Characterization of sodium alginate/d-limonene emulsions and respective calcium alginate/d-limonene beads produced by electrostatic extrusion

In this study, calcium alginate beads immobilizing d-limonene (solid systems) have been manufactured starting from emulsions of this flavor in sodium alginate (liquid systems). The effects of alginate concentration (0.02 and 0.03 g/mL) and flavor content (5 and 10 %w/w) on viscosity, conductivity and stability of emulsions were investigated. The flavor droplets in emulsions are bigger as polymer solution is more concentrated and contains more of the flavor. When emulsions have been subjected to electrostatic extrusion and upon Na+-Ca2+ ion exchange, smaller (∼960 to ∼1450 μm) and less spherical beads were obtained (sphericity factor 0.003–0.21) compared to beads produced by simple dripping technique (without electrostatic field). When wet beads were air dried, they shrunk less if they had higher content of the flavor. Novel mathematical model describing swelling kinetics of dried beads is developed. In this work, d-limonene was efficiently immobilized within Ca-alginate beads (immobilization efficiency ∼50 to ∼77%) and its thermal stability was confirmed by TG/MS analysis.