Antioxidant-Enhanced Kraft Lignin Nanoparticles for Stabilizing Pickering Emulsions: Implications for Lipid Oxidation Inhibition and Digestion Profiles

Lipid oxidation existed in various industries, such as food, pharmaceutical, biofuel, and coating, et al., which resulted in nutritional loss, toxicity, reduced stability and shelf life, and economic losses. This is especially true for some bioactive oils existed in the form of emulsion or nanoemulsion. Here, we translate kraft lignin, an underutilized wood-processing side-stream, into Pickering-type emulsifiers that simultaneously suppress oxidation and modulate digestion. Kraft lignin nanoparticles (LPs ≈ 50 nm) manufactured by antisolvent precipitation exhibited a 3-fold higher radical-scavenging capacity (IP50 0.075 mg mL–1) than the parent polymer and outperformed surfactants (Tween-80) in both aqueous-phase radical quenching and interfacial barrier formation. When deployed at 0.5 wt % in sunflower oil Pickering emulsions, LPs reduced primary lipid-hydroperoxide formation by 68% and secondary aldehydic volatiles by 55% relative to Tween-80 controls during accelerated storage (60 °C, 7 days). The emulsion performed excellent physical stability with unchanged droplet morphology across pH 3–8 and 4–60 °C, withstood industrial pasteurization conditions, and remained intact during gastric transit while releasing ≤35% of free fatty acids in simulated intestinal fluid, which is half the rate of Tween-stabilized systems. The work provides formulators with a clean-label, plant-derived ingredient that offers controlled delivery of lipophilic micronutrients, effective suppression of lipid oxidation, and establishes a circular-economy route for converting pulping waste into high-value functional additives.