title: Quality and statistical classification of Brazilian vegetable oils using mid-infrared and Raman spectroscopy.
abstract: Palm oil, soy oil, sunflower oil, corn oil, castor oil, and rapeseed oil were analyzed with Fourier transform infrared (FT-IR) and FT-Raman spectroscopy. The quality of different oils was evaluated and statistically classified by principal component analysis (PCA) and a partial least  squares (PLS) regression model. First, a calibration set of spectra was selected from one sampling batch. The qualitative variations in spectra are discussed with a prediction of oil composition (saturated, mono- and polyunsaturated fatty acids) from mid-infrared analysis and iodine value  from FT-Raman analysis, based on ratioing the intensity of bands at given wavenumbers. A more robust and convincing oil classification is obtained from two-parameter statistical models. The statistical analysis of FT-Raman spectra favorably distinguishes according to the iodine value, while  the mid-infrared spectra are most sensitive to hydroxyl moieties. Second, the models are validated with a set of spectra from another sampling batch, including the same oil types as-received and after different aging times together with a hydrogenated castor oil and high-oleic sunflower oil.  There is very good agreement between the model predictions and the Raman measurements, but the statistical significance is lower for mid-infrared spectra. In the future, this calibration model will be used to check vegetable oil qualities before using them in polymerization processes.
authors.affiliation: Albert-Lüdwigs-University Freiburg, Institute for Forest Utilization, Werthmannstrasse 6, D-79085 Freiburg, Germany. Pieter.Samyn@fobawi.uni-freiburg.de
authors.forename: Pieter
authors.initials: P
authors.lastname: Samyn
authors.forename: Dieter
authors.initials: D
authors.lastname: Van Nieuwkerke
authors.forename: Gustaaf
authors.initials: G
authors.lastname: Schoukens
authors.forename: Leo
authors.initials: L
authors.lastname: Vonck
authors.forename: Dirk
authors.initials: D
authors.lastname: Stanssens
authors.forename: Henk
authors.initials: H
authors.lastname: Van den Aabbeele
mesh_terms: D001938:Brazil; D016018:Least-Squares Analysis; D010938:Plant Oils / Q000737:chemistry / Q000145:classification* / Q000592:standards; D025341:Principal Component Analysis; D013055:Spectrophotometry, Infrared / Q000379:methods*; D013059:Spectrum Analysis, Raman / Q000379:methods*
chemical_list: D010938:Plant Oils