| In this paper, the lipid composition of animal-derived feedstuff was used to explore the species identification of different animal-derived feeds. The lipid composition of the samples was extracted by the automatic fat analyzer, and the lipid constitution and content was analyzed by gas chromatography(GC). Infrared and Raman spectroscopy were used to collect lipid spectra of different animal-derived feedstuffs. Principal component analysis (PCA), partial least squares-discriminant analysis (PLS-DA) and partial least squares (PLS) combined with spectra were adopted to analyze the species discrimination of animal-derived feedstuff. The identification ability and the mechanism of spectral technique were further discussed. FT-IR was also used to study qualitatively and quantitatively the animal-derived feedstuffs adulterated with ruminant ingredients. In addition, the differences and complementarity of infrared and Raman spectra in species identification based on lipid properties were discussed.(1) Fatty acid composition of animal-derived feed of different species is different. The contents of saturated fatty acids were decreased in bovine, ovine, porcine, poultry meat and bone meal and fish meal,and the content of polyunsaturated fatty acids in fish meal was significantly higher than that in meat and bone meal. C18: 2n6 was abundant in porcine and poultry meat and bone meal, C18: 1n9t was rich in bovine and ovine meat and bone meal, C18: 3n6, C20: 5n3 and C22: 6n3 were abundant in fish meal.Animal-derived feedstuffs of different species could be distinguished based on 37 fatty acid composition and content or CG, which meant species discrimination based on lipid would be possible.(2) Based on the lipid composition, bovine, ovine, porcine, poultry meat and bone meal and fish meal can be successfully identified by FT-IR combined with PCA and PLS-DA. The results showed that the peak at 968 cm-1 was proportional to the content of trans fatty acids. The peak ratio at around 1116 cm-1 and 1098 cm-1 was negatively correlated with the degree of unsaturation. Fish meal samples, compared to meat and bone meal, showed significantly absorption at 916 cm-1.(3) The lipid of animal-derived feed of different species was detected by Raman spectroscopy. The peak ratios of 1654/1748 and 1654/1445 were positively proportional to the degree of unsaturation of animal-derived feeds, with coefficient (r2) of approximately 0.95. It was found that the signal-to-noise ratio of 532 nm Raman spectrum is higher than that of FT-Raman spectrum, and the characteristic absorption peak is also obvious. Combined with PCA and PLS-DA, the species discrimination of 532 nm Raman was superior to FT-Raman.(4) The identification mechanism of infrared and Raman spectra based on lipid characteristics was discussed. The ratios of C=C/C and C=C/C-H and the bond values of C-H (-CH2) were calculated for the lipids of animal-derived feed of different species. The degrees of unsaturation of different kinds of animal-derived feedstuffs was different, which contributed to the difference of the corresponding peak or peak ratio in the spectra, and the difference of them was significant (P < 0.05). The cis fatty acids in animal-derived feedstuffs of different species was significantly different (P < 0.05). The difference of trans fatty acids in ruminant and non ruminant animals was obvious (P < 0.01). Based on the infrared and Raman spectroscopy of lipids, the complementarity of them in lipid discrimination was discussed.(5) In view of the good effect of FT-IR and FT-Raman on the species identification of different animal-derived feedstuffs, FT-IR and FT-Raman were used to qualitatively and quantitatively study the animal-derived feedstuffs adulterated with ruminant ingredients. PCA and PLS-DA results showed that animal-derived feeds with ruminant ingredients can be successfully identified. The PLS model was used to quantitatively detect the samples. |
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