Construction of Multilayer Liposomes and the Crucial Role of Chitosan in Stabilizing and Protecting Astaxanthin

Astaxanthin (AST) has poor stability, limiting its food applications. This study harnessed the excellent encapsulation properties and stability of chitosan (CS), combined with soy protein isolates (SPI) as the wall material, to prepare multilayer liposomes for AST delivery. Optimal encapsulation (92.81%) was achieved at 0.8 mg/mL AST and 0.5 mg/mL CS with the first sequence, 5.44% higher than without CS. Characterization showed a multilayered structure (polydispersity index 0.211, diameter 207.1 nm, Zeta potential 58.7 mV); X-ray diffraction (XRD) confirmed AST’s amorphous incorporation within liposomes, while ultraviolet and Fourier Transform infrared spectroscopy (FTIR) indicated hydrogen bonding and electrostatic interactions as main driving forces. CS reduced surface hydrophobicity. The liposomes offered the best protection at pH 5 and 85 °C, improving retention by 1.3% and 2.35%, respectively, over CS-free ones. Simulated gastrointestinal digestion retained 84.19% and 70.03% of AST. This work lays a strong theoretical foundation for advancing AST’s application in the food industry.