Determination of olive oil free fatty acid by fourier transform infrared spectroscopy |
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Authors: | Enriqueta Bertran Marcelo Blanco Jordi Coello Hortensia Iturriaga Santiago Maspoch Ivan Montoliu |
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Affiliation: | (1) Unitat de Química Analítica, Departament de Química, Edifici CN, Universitat Autònoma de Barcelona, E-08193 Bellaterra, Barcelona, Spain |
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Abstract: | A new procedure for determining free fatty acids (FFA) in olive oil based on spectroscopic Fourier transform infrared-attenuated
total reflectance spectroscopy measurements is proposed. The range of FFA contents of samples was extended by adding oleic
acid to several virgin and pure olive oils, from 0.1 to 2.1%. Calibration models were constructed using partial least-squares
regression (PLSR). Two wavenumber ranges (1775–1689 cm−1 and 1480–1050 cm−1) and several pretreatments first and second derivative; standard normal variate (SNV)] were tested. To obtain good results,
splitting of the calibration range into two concentration intervals (0.1 to 0.5% and 0.5 to 2.1%) was needed. The use of SNV
as a pretreatment allows one to analyze samples of different origins. The best results were those obtained in the 1775–1689
cm−1 range, using 3 PLSR components. In both concentration ranges, at a confidence interval of α = 0.05, no significant differences
between the reference values and the calculated values were observed. Reliability of the calibration vs. stressed oil samples
was tested, obtaining satisfactory results. The developed method was rapid, with a total analysis time of 5 min; it is environment-friendly,
and it is applicable to samples of different categories (extra virgin, virgin, pure, and pomace oil). |
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Keywords: | ATR free fatty acid FTIR multivariate calibration olive oil PLSR quality control |
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