Feasibility study of contaminant detection for food with ULF-NMR/MRI system using HTS-SQUID

•Feasibility of application of ultra-low field (ULF) NMR/MRI was studied.•ULF-NMR/MRI system utilized HTS-rf-SQUID and permanent magnet of 1.1 T.•Magnetic contaminants in water were successfully detected by NMR measurements.•Non-magnetic contaminants in water were distinguished by 1D-MRI measurements.

We have developed an ultra-low frequency (ULF) nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) system utilizing an HTS-SQUID for an application of contaminant detection in food and drink. In the system, a permanent magnet of 1.1 T was used to pre-polarize protons in a water sample. We measured NMR signals from water samples with or without various contaminants, such as stainless steel (SUS304), aluminum, and glass balls using the system. In the case that the contaminant was the SUS304 ball, the NMR signal intensity was reduced compared to that from the sample without the contaminant due to the remnant field of the contaminant. One-dimensional (1D) MRIs of the samples were also acquired to detect non-magnetic contaminants. In the 1D MRIs, changes of the MRI spectra were detected, corresponding to positions of the contaminants. These results show that the feasibility of the system to detect various contaminants in foods.