Modulating β-carotene bioaccessibility by controlling oil composition and concentration in edible nanoemulsions

Diets rich in carotenoids have been correlated with a reduced risk of developing certain types of chronic diseases, but these bioactive components have low intestinal absorption due to their hydrophobic nature. The aim of this work was to study the effect of carrier oil composition (medium-chain triglyceride (MCT) to long-chain triglyceride (LCT) ratio) and total carrier oil concentration (1% or 4% w/w) on the physical stability, lipid digestibility and bioaccessibility of β-carotene-loaded nanoemulsions, using a simulated digestion process. Lipolysis led to an appreciable increase in the size and negative charge on the particles in the system. The total fraction of triacylglycerols converted to free fatty acids decreased as the percentage of LCT within the lipid phase increased, particularly for the nanoemulsions with higher fat contents. There was an increase in β-carotene bioaccessibility as the LCT within the lipid phase increased for low fat nanoemulsions, which was attributed to the increased solubilisation capacity of mixed micelles formed by LCT. β-carotene bioaccessibility showed a complex relationship on LCT content for high fat nanoemulsions, due to the opposing effects of lipid digestion and micelle solubilisation. These results may facilitate the optimisation of delivery systems for lipophilic bioactive compounds for food or pharmaceutical applications.