Development of whey protein isolate–phytosterols complexes stabilized oil-in-water emulsion for β-carotene protection and delivery

Although β-carotene (BC) exerts beneficial effects on human health, the direct use of this compound as a nutritional supplement is hindered by its low water solubility and oxidation stability. Herein, we develop an oil-in-water emulsion stabilized by whey protein isolate (WPI)-phytosterols (PS) complexes as a delivery system for BC to overcome the above limitations. The rheology and stability of the emulsion were characterized, and the influence of the emulsion on the chemical stability and bioaccessibility of BC was discussed. The results showed that the PSs promoted the adsorption of WPI at the oil-water interface and improved the viscosity and viscoelasticity of the emulsion. The emulsion with a WPI:PS mass ratio of 25:2 (EWPI-PS) featured the highest fraction of interfacial adsorbed protein (88.73 %), excellent stability during 21-day storage at 25 °C. The BC retention rate of EWPI-PS (61.48 %) was significantly higher than that of the emulsion stabilized by WPI only (EWPI, 31.90 %) after 21-day storage at 50 °C. In addition, BC-loaded EWPI-PS showed higher freeze-thaw and thermal stability than BC-loaded EWPI, and a lower free fatty acid release rate and BC bioaccessibility than BC-loaded EWPI in simulated gastrointestinal digestion experiments. These results provide a theoretical basis for the WPI-PS complexes-stabilized emulsion as BC delivery system.