Mechanism of interaction between astaxanthin and soy protein fibrils: Effects on complexes structure, rheological properties and bioaccessibility

The aim of this research was to explore the mechanism of interaction between astaxanthin (AST) and soy protein fibrils (SPF) and its effect on the structure and rheological properties of SPF. Further, the bioaccessibility of AST after the formation of SPF/AST complexes were also investigated. The acid and thermal conditions (pH 2.0, 85 degrees C) could induce the hydrolysis of soy protein isolates (SPI) into peptides and self-assembly to form SPF with high surface hydrophobicity. Fluorescence spectroscopy analysis showed that AST statically quenched SPI or SPF with binding constants of 2.2511 and 2.9327 x 104 L/mol at 298 K, respectively. Hydrophobic interaction and hydrogen bonds acted as the prime driving forcesin in SPF/AST system. The results of synchronous fluorescence spectroscopy, UV-vis spectroscopy, surface hydrophobicity, and zeta potential showed that the addition of AST led to a conformational change of SPF and promoted the exposure of charged amino acids inside the SPF molecule. Infrared spectroscopy and Thioflavin T (Th T) fluorescence results showed that the beta-sheet content in SPF decreased significantly with increasing AST concentration, and its fibril structure was depolymerized and reconstructed by AST. Therefore, the viscosity of SPF/AST complex was significantly reduced. And the SPF/AST complexes had the greatest AST bioaccessibility (50.4%). This study contributed to a comprehensive understanding of the interaction mechanism between SPF and AST, expanding their application in the food and pharmaceutical industries.