Foreign Objects Contamination

Because of the vast variability between plants, processes, and products, as well as the number and types of "foreign objects" that could contaminate food, there are as many options for foreign object detectability and separation as there are places the equipment can be placed. Because of these same reasons, there is no single correct answer to placement, with the optimal solution dependent on the products and processes of the individual plant.

However, in most cases, a combination of solutions and equipment will better enable the detection and separation of various types of contaminants. "Some of these are complementary, but at the same time, it depends on your process, what your objective is, and where your problems are coming from," said Doug Britton, program manager of Georgia Tech Research Institute's Food Processing Technology Division.

While metal detection is frequently a CCP for food processors, it is not the be-all or end-all of foreign object detection. "Metal detection is a catch-all to go with everything else in a total quality control package," said Detectapro President Jim Elliott.

In some processes or areas, if no cutting or dicing is involved, a surface detection system can be beneficial; if there is a significant difference in density between the product and potential contaminants, then x-ray is viable; if the greatest risk is metallic objects, then metal detection equipment is essential; and if plastics are at issue, the use of metal-detectable plastics with metal detection equipment can be a plant's best protection.

It is often just such combinations of detection placed strategically along the process that will provide a processor with the best protection against the potential of foreign object contamination in foods.
 

Metal-Detectable Plastics: Making the Invisible Visible "One problem with plastic in food is that it is not metal detectable or x-ray visible," said Eriez Market Manager of Plastics and PolyMag Processing John Collins. "So how do you make them detectable?" That is where metal detectable plastics come into play. The plastics can be made with metal-detectable additives that are included like a colorant to the plastic resin prior to molding. Adding detection and magnetically susceptible characteristics to the plastic "makes a material that food processors like to use readily visible to their inspection equipment," Collins said. Adding detection and magnetically susceptible characteristics to plastic makes the material visible to inspection equipment. (Photo courtesy of Eriez) "Foreign object detection is of critical concern to all food processors as per their relevant GMP requirements," said Carl Frank, national accounts manager for Lomont Molding. And, as a part of that, "metal detectable plastics play a role in this process by helping to assure the quality of the food stream throughout the manufacturing facility." Food processors first began requesting metal-detectable plastics about 10 years ago, said Remco Products Director of Operations/Engineering Michael Garrison. As more and more requests were made, the detectable plastic became more available and used by more processors. "Most food processors feel that they are doing everything in their power to make sure there are no impurities in their products," Garrison said, explaining that the metal-detectable plastics can help with this goal. However, Garrison cautioned, "it is not a magic bullet, it is part of the equation." A variety of factors will impact detectability, including the density of the food product, placement and calibration of the equipment, and other plant- and process-specific practices. "In the end, it is still plastic. It is not 100 percent detectable, so each processor has to use it to the best of their own ability." Recent innovation has also seen the development of FDA-compliant metal detectable and x-ray visible pellets. Available in small batch sizes, the high-concentration pellets enable molders to select the concentration of additive, allowing them to customize plastic items to suit the detectability requirements of their customers, Collins said. Whether a plastic is metal detectable or not, its ability to be molded in colors is also advantageous. "You want to pick it up visually first," said Detectapro President Jim Elliott. Blue coloring is often used in plastics because it is the "least often eaten color." In addition, many plants color code items by area to reduce the potential for cross contamination; in these plants, plastic items can be color coordinated as well. In addition, Elliott said, "Plastics are gentler on equipment. If you do lose something and it gets ground up, it will not be as hard on the blades [as would metal items]," Elliott said. Plastics are also often less expensive and can be more easily molded. Metal-detectable plastics can be used in utensils, railings, conveyor guides, and other equipment parts, Garrison said. "It is of benefit anywhere that using plastic has significant advantage over metal."

Placement:
Before, During, or After?
Recommendation:
All of the Above

The primary purpose of a detector is to reduce the chance of contamination by a foreign object and a resulting recall or injury. Thus, metal detectors should be placed where instances have occurred or are most likely to occur, said Detectapro President Jim Elliott, "so you can catch a problem with production and can stop [a contaminated product] from going into the marketplace."

