Detection of melamine in foods using terahertz time-domain spectroscopy.

The aim of this study was to investigate the feasibility of detecting melamine in foodstuffs using terahertz imaging. The terahertz (THz) spectra and images of melamine mixtures were obtained in the frequency range of 0.1-3 THz at room temperature using THz time-domain spectroscopy. Characteristic absorption peaks of melamine were found at 2, 2.26, and 2.6 THz, and these peaks showed the same frequencies in the different food matrices. At 2 THz, the THz images of melamine were dose-dependently distinguishable from those of food components with or without the packaging materials used. The calibration curve of melamine showed a regression coefficient (R(2)) of >0.913 and a detection limit of <13%. These results suggest that terahertz imaging has the potential to be used for the qualitative detection of melamine in food as a nondestructive analytical tool.