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From: Food Quality & Safety magazine, December/January 2013

Testing Labs Play Detective When Food Processing Goes Wrong

by Greg Mann and Michael Porfilio

The science and process of keeping food safe for the consumer is highly regulated, as we all know. The industry’s biggest concern often revolves around contaminants that enter into the food handling system and somehow go out to market.

Yet, from time to time, unidentified matter such as metallic particles, hardened organic objects, paint or coatings, and industrial lubricants that originate from the process itself show up in our foods and liquids. Not only is this alarming for the consumer, incidents such as these can make the news and ruin the reputation of the food company.

To keep food safe, both government food regulators and companies that outsource food processing constantly demand the implementation of multiple redundant systems to prevent these events before the damage is done. Food producers are well aware that in offering consumable, edible products for the public, they must follow rigorous guidelines to ensure that fragments from contact items such as knives, augers, receiving bowls/containers, and other processing devices do not end up in the final product and reach consumers.

Unfortunately, the origin of these potentially harmful foreign particles is not always readily apparent. Quite often, a food operation must call upon an off-site materials laboratory to do the detective work necessary for identifying this material and, most importantly, determining how it got there.

This scanning electron microscopy image shows a high magnification of metallic debris found in a processed beef jerky sample.
This scanning electron microscopy image shows a high magnification of metallic debris found in a processed beef jerky sample.

Sleuthing for the Culprit

Food processing involves a tremendous number of mechanical devices to keep pace with demands and production schedules. There are knives, rollers, conveyors, gears, and a plethora of other devices required in production. And one thing all mechanical devices have in common is that they eventually wear out.

The designers and manufacturers of these devices intend for the processed food to stay clean and sanitary. Unfortunately, processing equipment can send unwanted particles and chips into the processed food stream, usually in the form of nylon, plastic, and other polymer items. At other times, the components can be metallic. Periodic maintenance and inspection of processing equipment are the front line defense against machine wear.

In-stream monitoring devices positioned throughout the processing sequence provide progressive testing to uncover any non-product matter. These precautions may include magnetic separation and collection units that are in the processing stream to quarantine these errant and stray metal flakes, chips, powder, and other forms of metallic debris. Most equipment that processes large volumes of product is designed to rigorous standards to ensure the highest quality product and eliminate consumer danger. A metallic shard can break teeth, cause broken bones in the jaw region, and result in intestinal damage.

If the fragment is not caught at the processing plant but goes off to market, simply recovering it is not enough. The manufacturer must determine the area of the machinery from which it came. A materials laboratory has the proper equipment and tools to analyze inorganic and organic contaminants found in food, deal with production contamination issues, and uncover the source of the foreign object.

This shard of metal was analyzed at a materials testing lab and determined to be a high-carbon steel typical of a cutting blade.
This shard of metal was analyzed at a materials testing lab and determined to be a high-carbon steel typical of a cutting blade. Analysis was achieved using energy dispersive spectroscopy, which is well-suited for small samples such as this 3mm specimen. Further investigation determined the cutting blade was excessively brittle caused by inappropriate heat treatment.

Sometimes pieces are so small that a special analytical approach is required. These pieces are typically analyzed using a scanning electron microscope that uses energy-dispersive X-ray spectroscopy to perform a chemical analysis. Determining the material family may allow the equipment manufacturer to laser in on the component that has been damaged or is failing.

At times, visual microscopy can perform the forensic evaluation required to identify the particle or particles. At other times, tools such as a portable X-ray fluorescence unit can perform the required chemical analysis. A skilled analyst using these and other tools can determine the root cause of the defect and identify the origin of the foreign body.

The following case studies illustrate how a materials laboratory can be useful in determining corrective measures to create a zero-defect situation for safe food handling and processing.

Despite the industry’s best efforts, the presence of foreign particles and matter in food products is inevitable. This problem is controlled when all engineering approaches and proper mechanical designs have been properly employed.

