Structural and physical properties of spray-dried fish oil microcapsules via pea protein isolate based emulsification or complex coacervation with sugar beet pectin

Abstract

The aim of this study is to compare the type of infeed dispersions, i.e., fish oil (FO) emulsions stabilized by single-shelled pea protein isolate (PPI) and FO–PPI–sugar beet pectin (SBP) double-shelled complex coacervates on structural and physical properties of spray-dried FO microcapsules. The results show that FO–PPI–SBP complex coacervates formed at pH 3.5 possess bigger particle size and denser network structures rather than those produced at higher pHs (4.5 and 4.0). Nevertheless, the encapsulation performance of both types of infeed dispersions is quiet similar, and they afford a relative low encapsulation efficiency (22.80%–27.78%). FTIR confirms that electrostatic interaction dominates the formation of complex coacervates based microcapsules. SEM shows the spherical shape of all microparticles without cracking or fissures; while oil spot is visualized in emulsification based microcapsules. Unlike emulsification, DSC indicates the raised denaturation temperature of PPI in the FO microcapsules due to PPI–SBP interactions. This study suggests that PPI alone with a lower concentration is insufficient to microencapsulate fish oil; while the addition of SBP for the formation of double-shelled PPI–SBP complex coacervates particularly at pH 3.5 could be a practical and economic solution for fish oil microencapsulation. • Plant protein (PPI) and pectin (SBP) are used to produce fish oil (FO) powders. • FO infeed dispersions are prepared via PPI emulsions or PPI-SBP complex coacervates. • pH is critical to determine physical properties of dispersions and microcapsules. • Encapsulation performance is independent of the type of infeed dispersions. • Smooth surface without cracks or holes are revealed for microcapsules with PPI-SBP