Effects of Wet-Blending on Detection of Melamine in Spray-Dried Lactose
2017
Yakes, Besty Jean | Bergana, Marti M. | Scholl, Peter F. | Mossoba, Magdi M. | Karunathilaka, Sanjeewa R. | Ackerman, Luke K. | Holton, Jason D. | Gao, Boyan | Moore, Jeffrey C.
During the development of rapid screening methods to detect economic adulteration, spray-dried milk powders prepared by dissolving melamine in liquid milk exhibited an unexpected loss of characteristic melamine features in the near-infrared (NIR) and Raman spectra. To further characterize this “wet-blending” phenomenon, spray-dried melamine and lactose samples were produced as a simplified model and investigated by NIR spectroscopy, Raman spectroscopy, proton nuclear magnetic resonance (1H NMR), and direct analysis in real time Fourier transform mass spectrometry (DART–FTMS). In contrast to dry-blended samples, characteristic melamine bands in NIR and Raman spectra disappeared or shifted in wet-blended lactose–melamine samples. Subtle shifts in melamine 1H NMR spectra between wet- and dry-blended samples indicated differences in melamine hydrogen-bonding status. Qualitative DART–FTMS analysis of powders detected a greater relative abundance of lactose–melamine condensation product ions in the wet-blended samples, which supported a hypothesis that wet-blending facilitates early Maillard reactions in spray-dried samples. Collectively, these data indicated that the formation of weak, H bonded complexes and labile, early Maillard reaction products between lactose and melamine contribute to spectral differences observed between wet- and dry-blended milk powder samples. These results have implications for future evaluations of adulterated powders and emphasize the important role of sample preparation methods on adulterant detection.
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