This unidentified nonmetallic chunk was found in a popular deli salad product.
This unidentified nonmetallic chunk was found in a popular deli salad product. This product was a component of a personal injury claim. Laboratory testing identified this debris as an organic contaminant most closely resembling a vegetable waste. It was determined this contaminant was a portion of a corn cob normally removed in processing. The remnant had been softened in brine solution during processing and was unlikely to have causes the dental damage in this case.
These popular promotional items were found to contain high levels of restricted heavy metals.
These popular promotional items were found to contain high levels of restricted heavy metals. Lab testing using portable X-ray fluorescence discovered the presence of cadmium on the outer surfaces. Cadmium was identified as an unwanted component of the ink used to print the colorful images.
This recovered section of a wood material was known to have come from a material-handling palette and was used as a visual comparison to help identify key features of the nonmetallic matter found in the commercial deli salad product effort.
This recovered section of a wood material was known to have come from a material-handling palette and was used as a visual comparison to help identify key features of the nonmetallic matter found in the commercial deli salad product effort.

Loose Metallic Shards in Meat Processing

  • Case study No. 1 – metallic debris found in processed beef jerky product. This piece of metallic debris was found within a quarantined piece of a beef jerky product. In-stream magnetic detection systems successfully isolated this sample from a consumer product at the processing plant. Laboratory analysis of the debris was able to identify the material to find a root cause. It was determined that a failing meat grinding refining plate used in the processing stream was misaligned, allowing metal shards to enter the food product pool.
  • Case study No. 2 – metallic debris found in a ground beef processing lot. Inspectors found a metal fragment within a rejected lot of ground beef at the processing plant. A materials testing lab analyzed the shard and determined it came from high-carbon steel typical of a cutting blade. The lab achieved the analysis using EDS, which is well-suited for small samples like this 3-mm specimen. Further investigation determined the cutting blade was excessively brittle and identified the cause as inadequate heat treatment of the cutting blade.
  • Case study No. 3 – nonmetallic matter found in a batch of deli salad. An unidentified nonmetallic chunk was found in a popular deli salad product, which led to a personal injury claim. Laboratory testing identified the debris as an organic contaminant that most closely resembled a vegetable waste—a portion of a corncob normally removed during processing. It was also determined that this corncob remnant had been softened in brine solution during processing and was unlikely to have caused the dental damage in this case. This lab-created section of a corncob was used to help identify key features of the nonmetallic matter found in the commercial deli salad product. The food processors took corrective measures by adding in-stream detection systems to identify and react to foreign material when present, and the process has not experienced a problem since implementation.
  • Case study No. 4 – novelty glassware with heavy metal paint contamination. These popular promotional items were found to contain high levels of a restricted heavy metal. Lab testing was performed using portable X-ray fluore­scence, which discovered the presence of cadmium on the outer surfaces. Cadmium was further identified as an unwanted component of the ink used to print the colorful images. The EPA, FDA, and other governing bodies carefully limit toxic metals levels in all consumer products. These restrictions also cover consumer toy products, which are carefully monitored for the presence of other elements, including lead, mercury, cadmium, and chromium. Though not a food product, it is a container of consumable liquids. The issue is germane to processing, because there are times when items in the food manufacturing cycle are in contact with painted or plated surfaces. The above-mentioned lab techniques, specifically XRF, were used for the detection of unwanted chemicals or heavy metals in this case.
  • Case study No. 5 – wood sample in snack product potato chip processing plant. An unidentified foreign matter was segregated using an air blast separator employing visual inspection techniques during final product packaging. Quality control required identification of all foreign matter found during processing. Because it was covered in product residue, the entire sample required analysis. Laboratory testing identified the debris as an organic contaminant most closely resembling wood. This recovered section of a wood material was suspected to have come from a material-handling palette. Based on the testing and analysis of the manufacturer’s process, the operation determined that the episode was unique to this batch, and no further procedural changes were necessary.

Controlling the Unavoidable

Despite the food processing industry’s best efforts, the presence of foreign particles and matter in food products is inevitable. This problem is controlled when all engineering approaches and proper mechanical designs have been properly employed. With that said, and in the spirit of continuous improvement, it is imperative that containment and root cause of system failures be quickly identified, especially when considering that the processor’s reputation is at stake.

Whether you are processing grains or vegetables, meats or fish, there is a potential for contamination by metallic or organic fragments. An ongoing relationship with a testing laboratory provides assurance that you will be able to investigate problems effectively when they occur, before government inspectors find out.


Greg Mann is chemical analysis group leader/materials specialist, Anderson Laboratories. Michael Porfilio is the company’s director of operations. Anderson Laboratories specializes in chemical analysis, mechanical testing, welding procedure and performance qualification, failure analysis, environmental and corrosion testing and on-site evaluations.

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