¹H NMR spectroscopy as tool to follow changes in the fatty acids of fish oils

High-resolution NMR spectroscopy is a fast and accurate tool to measure the content of n-3 PUFA in unoxidised oils. Four types of fish oils with a high amount of n-3 PUFA were oxidised under different conditions, and the changes in their fatty acid pattern were monitored with NMR spectroscopy and compared with traditional analytical methods, especially GC. Good compliances were obtained for unoxidised oils and for oils at the early oxidation stages. Distinct changes in signals or signal ratio intensities arose only in higher-oxidised oils that were irradiated or heated in the presence of oxygen over several days. Slight differences between values obtained by GC and NMR at this point were likely caused by accumulation of oxidation products. Detection of the terminal lipid oxidation products propanal and 2-propenal was only possible at late oxidation stages.