Rapid quantitative determination of free fatty acids in fats and oils by fourier transform infrared spectroscopy |
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Authors: | A A Ismail F R van de Voort G Emo J Sedman |
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Affiliation: | (1) Department of Food Science and Agricultural Chemistry, Macdonald Campus, McGill University, Ste. Anne de Bellevue, Box 187, H9X 1C0 Quebec, Canada |
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Abstract: | Rapid direct and indirect Fourier transform infrared (FTIR) spectroscopic methods were developed for the determination of
free fatty acids (FFA) in fats and oils based on both transmission and attenuated total reflectance approaches, covering an
analytical range of 0.2–8% FFA. Calibration curves were prepared by adding oleic acid to the oil chosen for analysis and measuring
the C=O band @ 1711 cm–1 after ratioing the sample spectrum against that of the same oil free of fatty acids. For fats and oils that may have undergone
significant thermal stress or extensive oxidation, an indirect method was developed in which 1% KOH/methanol is used to extract
the FFAs and convert them to their potassium salts. The carboxylate anion absorbs @ 1570 cm–1, well away from interfering absorptions of carbonyl-containing oxidation end products that are commonly present in oxidized
oils. Both approaches gave results comparable in precision and accuracy to that of the American Oil Chemists’ Society reference
titration method. Through macroprogramming, the FFA analysis procedure was completely automated, making it suitable for routine
quality control applications. As such, the method requires no knowledge of FTIR spectroscopy on the part of the operator,
and an analysis takes less than 2 min. |
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Keywords: | Fats and oils free fatty acids Fourier transform infrared spectroscopy quality control |
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