The U.S. Pharmacopeia has led an international collaborative project to develop a tool-box of screening methods and reference standards for the detection of milk powder adulteration. When adulterated milk powder reference standards were being prepared, it was discovered that the blending methods used to combine melamine and milk had unanticipated strong effects on the NIR spectrum of melamine.The prominent absorbance band at 1468 nm of melamine was retained when it was dry-blended with skim milk powder, but disappeared in wet-blended mixtures, where spray dried milk powder samples were prepared from solution. Using an array of other spectroscopic techniques, it was discovered that wet-blending promoted reversible and early Maillard reactions with lactose that are responsible for differences in melamine NIR spectra between wet- and dry-blended samples. Reliance on NIR detection of melamine using dry blended reference samples should be treated with caution.
Read the abstract at: NIR detection of melamine in milk powder
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