Raman spectroscopy: A rapid method to assess the effects of pasture feeding on the nutritional quality of butter

摘要

The animal diet is a critical variable affecting thecomposition and functionality of dairy products. As“Grass-Fed” labeling becomes more prominent on themarket, rapid and label-free methods for verification offeeding systems are required. This work proposes theuse of Raman spectroscopy to study the effects of 3different experimental cow feeding systems—perennialryegrass pasture, perennial ryegrass with white cloverpasture, and an indoor total mixed ration diet (TMR)—on the nutritional quality of sweet cream butter. Theresults demonstrate that Raman spectroscopy coupledwith multivariate analysis is a promising approach todistinguish butter derived from pasture or conventionalTMR feeding systems. A Pearson correlation analysisconfirmed high positive correlations between the spectralbin at 1,657 cm~(−1), ascribed to the stretching vibrationsof C=C bonds, and concentrations of α-linolenicacid and conjugated linolenic acid (CLA) in butter,and in general with the concentration of n-3 and n-3+CLA fatty acids and polyunsaturated fatty acids inthe samples. The yellow color indicative of the presenceof carotenoids in butter, which has previously beensuggested as a biomarker of pasture or “Grass-Fed”feeding, was also positively correlated with the dataobtained from the Raman spectra. Raman spectroscopycould also be used to accurately predict indicators ofthe nutritional quality of butter, such as the thrombogenicindex, which showed a strong negative correlationwith the spectral bin at 3,023 cm~(−1).