Comparative study on lipid digestion and carotenoid bioaccessibility of emulsions, nanoemulsions and vegetable-based in situ emulsions

Emulsions (d(43) 0.484-0.897 mu m) and nanoemulsions (d(43) 0.279-0.226 mu m) based on lipid fractions enriched with carotenoids from different sources were produced by increasing the amount of a non-ionic surfactant (Tween 80) at surfactant-to-oil ratio (SOR) 0.1 or 2, respectively. Alternatively, carrot puree in situ emulsions were fabricated by processing carrot puree with a non-enriched oil fraction and Tween 80 (SOR 0.1). Emulsions, nanoemulsions and in situ emulsion were subjected to in vitro digestion conditions with focus on the kinetics of lipid digestion, micelle formation and carotenoid bioaccessibility during the small intestinal phase. Nanoemulsions produced with a high amount of surfactant showed an almost complete lipid hydrolysis inhibition probably due to hindered lipase adsorption at oil-water interfaces. Emulsions presented a gradual lipid digestion during the intestinal phase and subsequent incorporation of lipid digestion products into mixed micelles. Interestingly, the in situ emulsion presented a similar lipid digestion trend than emulsions, yet a lower concentration of lipid digestion products incorporated into mixed micelles, which resulted in a lower carotenoid bioaccessibility. Overall, this study highlights the potential of using nanoemulsions to modulate lipid digestion. Moreover, it also indicates possible interactions between food components and lipid digestion products during the formation of mixed micelles and its implications on the bioaccessibility of lipophilic bioactives such as carotenoids.