Astaxanthin encapsulation in soybean protein isolate–sodium alginate complexes‐stabilized nanoemulsions: antioxidant activities, environmental stability, and in vitro digestibility

Abstract BACKGROUND Nanoemulsions (NEs) have been considered an effective carrier to protect environmentally labile bioactive compounds from degradation during food processing. Among the numerous types of NEs, biopolymer‐stabilized NEs have gained much attention to achieve this function because of the extensive sources, biocompatibility, and tunability. Therefore, the antioxidant activities, environmental stability, and in vitro digestibility of astaxanthin (AST)‐loaded soybean protein isolate (SPI)–alginate (SA) complexes‐stabilized NEs (AST‐SPI–SA‐NEs) were investigated in this study. RESULTS The AST‐SPI–SA‐NEs exhibited an encapsulation efficiency of 88.30 ± 1.67%, which is greater than that of the AST‐loaded SPI‐stabilized NEs (AST‐SPI‐NEs) (77.31 ± 0.83%). Both AST‐SPI–SA‐NEs and AST‐SPI‐NEs exhibited significantly stronger hydroxyl or diphenylpicryl‐hydrazyl radical‐scavenging activities than the free AST. The formation of SPI–SA complexes strengthened the thermal, light, and storage stability of AST‐SPI–SA‐NEs with no apparently increasing mean diameter (around 200 nm). AST‐SPI–SA‐NEs also exhibited a better freeze–thaw dispersibility behavior than AST‐SPI‐NEs. AST‐SPI–SA‐NEs were more stable than AST‐SPI‐NEs were under in vitro gastrointestinal digestion conditions and exhibited a greater bioaccessibility (47.92 ± 0.42%) than both AST‐SPI‐NEs (12.97 ± 1.33%) and free AST (7.87 ± 0.37%). Hydrogen bonding was confirmed to participate in the formation of AST‐SPI–SA‐NEs and AST‐SPI‐NEs based on the molecular docking results. CONCLUSIONS The construction of SPI–SA‐NEs is conducive to the encapsulation, protection, and absorption of AST, providing a promising method for broadening the application of AST in processed foods or developing novel ingredients of functional foods. © 2023 Society of Chemical Industry.