Characterization of core–shell calcium-alginate macrocapsules fabricated by electro-coextrusion

Spherical macrocapsules, where calcium-alginate shell enclosed olive oil as a model core medium, were fabricated by electro-coextrusion. The effects of three key process factors, including alginate concentration in shell fluid (0.5–4.0%), shell-to-core flow rate ratio (4–12 at a fixed core flow rate of 0.05 mL/min), and applied voltage (0–10 kV), on the morphological and textural characteristics of the macrocapsules were analyzed using response surface methodology. The analysis showed that the diameter, shell thickness, hardness, and breaking energy of the macrocapsules were in the ranges of 0.89–1.61 mm, 17.4–66.4 μm, 1.37–11.01 N, and 0.34–6.90 mJ, respectively, and strongly influenced by all the three factors, except that the surface appearance was only significantly affected by the shell-to-core flow rate ratio. The process factors were also optimized for the practically useful macrocapsules, having non-oily surface and hardness larger than 3 N, using a graphical optimization technique.