu also offers an Ultra HD diode that can detect glass and stones as small as 1.0 to 2.0mm in diameter.
Loma Systems created and installed three customized dual X-ray systems for the world’s largest manufacturer of chicken nuggets, where the second X-ray inspection operates as a second tier of examination, downstream from the first check.
Loma’s X4 single beam X-ray technology is at the heart of a complex line designed to meet a Six Sigma standard (four false rejects out of every one million inspections) while maintaining high productivity. “The most common form of false rejection is when two chicken nuggets become stuck together during the production process,” says Nicolas Prompt, commercial director at Loma Systems.
Loma designed the system so the first X4 unit analyzes the product for density, broken pieces, damage or malformations using the company’s 3-D modeling and image processing programs. If the first X-ray senses variation to set parameters, that product is directed to a second X-ray unit for additional inspection.
“The second unit provides a second opinion, where the operator can look more closely at the product and determine why it triggered a reject response from the first X-ray,” says Studwell. If the product is stuck together, it is redirected after the second X-ray to a special recirculation/reworking path, sent through the system again and diverted to the proper accept/reject conveyor.
Eagle Product Inspection offers two related dual energy technologies, according to Simon King, global head of sales, service and marketing. Material discrimination X-ray (MDX) targets general food processing applications. Eagle’s DEXA dual X-ray technology, designed specifically for fat and lean analysis determination in meat, uses two separately generated high-energy spectrums to evaluate material content. “The technologies look at the degree of energy absorption by the material. Different materials have varying absorption rates depending on their density; the higher the atomic number and density, the more X-ray energy is absorbed. We are able to look up on the atomic table what the reference of a material is and determine the composition of the material,” says King.
Both X-ray approaches rely on Eagle’s SimulTask software to process the data. The software allows users to set parameters and tolerances, and spot defects down to 1.2 to 1.5mm, a range where many manufacturers increasingly set their tolerances, says King. Eagle has extended the capabilities of the software to provide more detailed analyses of product throughput and quality-related issues. Line operators can tie the analysis to traceability software to achieve a more seamless view of product management flow. The new TraceViewer enhanced analysis package is scheduled to be made commercial in the Spring of 2013, says King. The software can be programmed to identify every product coming through, including products having several different ingredients with differing requirements, such as panettone bread or a ready meal.
The company will introduce a new Multi-Bulk product that will allow users to run multiple lines of product to and through a common X-ray inspection control point, or handle higher volumes of product. DEXA can measure all the densities and contrasts in the product, allowing for much higher contaminant detection. Pack 400 HC, a new sanitary unit for use with Multi-Bulk applications, is designed to eliminate potential food collection points while providing ease of disassembly and washdown.
Single X-ray beams
X-ray units have the ability to perform density-based inspection to check the weight of a product and more. Loma Systems says the X-Weigh software and the Box Erosion algorithm for its X4 technology solved a problem a well-known confectioner was experiencing with fruit snacks sold in packets of six to a box. The confectioner used checkweighing and hit its target weight accurately and repeatedly. However, customers were complaining that only five packets turned up in the box. Now Loma’s Box Erosion feature allows the X-ray to see through the box and past the metalized foil film of the packet, while the X-Weigh system confirms the product meets weight requirements, says Studwell.
Loma also wrote a special algorithm that helps a cheese wheel producer in Wisconsin inspect the wheel for holes without slicing it open. The number of holes and the size of the holes in the cheese determine its quality. The moment the wheel is cut, its value drops significantly. “X-ray will not reveal the age of the cheese, but it can provide the data to determine its quality,” says Studwell.
Heat and Control has rolled out an economical line of single beam X-ray units. The IX-EA series complements the fully featured IX-GA series the company offers from its Ishida Co. division. The unit is configured as an entry-level unit that handles a limited range of products compared to the company’s higher-end models, says Grube. “It won’t find the smallest contamination, but it can help processors meet several requirements they were not able to achieve with metal detection or checkweigh.”
