Novel approach to study fish oil oxidation using 1H nuclear magnetic resonance spectroscopy

Abstract

The oxidative degradation of omega-3 fatty acids-rich fish oil was investigated by 1H Nuclear Magnetic Resonance (NMR) Spectroscopy. The intensities of key distinct spectral signals corresponding to bis-allylic (RBAG) and terminal methyl groups (RO3TG) from omega-3 fatty acid residues were monitored in relation to the sn-2 glycerol peak from triacylglycerols, in fish oil oxidized under various conditions. Under oxygen-rich conditions and accelerated oxidation, RBAG and RO3TG decreased sharply over time, whereas under oxygen-limited conditions, they remained unchanged throughout the entire length of the storage, demonstrating that the method has a practical applicability for comparing storage conditions and antioxidants behaviors. At ambient temperature and limited oxygen availability, the NMR indicators declined steadily only after the initial period in which they increased. It was hypothesized that sn-2 hydrolysis followed by initiation of oxidation via electron transfer and decarboxylation may be responsible for these observations.