Study On Supercritical CO₂ Fluid Extraction And Microencapsulation Of Ginger Essential Oil

In this study, supercritical CO₂ fluid was used to extract ginger essential oil and gelatin and sodium alginate were used as wall materials to encapsulate ginger essential oil by polyelectrolyte complexation to expand the valuble of ginger. The main contents are as follows:1. The air-dried roots of ginger were ground in an attrition mill and separated to a size of 0.178 mm （80 mesh）. The optimal process parameters determined of ginger volatile oil extraction by using supercritical CO₂ fluid were as follows:pressure of 35 MPa, temperature of 35℃, flow of 30 kg/h for CO₂, processing time of 2 h. The extraction efficiency of ginger essential oil was 3.57%.2. The analysis of ginger essential oil chemical compounds and properties were carried out, which was obtained by supercritical CO₂ fluid extraction and steam distillation method. The results indicated that supercritical CO₂ fluid extracts were more complicated, including monoterpene hydrocarbons and 6-Gingerol, which were not detected in extracts by steam distillation method. This implied that supercritical CO₂ fluid extraction had the advantage on extracting essential oil.3. The antioxidant activity in vitro and antimicrobial activity of ginger essential oil were studied. Scavenging effect on 2,2-diphenyl-l-picryl hydrazyl radical （DPPH）, superoxide anion radical, and hydroxyl radical and reducing power were applied to access the antioxidant activity of ginger essential oil. The results showed that the ginger essential oil presented antioxidant activity compared with VC, BHT and VE. The ginger essential oil showed antimicrobial activity against all tested microbial strains, with the highest capacity for inhibition of penicillium, which MIC and MBC were 0.78% and 0.78% respectively. The ginger essential oil can also inhibit aspergillum, which MIC and MBC were 0.78% and 3.13% respectively. The microencapsulations of ginger essential oil exhibited antimicrobial activity against spoilage bacteria, including Escherichia coli and Salmonella, which MBC was over 50%.4. The optimum conditions for preparing microencapsulation of the ginger essential oil were found to be as follows:sodium alginate to gelatin of 1:6, polymer concentration of 1.0%, pH of 3.5, core material to wall of 2:1, reaction temperature of 40℃, reaction time of 60 min, calcium chloride of 3 mg/mL, harden temperature of below 10℃. The average particle size was 187.6 μm, and the encapsulation efficiency and loading efficiency were 68.22% and 36.73% respectively.5. The properties and characteristics were studied. The TGA thermograms showed that microencapsulation of the ginger essential oil was higher thermal stability than the neat gelatin, sodium alginate and ginger essential oil. The release study in vitro indicated that the release of ginger essential oil from microcapsules was much higher in pH6.8, compared with in pH1.2 and that microencapsulation may be responsible the controlled release. The storage stability study showed that microencapsulation can significantly protect the ginger essential oil in higher environment and that microencapsulation may block the light but not obviously in light.