| As a kind of vegebalbe oil squeezed from coconut pulp, coconut oil (CO) has antioxidant, antibacterial, antiviral, hypolipidemic and other excellent functional characteristics. It is widely used in food, medicine, chemical industry and so on. Bacterial cellulose (BC) fermentated by Gluconacetobacter xylinum resembles a solid "hydrogel"and it has been achived large scale commercial production with trade name "Nata de coco"in Hainan provience. Owing to its remarkable structure of BC, researches are focused on BC as nanobiological materials. To enlarge CO or BC applications in food, medicine and other fields and to improve products value, the CO microemulsion was prepared and then its characteristics and permeation kinetics of oil-soluble matter delivery in BC gel was studied . The main results and conclusions are as follows:1 Construction of CO microemulsion systemIt was found that CO microemulsion could be obtained with dripping cosurfactant method but it failed to be prepared by dripping water or oil method. It was found that CO microemulsion could be obtained with dripping cosurfactant method but it failed to be prepared by dripping water or oil method. Ultrasonic agitation method was used for CO microemulsion preparation which presented more stable characteristics comparing to stirring method or homogenizing supplemented with stirring method. By response surface analysis, CO microemulsions were prepared under optimum technological conditions:HLB value 11.68, ultrasonic power 330W, and ultrasonic time 7 min. SE-15 and GMS was selected as the composite surfactant based on the pseudo-ternary phase diagrams and glycerol used as a cosurfactant had higher effiency ability than others for emulsification.The mass ratio of composite surfactant to oil phase and water phase was 3.2% which was determined by apparent observation and microemulsion area of the phase diagrams.2 Properties of CO microemulsionThe prepared CO microemulsion samples appeared transparent and were considered as o/w type microemusions by observation. The particle size of CO microemulsion sample reached 15-60nm through the measurement of particle size analyzer.To test the stability of CO microemulsions, the microemulsion samples with 9:1, 8:2, 7:3, 6:45 5:5, 4:6 mass ratio of water phase to oil phase were centrifuged at the speed of 2000r/min for 3 0min,3000 r/min for 30min, 4000 r/min for 30min and 4000 r/min for an hour. The results showed that microemulsion samples were stable owing to no significant difference in samples of before and after centrifugation throgh light transmittance tests.The solubilizing capacity in different CO microemulsions (the mass ratio of water phase to oil phase from 9:1 to 7:3) was tested utilizing 5% wt glucose solution and 0.9%wtsodium chloride solution. It was found that the glucose solution (5% wt) presented a highersolubilizing capacity in microemulsions than sodium chloride solution (0.9% wt).Besides that, the solubilizing capacity no matter that of glucose solution or sodium chloride solution decreased along the mass ratio of water phase to oil phase from 9:1 down to 7:3.In terms of viscosity, refractive index, conductivity and pH value at-18??4??30? and 60? temperature for 21 day storage,the microemulsion samples (mass ratio of water phase to oil phase 9:1, 8:2,7:3) possesseda good stability of short-term storage without statistical significant difference. After storage for eight months at at -18? ?4??30?and 60? temperature for 8 months, the long-term storage stability of the samples was tested at the room temperature. Ultimately, the most samples were constantly clear and transparent except for the samples stored at 60? for 8 months to cause phase separation, which suggested good storage stability at low temperature and room temperature.3 Permeation kinetics of CO microemulsion delivering oil-soluble matter into BC gelTo form permeation system, BC gel was immerged into CO microemulsions in which tonyred ? was dissolved by oil phase. Following process of permeating with whirling vibration speed of 170r/min at 60 ? temperature,the concentration of tonyred ? in BC gel was measured by spectrophotometric method at the wavelength of 506 nm. By means of apparent observation and gas chromatography, the results indicated that CO containing oil-soluble tonyred ? was able to permeate into apertures of BC gel. The three microemulsion samples which mass ratio of water phase to oil phase was 9:1, 8.5:1.5 and 8:2 were prepared for regular pattern of permeation of CO emulsions delivering oil-soluble matter into BC gel. By data fitting, the content of tonyred ? penetrated into BC was in accordance with the model equation S = Aexp (-kt). The corresponding exponential model equation of permeation kinetics in the three microemulsions were S = 0.9458exp (-0.8485t),S=0.7946exp (-0.8021t), S =0.838exp (-0.6801t) and the fitting correlation coefficients of the model equations were all above 0.9 which indicated that the fitting model well predicted the content of tonyred ? into BC. Permeability tests were repeated under the same conditions as vitaminE substituting for tonyred ?.There was no significant statisticaldifference between the content values of vitamin E measured by liquid chromatograph and that predicted by model equation, which indicated that the model equation fitted wellon applicability and accuracy for delivering oil-solube matter through microemulsion into BC gel. |
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