During the realization of the project, the main key aspects for the production and stabilization of lipid nanoparticles loaded with carotenoids were systematically studied, being the particle size, surfactant type and concentration, lipid state (solid or liquid) and oil saturation degree. The implications of the formulation characteristics of lipid nanoparticles on the lipid digestion rate and extent (kinetics) and the subsequent formation of lipid digestion products was studied under simulated digestive conditions. Overall, the oil droplet size and surfactant type were found as the most determining factors affecting lipid digestion rate during the simulation of small intestine conditions. The smaller the particle size the faster the lipid digestion due to a higher surface active area for lipid digestion enzymes to adsorb. Moreover, the surfactant type determined the emulsion stability during digestion conditions. In this regard, stable small oil droplets after simulated gastric conditions were obtained by small-molecule non-ionic surfactants, and those were more efficiently digested during intestinal conditions.
Moreover, as a second phase of the project, the interactions between lipid nanoparticles and food components from vegetable origin, mainly pectin, were evaluated and their implications on the lipid digestibility were studied. It was observed that pectin from carrot or broccoli purées did not significantly affect lipid digestion. Also when emulsions were produced within vegetable purées, lipid digestion kinetics was not significantly affected in comparison to their respective model emulsion systems. However, a lower incorporation of lipid digestion products into mixed micelles was observed in emulsions formed within complex food matrices, which suggests that interaction between food components and lipid digestion products occurred.
Ultimately, it was consistently observed along the realization of the present project that there is a direct relationship between the lipolysis degree, micelle formation and the carotenoid bioaccessibility. It was identified that emulsion digestion kinetics is the rate limiting step for both releasing the carotenoids from the oil core and generating lipid digestion species that will contribute to increase the solubilisation capacity of mixed micelles. These two processes are crucial in the carotenoid bioaccessibility kinetics under intestinal conditions and are determined by emulsion characteristics and the presence of other food components.
