Nanoemulsion-Based Delivery Systems for Nutraceuticals: Influence of Long-Chain Triglyceride (LCT) Type on In Vitro Digestion and Astaxanthin Bioaccessibility

Astaxanthin (AST) exerts biological activities that is potentially beneficial to human health, but its utilization as a nutraceutical in foods and supplements is currently limited by its low oral bioavailability. The influence of three long chain triglyceride (LCT) oils (flaxseed, olive and corn oil) on the bioaccessibility of AST encapsulated within oil-in-water nanoemulsions was evaluated using a simulated gastrointestinal tract (GIT) model. The microstructure and particle properties (size and charge) of all three nanoemulsions followed similar patterns in simulated mouth, stomach, and small intestinal regions, which were appreciably different from the control (no lipid). Moreover, all three nanoemulsions significantly increased the bioaccessibility of AST compared to the control, which was attributed to their ability to form mixed micelles that could solubilize the hydrophobic carotenoids. However, LCT type did have an impact on lipid digestion and carotenoid bioaccessibilty, with the final amount of free fatty acids (FFAs) released and bioaccessibility decreasing in the following order: olive oil > flaxseed oil > corn oil. These effects were attributed to the impact of FFA unsaturation and chain length on lipid digestion and micelle formation. The results of this study highlight the potential of nanoemulsions for enhancing AST bioavailability in functional foods and supplements.