Improving Hydrophilic Barriers of Encapsulated Compounds in Ca-Alginate Microgel Particles through a New Ionotropic Gelation Method for Double Emulsion Droplets

The ability of encapsulation to protect hydrophilic–bioactive food compounds from harsh environments can be improved by strengthening the hydrophilic barriers of encapsulated food compounds in Ca-alginate microgel particles via the integration of oil into the microgels. This study introduces a one-step procedure to integrate water-in-oil (W/O) emulsion droplets directly into Ca-alginate microgels during the production using the impinging aerosols system. A water-in-oil-in-water (20 kg m⁻³ alginate solution) (W₁/O/W₂) double emulsion was prepared using a high speed homogeniser followed by a microfluidiser. The microstructure of the W₁/O/W₂ emulsion was analysed using optical and fluorescence microscopy. The mean diameters of the W₁/O/W₂ emulsion droplets and resultant microgels were in the range of 27.8–65.4 μm and 160–420 μm, respectively. Food dye was used as a proxy for a hydrophilic food compound and its release from the microgels was significantly decreased when it was encapsulated in the W/O emulsion droplets. Based on the numerical analysis, the presence of the W/O emulsion droplets in the gel network reduced the degree of gelation of the microgel because the diffusion rate of Ca²⁺ cation in the microgel is reduced. The degree of gelation of the W/O emulsion droplets encapsulated microgel is 0.6 when the diameter of the droplet is reduced to 77.5 μm and the concentration of CaCl₂ solution is doubled to 22 kg m⁻³. The potentiality of the impinging aerosol system to produce Ca-alginate microgels to encapsulate hydrophilic compounds with improved barriers is presented in this work.