Encapsulation of β-carotene in Nanoemulsion-Based Delivery Systems Formed by Spontaneous Emulsification: Influence of Lipid Composition on Stability and Bioaccessibility

Nanoemulsion-based delivery systems are finding increasing use in food, pharmaceutical, agrochemical, and personal care applications due to their ability to increase the stability and/or activity of lipophilic functional components. In this study, a low-energy homogenization method (spontaneous emulsification) was used to encapsulate beta-carotene in nanoemulsions. The main objective was to optimize lipid phase composition to form stable nanoemulsions that would effectively enhance beta-carotene bioavailability. Lipid phase composition was varied by mixing long chain triglycerides (LCT) with medium chain triglycerides (MCT) or flavor oil (orange oil). LCT was added to promote bioaccessibility, whereas MCT or orange oil was added to facilitate nanoemulsion formation. Our hypothesis was that an optimum level of LCT is required to form stable nanoemulsions with good bioaccessibility characteristics. Stable nanoemulsions could be formed at LCT-to-orange oil ratios of 1:1 (d (32) = 109 nm) and at LCT-to-MCT ratios of 1:2 (d (32) = 145 nm). Thus, higher LCT loading capacities and smaller droplet sizes could be obtained using orange oil. The influence of oil composition on the potential gastrointestinal fate of the nanoemulsions was studied using a simulated gastrointestinal tract (GIT) consisting of mouth, stomach, and small intestine phases. The transformation and bioaccessibility of beta-carotene in the GIT was highly dependent on lipid phase composition. In particular, beta-carotene bioaccessibility increased with increasing LCT level due to greater solubilization in mixed micelles. These results are useful for optimizing the design of nanoemulsion-based delivery systems for encapsulation and release of lipophilic nutraceuticals and pharmaceuticals.