Controllable Preparation Of Micro/nanocapsuie Of Ginger Essential Oil Via Complex Coacervation

Complex coacervation reaction is a polymer-forming reaction that happened betweentwo kinds of water-soluble macromolecules driven by electrostatic interactions. Themacromolecules are oppositely charged when the pH value changes. Mild reaction conditions,stable and efficient products are the advantages of this method. The products can becontrolled by changing the reaction conditions and the materials, so it is widely studied in allareas of food, medicines, cosmetics, construction materials.The paper was focused on preparing microcapsules and nanocapsules of ginger essentialoil via complex coacervation. Gelatin and gum arabic were used as the wall materials andginger essential oil was used as the core material. Factors affecting complex coacervationreaction and the optimal preparing conditions were studied. And the release of ginger essentialoil from microcapsules and nanocapsules under storage and high temperature conditions werestudied to evaluate their thermal stability and storage stability. The conclusion can provide atheoretical basis for the realization of industrial production in the future. The main contentsare as follows:The morphology, particle size, yield and encapsulation efficiency of the microcapsuleswere studied by changing the main parameters: wall material concentration, core/wall ratioand stirring rate. The optimized conditions were determined as follows: pH4.0, mass ratio ofgelatin and Arabic gum1:1, wall material concentration1%(w/v), ginger essential oilconcentration0.5%(w/v), stirring rate400rpm, TGase: gelatin1:4. Under this condition, theaverage size of microcapsules was about40μm, the yield was84.29%and encapsulationefficiency was81.61%. Good embedding effect of the microcapsules was showed bymicroscopy. Microscopic observation showed that microcapsule of ginger essential oil haveuniform size, moderate wall thickness, good shape and can remain stable for a long time. Themain ingredient of ginger essential oil did not change before and after embedding.The storage stability of microcapsules of ginger essential oil was studied, the resultsshowed that the microcapsules were stored at4°C and25°C after50days, the core materialloss were20.1%and30.35%, respectively. The release rate of the core material increasedwhen the temperature increased. The thermal stability of the microcapsules was studied, theresults showed that the core material loss was49.2%in80°C water; at150°C oven the corematerial loss was56.75%, whereas ginger essential oil ingredient lost82.15%. The resultshowed that ginger essential oil was protected by wall materials and the release rate wasreduced through microencapsulation even at high temperature environment.The release kinetics of the microcapsule were studied. The results showed that at the temperature of4°C,25°C and80°C hot water, the release of microcapsules obeyed the firstorder release equation, while at the temperature of150°C, the release of microcapsulesobeyed the zero order release equation, equations have high fitting degree.Through the analysis of particle distribution, pH4.90was chosen as the favorablecondition for the nanocapsule preparation. Based on the particle size, PDI and Zeta potential,the nanocapsules of ginger essential oil were prepared successfully. The optimized conditionswere selected as follows: gelatin and Arabic gum (1:1), the total concentration of wallmaterial0.5%(w/v); core material concentration0.5%(w/v); emulsifier composition Span80and Tween80(1:1), emulsifier concentration0.4%(w/v); concentration of TGase0.2%(w/v). Under this condition, the particle size of the nanocapsules was98.28nm, PDIvalue was0.144, Zeta potential was-14.40mV. The nanocapsules solution with gooddispersion was stable and homogeneous.Storage stability of the nanocapsules of ginger essential oil were studied, the resultsshowed that the solution was remain homogeneous and stable with no precipitation for anextended period. Thermal stability was compared between nanocapsules before and afterhardening processing in80°C water, the hardened nanocapsules were much more stable thanthe unhardened nanocapsules. The thermal analysis of the nanocapsules further illustrated thebetter heat-resistant capability of nanocapsules after hardening.