Optimizing soy protein-octenylsuccinylated starch emulsions to enhance lutein stability and bioavailability in infant-relevant models

Abstract Objective This study aimed to develop and optimize a biopolymer-stabilized lutein emulsion using octenylsuccinylated starch (OSS) and soy protein isolate (SPI) to enhance lutein stability, in vitro bioaccessibility, and in vivo bioavailability in neonatal rats. Background Lutein is an essential carotenoid with antioxidant and anti-inflammatory properties that support infant visual and cognitive development. However, its poor stability and bioavailability limit its effectiveness in functional food applications. Methods A simplex-centroid mixture design was used to determine optimal OSS-to-SPI ratios for improved emulsion performance. Emulsions were evaluated for emulsification index, droplet size, and microstructure using confocal laser scanning microscopy. Stability under UV light and heat was assessed, followed by in vitro infant digestion and an in vivo neonatal rat study. Results SPI-OSS emulsions demonstrated superior protection against lutein degradation compared with free lutein. In vitro digestion showed a 3.85-fold increase in bioaccessibility, and the in vivo study confirmed enhanced bioavailability, with significantly higher lutein concentrations in serum, brain, and eyes. Conclusions SPI-OSS emulsions represent an effective delivery system for improving lutein stability and absorption. This approach offers promising applications in infant nutrition and the development of functional foods enriched with bioactive carotenoids.