Eriez added to its product line a new X-ray inspection unit that detects foreign objects, product fill level and item presence in upright, non-glass containers. Its new E-Z Tec XR-SS unit provides side shoot scanning of missing or broken product and conducts mass inspection of metal, glass, stone, bone and some plastic contaminants. Product count, seal integrity, weight, shape, item position and presence/absence of product also can be detected. Other features include tool-less disassembly for cleaning ease, a low-profile design with compact 60-in. overall length and an auto-learn feature to quickly set operating parameters. The model joins the Eriez E-Z Tec X-ray line for packaging, meat, poultry and sanitary applications, and bulk flow materials.
Eriez has also developed a novel masterbatch additive for plastic products that make them metal- or X-ray-detectable. “Many major restaurant chains are mandating that food manufacturers use metal- and X-ray-detectable plastic and rubber articles as part of their HACCP programs,” says Eriez’s Spurgeon.
The additive is designed to detect and reject unwanted plastics that get into the food stream, including parts of scrapper tools, cable ties, pens, pallets, scoops, O-rings and belting. Eriez offers the PolyMag Beige XRD for X-ray detectable applications that require a high level of X-ray contrast and PolyMag Gray HSCP and PolyMag Black HSCP for metal detection and darker color pigmentation and black applications, respectively. The PolyMag additives applications are regulated by FDA for use in single- and repeat-use food contact plastic and rubber. Plastic molders typically include the additive at a 10 to 20 percent loading. Eriez says test cubes made with a 10 percent PolyMag loading were similar in detection to a 1mm mild steel sphere.
Mettler-Toledo Safeline launched a new energy-efficient single-beam model targeting small and medium-sized packaging inspection. The new X3310 X-ray inspection system employs a lower wattage generator that does not require cooling, reducing its power consumption by 20 percent, according to Rogers. The unit is offered with beam widths of 300 or 400mm. Although the system uses less energy, it can still detect an array of contaminants. “The imperfection does not have to be more dense than the product per se; it just needs to stand out within the image enough for the software to key in on it to understand it is a variation,” says Rogers.
Laser sorting can be used in applications to spot defects similar in color, structure, size and shape to the product. UV, IR and NIR ignore the color and look at how the product interacts with light, whether the light is absorbed, diffused or reflected. The basic premise behind the technology has been unchanged for decades, but its capability has evolved.
Hyperspectral technology is one of the more intriguing developments in inspection technology today. It examines the product by evaluating it through the electromagnetic spectrum, collecting hundreds of data points from multiple wavelengths in the NIR spectrum. The imaging systems divide light into hundreds of narrow bands over a continuous range that covers a vast portion of the electromagnetic spectrum. The data points are combined, creating a profile, signature or fingerprint unique to each product. The hardware and software program has to be capable of processing the hundreds of data points. Similarly, multispectral technology scans the same wide range of the spectrum, but it does not look at every single piece of the wavelength. It generates a less complex fingerprint.
Key Technology says a new era of digital sorting is arriving with the development of hyperspectral systems with new sensor technology and greater software-driven intelligence. “Key Technology continually develops more capable software and algorithms that enable the sorter to make new kinds of intelligent decisions,” says John Kadinger, market manager at Key Technology.
Key has developed “smart sorting” solutions that combine hyperspectral imaging technology with proprietary algorithms included in its software. Its BioPrint hyperspectral technology targets processors of potatoes, nuts and dried fruits. “With hyperspectral imaging, the sorter is not looking at the contrast between good and bad. It looks at a multitude of data points that define the overall product to tell you what is good. Any inspected item that does not exactly match the parameters for that product is considered bad,” says Kadinger.
Sugar ends and zebra chips are quality control issues in potatoes that cannot be detected reliably with traditional trichromatic cameras or lasers. Products processed from sugar end potatoes exhibit undesirable dark brown areas that only become visible after the product is fried. They are caused by a higher concentration of reducing sugars caramelizing. “Other technologies like UV cannot detect the reducing sugar because there is not enough contrast between the sugar and the flesh of the potato. Our BioPrint technology shows tremendous potential in detecting sugar end potatoes and other invisible defects,” says Kadinger.
