Multivariate prediction of clarified butter composition using Raman spectroscopy

• Published in: Lipids Vol. 39; no. 9; pp. 897 - 906
• Main Authors: Beattie, J.R, Bell, S.E.J, Borgaard, C, Fearon, A.M, Moss, B.W
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer‐Verlag 01-09-2004; Springer Nature B.V
• Subjects: Butter - analysis; Chromatography, Gas; Dairy cattle; Data collection; Fatty Acids - analysis; Fatty Acids - chemistry; High temperature; Iodine; Least-Squares Analysis; Lipids - analysis; Lipids - chemistry; Low temperature; Multivariate Analysis; Predictive Value of Tests; Quality control; Rapeseed oil; Sample preparation; Spectroscopy; Spectrum Analysis, Raman - methods; Triglycerides - analysis; Triglycerides - chemistry
• ISSN: 0024-4201; 1558-9307
• DOI: 10.1007/s11745-004-1312-5

Raman spectroscopy has been used to predict the abundance of the FA in clarified butterfat that was obtained from dairy cows fed a range of levels of rapeseed oil in their diet. Partial least squares regression of the Raman spectra against FA compositions obtained by GC showed that good prediction of the five major (abundance >5%) FA gave R2=0.74–0.92 with a SE of prediction (RMSEP) that was 5–7% of the mean. In general, the prediction accuracy fell with decreasing abundance in the sample, but the RMSEP was <10% for all but one of the 10 FA present at levels >1.25%. The Raman method has the best prediction ability for unsaturated FA (R2=0.85–0.92), and in particular trans unsaturated FA (best‐predicted FA was 18∶1tΔ9). This enhancement was attributed to the isolation of the unsaturated modes from the saturated modes and the significantly higher spectral response of unsaturated bonds compared with saturated bonds. Raman spectra of the melted butter samples could also be used to predict bulk parameters calculated from standard analyzes, such as iodine value (R2=0.80) and solid fat content at low temperature (R2=0.87). For solid fat contents determined at higher temperatures, the prediction ability was significantly reduced (R2=0.42), and this decrease in performance was attributed to the smaller range of values in solid fat content at the higher temperatures. Finally, although the prediction errors for the abundances of each of the FA in a given sample are much larger with Raman than with full GC analysis, the accuracy is acceptably high for quality control applications. This, combined with the fact that Raman spectra can be obtained with no sample preparation and with 60‐s data collection times, means that high‐throughput, on‐line Raman analysis of butter samples should be possible.