• Incoming materials – Placing detection and separation equipment right at the point where raw material is brought in enables a processor to catch issues before they can start. Detection of contaminants at this point can be a basis for product refusal, or, if accepted, can reduce the potential for equipment wear or breakage from metal pieces. It can also reduce a processor's overall cost, as the contaminant is being detected and removed prior to undergoing further processing, where removal of finished product can be significantly more expensive.

If equipment is placed later in the process with none at the beginning, it can be difficult to tell if the foreign object came in with an ingredient or if it came from within the plant—meaning a process or equipment may need to be inspected and fixed.

• In process – In-process placement will be different for every plant and product due to varying processes and equipment. However, in-process placement can, again, reduce further process expenses, and, in some cases, increase the ability for detection.

• Packaging – A final metal detector at packaging is a CCP for many plants, as this is the final checkpoint to detect metal that may have gotten into the product during the process (such as metal shavings, a bolt that fell off equipment, or even a metal-detectable-plastic utensil), prior to the product ending up in the hands—or mouth—of the consumer.

Tomorrow's Detection:
University Research and Innovative Technologies

At Georgia Tech Research Institute's Food Processing Technology Division, Program Manager Doug Britton and Principal Research Engineer Wayne Daley conduct studies on the feasibility of detecting foreign objects in food through new, innovative technologies.

While the use of metal detection equipment is well established in plants, what processors are finding to be a challenge is detection of objects such as plastic, glass and wood chips, Daley said, explaining, "None of the current technologies do that well."
 
Ultrasonic Holography. Daley's research on technologies to assist with such challenges has focused on ultrasonic holography for in-line screening of foreign objects in meat products. Holographic ultrasound is an extension of ultrasonic imaging that allows the extraction of 3D information that provides a more accurate description of the products being conveyed in the product stream, thus allowing for better detection of foreign material.

Recent innovation has seen the development of FDA-compliant metal detectable and x-ray visible pellets. (Photo courtesy of Eriez)

"Holographic ultrasound is the most interesting technology we've seen," Daley said. "But it is not commercially viable at this point. It's still in the research phase."

What research has shown so far, however, is that there is potential for eventual use of the technology in the food industry. Holography can "see through" most fully blended foods as well as their plastic containers. Tests have also shown that any foreign materials such as dense plastics, metals, and wood were easily detected visually, and the technology was successful at discriminating between plastic and bone fragments embedded in a meat.

On the down side, however, early tests revealed noticeable sensor noise, suggesting that the technology needs further development. Further development may also increase the system's viability for inspection of packaging seams and seal integrity. While currently possible, the package would need to be immersed or an edible ultraviolet material would need to be used on it to optimize such detection.
 
Image Screening. Britton's research on image screening also proves it to be a potentially viable detection option for the industry, however it can see only objects on the surface or between food items. "If a foreign object is imbedded in an object, it won't see it," Britton said. In its current state, the technology is best suited for foods packed in a liquid, such as marinated meats; product that is moved through a fluid-carrier pumping system; and foods that are completely blended, such as baby food or applesauce.

In this research, the feasibility of detecting small glove and belt material objects in streams of mechanically separated chicken and frozen, diced chicken meat were evaluated using computer-vision techniques. The greatest challenge was found to be material handling To be viable, the system would need to squeeze product into a thin stream, be easily cleaned, minimize air pockets and back pressure on pumping systems, suppress product heating, and have a durable inspection window.

Because of this, the research found more promise in detection of plastic conveyor and nitrile glove pieces, and liner material in frozen, diced chicken samples. Through simple color-discrimination algorithms, the image screening equipment was able to detect all types of foreign objects with a small number of false alarms.

Daley is also conducting further research on x-ray technologies. While x-ray is been beneficial because of its ability to penetrate foods and detect non-metal objects, it is still an expensive technology and can be difficult to work with, he said.