Lipid digestion, micelle formation and carotenoid bioaccessibility kinetics: Influence of emulsion droplet size

Carotenoid-enriched oil-in-water emulsions with different droplet sizes (small: d₄₃ 0.72μm; medium: d₄₃ 1.9μm; large: d₄₃ 15.1μm) were subjected to simulated gastrointestinal conditions. The kinetics of lipolysis, micelle formation and carotenoid bioaccessibility were monitored during the intestinal phase. The rates of all three processes increased with decreasing droplet size. The large droplet size emulsion contained undigested oil at the end of digestion, whereas an almost complete hydrolysis was observed for the other two emulsions. The sub-micron emulsion presented a higher conversion of MAGs to FFAs during digestion, which led to a higher concentration of FFAs in the mixed micelles. The incorporation of carotenoids into mixed micelles occurred faster and reached a higher final value for the small droplet size emulsion, leading to final carotenoids bioaccessibility values of around 70%. This work provides valuable information for developing in silico models to simulate the lipid digestibility and carotenoid bioaccessibility.