Abstract
Omega-3 fatty acids deliver essential health benefits but are highly prone to oxidation, limiting food applications. Clean-label strategies that combine natural antioxidants with protein-based emulsifiers are therefore critical for stabilizing ω-3-enriched emulsions. This study investigated pH-responsive antioxidant nanocarriers based on whey protein isolate (WPI) and thymol for stabilizing algal ω-3 oil emulsions. Fluorescence quenching confirmed static complex formation, with Stern–Volmer constants rising from 3.0 × 109 M−1 at pH 3.0 to 5.8 × 109 M−1 at pH 7.0, reflecting stronger binding as β-lactoglobulin unfolded. Complexation reduced WPI aggregate size near the isoelectric point from 256 to 108 nm and increased absolute ζ-potential from ±17 to ±24 mV, generating colloids that produced sub-micron emulsions (0.62–0.73 μm) stable for 10 days, with creaming index decreasing by about 6 %. Thymol retained 86–97 % of its antioxidant activity after binding and, when interfacially located, significantly reduced lipid oxidation. After 11 days at 4 °C, peroxide values were 5.5–6.8 mEq O2 kg−1 compared to 14.7 in bulk oil, while malondialdehyde levels were <6.2 μg kg−1 versus 23.0 μg kg−1 in bulk oil. Overall, WPI–thymol nanocarriers acted as dual emulsifiers and antioxidants, offering a clean-label approach for shelf-life extension. Future work should examine long-term storage and performance in complex foods.