Laura Salvia-Trujillo

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.

Structurally modified pectin for targeted lipid antioxidant capacity in linseed/sunflower oil-in-water emulsions

The present work explored the lipid antioxidant capacity of citrus pectin addition to 5%(w/v) linseed/sunflower oil emulsions stabilized with 0.5%(w/v) Tween 80, as affected by pectin molecular characteristics. The peroxide formation in the emulsions, containing tailored pectin structures, was studied during two weeks of storage at 35°C. Low demethylesterified pectin (≤33%) exhibited a higher antioxidant capacity than high demethylesterified pectin (≥58%), probably due to its higher chelating capacity of pro-oxidative metal ions (Fe2+), whereas the distribution pattern of methylesters along the pectin chain only slightly affected the antioxidant capacity. Nevertheless, pectin addition to the emulsions caused emulsion destabilization probably due to depletion or bridging effect, independent of the pectin structural characteristics. These results evidence the potential of structurally modified citrus pectin as a natural antioxidant in emulsions. However, optimal conditions for emulsion stability should be carefully selected.

Emulsion stability during gastrointestinal conditions effects lipid digestion kinetics

Oil-in-water emulsions were prepared with carrot- or tomato-enriched olive oil (5%w/v) and stabilized with Tween80 or sucrose esters (0.5%w/v) with different hydrophilic-lipophilic balance (8; 11 or 16). All emulsions had similar initial oil droplet sizes and were submitted to simulated gastrointestinal conditions using a kinetic digestion procedure. Sucrose esters induced an unstable system after gastric conditions leading to coalesced oil droplets, while Tween80 emulsions remained stable. Emulsion particle sizes at the end of the gastric phase were directly associated with the lipolysis kinetics during the intestinal phase. Moreover, a direct relationship was observed between lipolysis and carotenoid micellarisation for all emulsions, and depended mainly on the surfactant structure used. Tween80 emulsions led to a higher lipolysis extent (53-57%) and carotenoid bioaccessibility (17-42%) compared to sucrose ester emulsions (33-52% and 9-27%, respectively). These findings show the importance of the emulsifier structure and emulsion stability during gastrointestinal conditions in modulating lipolysis kinetics.

Pectin influences the kinetics of in vitro lipid digestion in oil-in-water emulsions

Oil-in-water emulsions were prepared with 5% (w/v) carrot-enriched olive oil and stabilized with Tween 80 (TW), phosphatidylcholine (PC), citrus pectin (CP) or a combination of these emulsifiers. Additionally, the methylesterification degree (DM) of citrus pectin was modified, resulting in three different studied pectin structures: CP82, CP38 and CP10. All initial emulsions presented small initial oil droplet sizes and were submitted to an in vitro simulated gastric and small intestinal phase. The latter was executed in a kinetic way to determine the time dependency of the lipolysis reaction, micelle formation and carotenoid bioaccessibility. The results showed that the pectin DM mainly influenced the reaction rate constants, while the emulsifier (combination) determined the extent of lipolysis and carotenoid bioaccessibility. Moreover, a direct relation was observed between the lipolysis reaction and bioaccessibility extent. The presented study showed that targeted emulsion design can be used to tailor lipid digestion kinetics.