Dietary Selenium Supplementation Improves the Antioxidant Capacity and Oxidative Stability of Camellia oleifera Seed Oil

The use of plant-based biofortification techniques presented only a limited increase in selenium enrichment in Camellia oleifera seed oil (COSO). Direct selenium enrichment represents a useful approach to increase both the selenium concentration and the nutraceutical value of COSO. Besides, the antioxidant properties of selenium-enriched COSO are not yet sufficiently characterized. Here, the total phenolic contents and total flavonoid contents of the COSO samples from different geographical origins were determined. Furthermore, DPPH radical scavenging, ABTS decolorization, and FRAP assays were used to evaluate the association between selenium concentration and the antioxidant capacity. The antioxidant assays showed that the ABTS radical cation scavenging capacity is mainly driven by the phenolics, while the DPPH radical scavenging capacity involves both the phenolics and polyphenolic contents. The supplementation of selenoprotein and Se-methylselenocysteine (SeMC) not only enhanced overall antioxidant capacity, but also conferred protection against lipid oxidation. Besides, the selenium-fortified samples in general kept the characteristic flavor profile, although a measurable reduction in overall aroma intensity was observed. Altogether, selenoprotein and SeMC demonstrated promise as selenium-fortifying agents for COSO, and direct selenium fortification of COSO is a technically feasible and nutritionally effective intervention to elevate its selenium concentration and enhance its nutraceutical functionality. These results support the antioxidant capacity of COSO and show the essential contribution of selenium to its functionality as a dietary supplement with nutraceutical properties.