Preparation and characterization of oregano essential oil microcapsules by gelatin/polysaccharide composite coagulation method

Abstract

Complex cohesions were formed through electrostatic interactions between gelatin (GE) and gum arabic, sodium carboxymethyl cellulose, pectin, and sodium alginate (SA). Of them, GE and SA served as an ideal wall material for encapsulating oregano essential oil (OEO). Applying the composite coalescence method, we here generated unique encapsulated OEO microcapsules (EOMs) by using GE–SA as the microcapsule wall material and OEO as the core material. At a concentration of 1 % (w/v), a core-to-wall ratio of 1:2, a recoalescence reaction temperature of 45 °C, and an emulsifier concentration of 5 % (w/w), EOMs exhibited excellent performance. Under the optimal conditions, the prepared EOMs (average particle size: 78.389 μm) had a homogeneous and complete spherical structure. Freeze-dried EOMs had a high encapsulation efficiency (71.20 %) and payload (56.08 %). Fourier transform infrared spectroscopy unveiled the presence of electrostatic interactions between GE and SA. The OEO in the EOMs had higher thermal stability and more stable antioxidant properties than the free OEO. Furthermore, in aqueous, acidic, oily, and alcoholic environments, EOMs exhibited some degree of slow-release ability. Additionally, EOMs exhibited strong antibacterial properties, with effective inhibition of Escherichia coli (E. coil), Staphylococcus aureus (S. aureus), and Curvularia lunata (C. lunata). Among them, the strongest inhibitory effect was on C. lunata. In summary, microcapsules prepared using GE–SA as a wall material had effectively improved OEO degradation-protecting, which enhanced the stability of OEO and controlled its antioxidant properties. Meanwhile, the microcapsules exhibited excellent antibacterial properties. This system exerted considerable potential in protecting the stability of essential oils and realizing slow release.