Bioaccessibility study of calcium and vitamin D3 co-microencapsulated in water-in-oil-in-water double emulsions

Calcium and vitamin D3 were co-encapsulated in three types of water-in-oil-in-water (W/O/W) double emulsions stabilized with biopolymers: gum arabic, sodium alginate (Alg) and chitosan (Ch). Three calcium salts with different solubility were used: calcium carbonate (CaC), tricalcium phosphate (CaP) and calcium gluconate (CaG). In order to study the bioavailability of calcium and vitamin D-3, the W/O/W double emulsions were subjected to digestion in simulated conditions using in vitro gastrointestinal models. The size of the oil droplets of all double emulsions increased in oral phase and decreased in gastric and intestinal phases. In the intestinal phase, the average diameter of oil globules in the W/O/W(Alg) and W/O/W(Ch) was d(23) = 6.56 +/- 0.09 and d(23) = 5.33 +/- 0.01 and the electro-kinetic potential was: zeta >> -25 mV and zeta >> -17 mV, respectively. Presence of calcium ions in the intestinal fluid decreased the free fatty acids content and decreased the bioaccessibility of vitamin D-3 due to the inhibition of micellization process.