Lactoferrin-based ethanol-tolerant emulsions reinforced by interfacial-bulk co-design: Enhancing β-carotene stability under multiple stresses.

Ethanol-aqueous environments severely compromise emulsion stability and accelerate the degradation of lipophilic nutraceuticals. In this study, ethanol-tolerant emulsions were engineered through an interfacial-bulk co-design strategy using tea saponin (TS)-reinforced lactoferrin (LF) interfacial layers and fructooligosaccharides (FOS) bulk modulation to improve β-carotene retention. LF-TS association markedly enhanced interfacial activity, reducing interfacial tension from 32.0 to 4.1 mN/m and increasing the emulsifying activity index by 32.8%. Interfacial dilatational rheology confirmed that the ternary LF-TS/FOS system formed the strongest and most elastic interfacial film, while adsorption kinetic analysis revealed a balanced diffusion-penetration-rearrangement pathway that supported efficient interfacial adsorption and film maturation. Meanwhile, FOS-enabled bulk co-structuring generated uniform nano-complexes and improved β-carotene encapsulation efficiency from 64.4% to 90.1%. The optimized emulsions showed enhanced β-carotene retention under multiple environmental stresses, with thermal retention increasing from 43.8% to 77.0% and UV-photodegradation half-life extending from 1.5 to 4.8 h. The co-designed system also maintained good physical stability under high ionic strength and during accelerated storage at 37 °C. Overall, this interfacial-bulk co-modulation strategy provides an effective approach for constructing ethanol-tolerant delivery systems for sensitive lipophilic bioactives.