Rapid nondestructive screening for melamine in dried milk by Raman spectroscopy

Melamine is a raw ingredient for the manufacture of plastics, but it is frequently misused by adding it to food to raise the nitrogen content, thereby giving the false impression of a high protein content. Varied amounts of melamine were added to samples of dried milk obtained from five manufacturers in Japan. The samples were illuminated by a small cross section of a laser beam and the scattered light was examined. The presence of melamine in milk could be immediately detected without any chemical or physical alteration of the milk by interpreting its Raman scattering spectra. Among the many Raman bands, an intense band at 676 cm−1 was the most useful for detecting melamine; the detection limit was about 1% (w/w). Because this method does not extract melamine from the dried milk sample, it reduces the risk of error that may occur during extraction or from interaction with chemical reagents. The method provides a very rapid screening test for melamineadulterated dried milk in food chemistry and forensic toxicology.