Investigating the effectiveness of coacervates produced from conjugated and unconjugated Spirulina protein in delivering unstable oil to the intestinal phase of digestion

Abstract

This study investigated the potential of complex coacervates produced using Spirulina protein concentrate (SPC) conjugated with maltodextrin (MD) and carrageenan (CG) for encapsulating and delivering sensitive oils. A wet-heating Maillard reaction was employed to conjugate SPC with MD, followed by coacervation with CG to form the conjugate-based coacervates. Additionally, a mixture of unconjugated SPC and MD was coacervated with CG to produce mixture-based coacervates. Both types of coacervates were utilised as wall materials for encapsulating canola oil. The in-vitro digestion of the resulting microcapsules was assessed in oral, gastric, and intestinal phases, focusing on physicochemical parameters such as droplet size, zeta-potential, microstructure, proteolysis, oil release and lipolysis. The findings revealed that microcapsules prepared using both (SPC-MD mixture)-CG and (SPC-MD conjugate)-CG coacervates were remarkably stable against gastric digestion, as evidenced by the minimal production of free amino acids (15 mM). Most of the encapsulated oil (62–67%) was released during the intestinal phase due to the breakdown of the coacervates. Notably, the microcapsules produced with (SPC-MD conjugate)-CG coacervates demonstrated a lower degree of lipolysis (41.77% free fatty acid content) compared to those prepared with (SPC-MD mixture)-CG coacervates (53.35% free fatty acid content). These results highlight the potential of complex coacervates produced using conjugated SPC as promising materials for the encapsulation and delivery of sensitive oils.