Comparison and chemical structure-related basis of species discrimination of animal fats by Raman spectroscopy using near-infrared and visible excitation lasers

The objective of present study is mainly to compare the discrimination capabilities of near-infrared Fourier transform Raman (FT-Raman, λex~1064 nm) and visible-Raman (vis-Raman, λex~532 nm) spectroscopy for animal fats. All animal fats were analysed by gas chromatography and then the spectra were collected using FT-Raman and vis-Raman spectroscopy. Although vis-Raman spectra partly presented fluorescence interference, the resulting Raman spectra still had higher signal-to-noise ratio than the corresponding FT-Raman spectra. Animal fats from different species produced obvious differences in peak intensity ratios at 1653/1745 and 1653/1441 cm−1, as well as shoulders at 1298 and 1264 cm−1. Chemometric analysis demonstrated that vis-Raman spectroscopy possessed better discrimination capability for animal fat compared to FT-Raman spectroscopy. According to the chemical structure-related basis, the differing degrees of unsaturated fatty acid and relative cis/trans fatty acid contents could be sufficiently reflected in Raman spectra and were the important factors for the successful species discrimination of animal fat.