Microcapsules with a fungal chitosan-gum Arabic-maltodextrin shell to encapsulate health-beneficial peppermint oil

Abstract

Microcapsules encapsulating peppermint oil (L-Carvone) were fabricated via two-stage encapsulation processes (complex coacervation followed by spray drying) using three plant-based biopolymers (fungal chitosan, gum Arabic, and maltodextrin). Transglutaminase was introduced to the formulation to crosslink the coacervate formed during microcapsule wall development. The microcapsules were assayed for their physical, structural, morphological, mechanical, and barrier properties, using several analytical techniques, including light scattering, spectrophotometry, SEM, TEM, and a micromanipulation technique. The size of the microcapsules ranged from 10–125 µm, with a Sauter mean diameter of 37.8 ± 1.4 µm and shell thickness of 0.91 ± 0.15 μm. The microcapsules were spherical with a relatively smooth surface. Nile red was employed as a fluorescent dye dopant in the peppermint oil to assess the presence of oil in microcapsules after spray drying. A micromanipulation technique was used to quantify the mechanical properties of microcapsules, such as rupture force (0.6 ± 0.1 mN) and nominal rupture stress (2.1 ± 0.3 MPa). Static oil leakage from dry microcapsules was negligible after storage for 50 days. The release rates of the oil from the microcapsules to aqueous ethanol solutions (5–20% w/w) were measured, and the effective diffusivity was quantified (Deff = 4.210−12 m2 s–1). These results show that the two-stage encapsulation processes could be an eco-friendly and sustainable methodology for the manufacture of active oil containing microcapsules, with potential applications in food, personal care, and cosmetics products. Furthermore, the use of plant based materials will overcome the growing issues associated with the consumer turning away from animal based products in favour of vegan alternatives.