Thermal oxidation process accelerates degradation of the olive oil mixed with sunflower oil and enables its discrimination using synchronous fluorescence spectroscopy and chemometric analysis.
We have investigated the effect of thermal treatment on the discrimination of pure extra virgin olive oil (EVOO) samples from EVOO samples adulterated with sunflower oil. Two groups of samples were used. One group was analyzed at room temperature (25°C) and the other group was thermally treated in a thermostatic water bath at 75°C for 8h, in contact with air and with light exposure, to favor oxidation. All samples were then measured with synchronous fluorescence spectroscopy. Fluorescence spectra were acquired by varying the excitation wavelength in the region from 250 to 720nm. In order to optimize the differences between excitation and emission wavelengths, four constant differential wavelengths, i.e., 20nm, 40nm, 60nm and 80nm, were tried. Partial least-squares discriminant analysis (PLS-DA) was used to discriminate between pure and adulterated oils. It was found that the 20nm difference was the optimal, at which the discrimination models showed the best results. The best PLS-DA models were those built with the difference spectra (75-25°C), which were able to discriminate pure from adulterated oils at a 2% level of adulteration. Furthermore, PLS regression models were built to quantify the level of adulteration. Again, the best model was the one built with the difference spectra, with a prediction error of 1.75% of adulteration.
Department of Biological Sciences & Chemistry, College of Arts and Sciences, University of Nizwa, Oman. Electronic address: mehboob@unizwa.edu.om.
Fazal
F
Mabood
Department of Analytical Chemistry and Organic Chemistry, Universitat Rovira i Virgili, Tarragona, Spain.
Ricard
R
Boqué
Department of Chemistry, University of Rome "Sapienza", P.e Aldo Moro 5, I-00185 Rome, Italy.
Rita
R
Folcarelli
Department of Analytical Chemistry and Organic Chemistry, Universitat Rovira i Virgili, Tarragona, Spain.
Olga
O
Busto
Department of Biological Sciences & Chemistry, College of Arts and Sciences, University of Nizwa, Oman.
Ahmed
A
Al-Harrasi
Department of Biological Sciences & Chemistry, College of Arts and Sciences, University of Nizwa, Oman.
Javid
J
Hussain
D006368:Helianthus; D006358:Hot Temperature; D031658:Olea; D000069463:Olive Oil / Q000737:chemistry*; D010084:Oxidation-Reduction; D010938:Plant Oils / Q000737:chemistry*; D013050:Spectrometry, Fluorescence; D000074242:Sunflower Oil
D000069463:Olive Oil; D010938:Plant Oils; D000074242:Sunflower Oil
Adulteration; Extra virgin olive oil (EVOO); PLS regression; PLS-DA; Synchronous fluorescence spectroscopy; Thermal treatment