Preparation Of The Multiple Emulsion And Encapsulation Of Water-soluble Active Componds

W₁/O/W₂ multiple emulsion is widely used in food,cosmetics and medicine fields,since it can encapsulate water-soluble active componds due to its special three-phase structure.However,complicated preparation process,low encapsulation efficiency,and poor stability make it difficult for the multiple emulsion to be commercialized.Therefore,the stability of multiple emulsion and the encapsulation of water-soluble active componds are still challenging work,which were the emphasis of the thesis.The main research contents are as follows:?1?Water-in-oil-in-water?W₁/O/W₂?multiple emulsion was prepared by two-step method with caprylic/capric triglyceride as oil phase,lauryl PEG-9 polydimethylsiloxyethyl dimethicone as the hydrophobic emulsifier,Tween 80,PEG1000 laurate or an amphiphilic random copolymer as the hydrophilic emulsifier.The stability of the multiple emulsion was evaluated with emulsion droplet size,the polydispersity of droplet size,as well as the appearance of the emulsion at normal temperature and 40 ^oC for 24 h.The effects of experimental parameters containing the amount of KF-6038,GTCC in the first-step emulsion?E1?,and the conent of E1,water-soluble emulsifying agent in the second-step emulsion?E2?on the stability of the multiple mulsion was invesitaged.It was found that the stability of the multiple was better as P?LMA-co-MAA?,rather than Tween80 and PEG1000 laurate used in the second-step emulsion.The stability was improved further by adding electrolyte NaCl and thickener xanthan gum.The optimum emulsion formulation was:60%GTCC,5.0%KF-6038,0.4%NaCl,residual water in E1,and 50%E1,1.0%P?LMA-co-MAA?,0.5%xanthan gum in E2.The emulsion at room temperature and at 40 ^oC could remain stable with droplet size of emulsion(D_3,2)of 14.6?m and the polydispersity of particle size?U?of 0.26.At room temperature for 6 months,the droplet size and its polydispersity of the emulsion fluctuated within 12.9±1.7?m and 0.28±0.02?n=15?,respectively.?2?Vitamin C was added in the internal aqueous phase?W₁?in W₁/O/W₂ emulsion.The stability of the multiple emulsion encapsulating vitamin C and the maximum vitamin C amount in the multiple emulsion were investigated.The effects of vitamin C and NaCl on phase interfacial tension,particle size and viscosity of the emulsion were studied.The stability of the emulsion was evaluated by microscopic examination and appearance of the emulsion.The results showed that the stability of the emulsion was poor as there was only vitamin C in the internal water phase W₁.NaCl added into W₁ phase could significantly reduce the interfacial tension of W₁/O,decrease the particle size of emulsion and increase the viscosity of the emulsion.When more than 0.2%NaCl was added to the external aqueous phase?W₂?,the interfacial tension of O/W₂ increased significantly.Compared with NaCl,vitamin C reduced W₁/O interfacial tension slightly.Therefore,NaCl in internal and external aqueous phases of W₁/O/W₂ emulsion were all controlled to be 0.2%.The influence of the amount of vitamin C on the microstructure and appearance of multiple emulsion was obvervated.When the content of vitamin C was 0.75%,the size of multiple emulsion particles was uniform and the appearance was stable.The droplet size of the emulsion and the polydispersity was 15.2?m and 0.33 when the vitamin C content was 0.75%.At room temperature for 30 days,the droplet size and polydispersity of the emulsion fluctuated within the range of 15.3±0.3?m and 0.33±0.12?n=5?,respectively.?3?The water-soluble and electrochemically active substance vitamin B6 was used as the marker and added to W₁ of the multiple emulsion.An electrochemical method was established to evaluate the stability of W₁/O/W₂ emulsion and encapsulation rate of water-soluble active components.It was found that W₁/O/W₂ emulsion could be stably dispersed in the electrolyte solution as its concentration less than or equal to 0.05mol/L,and the microstructure of W₁/O/W₂ emulsion remained stable after cyclic voltammetry?CV?measurement.There were three linear relationships between the concentration of vitamin B6and its peak current at 0.735 V?vs.SCE?in 0.05 mol/L?pH6.0?phosphate buffer?PBS?,blank W₁/O/W₂ emulsion added in PBS?PBS-ME?,and blank W₁/O/W₂ emulsion demulsified by ethanol in PBS?PBS-ME-EtOH?,respectively.The linear eqation was y=68.7 x+2.2?r=0.995?for PBS,y=40.8 x-1.4?r=0.995?for PBS-ME and y=52.9 x+0.7?r=0.998?for PBS-ME-EtOH,respectively.It was testified that vitamin B6 in W₁ could not be oxidized electrochemically owing to an electric shield.Therefore,the encapsulation rate of vitamin B₆ in W₁ could be measured by determining vitamin B₆ in W₂ of W₁/O/W₂ emulsion.On the other hand,the stability of the multiple emulsion could be evaluated by monitoring the vitamin B₆ in W₂,which leaked from W_1.?4?The encapsulation rate for vitamin C in W₁/O/W₂ emulsion and the stability were determined with the developed electrochemical method.The linear relationship between peak current and the concentration of vitamin C in different electrolyte background solutions was y=0.03 x+0.9?r=0.993?for PBS-ME and y=0.028 x–0.63?r=0.991?for PBS-ME-EtOH,respectively.The encapsulation rate for vitamin C in W₁/O/W₂ emulsion?Formulation:60%GTCC,5.0%KF-6038,0.4%NaCl,1.5%vitamin C,excess water in E1 and 1.0%P?LMA-co-MMA?,0.2%NaCl,0.5%xanthan gum,3.0%1,3-butanediol,50%E1,residual water in E2?was 91.3%.After 1 month at room temperature,the encapsulation rate decreased to87.3%.The results showed that the multiple emulsion had high encapsulation rate for vitamin C and good stability.