Influence of particle size on lipid digestion and β-carotene bioaccessibility in emulsions and nanoemulsions

• β-Carotene was encapsulated in nanoemulsions and emulsions.
• Initial droplet size influenced potential biological fate of delivery systems.
• Lipid digestion rate and extent increased with decreasing droplet size.
• β-Carotene bioaccessibility increased with decreasing droplet size.

The interest in incorporating carotenoids, such as β-carotene, into foods and beverages is growing due to their potential health benefits. However, the poor water-solubility and low bioavailability of carotenoids is currently a challenge to their incorporation into many foods. The aim of this work was to study the influence of particle size on lipid digestion and β-carotene bioaccessibility using corn oil-in-water emulsions with different initial droplet diameters: large (d43 ≈ 23 μm); medium (d43 ≈ 0.4 μm); and small (d43 ≈ 0.2 μm). There was a progressive increase in the mean particle size of all the emulsions as they passed through a simulated gastrointestinal tract (GIT) consisting of mouth, stomach, and small intestine phases, which was attributed to droplet coalescence, flocculation, and digestion. The electrical charge on all the lipid particles became highly negative after passage through the GIT due to accumulation of anionic bile salts, phospholipids, and free fatty acids at their surfaces. The rate and extent of lipid digestion increased with decreasing mean droplet diameter (small ≈ medium ≫ large), which was attributed to the increase in lipid surface area exposed to pancreatic lipase with decreasing droplet size. There was also an appreciable increase in β-carotene bioaccessibility with decreasing droplet diameter (small > medium > large). These results provide useful information for designing emulsion-based delivery systems for carotenoids for food and pharmaceutical uses.