Quality checks are a fundamental part of food and beverage processing, and companies make extensive use of them to assure that finished goods are consistent and safe.
Screening for biological contamination is necessarily done in a laboratory, and scientific advances have considerably shortened the turnaround time for test results. Nonetheless, thousands of pounds of product can move through a production line in the interim, putting a high cost on contaminant-positive results. The ideal solution is in-line inspection, and while that’s impossible with microbes, considerable progress has been made with other quality factors.
Metal detectors, checkweighers and X-ray machines are the industry’s core in-line tools. Production facilities lacking at least two of the three are few and far between. Checkweighers maintain a tight tolerance between short-weighting and product giveaway – a business essential but not a food safety concern. But potential customers would turn and run in the absence of either metal detectors or X-ray units.
Baby food manufacturers were among the first processors to adopt X-ray inspection to protect against glass fragments. Metalized film drove other firms to X-ray machines, and for awhile it seemed the X-ray option would become the technology of choice for end-of-line contaminant inspection. A funny thing happened on the way to market domination, however: metal detectors became more versatile and precise.
Multi-frequency machines have been introduced by most of the major metal detection suppliers in recent years, but “there was something of a Rube Goldberg feel” to the first generation, according to Steve Gidman, president of Fortress Technology Inc. (www.fortresstechnology.com), Toronto. Machines had too many moving parts, and outcomes represented only incremental improvements in the tradeoff between increased sensitivity and excessive false positives. Only recently have software algorithms that analyze signal data caught up with the potential value of both low- and high-frequency signals.
Fortress recently rolled out an enhanced Interceptor metal detector that simultaneously reads two frequencies and can accurately inspect products packaged in metalized film. “The gain we’ve made with a coil structure that can take advantage of multiple frequencies is thousands of times better,” Gidman says. “The performance with metalized film is comparable to an X-ray machine’s capabilities.”
The primary target of the detector, however, is products that are naturally conductive, those with high moisture, salt and acid content. Previously, detector adjustments to compensate for conductivity lost the ability to detect stainless steel and other nonmagnetic metals. “Non-ferrous metal detection suffered a bit, too,” notes Gidman.
Simultaneous multi-frequency systems overcome those limitations by distinguishing between signals that define the product and those that indicate anomalies.
Eriez Magnetics’ metal detectors can’t inspect products packaged in metalized film, concedes Ray Spurgeon, product manager-metal detectors at the Erie, Pa. firm (www.eriez.com). But for food companies that want to detect contaminants upstream of filling, Eriez now offers a compact detector called Vertical Xtreme.
The unit can be integrated with a vertical form/fill/machine, prior to filling, although Spurgeon suggests a more effective placement might be adjacent to a permanent magnet separator on a hopper for free-flowing materials. In that scenario, the detector verifies the thoroughness of the separator.
“Removing metal before the material is pulverized or crushed and metal is fragmented into a thousand pieces can save a lot of downtime,” he points out.
The detector itself doesn’t require a metal-free zone around the sensing head, making placement practical in close proximity with piping and machinery. Fragments as small as 1mm can be detected. Perhaps the biggest functional improvement is the operator's icon-based color touch screen. Spurgeon likens it to a smart phone: “It’s intuitive technology.”
A “user-friendly interface” and large color screen also is touted by Kathryn Bors, brand manager for Loma Systems’ IQ4 metal detectors. Both ferrous and nonferrous metal detection has improved incrementally, although Bors declines to say how much, but the HMI upgrade is more meaningful for food processors, she believes.
Operating parameters are communicated with visual prompts, and set-up time for different products is accomplished in 3-4 sample runs. But automating the learning process and communicating it in multiple languages may provide a bigger benefit to users, Bors suggests.
The product portfolio for Carol Stream, Ill.-based Loma (www.loma.com) includes checkweighers. Since metal detectors almost always are in close proximity to a checkweigher, single-source integration is desirable in avoiding the finger-pointing that inevitably occurs when a system malfunction occurs and two different vendors are involved. When Lomas delivers a turnkey system, operators access a single HMI.
Spectroscopy and vision systems are providing inspections that go beyond contaminant detection and short-weighting protection. Near infrared and mid-range infrared in the light spectrum in particular have sometimes obsoleted the need for off-line analysis of product samples.
A case in point is QVision 500, a system that can simultaneously measure fat, moisture, protein and collagen levels in meat. Based on how light from a spectral camera is scattered, the system performs multiple regression analyses of the different properties to produce a reliable measurement, according to Dirk Balthaser, technical director-R&D at Tomra Sorting GmbH (www.tomra.com), Koblenz, Germany.
The system, which automatically calibrates itself, relies on what Tomra labels “interactive spectroscopy,” suggesting that multiple wavelengths come into play, depending on the properties being measured and the product itself.
“The technology has been available for many years, but 25 years ago, spectrometers were only used in the lab,” says Balthaser. Those spectrometers could analyze 500 scan points per second. By comparison, today’s in-line spectrometers can analyze more than 2 million.
A similar dynamic is seen in the vision inspection systems from the CI-Vision division of Mettler Toledo Inc. (www.mt.com/ci-vision). Aurora, Ill.-based CI-Vision, which soon will relocate to Mettler’s Tampa, Fla., headquarters and be folded into Mettler Toledo Product Inspection, integrates up to six GigE cameras with telecentric lenses for high-speed inspection of bottles for multiple variables, such as label position, fill level and bar-code verification.
“One camera can do lot code verification, label identification and position, wrinkle and tear detection and cap height and integrity,” maintains Miles Kroner, CI-V national sales manager. More cameras come into play when different angles need to be taken because of the bottles’ orientation on the conveyor.
More powerful processors and improved software now permit inspection of labels created by low-resolution dot printers, and the system can inspect up to 1,400 bottles per minute, Kroner notes.
As with other in-line inspection systems, the core technology is stable, but precision and reliability keep ratcheting upward. “Processing capabilities have grown by leaps and bounds in the last 5-10 years,” Fortress’s Gidman observes. “That allows us to do things we couldn’t even dream about 10 years ago.”
Those improvements come at an affordable cost and enable the real-time decision-making that inline inspection is intended to deliver.