| Cellulose nanocrystals is a nanomaterial extracted from natural fibers,which has the characteristics of renewable,biodegradable,high specific surface area,high aspect ratio,and has become a research hotspot in many fields in recent years.Using cellulose nanocrystals as a stabilizer,the Pickering emulsion prepared had good stability,small droplet size,easy degradation,which had great application potential in the fields of pharmaceutical engineering,food engineering and material engineering.In addition,by modifying the hydroxyl groups on the surface of cellulose nanocrystals,or mixing them with other materials with complementary properties,the properties of the cellulose nanocrystals could be improved,thereby improving the stability of the Pickering emulsion.Therefore,two different types of cellulose were prepared by sulfuric acid method and high-pressure homogenization method.The morphology and structure of them were characterized by Fourier infrared transform spectroscopy,transmission electron microscopy,X-ray diffraction,thermogravimetric analysis.Research on the preparation of Pickering emulsion and its stabilization mechanism and application were studied in order to provide theoretical guidance and technical support for the preparation of cellulose nanocrystals.The preparation and application of cellulose nanocrystals-based Pickering emulsion.The main researches were as follows:Taking camellia oleifera abel shell as raw materials,cellulose nanocrystals(CNC)and cellulose nanofiber(CNF)were prepared by sulfuric acid method and high-pressure homogenization method separately.The results showed that the CNC prepared by sulfuric acid method tended to be optimal while the concentration was 62%,in which 54 nm of the average particle size,73 mV of the average Zeta potential,73.53%of the crystallinity,5.6 of the lengthto-diameter ratio,329.2℃ of the maximum thermal degradation temperature,and-34.44%of the maximum thermal degradation rate.The CNF prepared by high-pressure homogenization method could reach 140 nm in 5 times,in which 20 mV of the average Zeta potential,66.53%of the crystallinity,18.75 of the length-to-diameter ratio,333.9℃ of the maximum thermal degradation temperature,and-28.89%of the maximum thermal degradation rate.The stability of Pickering emulsion mainly depends on the hydrophobicity of particles.Improving the hydrophobicity of cellulose nanofibers could enhance the stability of Pickering emulsion.Using PDMS hydrophobic modified CNF as the stabilized particles,the effects of oil content,particle concentration and emulsification time on the storage stability and centrifugal stability of Pickering emulsion were studied.Compared with CNF,the FTIR of PDMS-CNF featured absorption peaks at 1261.2 cm-1 and 798.4 cm-1,the particle size increased slightly from 70 to 130 nm to 110 to 180 nm,and the contact angle increased from 27.4° to 87.1°.The optimal conditions for the preparation of Pickering emulsion were determined to be:oil content was 50%,particle concentration was 0.1%,and emulsification time was 6 min.Pickering emulsion was oil-in-water and decreased in size as the particle concentration increased.Rheological experiment results denoted that as the shear rate,shear stress,and frequency increased,the apparent viscosity,the |η*| and G’/G" all decreased,G’ was greater than G",while G" increased.The results of in vitro simulated digestion experiments with the hydrophobic drug Magnoliol showed that Magnoliol could be slowly and continuously released in the small intestine.Meanwhile the release rate decreased as the particle concentration increased,which meant PDMS-CNF had a good stabilizing effect as a stabilizer of Pickering emulsion,and Pickering emulsion could also be widely used in drug carriers to achieve sustained release.CNF or lignin alone could not stabilize the high internal phase Pickering emulsion well,while mixing the two might obtain a higher internal phase of Pickering emulsion.The effects of lignin content,total particle concentration and oil content on lignin-cellulose nanofiber synergistically stabilized high internal phase Pickering emulsion were systematically studied.Lignin-cellulose nanofiber with different lignin contents(0,10%,20%,30%and 40%)had similar functional groups,and the contact angle values were 42.1°,82.8°,88.5°,63.3° and 54.5°,indicating that it was the best when the lignin content was 20%as a stable particle.The storage stability,centrifugal stability,thermal stability and freeze-thaw stability of high internal phase Pickering emulsion were studied,and the optimal preparation process was determined to be:lignin content of 20%,total particle concentration of 0.5%,oil content of 85%.All the stability under these conditions was the best,and up to three freeze-thaw cycles could be realized.The low fatty acid release rate of high internal phase Pickering emulsion in vitro digestion indicated that it was expected to be applied to the development of low-fat foods. |
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