Oxidative stability of flaxseed oil: effects of tocopherols, phytosterols and extraction conditions

Flaxseed oil is rich in α-linolenic acid and bioactive compounds but highly susceptible to oxidation. This study evaluated the oxidative stability of flaxseed oil obtained by different cold-pressing methods and supplemented with natural antioxidants-tocopherols and phytosterols. Preheating flaxseeds (80 °C, 2 h) and double pressing improved oil yield and stability through a synergistic interaction between γ-tocopherol and co-extracted phenolics. γ-Tocopherol scavenges lipid peroxyl radicals, while phenolics donate hydrogen atoms and regenerate active γ-tocopherol, enhancing antioxidant capacity. TP supplementation exhibited a temperature-dependent behavior: high α-tocopherol levels showed a transient pro-oxidant effect at low temperatures but contributed to stabilization at moderate and high temperatures through γ-tocopherol persistence. Conversely, PS consistently improved oxidative stability by disrupting the autoxidation chain and stabilizing lipid radicals. The combined use of tocopherols and phytosterols achieved the most effective protection, providing mechanistic insight for developing stable PUFA-rich formulations.