Tailoring nano-scale reverse micelles in animal fats for enhanced thermal oxidation resistance: A green in situ extraction of rosemary antioxidants

Animal fats exhibit greater susceptibility to thermal degradation than vegetable oils, partly attributable to their lower content of endogenous minor components (e.g., natural antioxidants), which restricts their application in high-temperature food processing. This study pioneers a solvent-free strategy to stabilize animal fats (lard, beef tallow, chicken oil, and basa fish oil) via direct enrichment with rosemary antioxidants through in-situ reverse micelle-assisted extraction (IRMAE). To maximize polar polyphenol incorporation, food-grade emulsifiers were employed to tune the interfacial assembly of antioxidant-loaded reverse micelles. Among tested matrices, lard exhibited the highest extraction affinity, yielding rosmarinic acid (RA) and carnosic acid (CA) at 8.16% and 52.88%, respectively. Incorporation of lecithin further optimized the system, increasing RA concentration to 42.84 μg/g, a 5.22-fold enhancement over raw oil. Small-angle X-ray scattering (SAXS) revealed the presence of spherical nanostructures (radius ∼2 nm) consistent with reverse micelles, where the lecithin-based interfacial film is proposed to provide a robust micro-aqueous environment for sequestering polar antioxidants. Frying tests demonstrated that these nanostructure assemblies significantly inhibited increases in acid value (AV), total oxidation (TOTOX), and conjugated diene/triene (CD/CT) levels. This work proposes a clean-label approach for the long-term stabilization of traditional animal fats, integrating green extraction with advanced lipid protection strategies.