Food Safety / Packaging / Process and Operations

Inspection Technologies Keep Quality High in Packaging Systems

X-ray, metal detection and vision technologies keep the quality in your packaging systems.

By Judy Rice, Contributing Editor

No matter how much time, money and imagination you put into formulating and marketing your products, failed packaging can obliterate all your best efforts. Stale, spoiled or contaminated product almost certainly spells disaster. Under-filled packaging, leakers, cracked or dented containers, improperly applied closures and out-of-position or misprinted labels all do their share to erode consumer confidence in your product.

Quality control on the packaging line is crucial and should never be underestimated.

Protecting the quality and safety of your packaged products is paramount to your marketing and financial success. Adjusting and expanding packaging options to meet consumer expectations are keys to maintaining or building your position in the marketplace.

So as food and beverage companies incorporate new packaging concepts, they need to continually re-evaluate how these changes affect quality control procedures and how best to optimize packaging QC results on a consistent, cost-efficient basis.

Iron checking for iron

Metal detectors have become a front-line defense in packaging quality control. With quantum leaps in sensitivity, they can now detect pieces of ferrous and non-ferrous metal much smaller than previous generations of the machines could. But they still cannot detect all metal. They also are handicapped by product or packaging that includes metal.

Typical metal detector applications in the food industry included bakery (everything from bulk ingredients to finished packaged products), dairy products (which get into the issue of wet products), meat and poultry processing (which require washdown products) and snack foods/bulk solids, according to Fortress Technology Inc. (, Scarborough, Ontario.

For instance, food processors who use bulk bags of ingredients such as flour, sugar or spices and seasonings need assurance that these ingredients are free of metal contaminants. Fortress' Phantom metal detection systems inspect 50-100 lb. bags, finding particles as small as 2 mm.

Metal detection systems need to be sited at the end of main production flow, which places them in or just ahead of the packaging department. Conveyor-based detectors must include the following, according to supplier Loma Systems Inc. (, Carol Stream, Ill., for the most efficient performance:
  • An automatic rejection system.
  • A lockable box to receive the rejected product.
  • A full enclosure between the search head and the rejection bin.
  • A device to confirm that the contaminated products have been successfully rejected into the bin.
  • An automatic belt stop failsafe system, to activate if there is air pressure failure, a detector fault, failure of the reject system or when the reject product collection bin is full.
Pipeline systems must include an audible and visual indication of rejection, and free fall systems require the facility to produce a double pack, if an automatic reject system is not possible.

X-rays peer inside

X-ray systems are becoming a common feature of food processing plants throughout the world. X-ray inspection has a few advantages over metal detection and checkweighing systems. In addition to snagging metals, even when faced with metallic packaging, X-ray systems find calcified bone, glass, PVC, TFE and other plastics, stone, ceramic, cement and rubber. They also help identify clumps of ingredients, missing items and malformed or broken products.

Super Store Industries, a Stockton, Calif.-based captive food processing operation owned by two grocery chains, operates dairy plants in Turlock and Fairfield, Calif., as well as a dry and frozen food distribution center in Lathrop. The company decided to add foil membrane lidding as a tamper-evident/freshness-protecting enhancement for its plastic 6-oz. and 8-oz. yogurt cups before the plastic overcaps are applied. But the conversion required a reassessment of quality control procedures.

Super Store had been using metal detection systems to inspect the filled/sealed yogurt cups. But the change to foil lidding required a move away from metal detectors. "So we budgeted for new inspection equipment," says Yancy Hopper, chief engineer.

After evaluating options, Super Store chose the ScanTrac 200 X-ray system supplied by InspX (, a Fremont, Calif., joint venture between Key Technology Inc., Walla Walla, Wash., and Peco Controls Corp., Fremont, Calif. The unit provides inspection beyond metal contamination detection. Using low-energy X-ray and image processing software, it also detects glass shards, stones, bones, rubber and other dense foreign materials. In addition, it detects product voids and underfillls and damaged or out-of-spec containers.

