Optimization of Lutein Emulsion Stabilized by Octenylsuccinylated Starch-Soy Protein Isolate to Improve Lutein Stability and In Vitro Bioaccessibility

Objectives: Lutein, a hydrophobic carotenoid that acts as the macular pigment in the retina and is the dominant carotenoid in the brain of infants, plays a crucial role in their visual and cognitive development. However, the application of lutein as a nutritional intervention is limited due to its poor stability and water solubility. Oil-in-water emulsions are widely used delivery systems of lipophilic nutrients that can protect carotenoids from chemical degradation and improve their bioaccessibility. Octenylsuccinylated starch (OSS) and soy protein isolate (SPI) are biopolymer emulsifiers approved for use in infant foods. The purpose of this study was to determine the optimal concentrations of OSS and SPI in the emulsion system to improve the stability and in vitro infant bioaccessibility of lutein. Methods: A total of 17 biopolymer solutions containing various proportions of deionized water, OSS capsules TA®, and SPI were made according to a simplex-centroid mixture design. Lutein emulsions were prepared by mixing biopolymer dispersions and lutein in olive oil at a 70% oil volume fraction using a homogenizer. The microstructure, photo-stability, thermal stability, and simulated in vitro infant gastrointestinal release of lutein emulsions were assessed. Results: The OSS-SPI based lutein emulsions at biopolymer dispersions of 74%-87% water, 9%-22% CTA, and 0-8% SPI showed good emulsions without phase separation. The mean droplet size of lutein emulsions fell into the range from 2.09 ± 1.69 μm to 6.23 ± 8.46 μm and decreased with increasing SPI concentration. After 7-hour UV light exposure, OSS-SPI based lutein emulsions improved lutein stability than the solo OSS-based emulsion, and all emulsions had higher lutein retention than free lutein. After a 7-hour water bath at 80 °C, lutein retention was significantly higher in all emulsions than in free lutein. Using in vitro infant digestion model, the lutein release from the emulsions were higher than those of free lutein. Notably, while the emulsion with 78% water, 14% OSS, and 8% SPI was 2.16-fold higher, the other emulsions showed 1.11-1.92-fold higher release. Conclusions: The lutein emulsion stabilized with 78% water, 14% OSS, and 8% SPI had the best overall performance, offering promising potential for enhancing lutein's nutritional benefits in infant foods, such as infant formula. Funding Sources: USDA-NIFA.