Manufacturing nearly monodispersed complex coacervate microcapsules by membrane emulsification and spray drying

Complex coacervation is a phase separation process in which two oppositely charged polymers or macromolecules in a solution come together at the liquid-liquid interface to form a dense coacervate shell. The process can be employed to encapsulate oil droplets, creating stable microcapsules that protect and control the release of oil while achieving a high encapsulation efficiency of active ingredients. In this work dry coacervate microcapsules of different size and shell thickness were manufactured combining a continuous single pass cross-flow membrane emulsification system and spray drying to obtain a dry powder. A single-pass crossflow membrane emulsification system with a single cylindrical 10 × 100 mm membrane module with 10 μm pore produced emulsion droplets between 71 μm and 114 μm with a dispersed phase (oil content) in the final emulsion between 3.3 and 6.2 vol/vol% and a total emulsion output mass rate between 25.68 kg h⁻¹ – 49.68 kg h⁻¹. Emulsions manufactured by membrane emulsification were nearly monodispersed with the highest span not exceeding 0.68. Addition of maltodextrin to the emulsion prior to spray drying increased the viscosity and prevented the capsules breakage. Microcapsules up to a mean droplet diameter of 113.19 ± 0.81 μm preserved the shell and had a yield up to 78.43 ± 0.97 wt%, a surface oil as low as 9.35 ± 0.88 wt% and an encapsulation efficiency of 71.09 ± 0.87 wt%.