Pickering Emulsion Synergistically Stabilized By Zein Nanoparticles And Starch Nanocrystals

Pickering emulsion stabilized by colloidal particles derived from plants has attracted interests in various areas,such as food,pharmaceuticals and cosmetics due to edibility,biodegradability and biocompatibility.However,most plant-derived colloidal particles are usually too hydrophilic or hydrophobic to stabilize stable Pickering emulsion.After specific surface treatment,Pickering emulsion with higher stability stabilized by these colloidal particles can be obtained.But these methods are complexed and have poor controllability or use harmful chemicals.Therefore,it is of great theoretical significance and practical value to develop a new way to prepare high stability Pickering emulsion by using plant-derived colloidal particles.In this thesis,we propose a new method to prepare Pickering emulsion with plantderived colloidal particles,which is using oppositely charged colloidal particles to synergistically stabilize Pickering emulsion.Afterwards,we further investigate the application of Pickering emulsion in protecting bioactive materials and constructing bio-functional materials.Specific studies are as follows:(1)Preparation and stability mechanism of Pickering emulsion synergistically stabilized by zein nanoparticles(ZNPs)and starch nanocrystals(SNCs)In this chapter,Pickering emulsion synergistically stabilized by oppositely charged colloidal particles derived from plants is successfully prepared with positively charged ZNPs and negatively charged SNCs as stabilizers and soybean oil as oil phase.Then,stability mechanism of the resultant Pickering emulsion is revealed by studying the relationship between assembled structures of colloidal particles at oil/water interfaces and stability of Pickering emulsion.To be specific,ZNPs and SNCs can be similarly or oppositely charged by changing p H of water phase.When they are oppositely charged,ZNPs and SNCs will form unique particle bilayers at oil/water interfaces and highly stable Pickering emulsion is formed,while ZNPs and SNCs will irregularly adsorb at oil/water interfaces to form less stable Pickering emulsion when they are similarly charged.On the other hand,the amount of charge on the surface of ZNPs and SNCs can be controlled by changing ionic strength of water phase.When there are more charge on particle surface,there are stronger electrostatic attractions and Pickering emulsion is more stable.(2)Property and application of Pickering emulsion synergistically stabilized by ZNPs and SNCsAfter successfully prepared Pickering emulsion synergistically stabilized by ZNPs and SNCs and revealed emulsion stability mechanism,in this chapter influences of different factors on emulsion stability and stability of Pickering emulsion in different environmental stress are investigated.Specifically,increasing particle concentration,decreasing oil phase volume and increasing homogenizing speed will decrease the droplet size of Pickering emulsion and further increase emulsion stability,which could remain stable after centrifugation at 10000 g for 10 min.On the other hand,comparing with Pickering emulsion stabilized by ZNPs or SNCs alone,stability of Pickering emulsion synergistically stabilized by ZNPs and SNCs can be significantly improved under different temperatures.After being stored at room temperature for one year,Pickering emulsion synergistically stabilized by ZNPs and SNCs can remain stable and it can still remain stable for one month after being stored at 50 °C.In addition,Pickering emulsion stabilized by ZNPs and SNCs can be stable in a wide range of p H(3 – 9)and under high ionic strength(500 m M).Finally,it has been found out that such Pickering emulsion can effectively protect bioactive component such as β-carotene under UV radiation and heating.(3)Fabrication and application of high internal phase Pickering emulsions(HIPPEs)synergistically stabilized by ZNPs and SNCsIn this chapter,HIPPEs can be successfully prepared by ZNPs and SNCs.ZNPs cannot stabilize stable HIPPEs,while stability of HIPPEs can be significantly improved when ZNPs and SNCs are used together.Appearance and microstructure of HIPPEs synergistically stabilized by ZNPs and SNCs almost unchange after being stored at room temperature for two months.Increasing temperature to 50 °C,HIPPEs can still be stable for one month,which may be resulted from the gelatinized SNCs at oil/water interfaces.What’s more,the resultant HIPPEs are all-natural and edible.Therefore,rheological performance of HIPPEs are compared with that of mayonnaise and salad and results show that they have similar texture,which may provide a substitution for these products.On the other hand,all-natural porous materials can be prepared by using HIPPEs as templates and removing internal phase,which can be potentially used in pharmaceuticals and environmental protection.