Office of Regulatory Science, Center for Food Safety and Applied Nutrition, United States Food and Drug Administration , 5001 Campus Drive, College Park, Maryland 20740, United States.
Research and Development, Abbott Nutrition , 3300 Stelzer Road, Columbus, Ohio 43219, United States.
J Agric Food Chem. 2017 Jul 19;65(28):5789-5798. doi: 10.1021/acs.jafc.7b00834. Epub 2017 Jul 6.
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 (H 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 H 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.
在开发快速筛选方法以检测经济掺假的过程中，将三聚氰胺溶解在液态奶中制备的喷雾干燥奶粉在近红外（NIR）和拉曼光谱中表现出意想不到的三聚氰胺特征的损失。为了进一步表征这种“湿混”现象，制备了喷雾干燥的三聚氰胺和乳糖样品作为简化模型，并通过近红外光谱、拉曼光谱、质子核磁共振（H NMR）和实时直接分析傅里叶变换质谱（DART-FTMS）进行了研究。与干混样品相比，在湿混乳糖-三聚氰胺样品中，NIR 和拉曼光谱中的特征三聚氰胺带消失或移动。湿混和干混样品之间三聚氰胺 H NMR 光谱的细微偏移表明三聚氰胺氢键状态存在差异。粉末的定性 DART-FTMS 分析检测到湿混样品中乳糖-三聚氰胺缩合产物离子的相对丰度更大，这支持了一种假设，即湿混有助于喷雾干燥样品中早期美拉德反应的发生。这些数据表明，乳糖和三聚氰胺之间形成的弱氢键复合物和不稳定的早期美拉德反应产物导致了湿混和干混奶粉样品之间观察到的光谱差异。这些结果对未来掺假粉末的评估具有重要意义，并强调了样品制备方法对掺杂物检测的重要作用。
