Monitoring of fatty acid composition in virgin olive oil by Fourier transformed infrared spectroscopy coupled with partial least squares

A rapid Fourier transformed infrared (FTIR) attenuated total reflectance (ATR) spectroscopic method was applied to the determination of fatty acid (FA) profile and peroxide value (PV) of virgin olive oil. Calibration models were constructed using partial least squares (PLS) regression. A FA calibration model was constructed in the spectral range from 3033 to 700 cm-1. Oleic acid (62.0-80.0%), linoleic acid (5.3-15.0%), saturated fatty acids (SFA, 12.6-19.7%), mono-unsaturated fatty acids (MUFA, 64.4-81.0%) and poly-unsaturated fatty acids (PUFA, 6.0-15.9%) were considered for chemometric analysis. PV (5.7-15.7 meq O2 kg-1) was calibrated using the signal of the full spectral range 4000-700 cm-1 with first derivative pre-treatment. The LODs of the FTIR-chemometric methods were: 3.0% for oleic acid, 0.5% for linoleic acid, 1.3% for SFA, 3.0% for MUFA, 0.3% for PUFA and 1.0 meq O2 kg-1 for PV. Analytical methods were evaluated by use of validation samples (n = 25 for all the FA related parameters and n = 10 for PV) with nearly quantitative recovery rates (98-103%). The proposed method provided results comparable to official procedures, with the advantages of being less expensive and more rapid.