Spray-and freeze-drying of microcapsules prepared by complex coacervation method: A review

The charge neutralization between two oppositely charged polyelectrolytes can generate a rich colloidal polyelectrolyte phase known as complex coacervate. Complex coacervates can be applied to encapsulate bioactive ingredients. Drying of these rich colloidal polyelectrolytes encapsulating bioactive compounds attains excellent protection properties, high dispersibility and sustained release of core materials. However, drying stresses can disrupt the coacervates resulting in susceptibility to oxidation, poor rehydration and release properties. Meanwhile, crosslinking and protection of complex coacervates before drying is beneficial for ameliorating their properties. This review assesses the current state of research on spray- and freeze-dried microcapsules prepared by complex coacervation method. Specifically, the stability and release properties of the dried coacervated microcapsules are explored, focusing on the effects of various crosslinkers and protectants. The information presented here can be useful for the design and development of spray-dried and freeze-dried encapsulates with high loading capacity, oxidation stability, and controlled release of active ingredients.