In situ reverse micelle-assisted extraction of rosemary antioxidants: A green solvent-free strategy for extending the oxidative stability of flaxseed oils

Highly unsaturated flaxseed oil (rich in α-linolenic acid) is prone to oxidation. An in situ reverse-micelle-assisted extraction (IRMAE) strategy using flaxseed oil as a green solvent was developed to enhance rosemary antioxidant content within. Guided by the polar paradox theory, Ultrasound-assisted IRMAE achieved 45.45 ± 0.11 mg GAE/g DW TPC under optimized conditions (135 W, 11 min, 31 °C) via Box-Behnken design, while simulated IRMAE with 4 % monoglyceride further elevated TPC to 58.91 ± 0.44 mg/g, demonstrating the critical role of emulsifiers in the formation of reverse micelles for enhancing rosemary antioxidant extraction. IRMAE-treated oil showed 2-7 weeks’ longer shelf life than TBHQ-fortified oil, evidenced by lower PV, p-AV, and hexanal (p < 0.05). Small-angle X-ray scattering (SAXS) revealed the formation of spherical reverse micelles (≈2 nm) in the oil matrix after IRMAE, elucidating the enhanced antioxidant encapsulation mechanism. This study establishes IRMAE as a sustainable and efficient approach to improve the oxidative stability of high-unsaturated edible oils through synergistic integration of natural antioxidant extraction and microstructural engineering.