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.

Raman spectroscopy study of edible oils and determination of the oxidative stability at frying temperatures

“…Fatty acid (FA) composition is an important parameter for the evaluation of edible oils. It is also used to assure their authenticity and detect frauds . Table shows the major fatty acids present in the oils studied in this work.…”

“…Specially suitable for this purpose are 1 H and 13 C NMR spectroscopies . However, the use of Raman spectroscopy for this purpose has grown dramatically in recent years, especially for the quantitative detection of adulteration of extra virgin olive oil with other, cheaper edible oils , its authentication or even the determination of some chemical species such as antioxidants and free fatty acids present not only in olive oil, but also in other vegetable oils. In addition, Raman spectroscopy has been used to assess stability against oxidation in olive oil .…”

Hybrid palm-oil/styrene-maleimide nanoparticles synthesized in aqueous dispersion under different conditions

“…The oil composition and physical properties were previously characterized with spectroscopy (Samyn et al, 2012b) and thermal analysis (Samyn et al, 2012c): the PO has a iodine value of 54 g(I 2 )/100 g oil, peroxide value of 2.1 meq/kg, saponification value of 198 mg (KOH)/1 g oil and acid value of 0.10. The average fatty acid profile comprises 0.3% (C12:0), 0.7% (C14:0), 43.0% (C16:0), 4.5% (C18:0), 0.3% (C20:0), 0.3% (C16:1), 41.0% (C18:1), 0.1% (C20:1), 9.5% (C18:2), 0.4% (C18:3).…”

Synthesis of imidized nanoparticles containing soy oil under various reaction conditions

“…The oil composition and physical properties were previously characterized by spectroscopy [36], and thermal analysis [37]: it has a iodine value I.V. = 122 g(I 2 )/100 g oil, peroxide value = 2.7 meq/kg, saponification value = 195 mg (KOH)/1 g oil and acid value <1.…”