Nanoemulsion delivery systems: Influence of carrier oil on β-carotene bioaccessibility

Consumption of carotenoids may reduce the incidences of certain chronic diseases, but their use in foods is currently limited because of their poor water-solubility, low bioavailability and chemical instability. We examined the impact of carrier oil type on the bioaccessibility of β-carotene encapsulated within nanoemulsion-based delivery systems. Oil-in-water nanoemulsions (d < 200 nm) were formed using a non-ionic surfactant (Tween 20) as emulsifier and long chain triglycerides (LCT), medium chain triglycerides (MCT) or orange oil as carrier oils. The influence of carrier oil type on β-carotene bioaccessibility was established using an in vitro model to simulate the oral, gastric and small intestinal phases of the gastrointestinal tract. The rate and extent of free fatty acid production in the intestine decreased in the order LCT ≈ MCT ≫ orange oil; whereas β-carotene bioaccessibility decreased in the order LCT ≫ MCT > orange oil. The bioaccessibility of β-carotene was negligible (≈0%) in orange oil nanoemulsions because no mixed micelles were formed to solubilise β-carotene, and was relatively low (≈2%) in MCT nanoemulsions because the mixed micelles formed were too small to solubilise β-carotene. In contrast, β-carotene bioaccessibility was relatively high (≈66%) in LCT nanoemulsions. Our results have important implications for the design of effective delivery systems for encapsulation of carotenoids and other lipophilic bioactive components.