Determination of the acid values of edible oils via FTIR spectroscopy based on the O[sbnd]H stretching band.

A new method for determining the acid values (AVs) of edible oils based on the O H stretching band was developed. The oil sample was diluted with carbon tetrachloride and was placed in a quartz cuvette with a thickness of 1 cm to record the FTIR spectrum. The peak at 3535 cm −1 , which corresponds to the O H stretch of the carboxyl group in free fatty acids, together with the peak valley at 3508 cm −1 and the spectral data in the range of 3340–3390 cm −1 were used to determine the AV of the edible oil. The excellent linear relationship between the AVs measured in this work and those measured using a titration method, with a correlation coefficient (R) of 0.9929, indicates that the present procedure can be applied as an alternative to the classic method for determining the AVs of edible oils. [ABSTRACT FROM AUTHOR]