Astaxanthin Encapsulation in Zein/Chito-Oligosaccharide Composite Nanoparticles: Characterization, Stability, Antioxidant Efficacy and Bioaccessibility

Astaxanthin (AST) has been widely studied for its potential antioxidant and anti-inflammatory effects; however, its application is limited by poor water solubility and low bioavailability. To address this, zein and chito-oligosaccharides composite nanoparticles (ZCNps) were constructed using antisolvent precipitation for efficient AST delivery. At a zein to COS mass ratio of 10:1, AST-loaded ZCNps (ZCANps) achieved an encapsulation efficiency of 81.23% and drug loading of 4.18 mg/g. Structural characterization confirmed that AST was successfully encapsulated in an amorphous state, stabilized by hydrophobic interactions and hydrogen bonding. ZCANps demonstrated stability under a wide range of conditions, including pH levels of 2–8, NaCl concentrations of up to 50 mmol/L, temperatures of up to 80°C, and storage for 8 weeks at 4°C. Additionally, ZCANps provided 62% UV-light protection for AST. Compared to free AST, the encapsulated form showed significantly enhanced antioxidant activity and bioaccessibility. These results highlight ZCNps as a delivery system for improving the stability, bioavailability, and functional properties of AST in food applications.