Evaluation of the Oxidative Process of Chia Seed Oil by Means of ESR Combined with LF-NMR and SAXS

Chia seed oil, valued for its health-promoting omega-3 and omega-6 fatty acids, is highly susceptible to oxidation. This study employed a multi-technique approach based on electron spin resonance (ESR), low-field nuclear magnetic resonance (LF-NMR), and small-angle X-ray scattering (SAXS) to monitor its oxidative process. ESR identified alkyl (DMPO-•R) and peroxyl (DMPO-•OOR) radicals as primary species derived from unsaturated fatty acids. This was accompanied by a decrease in relaxation time of peak T₂₁, T₂₂, and T₂₃, and the peak area of S₂₁ gradually increased as the heating time increased. The SAXS intensity of chia seed oil at q = 3.4 nm^-1 increased markedly after heating for 20 h, and the peak shifted to the low q-region with Δq = 0.6 nm^-1, confirming the significant formation of nanoscale aggregates, which correlated with observed increases in oil turbidity. Our findings demonstrate the value of an integrated analytical strategy for a comprehensive understanding of oxidation in chia seed oil.