The change was worth it. "Going to foil seals and then placing plastic lids on the cups gave us tamper-resistant packaging as well as an air tight cover over the yogurt—with all this done on the same line," Hopper continues. "We were able to eliminate the shrink film neck banding equipment that was in place in the packaging area to apply tamper-evident bands around the overcapped cups."

The processor also was able to eliminate the high-speed weigh scales that previously were used to ferret out yogurt underfills. The quality assurance lab personnel, however, still do periodic checks of the finished product as an added safeguard to ensure proper fills.

Super Store dairy plants produce plain, pre-stirred and fruit-on-the-bottom yogurt varieties. Notes Hopper, "The X-ray system has no problem with fruit or yogurt densities. We only have to set up for size changes. Our product sizes are programmed into the system. So it is as simple as selecting the size on the operator screen and adjusting one guide rail to product width, and we're ready to run."

Hopper says the speed of our production lines, ranging between 180 to 280 cups per minute, is no problem for the system. "We can even run the cups touching side-by-side and still only reject the cup that is suspect," he continues. "This is unlike our metal detector, which needed spacing between the cups. This has helped significantly lower our error count of good product that gets wrongly rejected." He also notes no major conveyor modifications were required, and the set-up and control screens are operator-friendly.

Vision systems in focus

On today's high-speed production lines, it's increasingly challenging to check the integrity and critical features of packages, such as proper marking and logo placement. Increasing production line speeds and frequent changeovers further increase the difficulty of ensuring the proper filling, capping, sealing, labeling, and packaging of products.

Machine vision systems provide the watchful eye to assist with quality assurance. According to Cognex Inc. (, Natick, Mass., vision systems can perform such checks as:
  • Label presence and skew
  • Cap presence and position
  • Package integrity
  • Print presence verification
  • Print quality inspection
  • Date and lot code verification
  • Safety seal presence
  • Fill level detection
  • 1D and 2D code reading
  • Insert presence verification
  • Package color and shape sorting
  • Bottle counting
Private label frozen pizza maker Frozen Specialties Inc., Archbold, Ohio, uses a Cognex system to detect unboxed pizzas, pizzas damaged during wrapping and open carton flaps. The pies are inspected twice at 175 pizzas per minute.

Alltrista Consumer Products Co., Muncie, Ind., which manufactures two-piece canning closures, uses F160 vision systems from Omron Electronics LLC to achieve real-time lid defect detection. Alltrista captures an image of each lid. That image is sent to a PLC for comparison against programmed defect limits. After the PLC determines if the lid is good or bad, that status result is stored and tracked until it reaches a rejection station, where a PLC signal activates a mechanism to remove the bad lids. The F160 system inspects lids being transported from the curing oven to the final packaging area at the rate of 160 lids/minute.

Omron (, Schaumburg, Ill., also has several other vision sensor systems to accommodate on-line applications for a broad range of packaging types. The F500 vision sensor has a 1 million pixel digital camera to deliver high-precision image sensing. The system captures up to 200 images in compact flash, easily transmitted in batches to permanent storage. The system features two separate image processors: one for judgment and one for communication.

Antibody-based inks spell food safety

Toxin Guard, a patented package printing technology developed by Toxin Alert Corp. (, Jackson, Miss., provides consumers with a visual indicator to gauge freshness of products with moisture content.

The company prints flexible polymer films using inks embedded with antibody-based biochemical sensors that detect mold or mildew in the packaging. The inks employed to print "Best Used By" dates change color if mold or mildew is present.

Already being commercialized in Europe for meat and poultry product packaging, the ink technology can be customized with specific antibodies to meet specific product needs -- including seafoods, fruits and vegetables. Research is under way with the University of Southern Mississippi (Hattiesburg) to develop consumer product packaging applications that could detect and signal the presence of pathogens such as E.coli, listeria and salmonella.

Seafood processor Port Graham Corp., Port Graham, Alaska, recently won a contract to supply the armed forces with smoked fish products packaged in films incorporating Toxin Guard ink technology.

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