Top Technologies for Foreign Object Control

In March 2019, USDA issued a best practice guideline for meat and poultry producers to reinforce the requirement of notifying the agency within 24 hours of shipping products that are potentially contaminated with foreign objects. As the agency explained, although the rule had been in place since 2012, cases of foreign materials found by consumers had increased in recent years.

Foreign objects are an insidious issue for all food producers, not just meat and poultry processors. Unlike with pathogens, there is no kill step to eradicate or minimize the foreign object. Contaminations can occur at any point in the supply chain, with different materials and for various reasons: pieces of plastic from dough scrapers, bottle caps and golf balls, and broken metal from equipment or construction material are just a few examples from FDA’s product recall list.

Assessing Risk

The starting point to managing foreign objects in food production is to understand the hazards. “Risk is not a yes- or no-type question,” says De Ann Davis, food safety director at Commercial Food Sanitation in New Orleans. “Certain foreign materials present more of a health hazard than others. Some of them can be found readily through technology, while for others, like thin, clear plastics, it’s going to be very difficult.”

When you measure the likelihood of foreign object contamination, the quality of the information is important. “The best data comes from a strong near-miss program, which is a detailed library of materials found in partially or fully processed products before they end up on the shelf. Other important sources are your suppliers’ history and the validation of your own controls. It’s not just about how you can detect a piece of metal at the end of the line; it’s important to look at risk from a holistic standpoint,” adds Davis. The risk assessment will determine which foreign detection technologies to use and how to employ them.

You need a strong preventive maintenance program that avoids foreign material that may come off of equipment, such as pieces of conveyor belts, metal shavings, screws, or pieces of plastic. When foreign material is found on the equipment or within the facility, you also need a sanitation and GMP program that prevents it from entering the food-making process.—De Ann Davis, Commercial Food Sanitation

Sorters, Filters, and Magnets

Sorters, filters, and magnets are typically used with produce, powders, and liquids.

Produce is often washed first: “Water is a good segregation system because the produce usually floats, says Rob Kooijmans, CEO of the Food Strategy Institute in Amsterdam, Netherlands. “Wood floats on top and can be discarded later, soil dissolves, and stones sink.” In some cases, using magnets first might be a better option, as open fields could hide all sorts of foreign materials. That’s the case in the Netherlands and France, says Kooijmans, where it’s very common to find hand grenades from World War I or II with the produce.

A second, more sophisticated sorting level uses cameras, lasers, and infrared and ultraviolet (UV) radiations. “Cameras look at color and potentially shape, while lasers, infrared, and UV analyze reflection,” says Kooijmans. “By combining that information, you can detect foreign bodies that were not washed out in the beginning. A golf ball harvested with potatoes, for example, would float during the washing step and would probably deceive cameras and lasers too, but it will reflect UV light, while potatoes won’t.

Sieves are typically used with liquids and powders, while magnets offer a useful support, especially to detect any metal particles from grinding steel equipment left in dry powders, such as pepper and cocoa. “Sieves should be placed at the entry and exit of a processing step, because your process itself might introduce foreign objects. When only one option is possible for cost reasons, the best choice is the end of the line,” says Kooijmans.

X-Ray Systems and Metal Detectors

Metal detectors and X-ray systems detect foreign objects by recognizing the disturbance that they can cause to signals. In metal detectors, metal objects will change the electromagnetic field, generating a voltage signal; in X-rays, foreign objects with higher density will attenuate more energy, producing a darker area in the image.