RAPID QUANTITATIVE-DETERMINATION OF FREE FATTY-ACIDS IN FATS AND OILSBY FOURIER-TRANSFORM INFRARED-SPECTROSCOPY

Rapid direct and indirect Fourier transform infrared (FTIR) spectrosco pic 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. Ca libration 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 e xtensive oxidation, an indirect method was developed in which 1% KOH/m ethanol is used to extract the FFAs and convert them to their potassiu m salts. The carboxylate anion absorbs @ 1570 cm-1, well away from int erfering absorptions of carbonyl-containing oxidation end products tha t are commonly present in oxidized oils. Both approaches gave results comparable in precision and accuracy to that of the American Oil Chemi sts' Society reference titration method. Through macroprogramming, the FFA analysis procedure was completely automated, making it suitable f or 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.