Determination of cis/trans fatty acid contents in edible oils by 1H NMR spectroscopy in association with multivariate calibration

In this work, cis and trans fatty acid (FA) contents in edible oils was determined using H-1 nuclear magnetic resonance (H-1 NMR) spectroscopy. The comparison of H-1 NMR spectra of edible oil and cis-trans isomerized oil showed that they were different in three regions: (1) 2.880 - 2.650 ppm caused by bis-allylic protons; (2) 2.140 - 1.900 ppm due to allylic protons; and (3) 1.030 - 0.930 ppm due to methyl protons of linolenic acyl groups. The H-1 NMR signals in these regions were combined with partial least squares method to predict contents of cis/trans fatty acids in edible oils. The results showed that the predicted values were consistent with the gas chromatography-measured values and had a good linear relationship with a correlation coefficient (R-2) of above 0.98. This work demonstrates that H-1 NMR spectroscopy was successfully used to determine the composition of both cis and trans fatty acids in edible oils.