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.