The influence of iron source, hydrophilic emulsifiers, and positioning of encapsulates on in vitro bioaccessibility and simultaneous delivery of iron and curcumin by water-in-oil-in-water (W1/O/W2) double emulsions

Low bioavailability of iron in the presence of polyphenols can lead to its low uptake by the body resulting in iron-deficiency anaemia. Curcuminoids are polyphenols that possess anti-inflammatory, anti-cancer, antioxidant, and neuroprotective properties and if their iron chelation can be controlled, double fortification of foods with iron can overcome the problem of iron deficiency anaemia, while enhancing other healthy properties of foods. This study explored the co-delivery of ferric sodium EDTA or ferrous sulphate together with curcumin through double emulsions stabilized by protein-poly/oligosaccharide complexes as hydrophilic and PGPR as the lipophilic emulsifiers. The formed sodium caseinate (NaCas)-sodium alginate (NaAlg) and NaCas-sodium carboxymethyl cellulose (NaCMC) complexes increased the stability of the emulsion interface and resulted in high bioaccessibility of both ferric iron (~ 86–92%) and curcumin (~ 76–86%) due to the presence of EDTA in the iron complex’ molecular structure. The lower stability of emulsions stabilized with NaCas-ß-cyclodextrin (ßCD) was increased and the low intestinal bioaccessibility of curcumin (~ 33%) was enhanced to 69.5% when curcumin was incorporated inside ßCD cavity, positioned in the biopolymeric shell with the addition of NaAlg and formation of NaCas-NaAlg-ßCD-curcumin-inclusion complex (IC). Compared with ferric iron, low bioaccessibilities (~ 30%) were obtained for ferrous sulphate as iron was partially chelated with curcumin. For co-delivery of ferric sodium EDTA and curcumin, the emulsions stabilized by NaCas-NaAlg, NaCas-NaCMC, and NaCas-NaAlg-ßCD-curcumin-IC were stable during storage with negligible droplet coalescence, which suggests that co-fortification can be a valuable tool in improving the nutrition of iron deficient populations. Graphical abstract