Encapsulation of curcumin in polysaccharide-based hydrogel beads: Impact of bead type on lipid digestion and curcumin bioaccessibility

Abstract Curcumin was incorporated into three different delivery systems: free lipid droplets; lipid-loaded alginate beads; and, lipid-loaded carrageenan beads. Hydrogel beads were fabricated from polysaccharides (alginate or carrageenan) using an injection method combined with ion gelation (calcium or potassium, respectively). The delivery systems were passed through a simulated gastrointestinal tract (GIT) that included mouth, stomach, and small intestine phases. Light scattering and microscopy indicated that carrageenan beads had a relatively fragile structure that was easily disrupted in the GIT and released the encapsulated lipid droplets and curcumin. Conversely, alginate beads had a robust structure that remained relatively intact throughout the GIT and retained the lipid droplets and curcumin. The rate and extent of lipid digestion decreased in the following order: free lipid droplets > carrageenan beads > alginate beads. Curcumin bioaccessibility followed a similar order: free lipid droplets (73%) > carrageenan beads (33%) > alginate beads (16%). These results suggest that lipid droplets must be digested by lipase in order to release the encapsulated curcumin and to form mixed micelles capable of solubilizing the released curcumin. Overall, our results show that delivery systems with different structures and compositions can be designed to control the release of lipids and hydrophobic nutraceuticals in the GIT, which may be advantageous for the development of certain functional food products.