Continuous Gradient Temperature Raman Spectroscopy of Unsaturated Fatty Acids: Applications for Fish and Meat Lipids and Rendered Meat Source Identification

摘要

Continuous gradient temperature Raman spectroscopy (GTRS) is a simple, rapid technique for determining the unique structures of fatty acids, triacylglycerols and phospholipids. Improved lipid spectra and vibrational assignments have many applications in food safety and quality. Herein we analyze the residual lipid components in porcine and poultry meat and bone meal (MBM) collected directly from rendering operations. We are developing a rapid throughput GTRS method that requires no special extraction methods or toxic/expensive solvents, and can be adapted to field use. Crude ethanol, methanol and water extracts of pork, poultry samples and 20:80 pork:poultry MBM were investigated from -100 to 80°C. GTRS provides 20 Mb three-dimensional data arrays with 0.2°C increments and graphical first and second derivatives. Comparison of second derivative data showed good reproducibility among samples, with some vibrational modes distinct for either pork or chicken. The 20:80 pork:poultry data showed for the first time that lipid prepared from mixed MBM can be positively identified. Oil from pollack waste was also examined. GTRS and other methods can easily identify pure fishmeal or fishmeal mixed into terrestrial MBM; fishmeal is distinguished by its long-chain polyunsaturated fatty acid content. The analytical challenge is to determine economic or accidental adulteration whereby porcine, bovine or ovine MBM are mixed with each other, or mixed into poultry or fish meals.