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• Contents of trans fatty acids in oils was determined by 1H NMR spectroscopy in association with multivariate calibration. • The 1H NMR spectra of edible and cis-trans isomerized oils are different in three chemical shift regions. • The difference of the 1H NMR spectra of cis and tans unsaturated fatty acids was analyzed. • The PLS method were successfully applied to predict the contents of unsaturated fatty acids in oils. In this work, cis and trans fatty acid (FA) contents in edible oils was determined using 1H nuclear magnetic resonance (1H NMR) spectroscopy. The comparison of 1H 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 1H 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 (R2) of above 0.98. This work demonstrates that 1H NMR spectroscopy was successfully used to determine the composition of both cis and trans fatty acids in edible oils. [ABSTRACT FROM AUTHOR]