A simple and practical method for determining iodine values of oils and fats by the FTIR spectrometer with an infrared quartz cuvette

Abstract

A rapid and practical method for determining the iodine value (IV) of edible oils or fats with an FTIR spectrometer combined with a quartz cuvette was reported. The sample was diluted with carbon tetrachloride and poured into a quartz cuvette (thickness: 1 cm) to measure the FTIR spectrum in the wavenumber region from 2400 to 4000 cm⁻¹. The peak near 3009 cm⁻¹ corresponding to C–H stretching was corrected with a baseline connecting the absorbance values near 3030 and 2990 cm⁻¹ and used to determine the IV of edible oils and fats by the calibration curve method. A linear relationship between A_p/c, the ratio of the peak absorbance to the concentration of oil, and the IV of oil or fat obtained with the official AOCS titration method was established with a correlation coefficient of 0.9987, and the IVs of 36 samples were determined. The effect of unsaturated fatty acid composition of oil and fat on the FTIR spectra and the predicted IV was discussed. The proposed method was suitable for determining the IV of edible oils and fats in which almost all the olefinic bonds were in the cis configuration.