Simultaneous quantitative determination of isolated trans fatty acids and conjugated linoleic acids in oils and fats by chemometric analysis of the infrared profiles

Abstract

Trans fatty acids and conjugated linoleic acids (CLA) in edible oils and fats have been for the first time quantitatively determined simultaneously using infrared spectroscopy and chemometrics. The task has been achieved by establishing calibration models using the infrared spectral profiles of the mixtures of trans and CLA fatty acids in virgin olive oil which is free of trans and CLA. The infrared profiles were scanned in the region 1000–850 cm −1 where the CH bending vibrations of the trans fatty acids and CH deformation vibrations of the CLA fall. Two calibration models, one for trans and/or CLA in the range 1–2.5% in olive oil and a second for trans and/or CLA in the range 0–30% in olive oil were established. The partial-least-squares (PLA) technique was used in establishing calibration models. Cross validation procedure was used in validating the calibration models. These models were then used to predict some laboratory-prepared samples and a natural sample (beef fat) for their trans and CLA contents. The model established for the lower concentration range predicts trans and CLA contents with an error limit of ±0.1% and at the same time the model established for high concentration range predicts trans and CLA contents with error limits of ±0.9 and ±0.5%, respectively. The predicted values in beef fat are in the range reported for this sample in the literature. These values were further confirmed by addition technique.