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Title: Potential of Raman spectroscopy and imaging methods for rapid and routine screening of the presence of melamine in animal feed and foods

Author
item LIU, YONGLIANG - U-MD, COLLEGE PARK
item Chao, Kuanglin - Kevin Chao
item Kim, Moon
item TUSCHEL, DAVID - CHEMIMAGE CORP, PA
item OLKHOVYK, OKSANA - CHEMIMAGE CORP, PA
item PRIORE, RYAN - CHEMIMAGE CORP, PA

Submitted to: Applied Spectroscopy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/10/2009
Publication Date: 4/25/2009
Citation: Liu, Y., Chao, K., Kim, M.S., Tuschel, D., Olkhovyk, O., Priore, R.J. 2009. Potential of Raman spectroscopy and imaging methods for rapid and routine screening of the presence of melamine in animal feed and foods. Applied Spectroscopy. 63(4):477-480.

Interpretive Summary: Recent contamination incidents involving animal feed ingredients have raised public concerns about food safety. Melamine was found to have been added into animal feed, in amounts ranging from 0.2 percent to 8 percent of total mass, to improve the "total nitrogen content" that is indicative of protein content. FDA and other agencies have developed GC-MS and LC-MS/MS methods for the analysis of melamine and its derivatives. Although these methods can detect melamine in trace amounts, the time-consuming laboratory procedures require chemical solvents and multiple extraction and centrifugation steps. ARS and ChemImage Corp. have jointly developed detection/identification methods based on Raman spectroscopic and imaging techniques for the detection of melamine mixed into wheat flour, corn gluten, and soy meal, in the interest of developing methods for rapid and routine nondestructive screening methods that require minimal sample preparation. We found Raman shifts occurring in the melamine mixtures that are unique to chemical compounds with triazine structure. The Raman shift at wavenumber 670 cm-1 coupled with an adjacent band can be used for a two-band ratio for the detection of melamine. Raman chemical imaging technique was also applied to identify and image melamine in a wheat flour matrix. Raman spectral imaging is demonstrated as a promising method of detection of intentional tainting of agricultural commodities that affects the safety and security of foods and feed materials. Potential users of such rapid and routine detection methods have been identified to include US regulatory agencies such as the FDA, import companies which handle food and feed ingredients.

Technical Abstract: This study presented the usefulness of the FT-Raman technique for the screening of melamine contamination in food/feed materials. The characteristic melamine Raman band near 670 cm-1 was observed to be intense and well-separated from other bands attributed to food/feed components. This 670 cm-1 melamine band was used to develop simple ratio algorithms for melamine detection. The results revealed that the ratio algorithm could be used not only to perform the classification analysis between uncontaminated and melamine-contaminated classes at levels as low as 0.2 percent (w/w), but also to predict the melamine concentrations in contaminated products. Notably, the two-band algorithm approach is the most attractive and interesting since, in its simplest form, there is no calibration model that needs to be first built from a large sample set. In addition, the use of a ratio of wavelength intensities can reduce the influence measurement variation, and hence could be easily applied for fast, accurate, specific, and routine screening of melamine contaminant in unknown products. A Raman Chemical Imaging technique was applied to identify and image melamine in a wheat flour matrix. Raman spectral imaging is demonstrated as a promising method of detection of intentional tainting of agricultural commodities that affects the safety and security of foods and feeds.