SQUIDs Sift Out Metallic Contaminants In Food

Even metallic contaminants as small as 0.3 mm cannot escape the eye of this SQUID-based magnetic sensor.

AsianScientist (Aug. 11, 2015) – Scientists from the Department of Environmental and Life Sciences at Toyohashi Tech have developed a device to detect metallic contaminants in food. Based on superconducting quantum interference devices (SQUIDs), their system has been described in a paper published in the IEEE Transactions on Applied Superconductivity.

Metals are the most common contaminant found in food and pose a considerable safety hazard for consumers. However, existing inspection methods have limitations. For instance, the X-ray radiation method cannot detect contaminants with sizes smaller than 1 mm with current practical X-ray levels, and it cannot be applied for the inspection of foods that have lactic acid bacteria because X-ray radiation causes ionization of such foods.

Instead, researchers led by Professor Saburo Tanaka used a detection technique based on recording the remnant magnetic field of a contaminant. A strong magnetic field is first applied to food to magnetize the metal fragments within. Subsequently, the metallic contaminants can be detected by sensing their magnetic fields using the superconductivity-based SQUID.

“We have developed an inspection system that permits contaminant detection in a food package with a height of 100 mm with three high temperature superconductivity radio frequency 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,” Tanaka said.

The SQUID-based food contaminant detection system. Credit: Toyohashi University of Technology.
The SQUID-based food contaminant detection system. Credit: Toyohashi University of Technology.

“To reduce the impact of noise as much as possible, the sensor is placed inside a square metallic box designed such that food can be tested as it passes through this box. The box is made of 2-mm iron-nickel alloy plates. Magnetic fields have strong affinities to this iron-nickel alloy. Thus, magnetic fields around the sensor are concentrated in the walls of this box,” Tanaka added.

In experiments, the system was able to clearly detect a steel ball with a diameter as small as 0.3 mm. The system was robust and not affected by electromagnetic waves from nearby mobile phones or from the motion of nearby steel objects. Therefore, the system is a promising tool to detect contaminants in practical situations, and it can significantly aid in enhancing consumer health and safety.

The article can be found at: Tanaka et al. (2015) Development of Metallic Contaminant Detection System Using RF High-Tc SQUIDs for Food Inspection.

———

Source: Toyohashi University of Technology.
Disclaimer: This article does not necessarily reflect the views of AsianScientist or its staff.

Asian Scientist Magazine is an award-winning science and technology magazine that highlights R&D news stories from Asia to a global audience. The magazine is published by Singapore-headquartered Wildtype Media Group.

Related Stories from Asian Scientist