One new example of higher sorting intelligence is Key Technology’s Sort-to-Grade function for French fries. The Sort-To-Grade function, part of the company’s KeyWare control for potatoes, considers the size and color of each defect and how passing that particular defect will impact overall final product quality, in comparison to product specifications. It evaluates major and minor imperfections, always removing major flaws.
“However, if the sorter encounters a minor flaw that is surrounded by good product, the technology decides whether to let it pass or reject it. It may not eject the minor flaw at the risk of also ejecting good product,” says Kadinger. Sort-to-Grade notifies the operator to take corrective action when it is not possible to maintain final product quality due to the quality of the incoming product.
Key says technology and software enhancements like these move processors away from the traditional sieve approach, where operators subjectively adjust accept/reject thresholds to make grade while staying within acceptable limits of minor and moderate defects. “The sieve approach results in too many defects being expelled, along with inadvertent ejection of good product, translating to a significant loss in yield,” says Marco Azzaretti, Key Technology advanced inspection systems product manager.
Visys NV, a supplier of sorting equipment now merged with Key Technology, applied its hyperspectral technology in a reverse sorting application featuring a high incoming defect load. It removed 98 percent of the walnut flesh left in a waste stream of walnut shells and membranes. Last year, Key Technology introduced a new three-way sorter that divides the product into good produce, foreign material/rejects and a co-product or rework stream. The system, now an option for its Optyx and Manta sorters, lets the processor recover product that is not in grade with the premium product but useful in another application. For example, walnut processors use three-way sorting to sort out pieces from unbroken halves that command a premium price, while also removing shells and foreign material.
Best NV, an optical sorting technology supplier acquired by Tomra last year, launched its Slidex sorter, which relies on NIR hyperspectral imaging to detect foreign materials such as plastic or wood. Features of the unit include a 1,000mm inspection zone, detection capacities up to 4 tons/hr. with efficiencies as high as 98 percent, depending on the incoming product.
Tomra has delivered a new sorter it says can for the first time recover almonds from the reject stream at the cracker process. The solution uses hyperspectral technology Tomra commercialized less than two years ago. Almond hull and shell pieces create a lot of debris, but 1-3 percent of the almonds are discarded with them. “There was no optical or mechanical solution to recover the almonds from the reject stream of shells in an efficient way until now,” says Thumas. Tomra has also delivered sorting technology that can detect worms in native pecans. “The hyperspectral scan is so specific that it creates a unique fingerprint of the almond. It pulls the nut from the reject stream in a reverse sort,” says Thumas.
A new field potato sorter (FPS) launched in December by Odenberg and Best—part of Tomra Sorting Solutions—utilizes multi-spectral NIR technology to remove soil clods, stones, rotten potatoes and foreign materials at rates up to 80,000kg/hr. It is the first offering by the company into the unwashed potato market and replaces difficult-to-recruit human labor for this task.
Sorting product based on the presence or absence of chlorophyll is a new and novel approach to sorting contaminants from peas, green beans, spinach and leaves on fruits. A patented laser fluorescence technology developed by Best— through research with the University of Brussels—creates high contrast to detect color and texture differences.
Best’s Fluo laser technology can determine the level of chlorophyll in a product and can spot objects or parts of objects—such as rotten spots or leaves situated in between product—that also contain chlorophyll. Fluo results in high detection and low false rejects, says Thumas.
Key also offers a fluorescence-based laser technology that determines the presence or absence of chlorophyll. “The presence of chlorophyll in corn may indicate the husk or shank is there, so you can find it and remove it. The technology can distinguish between the pea pod, which has chlorophyll, and the pea, which does not, and reject the waste,” says Kadinger.
The detection and removal of Aflatoxin in nuts and dried fruit is area of development in optical inspection. Aflatoxin, said to be one of the most toxic substances known to man, is invisible, making it tougher to validate its removal from the product. Tomra’s Detox sorter subjects the fungus to a particular wavelength of energy and then captures the extremely low intensity of light reflected by the toxin. “It reflects light with a distinctive pattern or biological fingerprint. The laser system recognizes the biological signature of the Aflatoxin, even though it is invisible to the human eye, and can remove the contamination from the product at high flow rates,” says Thumas.
