The researchers at Toyohashi University of Technology (TUT) describe the present day use of X-ray radiation in detecting metal in food products, pointing out the limitations of these methods in detecting metal contaminants smaller than one millimeter in size.
They also point out that X-ray radiation methods cannot be used in detecting metal contamination in foods containing lactic-acid bacteria because the radiation causes ionization of these foods. To overcome these problems, the researchers say they have developed a practical magnetic metal contaminant detector using three high-Tc RF superconducting quantum interference devices (SQUIDs) for food inspection.
The TUT research team explained the process is based on recording any remnant magnetic field that would point to a contaminant, in a product using the SQUID sensors. During the process, a strong magnetic field is applied to the food product, magnetizing any metal contaminants inside the food being tested.
Subsequently, the SQUID sensors are then able to detect the remnant magnetic field of the metal contaminate. This is considered not only safe, but the SQUID gives the operator a high-resolution picture of the contaminant.
Dr. Saburo Tanaka, professor of Environmental and Life Science Engineering at TUT says, “We have developed an inspection system that permits contaminant detection in a food package with a height of 100 mm with three high-Tc RF SQUIDs. To accurately detect even smaller metallic fragments, digital filters have also been used to improve the signal-to-noise ratio. The target size of the metallic contaminant in food with a stand-off distance of 100 mm is 0.5 mm.”
Dr. Tanaka explained that to reduce the noise level as much as possible, the sensor was placed inside a metallic box, designed so that food can pass through the middle, much like present day food inspection devices work. The box is made of two-millimeter thick iron-nickel alloy plates. All this technology, plus the use of a computational program that runs the digital filter system makes for an almost magical piece of equipment that would add to the safety of our food products.
In writing this story about Toyohashi University of Technology’s development of a magnetic field detection system for metal contaminants in food, researching the field of metal contamination in our food supply, I came across some interesting methods being used today in the industry. One such method is a system developed in the E.U. and apparently in use since 2013. It may not be the same, but it is obviously close to what TUT is developing. See what you think.
Called the AluScan, this system uses a magnetic field sensor and is from the a group of so-called passive sensors, which do not generate dangerous rays and, therefore, do not need to be registered. For this reason, an x-ray technician, as required by law, is not required to operate an AluScan detector, says the company.