Monitoring of heat‐induced degradation of edible oils by proton NMR

The degradation process of edible oils of very different nature, submitted to 190 °C with aeration, is studied by means of 1H nuclear magnetic resonance (NMR). In this study, no primary oxidation products, such as hydroperoxides, are detected, the signals of aldehydes being the first to be observed in the 1H NMR spectra. Differences between this degradation process and those occurring at 70 °C with aeration or under microwave action are discussed, not only in relation to the degradation rate of the different acyl groups, but also in relation to the nature and proportions of some of the degradation products generated. Oils rich in oleic acyl groups are not only more resistant to degradation than oils rich in linoleic and linolenic acyl groups, but also produce lower proportions of toxic aldehydes.