Abstract
Essential oils (EOs) are common additives in daily products by virtue of their
olfactory, physicochemical, and biological characteristics. However, EOs are
physicochemically unstable and susceptible to degradation or loss, leading to limited
shelf life and inadequate efficacy. Here a new bi-layered encapsulation structure was
proposed in combination with complex coacervation and self-coating of polydopamine
(PDA) on membrane emulsified mono-dispersion of EOs droplets.
A uniform-sized EOs emulsion stabilized by nonionic surfactants was produced by
membrane emulsification, wherein the EOs droplets were applied as soft templates to
deposit a superficial PDA layer. Under alkaline conditions, gelatin (GE) was bound to
the PDA layer and further applied as in situ coacervation sites for gum Arabic (GA).
Structural identification and morphological observation proved the successful
preparation of bi-layered EOs capsules.
Compared with traditional complex coacervation strategies, current novel bilayered
capsules showed significantly improved structural stability and thermal stability,
providing better protection of EOs with sustained release properties. Moreover, the
encapsulation efficiency and loading content were both proved higher for the bi-layered
system. The first report on PDA-coating onto surfactants-absorbed macroemulsion
droplets also provides an in-depth insight into applying PDA as versatile intermediate
functional biomaterials.