Proceedings of International Congress on Bioactive Compounds and International Workshop on Bioactive Compounds
Proceedings of 2nd International Congress on Bioactive Compounds

Lutein intake is associated with a reduced risk of developing chronic diseases and positive effects on cognitive functions in child and aging populations. In many carotenoid sources, e.g., most fruits, lutein is naturally found acylated to fatty acids, being the main form ingested. Studies have reported that acylated carotenoids are less bioaccessible than their free forms. However, the carotenoid form impact on the mixed micelle structure has not been fully investigated. The bioaccessibility of lipophilic compounds directly relates to their amount within mixed micelles. That is why this issue is crucial, especially for them. In addition, the separation process used to recover mixed micelles is also relevant. In this context, the effect of carotenoid acylation on mixed micelle structure was assessed, besides the influence of the filtration step during the micellar fraction (MF) recovery on carotenoid bioaccessibility. For that, casein-stabilized emulsions without or with carotenoid extracts majorly composed of acylated or free lutein were subjected to in vitro gastrointestinal digestion. Marigold petals were used as a source of lutein-rich extracts. For emulsion preparation, 2% (w/w) carotenoid-enriched oily phase and 98% (w/w) NaCas stock solution were pre-mixed using a rotor-stator at 10000 rpm/2 min, followed by high-pressure microfluidization at 9000 psi/3 cycles. After one day of storage, emulsions were subjected to digestion. In the following, the chyme was centrifuged (20000 g at 4 °C /10 min). The precipitate was discarded, and the supernatant was retained and separated into two parts. One of them was stored in an ice bath, while the other was filtered with a syringe filter (0.2 μm pore), yielding the MF. The emulsions and digested samples before (supernatant) and after (MF) the filtration step were analyzed by LC-DAD-MS/MS and size measurements. SAXS and cryo-TEM were performed for the MFs. The filtration of the supernatants retained both forms of carotenoids but especially carotenoid esters. Before digestion, all emulsions showed an oil droplet size of about 275 nm. The Z-average of all supernatants was about 250 nm, except for that one rich in acylated carotenoids with an average size near 275 nm. After filtration, the Z-average was about 200 nm for all the samples. Although emulsions and MFs presented particle size distribution in the same range, their SAXS profiles were completely different. Before digestion, emulsions displayed a linear behavior, while MFs showed typical SAXS profiles of micellar structures. It suggests that the emulsion-based matrix destabilized under in vitro digestion conditions, leading to carotenoid release and incorporation into mixed micelles. All MFs’ SAXS curves overlapped, indicating that carotenoid form did not affect the micellar structure. However, cryo-TEM evidenced similar structures regardless of the carotenoid form, except for the presence of intact oil droplets (<100 nm) in the MF obtained from the digestion of carotenoid ester-rich emulsion. It suggests that carotenoid form affected the extent of lipid digestion and, consequently, micellization. In conclusion, our results showed that although the carotenoid form practically did not influence mixed micelle structure, it affected micellization and carotenoid retention during the filtration step to obtain the MF.