FTIR estimation of free fatty acid content in crude oils extracted from damaged soybeans

Abstract

A user-interactive computer-assisted Fourier transform infrared (FTIR) method has been developed for estimation of free fatty acids (FFA} in vegetable oil samples by deconvolution of the infrared {IR) absorbances corresponding to the triglyceride ester and FFA carbonyl bonds. Peak areas were used to determine FFA as a percentage of the total carbonyl areas in weighed standards of refined, bleached, deodorized soybean oil containing from 0 to 5% added oleic acid. These data for percent FFA by FTIR were compared to corresponding FFA data obtained by two titration methods--the AOCS Official Method Ca 5a-40 and the Official Method with a slight modification. Correlation coefficients were 0.999 for the Ca 5a-40, 0.999 for the modified and 0.989 for the FTIR methods. FFA in samples of crude soybean oils extracted from damaged beans {0.5 to 2.1% FFA) were measured by FTIR and compared to data obtained by titration of the same samples {correlation coefficient, 0.869}.

Rapid quantitative determination of free fatty acids in fats and oils by fourier transform infrared spectroscopy

“…By calibrating the method with oleic acid, the results obtained are expressed directly in terms of the reference method. A similar, but less straightforward, approach has been taken by other workers (17), who described the FTIR determination of the FFA content of soybean oil. Their analysis required the application of spectral deconvolution techniques because they did not ratio the spectra of samples against that of a reference oil, and therefore, the FFA peak was overlapped by the much stronger ester linkage carbonyl band.…”

Vibrational Spectroscopy of Food and Food Products

“…33 The principles of this PV method were also employed in the development of a PLS-based FT-NIR method. 34 FT-IR methods for the determination of other minor components present in oils, including free fatty acids in refined 35,36 and crude oils, 37,38 b-carotene in palm oil, 39 and phospholipids in vegetable oils, 40 have also been reported.…”

Determination of the acid values of edible oils via FTIR spectroscopy based on the OH stretching band

“…By ratioing against the spectrum of fatty acid-free oil, the spectral contribution of the oil could be eliminated, leaving only the spectrum of the fatty acids (Ismail, Voort, Emo, & Sedman, 1993). To distinguish between bands of the carbonyl groups of free acid and ester, Lanser, List, Holloway, and Mounts (1991) estimated the free fatty acid content in oil by deconvoluting the absorption bands between 2000 and 1600 cm À1 (Lanser et al, 1991). However, this characteristic peak is not applicable for the determination of the AVs of fats and oils that have been extensively oxidized or thermally stressed (Ismail et al, 1993).…”