SWIR for frozen fruits
Detecting contaminants in frozen fruit and vegetables based on water content is the targeted application for a unique laser-based technology that employs shortwave infrared. The SWIR technology, offered by Tomra, identifies the large contrast between good product and contaminants based on how the wavelength of the shortwave energy is treated. Water-based products such as frozen fruit absorb the light, whereas defects such as wood and plastic reflect it. Contaminants of glass, cardboard or metal can be detected and rejected by combining several wavelengths with SWIR.
Camera system in review
Mettler-Toledo CI-Vision says its camera-based technologies continue to add new techniques for label identification, label location and imaging styles. The company has developed a new method for 360-D inspection that can make accurate measurements of label position using four cameras set at 60° angles to get images of the complete container surface.
Mettler’s software stitches the images of the bottle together into a full image and then flattens it, creating a 2-D panoramic view of the inspection surface. “In the past systems, you could not accurately tell label position because the bottle may have shifted while it was on the conveyor,” says Aaron Poppleton, Mettler CI-Vision technical writer. Using the stitching algorithm, the resulting image can be measured to ensure labels—even multiple labels—are positioned correctly on the surface of the container.
Mettler-Toledo CI-Vision also offers a paneling or “mosaic” technology for 360° inspection, which employs six cameras and is designed to capture every angle of the bottle to obtain a complete image of the label. Regardless of how the bottle comes into the system, Poppleton says the machine can show operators if the label is printed correctly, is valid and is free of any rips or other defects.
Poppleton says new camera lens options also allow for the examination of unfilled bottles with smaller neck openings. Higher-resolution lenses help to produce a sharper image of containers with less distortion. The company is also developing technology that allows for inspection of a tight seal on rigid products with a foil top.
New detection solution designed to meet growing food safety standards
Thermo Fisher Scientific introduced the NextGuard X-ray detection system designed as an affordable unit with features often found in more costly higher-end systems. The new unit helps expand the technology to a wider customer base.
The first model, the NextGuard C330, is designed for packaged product contaminant detection and complements the mid- and high-end Thermo Scientific Xpert and POWERx X-ray inspection systems.
“Based on customer feedback, we’ve found that, traditionally, the total cost of ownership for X-ray systems has been too high for many companies to justify this technology,” says Bob Ries, lead product manager, metal detection and X-ray inspection, Thermo Fisher.
Based on Thermo Fisher testing, NextGuard offers up to 50 percent better detection sensitivity than Thermo Fisher’s previous value-based X-ray system, the EZx.
Features of the NextGuard system include its compact one-meter long size; multiple contaminant detection algorithms to increase detection probability; ability to modify, test and change detection parameters on the fly; wraparound detector intended to reduce ‘blind spots’; on-machine reject image storage for up to 90 days, and a QA check mode that automates operator audits and recordkeeping.
NextGuard’s features have also been driven by a changing industry landscape “where X-ray detection addresses a number of customer concerns, including evolving HACCP standards and requirements from some retailers for X-ray inspected product,” says Ries.
For more information:
Todd Grube, Heat and Control, 717-519-5240, firstname.lastname@example.org
John Kadinger, Key Technology, 509-394-3577, email@example.com
Christy Miller, Eagle Product Inspection, 813-342-2373, firstname.lastname@example.org
Aaron Poppleton, Mettler-Toledo CI-Vision, 630-446-7700, email@example.com
Ray Spurgeon, Eriez, 814-835-6298, firstname.lastname@example.org
Laura Studwell, Loma Systems, 630-681-2055, email@example.com
Bjorn Weyts, Tomra Sorting NV, 32 16 741 906, firstname.lastname@example.org
Christopher Young, Anritsu Industrial Solutions, 847-419-9729 ext. 306, email@example.com
Robert Rogers, Mettler-Toledo Safeline, 813-342-9138, firstname.lastname@example.org
Bob Ries, Thermo Fisher Scientific, 763-783-2794, email@example.com